Papers for Wednesday, Mar 12 2025

(abridged) To understand early star formation, it is essential to determine the dust mass budget of high-redshift galaxies. Sub-millimeter rest-frame emission, dominated by cold dust, is an unbiased tracer of dust mass. The NIKA2 camera conducted a deep blank field survey at 1.2 and 2.0 mm in the GOODS-N field as part of the NIKA2 Cosmological Legacy Survey (N2CLS), detecting 65 sources with SNR>=4.2. Thanks to a dedicated interferometric program with NOEMA and other high-angular resolution data, we identify the multi-wavelength counterparts of these sources and resolve them into 71 individual galaxies. We build detailed SEDs and assign a redshift to 68 of them, over the range 0.6<z<7.2. We fit these SEDs using MBB and Draine & Li (2007) models, and the panchromatic approaches MAGPHYS, CIGALE, and SED3FIT, thus deriving their dust mass, M(dust), infrared luminosity (LIR), and stellar mass, M(star). Eight galaxies require an AGN-torus component and other six require an unextinguished young stellar population. A significant fraction of our galaxies are classified as starbursts based on their position on the M(star) versus SFR plane or their depletion timescales. We compute the dust mass function in three redshift bins (1.6<z<=2.4, 2.4<z<=4.2 and 4.2<z<=7.2) and determine the Schechter function that best describes it. We observe an increase of the dust cosmic density, rho(dust), by at least an order of magnitude from z~7 to z~1.5, consistent with theoretical predictions. At lower redshift the evolution flattens; significant differences exist between results obtained with different selections and methods. The superb GOODS-N dataset enabled a systematic investigation into the dust properties of distant galaxies. N2CLS holds promise for combining these deep field findings with the wide COSMOS field into a self-consistent analysis of dust in galaxies both near and far.

We report the discovery of two new Galactic accreting compact objects consistent with the respective positions of the unassociated Fermi-LAT gamma-ray sources 4FGL J0639.1--8009 and 4FGL J1824.2+1231. A combination of new and archival X-ray data from Chandra, XMM-Newton, Swift/XRT, and eROSITA reveals a variable X-ray source in each gamma-ray error ellipse. Both candidate counterparts show power-law spectra with photon indices $\Gamma \sim 1.7-1.9$. Optical follow-up photometry and spectroscopy show rapid high-amplitude variability unrelated to orbital motion and persistent accretion disk spectra for both objects. We demonstrate that the properties of these X-ray/optical sources are at odds with the known phenomenology of accreting white dwarfs, but are consistent with the observed properties of the sub-luminous disk state of transitional millisecond pulsars. This brings the census of confirmed or candidate transitional millisecond pulsars in the Galactic field to nine. We show this potentially represents $\lesssim 10\%$ of the total population of transitional millisecond pulsars within 8 kpc.

Recent James Webb Space Telescope observations have revealed a peculiar class of galaxies at redshifts $z \gtrsim 6$, characterized by extremely high central stellar densities and overmassive central supermassive black holes (SMBHs), "little red dots" (LRDs). A critical question remains: If LRDs were common at high redshifts, how would they evolve into local elliptical galaxies with significantly lower central densities? To address this, we performed direct $N$-body simulations of LRD mergers, focusing on the coevolution of host galaxies and central SMBHs. We track the complete evolution of SMBH binaries into the three-body hardening and gravitational-wave (GW) emission phase. Our results demonstrate that during galaxy mergers, the central SMBHs can eject a substantial amount of mass from the galactic core via the three-body slingshot effect, leading to a decrease in central stellar surface density by an order of magnitude. Additionally, GW recoil can further contribute in making the galaxy centers less dense and more in alignment with low-redshift quiescent galaxies. This transformation occurs on a relatively short timescale of a few $\sim$100 Myr, implying that LRDs can evolve into lower-redshift elliptical galaxies by $z<4$. The timescales for our SMBH mergers vary between 100 Myr and 800 Myr, depending on the initial orbital parameters of the merging galaxies and the mass ratio of the SMBHs. Our findings provide a plausible mechanism for the transformation of LRDs into elliptical galaxies while highlighting the efficiency of SMBH mergers in such high-density environments, which plays a crucial role in SMBH growth.

Radio phoenixes are filamentary sources in the intracluster medium (ICM) of galaxy clusters, often extending over $>100$ kpc, arising from fossil radio lobes. Their soft, curved spectrum is widely attributed to aged relativistic electrons recently accelerated or compressed, but at high frequencies is shown to approach a power-law. Moreover, the full, curved spectrum is naturally reproduced by secondary $e^{\pm}$ from a pure power-law spectrum of relativistic ions, radiating in highly-magnetized filaments; this model provides a better fit to all phoenixes, with only three free parameters. Weaker magnetization shifts the curvature to low frequencies, explaining pure power-law phoenixes. Hadronic high-curvature phoenixes require $e^{\pm}$ heating, by a factor $\gtrsim 15$ if at ICM pressure. The $\sim$keV Compton- and $\sim$GeV $\pi^0$-decay-peaked counterparts of hadronic phoenixes may be detectable as non-thermal X-rays and $\gamma$-rays.

We present an analysis of the molecular specific angular momentum-mass ($j_{H_2}-M_{H_2}$) relation using a sample of 51 nearby disc galaxies from the PHANGS-ALMA survey with deep, high-resolution molecular gas rotation curves and surface density profiles. For the very first time, using a statistical sample, we report the discovery of a well-defined $j_{H_2}-M_{H_2}$ relation. We quantify the scaling law by fitting a power-law with a Bayesian framework, finding $j_{H_2} \propto M_{H_2}^{0.53}$. This slope closely resembles the well-known stellar $j_{\ast}$-$M_{\ast}$ (Fall) relation, highlighting the dynamical connection between molecular gas and stars. We show that the $j_{H_2}-M_{H_2}$ relation cannot be fully explained by analytic models of disc stability but instead is well recovered with more complex physics as implemented in the Shark semi-analytical model. These findings demonstrate the power of our novel $j_{H_2}-M_{H_2}$ relation in testing galaxy evolution theories and setting new constraints for models and simulations which aim to reproduce a realistic interstellar medium. Additionally, our findings provide a critical benchmark for upcoming high-redshift studies of molecular gas kinematics, offering a local baseline to study the evolution of cold gas dynamics across cosmic time.

Determining the dynamical mass profiles of dispersion-supported galaxies is particularly challenging due to projection effects and the unknown shape of their velocity anisotropy profile. Our goal is to develop a machine learning algorithm capable of recovering dynamical mass profiles of dispersion-supported galaxies from line-of-sight stellar data. Traditionally, this task relies on time-consuming methods that require profile parameterization and assume dynamical equilibrium and spherical symmetry. We train a convolutional neural network model using various sets of cosmological hydrodynamical simulations of galaxies. By extracting projected stellar data from the simulated galaxies and feeding it into the model, we obtain the posterior distribution of the dynamical mass profile at ten different radii. Additionally, we evaluate the performance of existing literature mass estimators on our dataset. Our model achieves more accurate results than any literature mass estimator while also providing enclosed mass estimates at radii where no previous estimators exist. We confirm that the posterior distributions produced by the model are well-calibrated, ensuring they provide meaningful uncertainties. However, issues remain, as the method loses performance when trained on one set of simulations and applied to another, highlighting the importance of improving the generalization of ML methods trained on specific galaxy simulations.

More than a decade ago, the IceCube Neutrino Observatory discovered a diffuse flux of 10 TeV - 10 PeV neutrinos from our Universe. This flux of unknown origin most likely emanates from an extragalactic population of neutrino sources, which are individually too faint to appear as bright emitters. We review constraints on extragalactic neutrino source populations based on the non-detection of the brightest neutrino source. Extending previous work, we discuss limitations of source populations based on general neutrino luminosity functions. Our method provides more conservative but also statistically more robust predictions for the expected number of observable sources. We also show that the combined search of the brightest neutrino sources via weighted stacking searches or the analysis of non-Poissonian fluctuations in event-count histograms can improve the discovery potential by a factor of 2-3 relative to the brightest source.

KELT-20b is a well-studied exoplanet within the highly observable ultra hot Jupiter (UHJ) regime, yet its multidimensional atmospheric structure remains largely unconstrained. Recent advances in instrumentation and increased general circulation model (GCM) complexity have enabled observers to resolve the imprints of more intricate physical mechanisms in time-resolved data. We performed high-resolution cross-correlation transmission spectroscopy (HRCCTS) on a single transit time series of KELT-20b, observed with PEPSI on the LBT. We detect Fe I $(11.9\sigma)$ and Fe II $(23.7\sigma)$ and tentatively detect Na I $(3.4\sigma)$ and Cr I $(3.3\sigma)$ upon combining nineteen in-transit exposures. The full-transit velocity offsets of the strongest absorbers are $\Delta V_{\text{Fe I}} = -1.0 \pm 0.7$ km s$^{-1}$ and $\Delta V_{\text{Fe II}}= 0.0\pm 0.5$ km s$^{-1}$. These results are discrepant with other HRCCTS studies of KELT-20b, but these studies are largely inconsistent with each other due to multiple possible factors, including self-inconsistent treatment of systemic velocity. In response, we establish a stringent set of detection criteria to promote reproducibility in future works. We present phase-resolved absorption traces of species with high detection significance. Fe I and Fe II's absorption traces are both redshifted at ingress, cross to a blueshift after mid-transit, then settle at a net blueshift at egress; concurrently, SNR increases with phase. This behavior is consistent with absorption traces post-processed from an active magnetic drag GCM for another UHJ. However, the net blueshift during transit could also result from limb asymmetry drivers and/or longitudinally variable wind structure. This ambiguity motivates future theoretical work on KELT-20b.

Ultra-hot Jupiters (UHJs) orbit close to their host stars and experience extreme conditions, making them important laboratories to explore atmospheric composition and dynamics. Transmission spectroscopy is a useful tool to reveal chemical species and their vertical and longitudinal distribution in the atmosphere. We use transmission spectra from the PEPSI spectrograph on the Large Binocular Telescope to search for species and measure their time-resolved wind velocities in the atmosphere of TOI-1518 b. We detect Fe I at 7.8$\sigma$ and Fe II at 8.9$\sigma$, and tentatively detect Cr I at 4.4$\sigma$ and Ni I at 4.0$\sigma$. The time-resolved wind velocities of Fe I show a velocity pattern that is consistent with the velocity pattern of Fe II. TOI-1518 b joins a small sample of UHJs for which time-resolved wind velocities have been measured.

Strong gravitational lenses enable direct inference of halo abundance and internal structure, which in turn enable constraints on the nature of dark matter and the primordial matter power spectrum. However, the density profiles of dark subhalos around the main deflector of a strong lens system also depend on tidal evolution inside the host, complicating the interpretation of strong-lensing inferences. We present a model for subhalo tidal evolution that accurately predicts the bound mass function and the density profiles of tidally-stripped subhalos that appear near the Einstein radius of a typical deflector for a variety of dark matter models. This model matches predictions from the semi-analytic model (SAM) {\tt{galacticus}}, but enables the simulation of subhalo populations in seconds, rather than hours. We use this model to examine the expected number of subhalos near the Einstein radius of a typical lens, and examine their lensing signals. We show that in cold dark matter the amplitude of the bound mass function is suppressed by a factor of $20$ relative to the infall mass function, and $87 \%$ of subhalos appearing in projection near the Einstein radius of a typical strong lensing deflector have lost more than $80\%$ of their mass since infall. Tidal stripping becomes increasingly severe in dark matter models with suppressed small-scale power, such as warm dark matter. This model will be used to forward model subhalo populations in forthcoming analyses of strong lens systems.

In this study, we utilize photometric and kinematic data from \textit{Gaia} DR3 and the {\sc ASteCA} package to analyze the sparsely studied open clusters, King 2 and King 5. For King 2, we identify 340 probable members with membership probabilities exceeding 50\%. Its mean proper motion components are determined as $(\mu_\alpha\cos\delta,~\mu_\delta) = (-1.407 \pm 0.008, -0.863 \pm 0.012)$ mas yr$^{-1}$, and its limiting radius is derived as $6.94_{-1.06}^{+0.22}$ arcminutes based on radial density profiles. The cluster has an estimated age of $4.80 \pm 0.30$ Gyr, a distance of $6586 \pm 164$ pc, and a metallicity of $\text{[Fe/H]} = -0.25$ dex ($z = 0.0088$). We detect 17 blue straggler stars (BSSs) concentrated in its core, and its total mass is estimated to be $356 \pm 19~M_{\odot}$. The computed apex motion is $(A_o,~D_o) = (-142^\circ.61 \pm 0^\circ.08, -63^\circ.58 \pm 0^\circ.13)$. Similarly, King 5 consists of 403 probable members with mean proper motion components $(\mu_\alpha\cos\delta,~\mu_\delta) = (-0.291 \pm 0.005, -1.256 \pm 0.005)$ mas yr$^{-1}$ and a limiting radius of $11.33_{-2.16}^{+5.45}$ arcminutes. The cluster's age is determined as $1.45 \pm 0.10$ Gyr, with a distance of $2220 \pm 40$ pc and a metallicity of $\text{[Fe/H]} = -0.15$ dex ($z = 0.0109$). We identify 4 centrally concentrated BSSs, and the total mass is estimated as $484 \pm 22~M_{\odot}$. The apex motion is calculated as $(A_o,~D_o) = (-115^\circ.10 \pm 0^\circ.09, -73^\circ.16 \pm 0^\circ.12)$. The orbital analysis of King 2 and King 5 indicates nearly circular orbits, characterized by low eccentricities and minimal variation in their apogalactic and perigalactic distances. King 2 and King 5 reach maximum heights of $499 \pm 25$ pc and $177 \pm 2$ pc from the Galactic plane, respectively, confirming their classification as young stellar disc population.

We have carried out a systematic search for galaxy-scale lenses exploiting multi-band imaging data from the third public data release of the Hyper Suprime-Cam (HSC) survey with the focus on false-positive removal, after applying deep learning classifiers to all 110 million sources with i-Kron radius above 0.8". To improve the performance, we tested the combination of multiple networks from our previous lens search projects and found the best performance by averaging the scores from five of our networks. Although this ensemble network leads already to a false-positive rate (FPR) of 0.01% at a true-positive rate (TPR) of 75% on known real lenses, we have elaborated techniques to further clean the network candidate list before visual inspection. In detail, we tested the rejection using SExtractor and the modeling network from HOLISMOKES IX, which resulted together in a candidate rejection of 29% without lowering the TPR. We carried out a comprehensive multi-stage visual inspection involving eight individuals and identified 95 grade A (average grade G >2.5) and 503 grade B (2.5 >G >1.5) lens candidates, including 92 discoveries reported for the first time. This inspection also incorporated a novel environmental characterization using histograms of photometric redshifts. We publicly release the average grades, mass model predictions, and environment characterization of all visually inspected candidates, while including references for previously discovered systems, which makes this catalog one of the largest compilation of known lenses. The results demonstrate that (1) the combination of multiple networks enhances the selection performance and (2) both automated masking tools as well as modeling networks, which can be easily applied to hundreds of thousands of network candidates, help reduce the number of false positives that is the main limitation in lens search to date.

The $\Lambda$CDM model predicts structure formation across a vast mass range, from massive clusters ($\sim10^{15}\,\text{M}_\odot$) to Earth-mass micro-haloes ($\sim 10^{-6} \, \text{M}_\odot$), resolving which far exceeds the capabilities of current simulations. Excursion set models are the most efficient theoretical tool to disentangle this hierarchy in mass. We test the excursion set paradigm by combining smoothed initial density fields with a "perfect" collapse model -- $N$-body simulations. We find that a core excursion set assumption -- small-scale perturbations do not impact larger-scale collapse -- is approximately fulfilled but exhibits small quantitative violations dependent on the smoothing filter. For a sharp $k-$space cut-off $\sim 20\%$ of mass elements revert collapse as the smoothing scale decreases, while only $3.5\%$ do for a Gaussian and $5\%$ for a top-hat. Further, we test the simple deterministic mass-mapping $M \propto R^3$ (first-crossing scale to halo mass) relation. We find that particles that are first accreted into haloes at the same smoothing scale may end up in haloes of significantly different masses, with a scatter of 0.4-0.8 dex. We also demonstrate that the proportionally constant of this relation should be considered as a degree of freedom. Finally, we measure the mass fraction in different structure morphologies (voids, pancakes, filaments and haloes) as a function of filter scale. Typical particles appear to be part of a large-scale pancake, a smaller-scale filament and a notably smaller halo. We conclude that validating predictions of excursion set models on a particle-by-particle basis against simulations may enhance their realism.

Using multi-element abundances from the SDSS APOGEE survey, we investigate the origin of abundance variations in Milky Way (MW) disk stars on the "high-$\alpha$ plateau," with $-0.8\leq\rm{[Fe/H]}\leq-0.4$ and $0.25\leq\rm{[Mg/Fe]}\leq0.35$. The elevated [$\alpha$/Fe] ratios of these stars imply low enrichment contributions from Type Ia supernovae (SNIa), but it is unclear whether their abundance patterns reflect pure core-collapse supernova (CCSN) enrichment. We find that plateau stars with higher [Fe/Mg] ratios also have higher [X/Mg] ratios for other iron-peak elements, suggesting that the [Fe/Mg] variations in the plateau population do reflect variations in the SNIa/CCSN ratio. To quantify this finding, we fit the observed abundance patterns with a two-process model, calibrated on the full MW disk, which represents each star's abundances as the sum of a prompt CCSN process with amplitude $A_{\text{cc}}$ and a delayed SNIa process with amplitude $A_{\text{Ia}}$. This model is generally successful at explaining the observed trends of [X/Mg] with $A_{\text{Ia}}/A_{\text{cc}}$, which are steeper for elements with a large SNIa contribution (e.g., Cr, Ni, Mn) and flatter for elements with low SNIa contribution (e.g., O, Si, Ca). Our analysis does not determine the value of [Mg/Fe] corresponding to pure CCSN enrichment, but it should be at least as high as the upper edge of the plateau at $\rm{[Mg/Fe]}\approx0.35$, and could be significantly higher. Compared to the two-process predictions, the observed trends of [X/Mg] with $A_{\text{Ia}}/A_{\text{cc}}$ are steeper for (C+N) but shallower for Ce, providing intriguing but contradictory clues about AGB enrichment in the early disk.

The feedback from massive stars drives the evolution of interstellar dust grains by altering their physical properties via a number of radiative and mechanical processes. Through these interactions, interstellar grains can achieve high rotational velocities due to unbalanced torques, potentially leading to their disruption. Mechanical torque disruption occurs when gas-grain collisions, induced by the passage of shocks, spin grains to critical rotational velocities. This study aims to investigate the effects of stochastic mechanical torque disruption on both pre-existent and supernova-condensed dust grains located within wind-blown bubbles. The impact of mechanical torque disruption on supernova-condensed dust and dust grains in wind-blown bubbles is investigated through post-processing of three-dimensional hydrodynamical simulation outputs. The associated timescale is then compared to those of kinetic sputtering and grain shattering. Before the supernova explosion, dust grain disruption timescales within wind-driven bubbles are on the order of millions of years due to the low-density environment. The timescales for mechanical torque disruption (METD) are longer than those for kinetic sputtering and comparable to those of grain shattering, primarily due the high grain drift velocities typical of these regions.

The coupling between the dark matter (DM) halo and the stellar disc is a key factor in galactic evolution. While the interaction between structures like the Galactic bar and DM halos has been explored (e.g. slowing down of the bar due to dynamical friction), the effect of spiral arms on the DM halo distribution has received limited attention. We analyze a suite of simulations featuring strong stellar spiral arms, ranging in complexity from test-particle models to fully cosmological hydrodynamical simulations. Using Fourier transforms, we characterize the phase and amplitude of the stellar spirals at different times and radii. We then apply the same methodology to DM particles near the stellar disc and compare trends in Fourier coefficients and phases between the two components. We detect a clear spiral arm signal in the DM distribution, correlated with the stellar spirals, confirming the reaction of the halo. The strength of the DM spirals consistently measures around 10\% of that of the stellar spiral arms. In the $N$-body simulation, the DM spiral persistently trails the stellar spiral arm by approximately $10^\circ$. A strong spiral signal of a few km\,s$^{-1}$ appears in the radial, azimuthal, and vertical velocities of halo particles, distinct from the stellar kinematic signature. In a test-particle simulation with an analytical spiral potential (omitting self-gravity), we reproduce a similar density and kinematic response, showing that the test-particle halo responds in the same way as the $N$-body halo. Finally, we also find the rest of the simulations, indicating that the dynamical signatures of the forced response in the DM halo are independent of the dynamical origin of the stellar spiral arms. We reveal the ubiquitous presence of DM spiral arms in Milky Way-like galaxies, driven by a forced response to the stellar spiral potential. (ABR)

The physical properties of stellar atmospheres in rapidly rotating massive stars, such as Be stars, are critical to understanding their evolution and their role as progenitors of supernovae. These stars, which often have near-critical rotation, exhibit equatorial stretching and gravity darkening, which significantly complicates the determination of parameters such as the inclination angle. Be stars, characterized by their extreme rotational velocities, serve as excellent candidates for exploring these phenomena. However, fundamental quantities such as polar and equatorial radii and inclination angles are typically derived from interferometry, which applies only to a limited number of stars. This study aims to enhance the determination of inclination angles for Be stars using the ZPEKTR spectral synthesis code. By incorporating advanced models of gravity darkening and stellar deformation, we evaluated the effectiveness of this method with a sample of ten Be stars from the BeSOS database, comparing results with established interferometric data. Methods. We used the ZPEKTR code to model the effects of stellar oblateness and gravity darkening on spectral lines, focusing on the HeI 4471 line. We applied a chi-squared test minimization approach to identify the best-fitting models, and we evaluated the inclination angles derived against interferometric measurements. Our analysis reveals a robust linear correlation between the inclination angles derived from ZPEKTR and using interferometric techniques, which demonstrates an excellent agreement. The ZPEKTR code effectively models high rotational velocity effects, providing precise stellar parameter determinations. The results underscore the potential of advanced spectroscopic techniques to yield inclination measurements comparable to interferometry, which offers a pathway to studying distant massive stars.

We use the deep NIRCam and MIRI imaging from the JWST PRIMER survey to study the properties of (sub)mm sources detected by ALMA in the centre of the COSMOS field, with the aim of better constraining the history of dust-enshrouded star formation. The wealth of ALMA data in this field enabled us to isolate a robust sample of 128 (sub)mm sources within the 175 sq. arcmin of the PRIMER COSMOS survey footprint, spanning two decades in (sub)mm flux density. The JWST imaging is deep/red enough to reveal secure galaxy counterparts for all of these sources. Moreover, 52% of the galaxies have spectroscopic redshifts, enabling us to refine the photo-zs for the remaining galaxies. Armed with this robust redshift information, we calculate the star-formation rates (SFR) and stellar masses of all 128 ALMA-detected galaxies, and place them in the context of other galaxies in the field. We find that the vast majority of star formation is dust-enshrouded in the ALMA-detected galaxies, with SFR ranging from ~1000 down to ~20 solar masses per year. We also find that virtually all (126/128) have high stellar masses, at all redshifts, with log(M/Msun) > 10. The unusually high quality of our sample enables us to make a robust estimate of the contribution of the ALMA-detected galaxies to cosmic star-formation rate density from z = 2 out to z = 7. Finally, to correct for the fact that the deep ALMA pointings cover < 20% of the PRIMER COSMOS area, we use our knowledge of all other massive galaxies in the field to produce a completeness-corrected estimate of dust-enshrouded star-formation rate density over cosmic time. This confirms that UV-visible star formation dominates at z > 4, but also indicates that dust-enshrouded star formation likely still made a significant contribution at higher redshifts: extrapolation of our results suggest a ~20% contribution at z = 8, and potentially still ~5% at z = 10.

Active Galactic Nuclei (AGN) feedback is one of the most important mechanisms in galaxy evolution. It is usually found in massive galaxies and regulates star formation. Although dwarf galaxies are assumed to be regulated by supernova feedback, recent studies show evidence for the presence of AGN outflows and feedback in dwarf galaxies. We investigate the presence of AGN outflows in a sample of 2292 dwarf galaxies with AGN signatures drawn from the MaNGA survey. Thanks to the integral field unit data from MaNGA we are able to spatially resolve these outflows and study their kinematics and energetics. Using the GELATO Python code, we fit the AGN-stacked spectrum of each galaxy, which is the stack of all the spaxels classified as AGN by emission line diagnostic diagrams, and in particular the [OIII]$\lambda$5007Å emission line. If the galaxies show a broad [OIII] emission line component in the stacked spectrum, we run GELATO through all the spaxels that are classified as AGN in the emission line diagnostic diagrams. We find 11 new dwarf galaxies that present outflow signatures based on the presence of a broad [OIII] emission line component. Their velocity W$_{80}$ (width containing 80$\%$ of the flux of the [OIII]$\lambda$5007Å emission line) ranges from 205 to 566 km s$^{-1}$ and the kinetic energy rate ranges from $\sim10^{35}$ to $\sim10^{39}$ erg s$^{-1}$. Stellar processes are unlikely to explain these outflow kinetic energy rates in the case of seven dwarf galaxies. We find a correlation between the W$_{80}$ velocity and the [OIII] luminosity and between the kinetic energy rate of the outflow and the bolometric luminosity spanning from massive to dwarf galaxies. This suggests a similar behavior between the AGN outflows in the dwarf galaxy population with those in massive galaxies.

We analyze the X-ray and radio properties of the galaxy cluster Abell 2009 (z=0.152) to complete the in-depth study of a subsample of objects from the ROSAT Brightest Cluster Sample with relatively high X-ray flux and H$\alpha$ line luminosity, which is a promising diagnostic of the presence of cool gas in the cluster cores. Our aim is to investigate the feedback from the AGN in the central galaxy and the ICM of relaxed clusters. In this work, we analyze archival data from JVLA and Chandra observations. We performed a morphological analysis of both the X-ray emission from the ICM of Abell 2009 and the radio emission from the AGN in the central galaxy. We also performed a spectral analysis of the X-ray emission to derive the global properties and radial profiles of the thermal gas. Our X-ray analysis confirms the expectations, based on the selection criteria, that Abell 2009 is a cool-core system. We estimate a cooling radius of 88 kpc within which the ICM is radiating its energy at rates of $L_{cool} \sim 4.4 \times 10^{44}$ erg s$^{-1}$. Radio observations of the central galaxy reveal a bright core surrounded by radio lobes on 30 kpc scales with a symmetric butterfly-shaped morphology. Although we did not detect any X-ray cavity at the position of the central radio lobes, we combined the volume of the lobes with the pressure of the surrounding ICM to derive the work done by the AGN on the gas to inflate them. By estimating a cavity age of about 20 Myr, this corresponds to a mechanical power of $\approx 10^{45}$ erg s$^{-1}$ which is sufficient to counterbalance the radiative cooling losses in Abell 2009. We finally discuss possible correlations between the global properties of the 18 objects from the BCS selection, finding in particular that the number of outbursts required to counterbalance the radiative ICM losses is linearly anticorrelated with the energy and power of the outburst.

Circumstellar disk dust polarization in the (sub)millimeter is, for the most part, not from dust grain alignment with magnetic fields but rather indicative of a combination of dust self-scattering with a yet unknown alignment mechanism that is consistent with mechanical alignment. While the observational evidence for scattering has been well established, that for mechanical alignment is less so. Circum-multiple dust structures in protostellar systems provide a unique environment to probe different polarization alignment mechanisms. We present ALMA Band 4 and Band 7 polarization observations toward the multiple young system L1448 IRS3B. The polarization in the two Bands is consistent with each other, presenting multiple polarization morphologies. On the size scale of the inner envelope surrounding the circum-multiple disk, the polarization is consistent with magnetic field dust grain alignment. On the very small scale of compact circumstellar regions, we see polarization that is consistent with scattering around source a and c, which are likely the most optically thick components. Finally, we see polarization that is consistent with mechanical alignment of dust grains along the spiral dust structures, which would suggest that the dust is tracing the relative gas flow along the spiral arms. If the gas-flow dust grain alignment mechanism is dominant in these cases, disk dust polarization may provide a direct probe of the small-scale kinematics of the gas flow relative to the dust grains.

Low-energy neutrinos from the cosmic background are captured by objects in the sky that contain material susceptible of single beta decay. Neutrons, which compose most of a neutron star, capture low-energy neutrinos from the cosmic neutrino background and release a high-energy electron in the MeV range. Also, planets contain unstable isotopes that capture the cosmic neutrinos. We show that this process is feasible and results in a non-negligible flux of electrons in the MeV range in neutron stars. We present a novel observable, the redshift evolution of the temperature of neutron stars due to neutrino capture, that could provide a route for detection of the cosmic neutrino background from future gravitational waves observatories. For planets the flux is significantly smaller and a measurement is not possible with currently envisioned technology. While the signature from neutron stars is small and challenging, it could result in a novel way to detect the cosmic neutrino background.

The long-duration Galactic-bulge microlensing event OGLE-2011-BLG-0462 produced relativistic astrometric deflections of the source star, which we measured using HST observations taken at 8 epochs over ~6 years. Analysis of the microlensing light curve and astrometry led our group (followed by other independent groups) to conclude that the lens is an isolated stellar-mass black hole (BH)--the first and only one unambiguously discovered to date. There have now been three additional epochs of HST observations, increasing the astrometric time baseline to 11 years. Additionally, the ground-based OGLE data have been updated. We have re-analyzed the data, including the new HST astrometry, and photometry obtained with 16 different telescopes. The source lies only 0.4 arcsec from a bright neighbor, making it crucial to perform precise subtraction of its point-spread function (PSF) in the astrometric measurements of the source. Moreover, we show that it is essential to perform a separate PSF subtraction for each individual HST frame as part of the reductions. Our final solution yields a lens mass of 7.15 +/- 0.83 solar mass. Combined with the lack of detected light from the lens at late HST epochs, the BH nature of the lens is conclusively verified. The BH lies at a distance of 1.52 +/- 0.15 kpc, and is moving with a space velocity of 51.1 +/- 7.5 km/s relative to the stars in the neighborhood. We compare our results with those of other studies and discuss reasons for the differences. We searched for binary companions of the BH at a range of separations but found no evidence for any.

V4641 Sgr is a low-mass black hole X-ray binary system with somewhat puzzling spectral characteristics during its soft state. Recent high-resolution spectroscopic studies of V4641 Sgr have revealed strong ionized emission line features in both the optical and X-ray bands, including P-Cygni signatures, and an unusually low soft state luminosity, indicating that the central engine is obscured. Here we present an analysis of five NuSTAR observations of V4641 Sgr taken during its recent outburst in 2021, when the source was in the soft state. We identify highly ionized Fe K emission lines, consistent with a combination of the near-neutral $6.4$~keV Fe K$\alpha$ line, and the H-like and He-like Fe K$\alpha$ and Fe K$\beta$ transitions found at $6.7\mbox{--}7$~keV and $\sim8$~keV, and find no evidence for strong relativistic broadening. The line fluxes correlate linearly with the observed disk continuum flux, implying a direct connection between the central engine and the reprocessing region. Most interestingly, all five spectra also show a persistent highly ionized Fe K continuum edge feature at $\sim9$~keV with a stable optical depth, which is likely smeared, implying a localized reprocessing zone. We find tentative supporting evidence for obscuration of the inner accretion disk based on its unusually low intrinsic luminosity, however, the NuSTAR spectra do not require obscuration from cold, optically thick gas.

We present a new analytical galactic chemical evolution (GCE) model with gas inflow, internally caused outflow, and extra gas loss after a period of time. The latter mimics the ram pressure stripping of a dwarf satellite galaxy near the pericenter of its orbit around a host galaxy. The new model is called Inflow with Ram Pressure Stripping (IRPS). We fit the $\alpha$-element ([$\alpha$/H]) distributions of the Draco, Sculptor, Fornax, Leo II, Leo I, and And XVIII dwarf spheroidal galaxies. We compared the best fits of IRPS with four other GCE models. The IRPS fits half of the galaxies in our set better than the Leaky Box, Pre-enriched, Accretion, and Ram Pressure Stripping models. Unlike previous models, none of the IRPS model parameters -- not even the effective yield -- correlates with galaxy properties, like luminosity. One of the IRPS parameters is the $\alpha$-abundance at which stripping began. That parameter can override the effective yield in determining the galaxy's mean $\alpha$-abundance.

High-resolution helioseismology observations with the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO) provide a unique three-dimensional view of the solar interior structure and dynamics, revealing a tremendous complexity of the physical processes inside the Sun. We present an overview of the results of the HMI helioseismology program and discuss their implications for modern theoretical models and simulations of the solar interior.

All-vs-all orbital evolutionary simulations for the low Earth orbit (LEO) simulate the long term evolution of the LEO environment. Although these simulations typically offer the highest fidelity, they are also highly computationally intensive. One factor that effectively reduces the efficiency of the approach is that all-vs-all approaches are stochastic and the distribution of the output has large variance. This paper introduces a new, quasi-deterministic all-vs-all simulator, whose variance is greatly reduced compared to traditional methods. The proposed approach virtually simulates collisions happening everywhere and all the time; however, their effect is appropriately reduced to maintain an unbiased estimate of the mean. Additional techniques are used to augment the proposed approach and obtain very precise estimates of any number of standard deviations from the mean, for the evaluation of the Value at Risk (VaR) with a single, low-variance run. Depending on the settings, results show that the variance in total number of debris generated can be reduced by a factor that averages 1,500, while increasing the computational cost by a factor of less than 1.5. Variance can be reduced even more when computing the VaR, albeit a no longer negligible bias is introduced. Low-variance results enable several key applications, such as sensitivity analysis, sustainability assessment of small missions, and fast evaluation of collision risk induced by existing debris. Additionally, rapid computations of the VaR can improve the evaluation of policy robustness, and include confidence intervals in risk assessment.

Observational cosmology has provided an extraordinary perspective on our universe and our place within it. However, as our understanding of the universe has increased, some glaring holes in our knowledge have become apparent: What physics is responsible for the super-luminal expansion of the universe at early times? What drives the accelerating expansion of the universe at late times? What is the nature of the mysterious dark matter that makes up 83\% of the matter in the universe? These fundamental physical questions are intimately linked to fundamental astronomical questions about how galaxies and stars have formed and evolved within our universe. Cosmic surveys are the primary means by which we study the origin, structure, composition, and evolution of our universe. In particular, many of these questions require the spectroscopy of large numbers of astronomical sources. Spectroscopy provides key data on the physics of primordial inflation and late-time cosmic acceleration, the astrophysics of galaxy evolution, and the nature and effects of dark matter in galaxies. For example, observable features in the three-dimensional structure of the universe are key predictions of cosmological models, and their time evolution provides unique constraints on the nature of dark energy, inflation and the gravitational effects of dark matter. The next major advance in our understanding of the universe requires spectroscopic measurements of hundreds of millions of astronomical objects.

Multiple-Amplifier Sensing (MAS) charge-coupled devices (CCDs) have recently been shown to be promising silicon detectors that meet noise sensitivity requirements for next generation Stage-5 spectroscopic surveys and potentially, future space-based imaging of extremely faint objects such as the Habitable Worlds Observatory. Building upon the capability of the Skipper CCD to achieve deeply sub-electron noise floors, MAS CCDs utilize multiple floating-gate amplifiers along the serial register to increase the readout speed by a factor of the number of output nodes compared to a Skipper CCD. We introduce and experimentally demonstrate on a 16-channel prototype device new readout techniques that exploit the MAS CCD's floating-gate amplifiers to optimize the correlated double sampling (CDS) by resetting once per line instead of once per pixel. With this new mode, we find an optimal filter to subtract the noise from the signal during read out. We also take advantage of the MAS CCD's structure to tune the read time by independently changing integration times for the signal and reference level. Together with optimal weighted averaging of the 16 outputs, these approaches enable us to reach a sub-electron noise of 0.9 e$^-$ rms pix$^{-1}$ at 19 $\mu$s pix$^{-1}$ for a single charge measurement per pixel - simultaneously giving a 30% faster readout time and 10% lower read noise compared to performance previously evaluated without these techniques.

HCN and HCO$^+$ are the most common dense gas tracers used both in the Milky Way and external galaxies. The luminosity of HCN and HCO$^+$ $J = 1-0$ lines are converted to a dense gas mass by the conversion factor, $\alpha_{Q}$. Traditionally, this $\alpha_{Q}$ has been considered constant throughout the Galaxy and in other galaxies, regardless of the environment. We analyzed 17 outer Galaxy clouds and 5 inner Galaxy clouds with metallicities ranging from 0.38 Z$_{\odot}$ to 1.29 Z$_{\odot}$. Our analysis indicates that $\alpha_{Q}$ is not constant; instead, it varies with metallicity. The metallicity-corrected $\alpha_{Q}$ derived from the HCN luminosity of the entire cloud is almost three times higher in the outer Galaxy than in the inner galaxy. In contrast, HCO$^+$ seems less sensitive to metallicity. We recommend using the metallicity-corrected dense gas conversion factors $\alpha^{'}_{\rm tot, Gas}(\rm HCN) = 19.5^{+5.6}_{-4.4} Z^{(-1.53 \pm 0.59)}$ and $\alpha^{'}_{\rm tot, Gas}(\rm HCO^{+}) = 21.4^{+5.5}_{-4.4} Z^{(-1.32\pm0.55)}$ for extragalactic studies. Radiation from nearby stars has an effect on the conversion factor of similar magnitude as that of the metallicity. If we extend the metallicity-corrected scaling relation for HCN to the Central Molecular Zone, the value of $\alpha(\rm HCN)$ becomes $1/3$ to $1/2$ of the local values. This effect could partially account for the low star formation rate per dense gas mass observed in the CMZ.

The emerging population of long-period radio transients (LPTs) show both similarities and differences with normal pulsars. A key difference is that their radio emission is too bright to be powered solely by rotational energy. Various models have been proposed (including both white-dwarf or neutron star origins), and their nature remains uncertain. Known LPTs have minutes to hours long spin periods, while normal pulsars have periods ranging from milliseconds to seconds. Here, we report the discovery of PSR J0311+1402, an object with an intermediate spin period of 41 seconds, bridging the gap between LPTs and normal pulsars. PSR J0311+1402 exhibits low linear ($\sim25\%$) and circular polarisation ($\sim5\%$) and a relatively steep spectral index ($\sim-2.3$), features similar to normal pulsars. However, its observed spin-down properties place it below the pulsar death line, where pair production and thus radio emission are expected to cease. The discovery of PSR J0311+1402 suggests the existence of a previously undetected population within this intermediate period range, presumably missed due to selection biases in traditional pulsar search methods. Finding more such objects is important to fill the current gap in neutron star spin periods, improving our understanding of the relationships among rotation-powered pulsars and LPTs.

Modelling is essential for studies that quantify the impact from satellite downlinks on radio astronomy sites. To estimate this impact it is necessary to know not only the position and velocity of satellites but also their behaviour in the radio spectrum domain. As many large satellite constellations are using steerable beam antennas, deterministically predicting the transmitted power towards a defined direction (in this case where a radio telescope points) becomes an almost impossible task and therefore another approach has to be used. This work presents a method to simulate and estimate the percentiles of the radiation pattern of satellites with steerable beam patterns based on simulations and a comparison with measurements of Starlink satellites using the Onsala Twin Telescopes in Sweden.

Quasars, powered by supermassive black holes (SMBH), are among the brightest objects in the universe. In the vicinity of an SMBH, X-ray photons from an active galactic nucleus (AGN) can heat the surrounding gas to several hundred kelvin. Here we report observations of dust continuum and CO J=13-12 and J=14-13 line emissions at a resolution of 130 parsecs in a luminous quasar at z=6. We successfully detected these high-J CO line emissions from warm gas in a compact disk component. The CO luminosity ratio in the central region of the compact disk is consistent with theoretical models in which X-ray heating dominates the CO excitation and the gas column density is as high as 10$^{25}$ cm$^{-2}$. This demonstrates that high-resolution observations of high-J CO lines are promising ways to identify extremely dust-obscured quasars in the early universe.

The solar system object 2005 VL1 passed close to Earth in late 1965. It has been suggested that it is actually the space probe Venera-2. However, a comparison of the orbits presented in this note demonstrates that the proposed association is incorrect.

We summarise a new approach for measuring the Hubble constant using standard sirens and the reconstructed matter density field obtained from observed galaxy surveys. Specifically, we describe and test this method using the Bayesian forward-modelled software BORG. This software evolves the initial density field to the present, sampling plausible density fields from the posterior, accounting for peculiar velocities, and automatically incorporating higher-order correlation functions. The advantage of adding additional information from correlations is expected to make this method more effective in low-signal-to-noise regimes, such as those with modest galaxy number density or incomplete surveys. Our results show that developing a cross-correlation framework between gravitational waves and galaxy surveys, based on the forward-modelled reconstructed density field, to measure H0 is promising. This review is based on the research conducted as part of Boruah's Ph.D. thesis.

The high-frequency radio sky is bursting with synchrotron transients from massive stellar explosions and accretion events, but the low-frequency radio sky has so far been quiet beyond the Galactic pulsar population and the long-term scintillation of AGN. The low-frequency band, however, is sensitive to exotic coherent and polarised radio emission processes such as electron cyclotron maser emission from flaring M-dwarfs [1], stellar magnetospheric plasma interactions with exoplanets [2], and a population of steep-spectrum pulsars [3], making Galactic plane searches a prospect for blind transient discovery. Here we report an analysis of archival low-frequency radio data that reveals a periodic, low-frequency radio transient. We find that the source pulses every 18.18 minutes, an unusual periodicity not previously observed. The emission is highly linearly polarised, bright, persists for 30--60 s on each occurrence, and is visible across a broad frequency range. At times the pulses comprise short ($<0.5$-s) duration bursts; at others, a smoother profile is observed. These profiles evolve on timescales of hours. By measuring the dispersion of the radio pulses with respect to frequency, we have localised the source to within our own Galaxy, and suggest that it could be an ultra-long period magnetar.

Recently several long-period radio transients have been discovered, with strongly polarised coherent radio pulses appearing on timescales between tens to thousands of seconds [1,2]. In some cases the radio pulses have been interpreted as coming from rotating neutron stars with extremely strong magnetic fields, known as magnetars; the origin of other, occasionally periodic and less well-sampled radio transients, is still debated [3]. Coherent periodic radio emission is usually explained by rotating dipolar magnetic fields and pair production mechanisms, but such models do not easily predict radio emission from such slowly-rotating neutron stars and maintain it for extended times. On the other hand, highly magnetic isolated white dwarfs would be expected to have long spin periodicities, but periodic coherent radio emission has not yet been directly detected from these sources. Here we report observations of a long-period (21 minutes) radio transient, which we have labeled GPMJ1839-10. The pulses vary in brightness by two orders of magnitude, last between 30 and 300 seconds, and have quasi-periodic substructure. The observations prompted a search of radio archives, and we found that the source has been repeating since at least 1988. The archival data enabled constraint of the period derivative to $<3.6\times10^{-13}$s s$^{-1}$, which is at the very limit of any classical theoretical model that predicts dipolar radio emission from an isolated neutron star.

The ASTRO 3D Galaxy Evolution with Lenses (AGEL) Survey is an ongoing effort to spectroscopically confirm a diverse sample of gravitational lenses with high spatial resolution imaging, to facilitate a broad range of science outcomes. The AGEL systems span single galaxy-scale deflectors to groups and clusters, and include rare targets such as galaxy-scale lenses with multiple sources, lensed quiescent galaxies, and Einstein rings. We build on the 77 systems presented in Tran et al. 2022 (AGEL data release 1) to present a total 138 lenses, and high resolution F140W and F200LP Hubble Space Telescope images for 71 lenses from a completed HST SNAP program. Lens candidates were originally identified by convolutional neural networks in the DES and DECaLS imaging fields, and of the targets with follow-up spectroscopy we find a high (96%) success rate. Compared with other spectroscopic lens samples, AGEL lenses tend to have both higher redshift deflectors and sources. We briefly discuss the common causes of false-positive candidates, and strategies for mitigating false-positives in next generation lens searches. Lastly, we present 6 galaxy-scale double-source plane lenses useful for cosmological analyses. With next-generation telescopes and surveys such as Euclid, Vera Rubin's Legacy Survey of Space and Time, Keck Observatory's KAPA program, and 4MOST's 4SLSLS surveys on the horizon, the AGEL survey represents a pathfinder for refining automated candidate search methods and identifying and triaging candidates for followup based on scientific potential.

Barnard's Star is an old, single M dwarf star that comprises the second-closest extrasolar system. It has a long history of claimed planet detections from both radial velocities and astrometry. However, none of these claimed detections have so far withstood further scrutiny. Continuing this story, extreme precision radial velocity (EPRV) measurements from the ESPRESSO instrument have recently been used to identify four new sub-Earth-mass planet candidates around Barnard's Star. We present here 112 radial velocities of Barnard's Star from the MAROON-X instrument that were obtained independently to search for planets around this compelling object. The data have a typical precision of 30\,cm\,s$^{-1}$ and are contemporaneous with the published ESPRESSO measurements (2021 -- 2023). The MAROON-X data on their own confirm planet b ($P$\,=\,3.154\,d) and planet candidates c and d ($P$\,=\,4.124\,d and 2.340\,d, respectively). Furthermore, adding the MAROON-X data to the ESPRESSO data strengthens the evidence for planet candidate e ($P$\,=\,6.739\,d), thus leading to its confirmation. The signals from all four planets are $<$50\,cm\,s$^{-1}$, the minimum masses of the planets range from 0.19 to 0.34\,$M_{\oplus}$, and the system is among the most compact known among late M dwarfs hosting low-mass planets. The current data rule out planets with masses $>0.57\,M_{\oplus}$ (with a $99\%$ detection probability) in Barnard Star's habitable zone ($P$\,=\,10 -- 42\,d).

The interaction between the accretion disc and its corona plays a critical role in the energy balance and emission mechanisms in astrophysical systems such as active galactic nuclei and X-ray binaries. However, the detailed physics of disc-corona interactions, including the mechanisms driving disc evaporation, and the impact of accretion rate and viscosity, remains poorly understood. Our study aims to extend the well-known disc evaporation model to investigate the disc-corona interaction in a 2D axisymmetric, time-dependent hydrodynamic model, focusing on the effects of viscosity, accretion rate, and their influence on disc evaporation, luminosity, and corona formation. We develop a hydrodynamic model consisting of a thin accretion disc, a corona, and a vacuum region. Our model is implemented in \textit{Athena++}, with the gas-vacuum interface tracking algorithm to handle the vacuum regions. We perform simulations incorporating turbulent viscosity, thermal conduction, Bremsstrahlung cooling, and artificial disc cooling, starting from an adiabatic state to explore the disc-corona interaction. We demonstrate the presence of acoustic shock heating, a mechanism widely studied in the solar physics community but less explored in the context of accretion discs. We find that the viscosity dominates the intensity of disc evaporation, the accretion rate primarily determines the disc truncation radius and the disc luminosity, and there may be a positive correlation between the corona luminosity and the evaporation intensity. We also compare our results with the observations and simulations, and estimate the $y$-parameters to explore the potential effects of Compton cooling.

The identification of star clusters holds significant importance in studying galaxy formation and evolution history. However, the task of swiftly and accurately identifying star clusters from vast amounts of photometric images presents an immense challenge. To address these difficulties, we employ deep learning models for image classification to identify young disk star clusters in M31 from the Pan-Andromeda Archaeological Survey (PAndAS) images. For training, validation, and testing, we utilize the Panchromatic Hubble Andromeda Treasury (PHAT) survey catalogs. We evaluate the performance of various deep learning models, using different classification thresholds and limiting magnitudes. Our findings indicate that the ResNet-50 model exhibits the highest overall accuracy. Moreover, using brighter limiting magnitudes and increasing the classification thresholds can effectively enhance the accuracy and precision of cluster identification. Through our experiments, we found that the model achieves optimal performance when the limiting magnitude is set to brighter than 21 mag. Based on this, we constructed a training dataset with magnitudes less than 21 mag and trained a second ResNet-50 model. This model achieved a purity of 89.30%, a recall of 73.55%, and an F1 score of 80.66% when the classification threshold was set to 0.669. Applying the second model to all sources in the PAndAS fields within a projected radius of 30 kpc from the center of M31, we identified 2,228 new unique star cluster candidates. We conducted visual inspections to validate the results produced by our automated methods, and we ultimately obtained 1,057 star cluster candidates, of which 745 are newly identified.

We investigate the effects of low--velocity impacts of rocks and boulders, originally released after the DART impact, on the surface of Didymos and the dynamics of dust particles released by those impacts. We determine if any of those effects can be observed by the Hera mission. The iSALE-2D shock physics code was used to simulate the re-impacts of boulders on the surface of the asteroid. To model the dynamics of the boulders, we used a numerical model that includes the gravity of non-spherical Didymos and Dimorphos, the solar gravity, and the radiation pressure. The sesquinary impacts can result in small, shallow craters on the surface of Didymos. For the given low impact speeds, the ejected mass depends mostly on the boulder mass. Ejection speeds range from 10 \% to 80 \% of the impact speed. The majority of the ejected dust falls back covering a large area of the surface, mostly at low/medium latitudes. Less than 20 \% of the ejected dust is escaping the system after a few days. The space surrounding the asteroids becomes free from dust after 15-30 days following each sesquinary impact. Results. The sesquinary impacts can result in small, shallow craters on the surface of Didymos. For the given low impact speeds, the ejected mass depends mostly on the boulder mass. Ejection speeds range from 10 \% to 80 \% of the impact speed. The majority of the ejected dust falls back covering a large area of the surface, mostly at low and medium latitudes. Less than 20 \% of the ejected dust is escaping the system after a few days. The space surrounding the asteroids becomes free from dust after 15-30 days following each sesquinary impact.

Most (or possibly all) massive stars reside in multiple systems. From stellar evolution models, numerous systems with an OB star coupled to a black hole would be expected to exist. There have been several claimed detections of such pairs in recent years and this is notably the case of HD96670. Using high-quality photometry and spectroscopy in the optical range, we revisited the HD96670 system. We also examined complementary X-ray observations to provide a broader view of the system properties. The TESS light curves of HD96670 clearly show eclipses, ruling out the black hole companion scenario. This does not mean that the system is not of interest. Indeed, the combined analysis of photometric and spectroscopic data indicates that the system most likely consists of a O8.5 giant star paired with a stripped-star companion with a mass of ~4.5Msol, a radius of ~1Rsol, and a surface temperature of ~50kK. While several B+sdOB systems have been reported in the literature, this would be the first case of a Galactic system composed of an O star and a faint stripped star. In addition, the system appears brighter and harder than normal OB stars in the X-ray range, albeit less so than for X-ray binaries. The high-energy observations provide hints of phase-locked variations, as typically seen in colliding wind systems. As a post-interaction system, HD96670 actually represents a key case for probing binary evolution, even if it is not ultimately found to host a black hole.

Machine-learning is playing an increasing role in helping the astronomical community to face data analysis challenges, in particular in the field of Galactic Archaeology and large scale spectroscopic surveys. We present recent developments in the field of convolutional neural-networks (CNNs) for stellar abundances in the context of the Galactic spectroscopic surveys Gaia-ESO, and Gaia-RVS. Especially, by combining the full Gaia data product, we manage to characterize for the first time the [alpha/M] vs. [M/H] bimodality in the Galactic disc with Gaia-RVS spectra at low-S/N. This work is highly relevant for the next generation of large scale surveys such as MSE, 4MOST, and WST.

The study of molecular clouds in galaxies beyond the Local Group is limited by the need to efficiently sample diverse galactic environments across galactic discs, typically resulting in a loss of resolution. Using a high-resolution dust extinction technique, we image the dust (and gas) of 4 nearby galaxies (<18 Mpc; NGC 4689, NGC 628, NGC 1566, and NGC 4321) with resolutions between 5-9 pc. We present catalogues of spatially-resolved clouds for these galaxies, with which we investigate whether different galactic environments and morphologies have a significant impact on observed cloud properties. We find no systematic differences in cloud size, aspect ratio, or morphology with galactic environment or radius. We do find changes in cloud masses/surface densities between the centres and discs of galaxies, with clouds in centres typically displaying higher values of mass/surface density. Furthermore, we find distinct distributions of cloud surface densities across the bars of NGC 1566 and NGC 4321. Differences between the arm and inter-arm populations are more subtle, with some galaxies in the sample having much higher cloud masses/surface densities in their spiral arms, and other galaxies showing fairly similar arm/inter-arm distributions. These results suggest that, even within this small sample of galaxies, not all spiral arms and bars seem to behave and affect the interstellar medium equally. Therefore, performing a qualitative environment analysis, where clouds of different galaxies are all binned together under the same visual environmental classification, leads to the loss of information on interesting property variations which in turn demonstrate the impact of the underlying dynamics.

High-resolution X-ray spectroscopy is a key to understanding the mass inflow and outflow of compact objects. Spectral lines carry information about the ionization, density, and velocity structures through their intensity ratios and profiles. They are formed in non-local thermodynamic equilibrium conditions under the intense radiation field from the compact objects, thus radiative transfer (RT) calculation is a requisite for proper interpretations. We present such a study for a low-mass X-ray binary, Circinus X-1, from which the P Cygni profile was discovered using the X-ray grating spectrometer onboard Chandra. We observed the source using the X-ray microcalorimeter onboard XRISM at an orbital phase of 0.93-0.97 and revealed many spectral features unidentified before; the higher series transitions (n to 1; n > 2) of highly-ionized (H- and He-like) S, Ca, Ar, and Fe in emission and absorption, the Fe K{\alpha} and K\b{eta} inner-shell excitation absorption of mildly-ionized (O- to Li-like) Fe, and resolved fine-structure level transitions in the Fe Ly{\alpha} and He{\alpha} complexes. They blend with each other at different velocity shifts on top of apparently variable continuum emission that changed its flux by an order of magnitude within a 70 ks telescope time. Despite such complexity in the observed spectra, most of them can be explained by a simple model consisting of the photoionized plasma outflowing at ~300 km s-1 and the variable blocking material in the line of sight of the incident continuum emission from the accretion disk. We demonstrate this with the aid of the RT code cloudy for the line ratio diagnostics and spectral fitting. We further constrain the physical parameters of the outflow and argue that the outflow is launched close to the outer edge of the accretion disk and can be driven radiatively by being assisted by the line force calculated using the RT simulation.

We investigate anisotropic inflation within the single-field model featuring an intermediate scale factor. Our analysis reveals that the anisotropic nature of the Friedmann equations in this framework affects the slow-roll parameters, which in turn influence key perturbation parameters. Using a numerical approach, we derive constraints on the intermediate parameter $\beta$ and the anisotropic parameter $c$. Our results show that the model is consistent with Planck2018 TT, TE, EE +lowE+lensing+BK14+BAO data at $68\%$ CL, for $0.84<\beta<1$ and $7.34<c<27.7$. At $95\%$ CL the consistency holds for $0.77<\beta<1$ and $7.17<c<28.9$. The model is also consistent with Planck2018 TT, TE, EE +lowE+lensing+BK18+BAO data, for $0.91<\beta<1$ and $8.00<c<27.4$ (at $68\%$ CL), and $0.88<\beta<1$ and $7.40<c<28.8$ (at $95\%$ CL). Additionally, we examine the reheating phase using these constraints on constraints on $\beta$ and $c$ and determine the observationally consistent ranges for the number of e-folds and the temperature during the reheating phase.

OB stars are crucial for our understanding of Galactic structure, star formation, stellar feedback and multiplicity. In this paper we have compiled a census of all OB stars within 1 kpc of the Sun. We performed evolutionary and atmospheric model fits to observed spectral energy distributions (SEDs) compiled from astro-photometric survey data. We have characterized and mapped 24,706 O- and B-type stars ($T_{\rm eff} > 10,000$ K) within 1 kpc of the Sun, whose overdensities correspond to well-studied OB associations and massive star-forming regions such as Sco-Cen, Orion OB1, Vela OB2, Cepheus and Circinus. We have assessed the quality of our catalogue by comparing it with spectroscopic samples and similar catalogues of OB(A) stars, as well as catalogues of OB associations, star-forming regions and young open clusters. Finally, we have also exploited our list of OB stars to estimate their scale height (76 $\pm$ 1 pc), a local star formation rate of $2896^{+417}_{-1}$ M$_{\odot}$ Myr$^{-1}$ and a local core-collapse supernova rate of $\sim$15--30 per Myr. We extrapolate these rates to the entire Milky Way to derive a Galactic SFR of $0.67^{+0.09}_{-0.01}$ M$_{\odot}$ yr$^{-1}$ and a core-collapse supernova rate of 0.4--0.5 per century. These are slightly lower than previous estimates, which we attribute to improvements in our census of OB stars and changes to evolutionary models. We calculate a near-Earth core collapse supernova rate of $\sim$2.5 per Gyr that supports the view that nearby supernova explosions could have caused one or more of the recorded mass extinction events on Earth.

The detection of GW170817, together with its electromagnetic counterparts, has proven that binary neutron star mergers are of central importance to the field of nuclear astrophysics, e.g., through a better understanding of the formation of elements and novel constraints on the supranuclear dense equation of state governing the matter inside neutron stars. Essential for understanding the binary coalescence are numerical-relativity simulations, which typically come with high computational costs requiring high-performance computing facilities. In this work, we build on recent studies to investigate whether novel techniques, such as neural networks, can be employed in the conversion of conservative variables to primitive hydrodynamical variables, such as pressure and density. In this regard, we perform -- to the best of our knowledge -- the first binary neutron star merger simulations in which such methods are employed. We show that this method results in stable simulations, reaching accuracies similar to traditional methods with an overall comparable computational cost. These simulations serve as a proof of principle that, in the future, deep learning techniques could be used within numerical-relativity simulations. However, further improvements are necessary to offer a computational advantage compared to traditional methods.

We report on the discovery of circular polarization modulated with a period of 1.943 +- 0.002 h in the cataclysmic variable V1082 Sgr. These findings unambiguously reveal the rotation of a magnetic white dwarf and establish its intermediate polar (IP) nature. Along with its extraordinary long orbital period, Porb, of 20.8 h, the spin period (Pspin) places this system in an extreme position of the Pspin versus Porb distribution. The circular polarization phase diagram has a single peak and an amplitude smaller than 1%. These data were used to model the post-shock region of the accretion flow on the white-dwarf surface using the CYCLOPS code. We obtained a magnetic field in the white-dwarf pole of 11 MG and a magnetospheric radius consistent with the coupling region at around 2 - 3 white-dwarf radii. The Pspin/Porb value and the estimated magnetic field momentum suggest that V1082 Sgr could be out of spin equilibrium, in a spin-up state, possibly in a stream accretion mode.

Several planet formation models have been proposed to explain the gap in the population of planets between $1.8$ $R_\oplus$ to $2.0$ $R_\oplus$ known as the Radius Valley. To apply these models to confirmed exoplanets, accurate and precise host star and planet parameters are required to ensure the observed measurements correctly match model predictions. Previous studies have emphasized the need for a larger, more precise sample to further confirm dominant formation processes. By enhancing standard SED (Spectral Energy Distribution) fitting using Bayesian methods we derived highly accurate and precise host star and planet parameters. Specifically, we achieved median fractional uncertainties for stellar and planet radii of 2.4% and 3.4%, respectively. We then produced the largest, most precise sample to date of 1923 planets when compared to previous studies. This full sample, as well as a sampled filtered for host stellar masses between $0.8$ and $1.2$ $M_\odot$, are then used to derive the slope and position of the radius valley as a function of orbital period, insolation flux and stellar mass to compare them to predictive models and previous observational results. Our results are consistent with thermally-driven mass loss with a planet radius vs. orbital period slope of $-0.142$ $\pm0.006$ for the full sample leaning toward core-powered mass loss. The planet radius vs. insolation flux slope of $0.136$ $\pm0.014$ for the filtered sample leaned toward photoevaporation. Also, the slope as a function of stellar mass for both samples appear more consistent with thermally driven processes when compared to models and previous studies.

The search for weak components outside the main pulse (MP) in the radiation of pulsars at a frequency of 110 MHz observed on the LPA LPI telescope in the Pushchino Multibeam Pulsar Search (PUMPS) has been carried out. The sample included 96 pulsars, for which the signal-to-noise ratio (S/N) in the MP of the average profile during accumulation over 10 years was more than 40. It was found that PSR J1543+0929 has radiation for almost the entire period. The profile is three-component. The relative amplitudes of the lateral weak components are 0.013 and 0.026. For PSR J2234+2114, a precursor was detected that is $53^o$ away from MP.

We present predictions of the number and properties of strongly-lensed submillimetre galaxies, based on an adaption of the physically-motivated LensPop model covering galaxy-galaxy strong lensing by elliptical galaxies, which successfully predicted optical and near-infrared lenses. For submillimetre-luminous lensed galaxies, the most efficient observational selection identifies sources with high fluxes (S500um > 80 mJy), where lensed sources outnumber bright unlensed sources; several hundred candidates from Herschel surveys have been identified, and confirmed by follow-up observations. We have tested our model against these observations. The model predicts an all-sky number density of 0.09+/-0.05 deg-2 (in absolute numbers, 3,600+/-1,800) of bright lensed galaxies detectable by this method. Observations show considerable variation in sky density between fields, 0.08 - 0.31 deg-2. Predictions of redshift and magnification distributions are comparable to observations, although the model appears to under-predict lenses at the highest magnifications ( > 20). We predict that the apparent AB magnitudes at visible wavelengths of the foreground lenses will be as faint as 28, whereas observations typically reach ~ 23, implying that some apparently unlensed bright submillimetre galaxies may have lensing galaxies below this detection limit. For fainter lensed galaxies, the model predicts over 130,000 systems with flux S500um > 10 mJy across the sky, of which ~ 3,400 remain be be discovered in the Herschel catalogues. We also predict that Euclid should be able to detect some 25,000 lensed submillimetre galaxies that are VIS-band 'dropouts' - detectable in the near-infrared but not at optical wavelengths.

We present a comprehensive study of the X-ray spectral variability observed in 13 TeV photon emitting high energy peaked BL Lacs(HBLs). These data come from 54 XMM-Newton EPIC-PN pointed observations made during its operational period from June 2001 through July 2023. We performed spectral studies in the energy range 0.6-10 keV by fitting X-ray spectra of the pointed observations with power law (PL) and log parabolic (LP) models. We found at 99% confidence level that 31 of these X-ray spectra were best fitted with a range of LP models with local photon indices (at 1.0 keV), alpha in the range of 1.75-2.66, and convex curvature parameter beta in the range of 0.02-0.25. PL models with photon index Gamma in the range of 1.78-2.68 best described the spectra of fourteen-pointed observations. Nine PN spectra resulted in negative curvature parameters in fitting an LP model, and eight among them were significant (beta is at least twice beta_err). We fitted broken power law (BPL) models to these eight X-ray spectra and found spectral hardening (Delta_Gamma) in the range of 0.06-0.54 for these observations. EPIC-MOS spectra were also studied for those eight observations to search for similar trends, and we were able to find them in only two, one observation each of PKS 0548-322 and Mrk 501. This indicates the possibility of the co-existence of an inverse Compton component along with the dominant synchrotron component for these two observations. We also performed correlation studies between various log-parabolic spectral parameters and briefly discuss their possible implications.

The low masses of M dwarfs create attractive opportunities for exoplanet radial-velocity (RV) detections. These stars, however, exhibit strong stellar activity that may attenuate or mimic planetary signals. We present a velocimetric analysis on one such M dwarf, GJ 3998 ($d=18.2\,\text{pc}$), with two published short-period super-Earths: GJ 3998 b and GJ 3998 c. We use additional data from the HARPS-N spectrograph to confirm these two planets and to look for more. We carry out joint modelling of: (i) RV planetary signals, (ii) stellar rotation in RV and activity indicators through Gaussian processes, (iii) long-term trends in RV and activity indicators. We constrain the rotational period of GJ 3998 to $P_\text{rot}=30.2\pm 0.3\,\text{d}$ and discover long-term sinusoidal imprints in RV and FWHM of period $P_\text{cyc}=316^{+14}_{-8}\,\text{d}$. We confirm GJ 3998 b and GJ 3998 c, and detect a third planet: GJ 3998 d, whose signal had been previously attributed to stellar activity. GJ 3998 d has an orbital period of $41.78\pm 0.05\,\text{d}$, a minimum mass of $6.07^{+1.00}_{-0.96}\,\text{M}_\oplus$ and a mean insolation flux of $1.2^{+0.3}_{-0.2}\,\Phi_\oplus$. This makes it one of the few known planets receiving Earth-like insolation flux.

Fast radio bursts (FRBs) are increasingly being used for cosmological applications such as measuring the Hubble constant and baryon abundance. The increasing number of localized FRBs and precise measurement of dispersion measure (DM) make them a suitable probe for such an approach. We use a sample of 110 localized FRBs as well as a small sub-sample of 24 FRBs with scattering timescale measurements or limits. We infer the Hubble constant ($H_0$) and the DM distribution of the host galaxies simultaneously by fitting our model to the FRB DM measurements. With current data, our results are in agreement with both high and low redshift measurements of $H_0$, obtained using Cosmic Microwave Background (CMB) and Type Ia supernovae data respectively. We project that with about 200 localized FRBs, we would be in a position to distinguish between the two scenarios at 4$\sigma$ confidence. In addition, the host DM is expected to be related to star formation in the host galaxy and the stellar age of the progenitors. Using our inferred host galaxy DMs, we are able to rule out (at 95 percent confidence) a majority of localized FRB progenitors originating from young sources with stellar ages less than 10 Myr. This might reflect a large population of old sources or an observational bias against detecting FRBs from young sources, which may be associated with long scatter broadening times and large DM from their source environments. Indeed, we find that scatter broadening times of FRBs are inconsistent with the Milky Way ISM, but at the same time, do not appear to be strongly correlated with the FRBs' redshift or with the SFR or stellar mass of their host galaxies. This suggests that scattering is dominated by the immediate environment of the sources.

Black holes can launch powerful jets through the Blandford-Znajek process. This relies on enough plasma in the jet funnel to conduct the necessary current. However, in some low luminosity active galactic nuclei, the plasma supply near the jet base may be an issue. It has been proposed that spark gaps -- local regions with unscreened electric field -- can form in the magnetosphere, accelerating particles to initiate pair cascades, thus filling the jet funnel with plasma. In this paper, we carry out 2D general relativistic particle-in-cell (GRPIC) simulations of the gap, including self-consistent treatment of inverse Compton scattering and pair production. We observe gap dynamics that is fully consistent with our earlier 1D GRPIC simulations. We find strong dependence of the gap power on the soft photon spectrum and energy density, as well as the strength of the horizon magnetic field. We derive physically motivated scaling relations, and applying to M87, we find that the gap may be energetically viable for the observed TeV flares. For Sgr A$^*$, the energy dissipated in the gap may also be sufficient to power the X-ray flares.

The systemic velocity or redshift of galaxies is a convenient tool to calculate their distances in the absence of primary methods, but the uncertainties on these flow distances may be substantial due to galaxy peculiar motions. Here, we derive a simple and easily applicable method to assign uncertainties to flow distances from four different methodologies, namely the Hubble law with both heliocentric and local-sheet velocities, the Cosmicflows-4 model, and the Numerical Action Methods model. Our uncertainty scheme is derived by comparing these flow distances to accurate, redshift-independent distances of a subsample of ~2000 galaxies from the Cosmicflows-4 database, using the tip magnitude of the red giant branch, Cepheids, surface brightness fluctuations, supernovae type Ia, masers, and supernovae type II. We provide simple functions and tables to calculate the distance uncertainties for all the flow models considered. This uncertainty scheme is generally applicable except for the region around the Virgo cluster, where we assign increased uncertainties due to larger peculiar motions.

Near-infrared spectra from the IRTF/SpeX and Blanco/ARCoIRIS telescope/instrument combinations are used for spectroscopic classification, to measure radial velocities and for the inference of astrophysical properties of 51 Gaia-selected nearby ultracool dwarfs. In this sample, 44 are newly classified in the near infrared. All but one of the UCDs are within 100 pc, and 37 lie within 50 pc. We find a total of 26 M-types, 24 L-types and one T-type in our sample. The positions of the majority of the UCDs on colour-magnitude diagrams and with evolutionary cooling track plots indicate that they are largely old and stellar in nature. There are a few UCDs of particular interest which lie away from expected trends, highlighting potential young, binary and thick disc/subdwarf UCDs. From spectral and kinematic analyses, we identify UCDs of particular interest for further investigation, including seven potentially young UCDs, three thick disc UCDs, one subdwarf, six wide binaries, and six unresolved binaries.

We study the impact of nuclear input related to weak-decay rates and neutron-capture reactions on predictions for the $s$ process in AGB stars. We provide the first database of surface abundances and stellar yields of the isotopes heavier than iron from the $Monash$ models. We run nucleosynthesis calculations with the $Monash$ post-processing code for 7 stellar structure evolution models of low-mass AGB stars with 3 different sets of nuclear input. The reference set has constant decay rates and represents the set used in the previous $Monash$ publications. The second set contains the temperature and density dependence of $\beta$ decays and electron captures based on the default rates of NETGEN. In the third set, we update 92 neutron-capture rates based on reevaluated experimental cross sections from the ASTRAL. We compare and discuss the predictions of each set relative to each other in terms of isotopic surface abundances and total stellar yields. We also compare results to isotopic ratios measured in presolar stardust SiC grains from AGB stars. The new sets of models resulted in a $\sim$66% solar $s$-process contribution to the $p$-nucleus $\mathrm{^{152}Gd}$, confirming that this isotope is predominantly made by the $s$ process. The nuclear input updates resulted in predictions for the $\mathrm{^{80}Kr/^{82}Kr}$ ratio in the He intershell and surface $\mathrm{^{64}Ni/^{58}Ni}, \mathrm{^{94}Mo/^{96}Mo}$ and $\mathrm{^{137}Ba/^{136}Ba}$ ratios more consistent with the corresponding ratios measured in stardust, however, the new predicted $\mathrm{^{138}Ba/^{136}Ba}$ ratios are higher than the typical values of the stardust SiC grain data. The W isotopic anomalies are in agreement with data from analysis of other meteoritic inclusions. We confirm that the production of $\mathrm{^{176}Lu}$ and $\mathrm{^{205}Pb}$ is affected by too large uncertainties in their decay rates from NETGEN.

Solitons are predominantly observed in near-earth plasmas as well as planetary magnetospheres; however, their existence in the solar corona remains largely unexplored, despite theoretical investigations. This study aims to address this gap by examining the presence and dynamics of solitons in the solar corona, particularly in the context of coronal heating. Utilizing observational data from the Parker Solar Probe (PSP) and Solar and Heliospheric Observatory (SOHO) during the onset of a strong Coronal Mass Ejection (CME) event, the analyses reveal a train of aperiodic solitons with increasing amplitude preceding the eruption. A key finding of this study is that the observed aperiodic soliton train serves as a potential candidate in facilitating energy transfer through dissipation within the coronal plasma, hereby, influencing the initiation of solar eruptive events such as a CME. A defining characteristic of this solitary train is its hypersonic and super-Alfvenic nature, evident from the presence of high Mach numbers that reinforces its role in plasma energy equilibration in the solar corona, thereby contributing to plasma heating.

T CrA is a Herbig Ae-type young star in a complex circumstellar environment; it includes a circumstellar disk, accretion streamers, jets, and outflows. It has long been suspected to be a binary. However, until now, there has been no direct detection of a companion. Here we present new VLTI/MATISSE L- and N-band observations of T CrA taken between 2023 May and 2024 August with the aim of testing the binary nature of the system. We modeled the data with a geometric model using the Python tool oimodeler. We detected a companion (T CrA B) with a projected separation of $\Delta r = 153.2 \pm 1.2$ mas ($\approx 23$ au) toward the west direction at a position angle of $275.4 \pm 0.1^\circ$, in 2024 May-August. Our results support that the companion has a nearly edge-on orbit that is highly misaligned with respect to the circumprimary disk. Such a configuration could cause warping and tearing of the disk around the primary, which has been proposed by recent studies. In the L band the companion is extended, with a full width at half maximum (FWHM) size of $\sim 1$ au, suggesting that the emission comes from a disk around the secondary star. The companion flux is 0.2-0.3 Jy in the L band, and 0.2-0.7 Jy in the N band, accounting for 4-20% of the total emission at those wavelengths. The SED of the companion is compatible with thermal radiation of warm dust (600-800 K).

We report on the astrophysical properties of a sample of star clusters in the Small Magellanic Cloud (SMC). They have been selected with the aim of looking for the connection between their ages, heliocentric distances and metallicities with the existence of tidally perturbed/induced outermost SMC regions. We derived the star cluster fundamental parameters from relatively deep Survey of the Magellanic Stellar History (SMASH) DR2 color magnitude diagrams, cleaned from field star contamination, and compared to thousand synthetic CMDs covering a wide range of heliocentric distances, ages and metal content. Heliocentric distances for 15 star clusters are derived for the first time, which represents an increase of 50 per cent of SMC clusters with estimated heliocentric distances. The analysis of the age-metallicity relationships (AMRs) of cluster located in outermost regions distributed around the SMC and in the SMC Main Body reveals that they have followed the overall galaxy chemical enrichment history. However, since half of the studied clusters are placed in front of or behind the SMC Main Body, we concluded that they formed in the SMC and have traveled outward because of the tidal effects from the interaction with the Large Magellanic Cloud (LMC). Furthermore, metal rich clusters formed recently in some of these outermost regions from gas that was also dragged by tidal effects from the inner SMC. This outcome leads to consider the SMC as a galaxy scarred by the LMC tidal interaction with distance-perturbed and newly induced outermost stellar substructures.

The Cosmic Microwave Background (CMB) is a fundamental observational tool in modern cosmology. The linear polarization of the CMB provides a crucial observational tool for exploring new physics, including the inflationary paradigm and parity-violating phenomena. The spectral distortion of the CMB can be used as a probe of the intracluster medium (ICM) of galaxy clusters (GCs) and to infer cosmological parameters. However, precise measurements are limited by foreground contamination and instrumental systematics. This work examines the non-thermal energy budget in GCs with the non-thermal Sunyaev-Zeldovich (ntSZ) effect. Using $Planck$ all-sky maps, we measure the ntSZ effect in GCs hosting radio halos, enabling constraints on the volume-averaged magnetic field strength within the ICM. We further assess how observations from upcoming ground-based CMB experiments improve these constraints. The imprints of parity-violating physics on the polarization of the CMB are predicted theoretically and recently, several methods have been used to measure the effect of cosmic birefringence from $Planck$ and $WMAP$ data. The miscalibration of polarization-sensitive detectors is found to be one of the limiting factors in this endeavour. We perform a relative and an absolute polarization angle calibration of the $Planck$ detectors using microwave and X-ray observations of the Crab nebula. Additionally, we develop a simulation pipeline to generate time-ordered data for an upcoming ground-based sub-mm telescope, analyzing the impact of correlated detector and atmospheric noise on CMB map reconstruction. Our findings in this thesis emphasize the importance of broad-frequency coverage for better foreground characterization and highlight the need for dedicated ground-based calibration to achieve accurate CMB polarization measurements. [abridged]

Most Sun-like and higher-mass stars reside in systems that include one or more gravitationally bound stellar companions. These systems offer an important probe of planet formation in the most common stellar systems, while also providing key insights into how gravitational perturbations and irradiation differences from a companion star alter the outcomes of planet formation. Recent dynamical clues have begun to emerge that reveal systematic, non-random structure in the configurations of many planet-hosting binary systems: in close- to moderate-separation ($s < 800$ au) binary star systems, the orbits of exoplanets around individual stellar components are preferentially aligned with the orbital plane of their host stellar binary. In this work, we flip this narrative and search for nearby, edge-on binary star systems that, due to this preferential alignment, are top candidates for radial velocity and transiting exoplanet searches. We present a sample of 591 moderate-separation, relatively bright ($G < 14$) Gaia-resolved binary star systems in likely near-edge-on configurations. Using a simulated population of exoplanets drawn from transit survey occurrence rate constraints, we provide an overview of the expected planet yields from a targeted search in these systems. We describe the opportunities for comparative exoplanet demographics in the case that both stars can be inferred to host edge-on planetary systems - a configuration toward which the presented sample may be biased, given recent observations of orbit-orbit alignment in exoplanet-hosting binary systems.

Galaxy-galaxy strong lensing provides a powerful probe of galaxy formation, evolution, and the properties of dark matter and dark energy. However, conventional lens-modeling approaches are computationally expensive and require fine-tuning to avoid local optima, rendering them impractical for the hundreds of thousands of lenses expected from surveys such as Euclid, CSST, and Roman Space Telescopes. To overcome these challenges, we introduce TinyLensGPU, a GPU-accelerated lens-modeling tool that employs XLA-based acceleration with JAX and a neural-network-enhanced nested sampling algorithm, nautilus-sampler. Tests on 1,000 simulated galaxy-galaxy lenses demonstrate that on an RTX 4060 Ti GPU, TinyLensGPU achieves likelihood evaluations approximately 2,000 times faster than traditional methods. Moreover, the nautilus-sampler reduces the number of likelihood evaluations by a factor of 3, decreasing the overall modeling time per lens from several days to roughly 3 minutes. Application to 63 SLACS lenses observed by the Hubble Space Telescope recovers Einstein radii consistent with the literature values (within $\lesssim 5\%$ deviation), which is within known systematic uncertainties. Catastrophic failures, where the sampler becomes trapped in local optima, occur in approximately 5\% of the simulated cases and 10\% of the SLACS sample. We argue that such issues are inherent to automated lens modeling but can be mitigated by incorporating prior knowledge from machine learning techniques. This work thus marks a promising step toward the efficient analysis of strong lenses in the era of big data. The code and data are available online: this https URL.

The upcoming extremely large telescopes will provide the first opportunity to search for signs of habitability and life on non-transiting terrestrial exoplanets using high-contrast, high-resolution instrumentation. However, the suite of atmospheric gases in terrestrial exoplanet environments that are accessible to ground-based reflected light observations has not been thoroughly explored. In this work, we use an upgraded Extremely Large Telescope (ELT) detectability pipeline to simulate the detectability of gases that can serve as habitability markers, potential biosignatures, and false positive discriminants in the atmospheres of Earth-sized and sub-Neptune planets. We calculate molecular detectability for five photochemically self-consistent atmosphere types, including the modern and Archean Earth, uninhabited biosignature ``false positive'' environments, and a sub-Neptune, over a grid of observational configurations for non-transiting targets within 10pc of Earth. For the most accessible nearby target, Proxima Centauri b, our results suggest that we may be able to rule out a sub-Neptune atmosphere in as little as a single hour of observing, and two biosignature disequilibrium pairs (O$_2$/CH$_4$ and CO$_2$/CH$_4$) may be accessible in $\sim 10$ hours for the most optimistic scenario. It may also be possible to discriminate uninhabited worlds, and rule out biosignature false positives by identifying contextual indicators (CO and H$_2$O) of abiotic O$_2$ and/or CH$_4$ buildup on similar timescales. In the near term, ELT reflected light observations will likely allow us to characterize multiple nearby terrestrial atmospheres, and ultimately search for signs of habitability and life.

Although protostars and disks are often studied separately owing to numerical and observational challenges, breakthroughs in recent years have highlighted the need to study both objects in concert. The role of magnetic fields in this regard must be investigated. We aim to describe the birth of the protostar and that of its disk, as well as their early joint evolution following the second collapse. We wish to study the structure of the nascent star-disk system, while focusing on the innermost sub-AU region. We carry out high resolution 3D RMHD simulations, describing the collapse of dense cloud cores to stellar densities. The calculations reach $\approx 2.3$ yr after protostellar birth. Our simulations are also compared to their hydro counterpart to better isolate the role of magnetic fields. When accounting for ambipolar diffusion, the efficiency of magnetic braking is drastically reduced and the nascent protostar reaches breakup velocity, thus forming a rotationally supported disk. The diffusion of the magnetic field also allows for the implantation of a $\sim \mathrm{kG}$ field in the protostar, which is thereafter maintained. The magnetic field is mainly toroidal in the star-disk system, although a notable vertical component threads it. We also show that the nascent disk is prone to the MRI, although our resolution is inadequate to capture the mechanism. We note a sensitivity of the disk's properties with regards to the angular momentum inherited prior to the second collapse, as well as the magnetic field strength. These calculations carry multiple implications on several issues in stellar formation theory, and offer perspectives for future modeling of the system. Should the fossil field hypothesis to explain the origins of magnetic fields in young stellar objects hold, we show that a $\sim \mathrm{kG}$ field strength may be implanted and maintained in the protostar at birth.

Mid-infrared (MIR) emission from tidal disruption events (TDEs) is a powerful probe of the circumnuclear environment around dormant supermassive black holes. This emission arises from the reprocessing of intrinsic emission into thermal MIR emission by circumnuclear dust. While the majority of optical- and X-ray-selected TDEs show only weak dust echoes consistent with primarily unobscured sight lines, there have been growing efforts aimed at finding TDEs in obscured environments using MIR selection methods. In this work, we present the first JWST observations of 4 MIR-selected TDEs with JWST Mid-Infrared Instrument (MIRI) Medium-Resolution Spectrometer (MRS). Two of these sources show flares in other wavelength bands (one in optical, one in X-ray), while the other two are MIR-only transients. None of these TDEs showed pre-outburst nuclear activity, but all of the MIRI/MRS observations reveal emission lines associated with highly ionized gas, implying ionization from TDE accretion. Additionally, all four sources show silicate emission features around 10 and 18 $\mu$m that are much stronger than the features seen in active galactic nuclei (AGN). We suggest that the emitting dust is optically thin to its own emission and show that the MIR spectrum is consistent with emission from optically thin dust along an isodelay surface. All four sources show an excess at short wavelengths ($\lambda < 8\, \mu$m), which could arise from a late-time plateau in the intrinsic flare, akin to what is seen in late-time UV observations of unobscured TDEs, although self-consistent dust modeling is required to fully assess the strength of this late-time plateau.

Recent cosmological surveys have provided unprecedented datasets that can be used to reconstruct the history of the dark energy equation of state. In this work, a free-form "flexknot'' parameterisation is employed to represent $w(a)$ as a linear spline between free-moving nodes, the number of which may vary. By combining DESI Baryon Acoustic Oscillation measurements with Pantheon+ or DES5Y supernovae, the functional posteriors of $w(a)$ reveal an unexpected W-shaped structure. While the Bayesian evidence may still favour $\Lambda$CDM, the robustness of these results suggests the structure is indeed present in the data. The tension $R$-statistic and suspiciousness have been marginalised over models, and demonstrate that while the reconstructions from DESI and Pantheon+ agree, DESI and DES5Y do not. We conclude that, while there is no smoking gun for dynamical dark energy, the structure unearthed in this work is generally too complex to be captured by the restrictive $w$CDM or CPL parameterisations.

Bright blazars were found to be prominent neutrino sources, and a number of IceCube events were associated with them over recent years. A particularly strong observational connection is present between neutrinos and blazars with bright, Doppler-boosted, parsec-scale radio emission. In this work, we further explore the nature of this connection by examining the jet geometry and kinematics of neutrino-associated blazars. We find that these blazars demonstrate remarkably strong jet beaming, even compared to other radio-bright sources. Their Doppler and Lorentz factors are larger, and viewing angles are smaller than for other blazars in the complete uniformly selected MOJAVE sample. Observationally, this serves as yet another piece of evidence for blazars forming a major population of neutrino sources. The strong neutrino-beaming correlation indicates that high-energy neutrino velocity is predominantly oriented along the jet, and the original PeV-scale protons exhibit a relativistic bulk motion along the jet. It suggests that neutrino production happens not too close to the black hole, but rather at sub-parsec distances, where the jet is already accelerated.

The Taurid Complex is a large interplanetary system that contains comet 2P/Encke, several meteoroid streams, and possibly a number of near-Earth asteroids. The size and nature of the system has led to the speculation that it was formed through a large-scale cometary breakup. Numerical investigations have suggested that planetary dynamics can create a resonant region with a large number of objects concentrated in a small segment of the orbit, known as the Taurid swarm, which approaches the Earth in certain years and provides favorable conditions to study the Taurid Complex. Recent meteor observations confirmed the existence of the swarm for mm- to m-sized objects. Here we present a dedicated telescopic search for potentially hazardous asteroids and other macroscopic objects in the Taurid swarm using the Zwicky Transient Facility survey. We determine from our non-detection that there are no more than 9--14 $H\leq24$ (equivalent to a diameter of $D\gtrsim100$~m) objects in the swarm, suggesting that the Encke--Taurid progenitor was $\sim10$~km in size. A progenitor of such a size is compatible with the prediction of state-of-the-art Solar System dynamical models, which expects $\sim0.1$ $D>10$~km objects on Encke-like orbits at any given time.

We study the eigenmodes of the spin-2 Laplacian in orientable Euclidean manifolds and their implications for the tensor-induced part of the cosmic microwave background (CMB) temperature and polarization anisotropies. We provide analytic expressions for the correlation matrices of Fourier-mode amplitudes and of spherical harmonic coefficients. We demonstrate that non-trivial spatial topology alters the statistical properties of CMB tensor anisotropies, inducing correlations between harmonic coefficients of differing $\ell$ and $m$ and across every possible pair of temperature and $E$- and $B$-modes of polarization. This includes normally forbidden $TB$ and $EB$ correlations. We compute the Kullback-Leibler (KL) divergence between the pure tensor-induced CMB fluctuations in the usual infinite covering space and those in each of the non-trivial manifolds under consideration, varying both the size of the manifolds and the location of the observer. We find that the amount of information about the topology of the Universe contained in tensor-induced anisotropies does not saturate as fast as its scalar counterpart; indeed, the KL divergence continues to grow with the inclusion of higher multipoles up to the largest $\ell$ we have computed. Our results suggest that CMB polarization measurements from upcoming experiments can provide new avenues for detecting signatures of cosmic topology, motivating a full analysis where scalar and tensor perturbations are combined and noise is included.

We measure surface brightness fluctuations in Chandra X-ray images of the cores of the galaxy clusters Abell 2029, Abell 2151, Abell 2107, RBS0533, and RBS0540. Their relatively structureless X-ray atmospheres exhibit the thermodynamic properties of cool cores including short central cooling times and low entropy. However, unlike typical cool-core clusters, molecular gas, star formation, and bubbles associated with radio jets are faint or absent near their central galaxies. Four clusters show typical gas density fluctuation amplitudes of $\sim$ 10 per cent on the scales probed, apart from RBS0540, which exhibits lower amplitudes, suggesting that its gas is mildly disturbed. Under the assumption that gas density fluctuations are indicative of random gas velocities, we estimate scale-dependent velocity amplitudes of gas motions across all studied clusters, which range from 100 km/s to 200 km/s in Abell 2029, Abell 2151, and Abell 2107. These velocity estimates are comparable to the atmospheric velocity dispersion in the Perseus cluster measured by the Hitomi X-ray Observatory. The turbulent heating rates implied by our measurements are of the same order as the radiative cooling rates. Our results suggest that atmospheric sloshing and perhaps turbulent motion may aid radio jets in stabilizing atmospheric cooling.

In the merger-driven galaxy evolution scenario, the central supermassive black holes (SMBHs) in dust obscured galaxies grow rapidly. Interestingly, a recent work \citep{suh24} on a dust-obscured galaxy, LID-568 at $z=3.965$, has shown that its SMBH is growing extremely fast at about 40 times of the Eddington-limited accretion rate (i.e., super-Eddington accretion). However, the heavy dust extinction of the host galaxy could affect the result if not corrected properly. Here, we analyze James Webb Space Telescope (JWST) NIRSpec/IFU and MIRI spectra of LID-568. By measuring its bolometric luminosity ($L_{\rm bol}$) and BH mass ($M_{\rm BH}$) using an extinction-free estimator based on mid-infrared spectra, we obtain $L_{\rm bol} = 10^{46.83\pm0.07}\,{\rm erg\,s^{-1}}$ and $M_{\rm BH} = 10^{8.43\pm0.15}\,M_{\odot}$. The measured Eddington ratio ($\lambda_{\rm Edd}$) is 1.97$\pm$0.88, consistent with the accretion rate at the Eddington limit; in other words, not in super-Eddington in a significant manner. This result underscores challenges and the importance of carefully considering dust extinction when analyzing the BH growth in dust-obscured quasars.

We examine the classical and quantum evolution of inflationary cosmological perturbations from quantum initial conditions, using the on-shell and off-shell contributions to correlators to investigate the signatures of interactions. In particular, we calculate the Keldysh contributions to the leading order bispectrum from past infinity, showing that the squeezed limit is dominated by the on-shell evolution. By truncating the time integrals in the analytic expressions for contributions to the bispectrum, we define a `quantum interactivity' and quantitatively identify scales and times for which it is sufficient to only assume classical evolution, given a fixed precision. In contrast to typical perceptions inspired by free two-point functions, we show that common non-linear contributions to inflationary perturbations can be well-described by classical evolution even prior to horizon crossing. The insights gained here can pave the way for quantitative criteria for justifying the validity of numerically simulating the generation and evolution of quantum fluctuations in inflation. In particular, we comment on the validity of using stochastic inflation to reproduce known in-in perturbative results. An extensive appendix provides a review of the Keldysh formulation of the in-in formalism with the initial state set at a finite, as opposed to infinite past, emphasizing the importance of considering temporal boundary terms and the initial state for correctly obtaining the propagators. We also show how stochastic dynamics can emerge as a sufficiently accurate approximation to the full quantum evolution. This becomes particularly transparent in the Keldysh description.

Black hole solutions in general scalar-tensor theories are known to permit hair, i.e. non-trivial scalar profiles and/or metric solutions different from the ones of General Relativity (GR). Imposing that some such solutions$\unicode{x2013}$e.g. Schwarzschild or de Sitter solutions motivated in the context of black hole physics or cosmology$\unicode{x2013}$should exist, the space of scalar-tensor theories is strongly restricted. Here we investigate precisely what these restrictions are within general quadratic/cubic higher-order scalar-tensor theories for stealth solutions, whose metric is given by that in GR, supporting time-dependent scalar hair with a constant kinetic term. We derive, in a fully covariant approach, the conditions under which the Euler-Lagrange equations admit all (or a specific set of) exact GR solutions, as the first step toward our understanding of a wider class of theories that admit approximately stealth solutions. Focusing on static and spherically symmetric black hole spacetimes, we study the dynamics of linear odd-parity perturbations and discuss possible deviations from GR. Importantly, we find that requiring the existence of all stealth solutions prevents any deviations from GR in the odd-parity sector. In less restrictive scenarios, in particular for theories only requiring the existence of Schwarzschild(-de Sitter) black holes, we identify allowed deviations from GR, derive the stability conditions for the odd modes, and investigate the generic deviation of a non-trivial speed of gravitational waves. All calculations performed in this paper are reproducible via companion $\texttt {Mathematica}$ notebooks.

We perform an updated global analysis of the known and unknown parameters of the standard $3\nu$ framework as of 2025. The known oscillation parameters include three mixing angles $(\theta_{12},\,\theta_{23},\,\theta_{13})$ and two squared mass gaps, chosen as $\delta m^2=m^2_2-m^2_1>0$ and $\Delta m^2=m^2_3-{\textstyle\frac{1}{2}}(m^2_1+m^2_2)$, where $\alpha=\mathrm{sign}(\Delta m^2)$ distinguishes normal ordering (NO, $\alpha=+1$) from inverted ordering (IO, $\alpha=-1$). With respect to our previous 2021 update, the combination of oscillation data leads to appreciably reduced uncertainties for $\theta_{23}$, $\theta_{13}$ and $|\Delta m^2|$. In particular, $|\Delta m^2|$ is the first $3\nu$ parameter to enter the domain of subpercent precision (0.8\% at $1\sigma$). We underline some issues about systematics, that might affect this error estimate. Concerning oscillation unknowns, we find a relatively weak preference for NO versus IO (at $2.2\sigma$), for CP violation versus conservation in NO (1.3$\sigma$) and for the first $\theta_{23}$ octant versus the second in NO ($1.1\sigma$). We discuss the status and qualitative prospects of the mass ordering hint in the plane $(\delta m^2,\,\Delta m^2_{ee})$, where $\Delta m^2_{ee}=|\Delta m^2|+{\textstyle\frac{1}{2}}\alpha(\cos^2\theta_{12}-\sin^2\theta_{12})\delta m^2$, to be measured by the JUNO experiment with subpercent precision. We also discuss upper bounds on nonoscillation observables. We report $m_\beta<0.50$~eV and $m_{\beta\beta}<0.086$~eV ($2\sigma$). Concerning the sum of neutrino masses $\Sigma$, we discuss representative combinations of data, with or without augmenting the $\Lambda$CDM model with extra parameters accounting for possible systematics or new physics. The resulting $2\sigma$ upper limits are roughly spread around the bound $\Sigma < 0.2$~eV within a factor of three. [Abridged]

Recently, a high-energy neutrino event, designated KM3-230213A, was observed by the KM3NeT/ARCA detector in the Mediterranean Sea. This event is characterized by a reconstructed muon energy of approximately 120 PeV, corresponding to a median neutrino energy of roughly 220 PeV. To understand the origin, it is essential to investigate consistency with multi-messenger observations--particularly gamma-ray constraints--in various theoretical scenarios within and beyond the Standard Model. Motivated by this, we explore the possibility that the detected event does not originate from conventional neutrinos but rather from right-handed neutrinos (sterile neutrinos) mixing with active neutrinos, leading to the observed muon signal. Such cosmic-ray dark radiation may have originated either in the early Universe or through dark matter decay in the present epoch. We show that in both cases, while satisfying existing general constraints on light sterile neutrinos, the stringent multi-messenger gamma-ray limits can be significantly alleviated. A distinct prediction of this scenario is that such events can arrive from directions through Earth that would typically attenuate conventional neutrinos. A related scenario involving cosmic-ray boosted WIMP dark matter is also discussed.

Continuous gravitational-wave signals (CWs), which are typically emitted by rapidly rotating neutron stars with non-axisymmetric deformations, represent particularly intriguing targets for the Advanced LIGO-Virgo-KAGRA detectors. These detectors operate within sensitivity bands that encompass more than half of the known pulsars in our galaxy existing in binary systems (i.e., over 417 pulsars), which are the targeted sources of this paper. However, the detection of these faint signals is especially challenged by the Doppler modulation due to the source's orbital motion, typically described by five Keplerian parameters, which must be determined with high precision to effectively detect the signal. This modulation spreads the signal across multiple frequency bins, resulting in a notable reduction of signal-to-noise ratio and potentially hindering signal detection. To overcome this issue, a robust five-vector resampling data-analysis algorithm has been developed to conduct thorough directed/narrowband CW searches at an affordable computational cost. We employ this methodology for the first time to search for CWs from Scorpius X-1, using publicly available data from the third observing run of the Advanced LIGO-Virgo-KAGRA detectors. No statistically significant CW signals can be claimed. Hence, we proceeded setting 95% confidence-level upper limits in selected frequency bands and orbital parameter ranges, while also evaluating overall sensitivity.

The Pierre Auger Observatory, the world's largest cosmic ray detector, plays a pivotal role in exploring the frontiers of physics beyond the standard model of particle physics. By the observation of ultra-high energy cosmic rays, Auger provides critical insights into two major scenarios: super heavy dark matter and Lorentz invariance violation. Super heavy dark matter, hypothesized to originate in the early universe, offers a compelling explanation for the dark matter problem and is constrained by Auger through searches for photons and neutrinos resulting from its decay. Lorentz invariance violations, motivated by quantum gravity theories implying deviations from fundamental symmetries, are probed by Auger through alterations of the particle dispersion relation and the energy thresholds of their interactions with astrophysical photons backgrounds.

Recent advancements of very long baseline interferometry (VLBI) have facilitated unprecedented probing of superradiant phenomena in the vicinities of supermassive black holes (SMBHs), establishing an ideal laboratory to detect ultralight bosons beyond the Standard Model. In this study, we delve into how ultralight dilaton clouds, formed via SMBH superradiance, impact the black hole photon rings. Our focus is on the dilaton-electromagnetic coupling term of the form $f(\phi)F_{\mu\nu}F^{\mu\nu}$. By integrating geometric optics with plasma refractive effects in accretion environments, we demonstrate that the dilaton cloud dynamically alters the plasma frequency. Through systematic ray-tracing simulations covering a range of plasma densities and dilaton coupling strengths, we reveal a periodic distortion in the photon ring morphology, with the periodicity aligning with that of the dilaton-driven plasma frequency oscillations. We then assess the magnitude of this effect under the current angular resolution constraints of VLBI observations. Our analysis indicates that a comprehensive search for superradiant dilaton clouds based on the dilaton-electromagnetic coupling would necessitate radio interferometric baselines significantly exceeding the Earth's diameter to resolve the corresponding signatures.

Einstein's theory of general relativity predicts that gravitational waves (GWs) are tensor-polarized, with two modes of polarization: plus ($h_+$) and cross ($h_\times$). The unmodeled GW burst analysis pipeline, \textit{BayesWave}, offers two tensor-polarized signal models: the elliptical polarization model ($E$) and the relaxed polarization model ($R$). Future expansion of the global GW detector network will enable more accurate studies of GW polarizations with GW bursts. Here a multi-detector analysis is conducted to compare the performance of $E$ and $R$ in characterizing elliptical and nonelliptical GW polarizations, using nonprecessing and precessing binary black holes (BBHs) respectively as representative synthetic sources. It is found that both models reconstruct the elliptical nonprecessing BBH signals accurately, but $E$ has a higher Bayesian evidence than $R$ as it is has fewer model parameters. The same is true for precessing BBHs that are reconstructed equally well by both models. However, for some events with high precession and especially with three or more detectors, the reconstruction accuracy and evidence of $R$ surpass $E$. The analysis is repeated for BBH events from the third LIGO-Virgo-KAGRA observing run, and the results show that $E$ is preferred over $R$ for existing detections. Although $E$ is generally preferred for its simplicity, it insists on elliptical polarizations, whereas $R$ can measure generic GW polarization content in terms of Stokes parameters. The accuracy of $R$ in recovering polarization content improves as the detector network expands, and the performance is independent of the GW signal morphology.

Extensions of equivalent representations of gravity are discussed in the metric-affine framework. First, we focus on: (i) General Relativity, based upon the metric tensor whose dynamics is given by the Ricci curvature scalar $R$; (ii) the Teleparallel Equivalent of General Relativity, based on tetrads and spin connection whose dynamics is given by the torsion scalar $T$; (iii) the Symmetric Teleparallel Equivalent of General Relativity, formulated with respect to both the metric tensor and the affine connection and characterized by the non-metric scalar $Q$ with the role of gravitational field. They represent the so-called Geometric Trinity of Gravity, because, even if based on different frameworks and different dynamical variables, such as curvature, torsion, and non-metricity, they express the same gravitational dynamics. Starting from this framework, we construct their extensions with the aim to study possible equivalence. We discuss the straightforward extension of General Relativity, the $f(R)$ gravity, where $f(R)$ is an arbitrary function of the Ricci scalar. With this paradigm in mind, we take into account $f(T)$ and $f(Q)$ extensions showing that they are not equivalent to $f(R)$. Dynamical equivalence is achieved if boundary terms are considered, that is $f(T-\tilde{B})$ and $f(Q-B)$ theories. The latter are the extensions of Teleparallel Equivalent of General Relativity and Symmetric Teleparallel of General Relativity, respectively. We obtain that $f(R)$, $f(T-\tilde{B})$, and $f(Q-B)$ form the Extended Geometric Trinity of Gravity. The aim is to show that also if dynamics are equivalent, foundations of theories of gravity can be very different.

Taking into account the temperature corrections of the energy equipartition law for the bits of information that are coarse-grained on the holographic screen leads to a modification of Einstein's gravitational field equations. In the very high-temperature limit, which corresponds to strong gravitational fields, the modified gravitational equations reduce to the standard Einstein equations of general relativity, but in the low-temperature limit, which corresponds to the weak gravity regime, the modified equations show significant deviations from the standard Einstein equations. We solve the modified Einstein equations for the FRW metric and obtain the modified Friedmann equations. We see that the Friedmann equations obtained with this approach agree with the Friedmann equations previously obtained from the thermodynamic corrections of classical Newtonian mechanics. Using the modified Friedmann equations for a flat universe, we investigate the implications of our modified entropic cosmology (MEC) model. We show that our model can explain the dynamics of the universe without requiring any kind of dark energy. Using the Pantheon supernovae dataset, BAO data, Planck 2018 CMB data, and SH0ES measurements for $H_0$, we test the MEC model against observations. We will see that MEC fits the observational data better than the standard cosmological model of $\Lambda$CDM. We also see that our model can successfully solve the $H_0$ tension that challenges the standard cosmological model.

The origin of neutrino masses remains unknown to date. One popular idea involves interactions between neutrinos and ultralight dark matter, described as fields or particles with masses $m_\phi \ll 10\,\mathrm{eV}$. Due to the large phase-space number density, this type of dark matter exists in coherent states and can be effectively described by an oscillating classical field. As a result, neutrino mass-squared differences undergo field-induced interference in spacetime, potentially generating detectable effects in oscillation experiments. We demonstrate that if $m_\phi\gg 10^{-14}\,\mathrm{eV}$, the mechanism becomes sensitive to dark matter density fluctuations, which suppresses the oscillatory behavior of flavor-changing probabilities as a function of neutrino propagation distance in a model-independent way, thereby ruling out this regime. Furthermore, by analyzing data from the Kamioka Liquid Scintillator Antineutrino Detector (KamLAND), a benchmark long-baseline reactor experiment, we show that the hypothesis of a dark origin for the neutrino masses is disfavored for $m_\phi \ll 10^{-14}\,\mathrm{eV}$, compared to the case of constant mass values in vacuum. This result holds at more than the 4$\sigma$ level across different datasets and parameter choices. The mass range $10^{-17}\,\mathrm{eV} \lesssim m_\phi \lesssim 10^{-14}\,\mathrm{eV}$ can be further tested in current and future oscillation experiments by searching for time variations (rather than periodicity) in oscillation parameters.

The environment surrounding a black hole or black hole binaries is generally expected to play an important role in understanding various astrophysical phenomena around them. In this paper, we study relativistic, low angular momentum, inviscid, and advective hot accretion flow onto a galactic supermassive black hole dressed with a cold dark matter halo. Focusing on different relativistic dark matter distributions with an inner density spike, we analyze the effect of the dark matter halo on the topology and properties of the accretion flow. Our results show enhancement of disk luminosity in the presence of dark matter, which depends on the nature and properties (halo mass and compactness) of the dark matter distribution. Since the dominant contribution to the disk luminosity for compact and massive halo comes from the inner region of the accretion disk, our analysis suggests that luminosity measurement can indeed be useful to probe the exact nature of the dark matter density spike.