Papers for Friday, Jun 20 2025

Heartbeat stars are a subclass of binary stars with short periods, high eccentricities, and phase-folded light curves that resemble an electrocardiogram. We start from the $\textit{Gaia}$ catalogs of spectroscopic binaries and use $\textit{TESS}$ photometry to identify 112 new heartbeat star systems. We fit their phase-folded light curves with an analytic model to measure their orbital periods, eccentricities, inclinations, and arguments of periastron. We then compare these orbital parameters to the $\textit{Gaia}$ spectroscopic orbital solution. Our periods and eccentricities are consistent with the $\textit{Gaia}$ solutions for 85$\%$ of the single-line spectroscopic binaries but only 20$\%$ of the double-line spectroscopic binaries. For the two double-line spectroscopic binary heartbeat stars with consistent orbits, we combine the $\textit{TESS}$ phase-folded light curve and the $\textit{Gaia}$ velocity semi-amplitudes to measure the stellar masses and radii with $\texttt{PHOEBE}$. In a statistical analysis of the HB population, we find that non-giant heartbeat stars have evolved off the main sequence and that their fractional abundance rises rapidly with effective temperature.

We present a broad-line active galactic nucleus (AGN) at z = 5.077, observed with both NIRSpec/MSA and NIRSpec/IFU by the JADES and BlackTHUNDER surveys. The target exhibits all the hallmark features of a 'Little Red Dot' (LRD) AGN. The combination of spatially resolved and high-resolution spectroscopy offers deeper insight into its nature. The H$\alpha$ line has multiple components, including two broad Gaussians, yielding a black-hole mass of $\log(M_{\rm BH}/M_\odot) = 7.65$, while the narrow [O III]$\lambda$5007 gives a galaxy dynamical mass of $\log(M_{\rm dyn}/M_\odot) = 9.1$, suggesting a dynamically overmassive black hole relative to the host galaxy. The target has two satellites, and is immersed in a 7-kpc wide pool of ionized gas. A spatially detached outflow is also tentatively detected. H$\alpha$ shows strong absorption with high equivalent width (EW), ruling out a stellar origin, and with velocity and velocity dispersion of v = -13 km s$^{-1}$ and $\sigma$ = 120 km s$^{-1}$. There is tentative evidence (2.6 $\sigma$) of temporal variability in the EW of the H$\alpha$ absorber over two rest-frame months. If confirmed, this would suggest a highly dynamic environment. Notably, while the H$\alpha$ absorber is clearly visible and even dominant in the high-resolution G395H observations, it is not detected in the medium-resolution G395M data of the same epoch. This implies that the current incidence rate of absorbers in LRDs - and especially of rest-frame absorbers - may be severely underestimated, because most LRDs rely on lower-resolution spectroscopy. In this context, the high incidence rate of rest-frame absorbers in LRDs may indicate a configuration that is either intrinsically stationary, such as a rotating disc, or that exhibits time-averaged stability, such as an oscillatory 'breathing mode' accretion of cyclic expansion and contraction of the gas around the SMBH.

The ASAS-SN Low Surface Brightness Survey utilizes the $\sim7$ years of g-band CCD data from ASAS-SN (The All-Sky Automated Survey for Supernovae) to create stacked images of the entire sky. It is significantly deeper than previous photographic surveys. Our median/95th percentile cumulative exposure time per field is 58.1/86.8 hours, and our median $3{\sigma}$ g-band surface brightness limit off the Galactic plane ($|b| > 20°$) is 26.1 mag arcsec$^{-2}$. We image large-scale diffuse structures within the Milky Way, such as multiple degree-spanning supernova remnants and star-forming nebulae, and tidal features of nearby galaxies. To quantify how effective our deep images are, we compare with a catalog of known ultra-diffuse galaxies and find a recovery rate of 82$\%$. In the future, we intend to use this data set to perform an all-sky search for new nearby dwarf galaxies, create an all-sky Galactic cirrus map, create an all-sky low surface brightness mosaic for public use, and more.

We test the isotropy of cosmic expansion by combining several probes for the first time, constructing full-sky maps of expansion rate variation using Type Ia supernovae, fundamental plane galaxies, and CMB temperature fluctuations. We find no hint of anisotropy or correlation between early- and late-Universe expansion across all systematic models. The 99% confidence upper limits on expansion rate anisotropy are 0.39% for low-redshift supernovae, 0.95% for high-redshift CMB, and 0.37% when combined at a 60-degree smoothing scale. A significant anomaly in the fundamental plane residual map may reflect systematics in the current DESI dataset, as evidenced by the absence of cross-correlation with other tracers and its correlation with spatial density variations.

Revealing the nature of the nanoHz gravitational wave (GW) signal recently reported by Pulsar Timing Arrays (PTAs) collaborations around the world is the next goal of low-frequency GW astronomy. The signal likely originates from the incoherent superposition of GWs emitted by a cosmological population of supermassive black hole binaries (SMBHBs). Those binaries can be highly eccentric and/or strongly coupled to their nuclear environment, resulting in an attenuation of the overall GW signal at low frequencies. In this paper, we propose to use the correlation properties of the distributed GW power in the sky across the frequency spectrum as a smoking gun for eccentric SMBHBs thus allowing to break the spectral degeneracy between eccentricity and environmental effect. The simple underlying idea is that, contrary to circular binaries, eccentric ones emit a broadband spectrum thus resulting in similar sky maps at different frequencies. We first demonstrate the applicability of this simple concept on sky maps constructed directly from the theoretical sky distribution of the GWB power induced by realistic populations of SMBHBs. We then demonstrate the viability of this analysis on simulated SKA-like PTA data. By statistically comparing sky maps reconstructed from hundreds injected circular and highly eccentric SMBHB populations, we find that eccentricity can be detected at $3\sigma$ in more than $50\%$ of cases.

Four neutron star radius measurements have already been obtained by modeling the X-ray pulses of rotation-powered millisecond pulsars observed by the Neutron Star Interior Composition ExploreR (NICER). We report here the radius measurement of PSR J0614$-$3329 employing the same method with NICER and XMM-Newton data using Bayesian Inference. For all different models tested, including one with unrestricted inclination prior, we retrieve very similar non-antipodal hot regions geometries and radii. For the preferred model, we infer an equatorial radius of $R_{\rm eq}=10.29^{+1.01}_{-0.86}\,$km for a mass of $M=1.44^{+0.06}_{-0.07} \, M_{\odot}$ (median values with equal-tailed $68\%$ credible interval), the latter being essentially constrained from radio timing priors obtained by MeerKAT. We find that, for all different models, the pulse emission originates from two hot regions, one at the pole and the other at the equator. The resulting radius constraint is consistent with previous X-ray and gravitational wave measurements of neutron stars in the same mass range. Equation of state inferences, including previous NICER and gravitational wave results, slightly soften the equation of state with PSR J0614$-$3329 included and shift the allowed mass-radius region toward lower radii by $\sim 300\,$m.

The morphology of X-ray halos in early-type galaxies depends on key structure assembly processes such as feedback and mergers. However, the signatures of these processes are difficult to characterize due to their faint and amorphous nature. We demonstrate that the truncation in the temperature profile of X-ray halos, defined by the radial location of the peak temperature, is significantly more impacted by recent mergers or galaxy interactions than feedback processes. At a fixed stellar mass, a highly asymmetric X-ray halo can be nearly a factor of ten more truncated than a relaxed one. This analysis led to a discovery of previously unknown asymmetric features in the optical and X-ray halos of three massive galaxies. We detect the intra-group star light and a large ~45 kpc size stellar stream connected to NGC 0383, suggesting that a recent stellar accretion event has triggered its active galactic nuclei to emit a powerful radio jet. While the disturbed X-ray halo of NGC 1600 is also related to a galaxy-satellite tidal interaction detected in optical imaging, the X-ray shape and asymmetry of NGC 4555 is highly unusual for a galaxy in a low dense environment, requiring further investigation. These results highlight the importance of truncations and deep imaging techniques for untangling the formation of X-ray halos in massive galaxies.

The cosmic X-ray background (CXB) is produced by the emission of unresolved active galactic nuclei (AGN), thus providing key information about the properties of the primary and reprocessed X-ray emission components of the AGN population. Equally important, studies of individual sources provide additional constraints on the properties of AGN, such as their luminosity and obscuration. Until now, these constraints have not been self-consistently addressed by intrinsically linking emission, absorption, and reflection. Here we perform numerical simulations with the ray-tracing code, RefleX, which allows us to self-consistently model the X-ray emission of AGN with flexible geometries for the circumnuclear medium. Using the RefleX-simulated emission of an AGN population, we attempt to simultaneously reproduce the CXB and absorption properties measured in the X-rays, namely the observed fraction of $N_{\mathrm{H}}$ in bins of log($N_{\mathrm{H}}$) and the fraction of absorbed AGN, including their redshift and luminosity evolution. We sample an intrinsic X-ray luminosity function and construct gradually more complex physically motivated geometrical models. We examine how well each model can match all observational constraints using a simulation-based inference (SBI) approach. We find that, while the simple unification model can reproduce the CXB, a luminosity dependent dusty torus is needed to reproduce the absorption properties. When adding an accretion disc, the model best matches all constraints simultaneously. Our synthetic population is able to reproduce the dependence of the covering factor on luminosity, the AGN number counts from several surveys, and the observed correlation between reflection and obscuration. Finally, we derive an intrinsic Compton-thick fraction of 21$\pm$7%, consistent with local observations.

Giant pulses (GPs) occur in high magnetic-field millisecond pulsars (MSPs) and young Crab-like pulsars. Motivated by the fast radio bursts (FRBs) discovered in a globular cluster (GC) in the M81, we undertook baseband observations of PSR J1823$-$3021A, the most active GP emitter in a GC with the MeerKAT UHF band receiver (544-1088 MHz). The steep spectral index of the pulsar yields a GP rate of over 37,000 GPs/hr with $S/N>7$, significantly higher than the 3000 GPs/hr rate detected by Abbate et al. 2020 with the L-band (856-1712 MHz) receiver. Similarly to Abbate et al 2020, we find that the GPs are (1) strongly clustered in 2 particular phases of its rotation, (2) well described by a power-law in terms of energies, (3) typically broadband, and have steep spectral indices of $\approx-3$. Although the integrated pulse profile is not significantly polarised ($<1\%$ linear and $<3\%$ circular), one of the brightest GPs displays notable polarisation of $7\%$ (linear) and $8\%$ (circular). The high-time resolution data reveals the GPs have a range of single-peak and multi-peak morphologies, including GPs with three distinct peaks. For the first time, we measured the temporal scattering of the pulsar using 49 bright, narrow, single-pulse GPs, obtaining a mean value of $5.5\pm0.6$ $\mu$s at 1 GHz. The distinct periodicity and low polarisation of GPs differentiate them from typical FRBs, although potential quasi-periodicity substructures in some GPs may suggest a connection to magnetars/FRBs.

Optical observations of solar corona provide key information on its magnetic geometry. The large-scale open field of the corona plays an important role in shaping the ambient solar wind and constraining the propagation dynamics of the embedded structures, such as interplanetary coronal mass ejections. Rigorous analysis of the open-flux coronal regions based on coronagraph images can be quite challenging because of the depleted plasma density resulting in low signal-to-noise ratios. In this paper, we present an in-depth description of a new image segmentation methodology, the Quasi-Radial Field-line Tracing (QRaFT), enabling a detection of field-aligned optical coronal features approximating the orientation of the steady-state open magnetic field. The methodology is tested using synthetic coronagraph images generated by a three-dimensional magnetohydrodynamic model. The results of the numerical tests indicate that the extracted optical features are aligned within $\sim 4-7$ degrees with the local magnetic field in the underlying numerical solution. We also demonstrate the performance of the method on real-life coronal images obtained from a space-borne coronagraph and a ground-based camera. We argue that QRaFT outputs contain valuable empirical information about the global steady-state morphology of the corona which could help improving the accuracy of coronal and solar wind models and space weather forecasts.

A significant population of quasars have been found to exist within the first Gyr of cosmic time. Most of them have high black hole (BH) masses ($M_{\rm BH} \sim 10^{8-10} M_{\odot}$) with an elevated BH-to-stellar mass ratio compared to typical local galaxies, posing challenges to our understanding of the formation of supermassive BHs and their coevolution with host galaxies. Here, based on size measurements of [CII] 158$\mu$m emission for a statistical sample of $z \sim 6$ quasars, we find that their host galaxies are systematically more compact (with half-light radius $R_{\rm e} \sim 1.6$ kpc) than typical star-forming galaxies at the same redshifts. Specifically, the sizes of the most compact quasar hosts, which also tend to contain less cold gas than their more extended counterparts, are comparable to that of massive quiescent galaxies at $z \sim 4-5$. These findings reveal an intimate connection between the formation of massive BHs and compactness of their host galaxies in the early universe. These compact quasar hosts are promising progenitors of the first population of quiescent galaxies.

In two-component SIDM models with inter-species interactions, mass segregation arises naturally from collisional relaxation, enhancing central densities and gravothermal evolution without requiring large cross sections. We propose a model with velocity-dependent interactions, both within and between species, that connects observations across several halo mass scales while remaining consistent with cluster-scale constraints. This combination enables modest mass segregation in low-mass and typical-concentration halos, consistent with recent dwarf galaxy clustering measurements. Using cosmological zoom-in simulations and controlled isolated halo studies, we show that this model produces dwarf galaxy cores that grow over time, explains the structure of dark perturbers observed in strong lensing systems, and significantly increases the number and efficiency of small-scale lenses, consistent with the galaxy-galaxy strong lensing excess reported in clusters. Our results establish mass segregation in two-component SIDM as a self-consistent and testable model capable of simultaneously addressing multiple small-scale challenges in structure formation.

Due to dust grain alignment with magnetic fields, dust polarization observations of far-infrared emission from cold molecular clouds are often used to trace magnetic fields, allowing a probe of the effects of magnetic fields on the star formation process. We present inferred magnetic field maps of the Pillars of Creation region within the larger M16 emission nebula, derived from dust polarization data in the 89 and 154 micron continuum using SOFIA/HAWC+. We derive magnetic field strength estimates using the Davis-Chandrasekhar-Fermi method. We compare the polarization and magnetic field strengths to column densities and dust continuum intensities across the region to build a coherent picture of the relationship between star forming activity and magnetic fields in the region. The projected magnetic field strengths derived are in the range of 50-130 microGauss, which is typical for clouds of similar n(H2), i.e., molecular hydrogen volume density on the order of 10^4-10^5 cm^(-3). We conclude that star formation occurs in the finger tips when the magnetic fields are too weak to prevent radial collapse due to gravity but strong enough to oppose OB stellar radiation pressure, while in the base of the fingers the magnetic fields hinder mass accretion and consequently star formation. We also support an initial weak field model (<50 microGauss) with subsequent strengthening through realignment and compression, resulting in a dynamically important magnetic field.

A significant fraction of the local Universe's baryonic content remains undetected. Cosmological simulations indicate that most of the missing baryons reside in cosmic filaments in the form of warm-hot intergalactic medium (WHIM). The latter shows low surface brightness and soft X-ray emission, making it challenging to detect. Until now, X-ray WHIM emission has been detected only in very few individual filaments, whereas in even fewer filaments, WHIM has been spectroscopically analyzed. In this work, we used four Suzaku pointings to study the WHIM emission of a filament in the Shapley supercluster, connecting the galaxy cluster pairs A3530/32 and A3528-N/S. We additionally employ XMM-Newton observations to robustly account for point sources in the filament and to fully characterize the neighboring clusters and their signal contamination to the filament region. We report the direct imaging and spectroscopic detection of extended thermal WHIM emission from this single filament. Our imaging analysis confirms the existence of $(21\pm 3)\% $ excess X-ray emission throughout the filament compared to the sky background at a $6.1\sigma$ level. We constrain the filament gas temperature, electron density, and baryon overdensity to be $k_{\text{B}}T\approx (0.8-1.1)$ keV, $n_{\text{e}}\approx 10^{-5}$ cm$^{-3}$, and $\delta_{\text{b}}\approx (30-40)$, respectively, at a $>3\sigma$ detection level, in agreement with cosmological simulations for the first time for a single filament. Independent of the X-ray analysis, we also identify a spectroscopic galaxy overdensity throughout the filament using the Shapley Supercluster velocity Database and constrain the filament's 3D length to be 7.2 Mpc. Overall, this is the first X-ray spectroscopic detection of pure WHIM emission from an individual, pristine filament without significant contamination from unresolved point sources and gas clumps.

NGC 253, the Sculptor galaxy, is the southern, massive, star-forming disk galaxy closest to the Milky Way. In this work, we present a new 103-pointing MUSE mosaic of this galaxy covering the majority of its star-forming disk up to 0.75xR25. With an area of ~20x5 arcmin2 (~20x5 kpc2, projected) and a physical resolution of ~15 pc, this mosaic constitutes one of the largest, highest physical resolution integral field spectroscopy surveys of any star-forming galaxy to date. Here, we exploit the mosaic to identify a sample of ~500 planetary nebulae (~20 times larger than in previous studies) to build the planetary nebula luminosity function (PNLF) and obtain a new estimate of the distance to NGC 253. The value obtained is 17% higher than estimates returned by other reliable measurements, mainly obtained via the top of the red giant branch method (TRGB). The PNLF also varies between the centre (r < 4 kpc) and the disk of the galaxy. The distance derived from the PNLF of the outer disk is comparable to that of the full sample, while the PNLF of the centre returns a distance ~0.9 Mpc larger. Our analysis suggests that extinction related to the dust-rich interstellar medium and edge-on view of the galaxy (the average E(B-V) across the disk is ~0.35 mag) plays a major role in explaining both the larger distance recovered from the full PNLF and the difference between the PNLFs in the centre and in the disk.

We present a spatially resolved Baldwin-Phillips-Terlevich analysis of the narrow-line region (NLR) in the low-ionization nuclear emission-line region (LINER) I galaxy NGC 5005 using Hubble Space Telescope narrowband imaging of [O III]${\lambda}$5007, H${\beta}$, H${\alpha}$, and [S II]${\lambda}{\lambda}$6717,6731. With a resolution of ${\lesssim}$0.1 (${\lesssim}$10 pc at z = 0.003), we dissect the NLR into H II (star-forming), Seyfert, and LINERs across spatial scales extending up to r$\sim$8 kpc from the nucleus. Our results reveal a compact nuclear region exhibiting Seyfert-like emission, consistent with photoionization by a low-luminosity active galactic nucleus (AGN). Surrounding this Seyfert-like nucleus is a thin ($\sim$20 pc thick) higher-excitation LINER-like cocoon, likely arising from shock-excited gas in the interstellar medium (ISM). Beyond this cocoon, a centrally localized extended (r$\sim$1 kpc) LINER-like region surrounds the Seyfert-like nucleus and cocoon, likely ionized by the AGN, while a more extended (r${\gtrsim}$2 kpc) LINER-like zone may be ionized by a combination of post-AGB stars and shocks from gas inflows. We also detect H II-like regions at both small and large scales. In the inner 500 pc, these regions may be triggered by jet-ISM interactions, potentially inducing localized star formation. At r$\sim$4 kpc, we identify an outer H II-like region tracing a large-scale star-forming ring, where ionization is dominated by young stars.

A major issue in contemporary cosmology is the persistent discrepancy, known as the Hubble tension, between the Hubble constant ($H_0$) estimates from local measurements and those inferred from early-Universe observations under the standard $\Lambda$ cold dark matter ($\Lambda$CDM) paradigm. Recent advances have identified fast radio bursts (FRBs), a class of extragalactic phenomena observable at considerable redshifts, as a promising observational tool for probing late-time cosmology. In this study, we incorporate two complementary methodologies, machine learning algorithms and Bayesian analysis, on a set of localized FRBs to rigorously test the consistency of the $\Lambda$CDM model at late cosmic epochs. Our results reveal a statistically significant redshift-dependent variation of $H_0$, which contradicts the core postulate of $\Lambda$CDM. We further validate that the redshift dependency of $H_0$ can be removed within the more flexible framework of $w_0w_a$CDM model. These findings highlight that the redshift evolution of $H_0$ is not merely an artifact of the standard model but an indication of a deeper inadequacy in the $\Lambda$CDM model, supporting the need for a more flexible cosmological framework.

We consider the question of whether core-collapse supernovae (CCSNe) can produce rapid neutron capture process (r-process) elements and how future MeV gamma-ray observations could address this. Rare types of CCSNe characterized by substantial magnetic fields and rotation, known as magnetorotational supernovae (MR-SNe), are theoretically predicted to produce these elements, although direct observational evidence is lacking. We suggest that this critical question be addressed through the study of some of the eleven CCSN remnants located within 10 kpc, as well as through the detection of gamma-ray emission from a future Galactic supernova. We use a two-dimensional MR-SN model to estimate the expected gamma flux stemming from nuclear decays in the range of a few tens of keV to a few MeV. Our results indicate that an observation of Sn-126 (Sb-126) in a remnant stands out as a signature of an r-process-producing supernova. Since the neutron-rich conditions that lead to the production of the r-process could also enhance the production of Fe-60, the detection of substantial Fe-60 (Co-60) would be indicative of favorable conditions for the r-process. In the case of a future supernova explosion, when the evolution of the spectrum is studied over ten days to a few years, a rich picture emerges. At various epochs, second peak r-process isotopes such as Sb-125, I-131, Te-132, I-132 and La-140 produce gamma-ray signals that emerge above the background from explosive burning products and electron-positron annihilation. The weak r-process isotopes Nb-95, Ru-103, Rh-106 also have periods of prominence. While MR-SNe are predicted to have a relatively small main r-process contribution, third peak isotopes like Ir-194 could still be above next-generation MeV gamma instrument sensitivities.

This work revises the Brane World Theory known as Randall-Sundrum with the modification of an exponential, redshift-dependent brane tension. This model is studied in a scenario assuming no dark energy, with the aim of determining whether it can reproduce the universe's acceleration on its own, without the addition of a dark energy fluid. Bayesian statistical analysis is performed in order to constrain the free parameters of each scenario using SLS, SNIa, OHD, and BAO data samples, the last two considering newly added data points. Both Planck and Riess priors for h are used and compared. In both cases, we are able to reproduce the late-time accelerated expansion in agreement with observational data. Interesting consistencies at the transition redshift zt with LCDM are found, suggesting that this might be a suitable model for studying the evolution of the universe up to the present date. However, some pathologies are detected in this model, namely a "Big Rip" divergence of H(z) at z = 1, as well as a strong dependence between the functional form of the brane tension and the future evolution of the universe.

WASP-4 b is a hot Jupiter exhibiting a decreasing orbital period, prompting investigations into potential mechanisms driving its evolution. We analyzed 173 transit light curves, including 37 new observations, and derived mid-transit timings with EXOFAST, forming the most extensive TTV dataset for this system. Adding 58 literature timings and removing unreliable data, we constructed a TTV diagram with 216 points. Our analysis considered linear, quadratic, and apsidal motion models, with the quadratic model proving to be significantly superior in all model comparison statistics. We found no significant periodic signals in the data. The quadratic model allows us to infer a tidal quality factor of Q' ~ 80,000 from the orbital decay rate if this is due to stellar tides. Theoretical considerations indicate that such efficient dissipation is possible due to internal gravity waves in the radiative core of WASP-4, but only in our models with a more evolved host star, possibly near the end of its main-sequence lifetime, and with a larger radius than the observed one. Our main-sequence models produce only about a third of the required dissipation (Q' ~ 200,000 - 500,000). Therefore, the observed orbital decay can only be explained by a slightly larger or more evolved host, resembling the case for WASP-12. Our findings highlight the need for further stellar modeling and improvement in our current understanding of tidal dissipation mechanisms driving orbital decay in close-in exoplanetary systems.

More and more observations have indicated the existence of slow diffusion phenomena in astrophysical environments, such as around the supernova remnants and pulsar $\gamma$-ray halos, where the diffusion coefficient of cosmic rays (CRs) near the source region is significantly smaller than that far away from the source region. The inhomogeneous diffusion indicates the existence of multiple diffusion this http URL the CR mirror diffusion with the scattering one, we aim to explore their diffusion characteristics in different magnetohydrodynamic (MHD) turbulence regimes and understand the effect of different MHD modes on mirror and scattering diffusion. We perform numerical simulations with the test particle method. Within the global frame of reference, we first measure parallel and perpendicular CR diffusion and then determine the mean free path of CRs with varying this http URL main results demonstrate that: (1) CRs experience a transition from superdiffusion to normal diffusion; (2) mirror diffusion is more important than scattering diffusion in confining CRs; (3) CR diffusion strongly depends on the properties of MHD turbulence; and (4) magnetosonic and Alfvén modes dominate the parallel and perpendicular diffusion of CR particles, respectively. The diffusion of CRs is a complex problem of mixing the mirror diffusion and scattering diffusion. The property of turbulent magnetic fields influences CR diffusion. The CR slow diffusion due to the presence of magnetic mirrors in turbulence has important implications for explaining observations near a CR source.

ASASSN-14ko is a periodically repeating nuclear transient. We conducted high-cadence, multiwavelength observations of this source, revealing several recurrent early bumps and rebrightenings in its UV/optical light curves. The energy released during these bumps and rebrightenings shows a diminishing trend in recent UV/optical outbursts, which we monitored through multiwavelength observations. These features can be ascribed to the interaction between stream debris and the expanded disk in the repeated partial tidal disruption event. The X-ray light curve exhibits an inverse pattern compared to the UV/optical bands, displaying sporadic outbursts. Furthermore, our observations demonstrate that the blackbody temperature and radius in each outburst increase with the UV/optical luminosity, and such evolution resembles that observed in X-ray quasiperiodic eruptions, whereas distinguishing it from typical tidal disruption events.

The Gaia satellite revealed a remarkable spiral pattern ('phase spiral', PS) in the z-Vz phase plane throughout the solar neighbourhood, where z and Vz are the displacement and velocity of a star perpendicular to the Galactic plane. As demonstrated by many groups, the kinematic signature reflects the Galactic stellar disc's response to a dynamical disturbance in the recent past (~0.3-3 Gyr). However, previous controlled simulations did not consider the impact of the multiphase interstellar medium (ISM) on the existence of the PS. This is crucial because it has been suggested that this weak signal is highly susceptible to scattering by small-scale density fluctuations typical of the ISM. This has motivated us to explore the formation and fate of the PS in a high-resolution, N-body/hydrodynamical simulation of an idealised Galaxy analogue bearing a realistic ISM, which interacts impulsively with a massive perturber. In our models, high gas surface densities within the disc encourage vigorous star formation, which in turn couples with the gas via feedback to drive turbulence. We find that the PS is almost non-existent if the ISM has an excess of power on sub-kiloparsec scales compared to longer wavelengths. This can happen in the absence of star formation and feedback when the gas is allowed to cool. In the presence of turbulent gas maintained by stellar feedback, the PS has a patchy spatial distribution and a high degree of intermittency on kiloparsec scales. We anticipate that future studies of the phase-spiral behaviour on all scales will provide crucial information on star-gas dynamics.

To advance research on galaxies in the era of large-scale sky surveys, we introduce GalaxyGenius, a Python package designed to produce synthetic galaxy images tailored to different telescopes based on hydrodynamical simulations. The package comprises three main modules: data preprocessing, ideal data cube generation, and mock observation. Specifically, the preprocessing module extracts necessary properties of star and gas particles for a selected subhalo from hydrodynamical simulations and creates the execution file for the following radiative transfer procedure. Subsequently, building on the above information, the ideal data cube generation module executes a widely-used radiative transfer project, specifically the SKIRT, to perform the SED assignment for each particle and the radiative transfer procedure to produce an IFU-like ideal data cube. Lastly, the mock observation module takes the ideal data cube and applies the throughputs of aiming telescopes while also incorporating the relevant instrumental effects, point spread functions (PSFs), and background noise to generate desired mock observational images of galaxies. To showcase the outcomes of GalaxyGenius, We create a series of mock images of galaxies based on the IllustrisTNG and EAGLE simulations for both space and ground-based surveys spanning from the ultraviolet to infrared wavelength coverages, including CSST, Euclid, HST, JWST, Roman, and HSC. GalaxyGenius offers a flexible framework developed to generate mock galaxy images with customizable recipes. These generated images can serve as valuable references for verifying and validating new approaches in astronomical research, and they can also act as training sets for deep learning relevant studies where real observational data are insufficient.

We present a high-resolution radio-continuum view and a multi-frequency analysis of the Large Magellanic Cloud (LMC) Supernova Remnant (SNR) J0450.4-7050, which we give the nickname Veliki. These high-resolution observations reveal a larger extent than previously measured, making J0450.4-7050 one of the largest SNRs that we know of. Additionally, we observe a higher than expected radio surface brightness and an unusually flat spectral index ($\alpha = -0.26 \pm 0.02$), with little spectral variation over the remnant. We observe a bright H$\alpha$ shell indicating significant cooling over the remnant, but also an excess of [Oiii] on the eastern shock front. We investigate several theoretical scenarios to explain the emission and radio evolution of J0450.4-7050 in the context of the LMC environment, and determine that this is most likely an older, predominantly radiative, SNR with a higher shock compression ratio, which gives a flatter non-thermal spectrum, in combination with a thermal (bremsstrahlung) emission contribution.

Cosmic hot gas emission is closely related to halo gas acquisition and galactic feedback processes. Their X-ray observations reveal important physical properties and movements of the baryonic cycle of galactic ecosystems. However, the measured emissions toward a target at a cosmological distance would always include contributions from hot gases along the entire line of sight to the target. Observationally, such contaminations are routinely subtracted via different strategies. In this work, we aim at answering an interesting theoretical question regarding the amount of soft X-ray line emissions from intervening hot gases of different origins. We tackle this problem with the aid of the TNG100 simulation. We generated typical wide-field lightcone and estimated their impacts on spectral and flux measurements toward X-ray-emitting galaxy-, group- and cluster-halo targets at lower redshifts. We split the intervening hot gases into three categories, that is, the hot gas that is gravitationally bound to either star-forming or quenched galaxy halos, and the diffuse gas which is more tenuously distributed permeating the cosmic web structures. We find that along a given line of sight, the diffuse gas that permeates the cosmic web structures produces strong oxygen and iron line emissions at different redshifts. The diffuse gas emission in the soft X-ray band can be equal to the emission from hot gases that are gravitationally bound to intervening galaxy halos. While the hot gas emission from the quiescent galaxy halos can be significantly less than that from star-forming halos along the line of sight. The fluxes from all of the line-of-sight emitters as measured in the energy band of 0.4--0.85 keV can reach ~20--200 % of the emission from the target galaxy, group, and cluster halos.

We present EMUSE (Evolutionary Map of the Universe Search Engine), a tool designed for searching specific radio sources within the extensive datasets of the EMU (Evolutionary Map of the Universe) survey, with potential applications to other Big Data challenges in astronomy. Built on a multimodal approach to radio source classification and retrieval, EMUSE fine-tunes the OpenCLIP model on curated radio galaxy datasets. Leveraging the power of foundation models, our work integrates visual and textual embeddings to enable efficient and flexible searches within large radio astronomical datasets. We fine-tune OpenCLIP using a dataset of 2,900 radio galaxies, encompassing various morphological classes, including FR-I, FR-II, FR-x, R-type, and other rare and peculiar sources. The model is optimized using adapter-based fine-tuning, ensuring computational efficiency while capturing the unique characteristics of radio sources. The fine-tuned model is then deployed in EMUSE, allowing for seamless image- and text-based queries over the EMU survey dataset. Our results demonstrate the model's effectiveness in retrieving and classifying radio sources, particularly in recognizing distinct morphological features. However, challenges remain in identifying rare or previously unseen radio sources, highlighting the need for expanded datasets and continuous refinement. This study showcases the potential of multimodal machine learning in radio astronomy, paving the way for more scalable and accurate search tools in the field. The search engine is accessible at this https URL and can be used locally by cloning the repository at this https URL.

Recent data from DESI Year 2 BAO, Planck CMB, and various supernova compilations suggest a preference for evolving dark energy, with hints that the equation of state may cross the phantom divide line ($w = -1$). While this behavior is seen in both parametric and non-parametric reconstructions, comparing reconstructions that support such behavior (such as the best fit of CPL) with those that maintain $w>-1$ (like the best fit algebraic quintessence) is not straightforward, as they differ in flexibility and structure, and are not necessarily nested within one another. Thus, the question remains as to whether the crossing behavior that we observe, suggested by the data, truly represents a dark energy model that crosses the phantom divide line, or if it could instead be a result of data fluctuations and the way the data are distributed. We investigate the likelihood of this possibility. For this analysis we perform 1,000 Monte Carlo simulations based on a fiducial algebraic quintessence model. We find that in $3.2 \% $ of cases, CPL with phantom crossing not only fits better, but exceeds the real-data $\chi^2$ improvement. This Monte Carlo approach quantifies to what extent statistical fluctuations and the specific distribution of the data could fool us into thinking the phantom divide line is crossed, when it is not. Although evolving dark energy remains a robust signal, and crossing $w=-1$ a viable phenomenological solution that seems to be preferred by the data, its precise behavior requires deeper investigation with more precise data.

Relativistic jets of radio galaxies (RGs) are possible sources of ultra-high-energy cosmic rays (UHECRs). Recent studies combining relativistic hydrodynamic simulations with Monte Carlo particle transport have demonstrated that UHECRs can be accelerated to energies beyond $10^{20}$ eV through shocks, turbulence, and relativistic shear in jet-induced flows of Fanaroff-Riley (FR) type RGs. The resulting time-asymptotic UHECR spectrum is well modeled by a double power law with an ``extended'' exponential cutoff, primarily shaped by relativistic shear acceleration. In this study, we adopt this novel source spectrum and simulate the propagation of UHECRs from nearby RGs using the CRPropa code. We focus on Virgo A, Centaurus A, Fornax A, and Cygnus A, expected to be the most prominent UHECR sources among RGs. We then analyze the energy spectrum and mass composition of UHECRs arriving at Earth. We find that, due to the extended high-energy tail in the source spectrum, UHECRs from Virgo A, which has a higher Lorentz factor, exhibit a higher flux at the highest energies and a lighter mass composition at Earth, compared to those from Centaurus A and Fornax A with lower Lorentz factors. Despite Cygnus A having an even higher Lorentz factor, the large distance limits its contribution. With a small number of nearby prominent RGs, our findings suggest that if RGs are the major sources of UHECRs, the energy spectrum and mass composition of observed UHECRs would exhibit hemispheric differences between the Northern and Southern skies at the highest energies.

We present the photometric and spectroscopic analysis of five Type Ibn supernovae (SNe): SN 2020nxt, SN 2020taz, SN 2021bbv, SN 2023utc, and SN 2024aej. These events share key observational features and belong to a family of objects similar to the prototypical Type Ibn SN 2006jc. The SNe exhibit rise times of approximately 10 days and peak absolute magnitudes ranging from $-$16.5 to $-$19 mag. Notably, SN 2023utc is the faintest Type Ibn supernova discovered to date, with an exceptionally low r-band absolute magnitude of $-16.4$ mag. The pseudo-bolometric light curves peak at $(1-10) \times 10^{42}$ erg s$^{-1}$, with total radiated energies on the order of $(1-10) \times 10^{48}$ erg. Spectroscopically, these SNe display relatively slow spectral evolution; the early spectra are characterised by a hot blue continuum and prominent He I emission lines. Early spectra show blackbody temperatures exceeding $10000~\mathrm{K}$, with a subsequent decline in temperature during later phases. Narrow He I lines, indicative of unshocked circumstellar material (CSM), show velocities of approximately $1000~\mathrm{km~s^{-1}}$. The spectra suggest that the progenitors of these SNe underwent significant mass loss prior to the explosion, resulting in a He-rich CSM. Light curve modelling yields estimates for the ejecta mass ($M_{\rm ej}$) in the range $1-3~M_{\odot}$, with kinetic energies ($E_{\rm Kin}$) of $(0.1-1) \times 10^{50}$ erg. The inferred CSM mass ranges from $0.2$ to $1~M_{\odot}$. These findings are consistent with expectations for core-collapse events arising from relatively massive, envelope-stripped progenitors.

Interstellar complex organic molecules (COMs) in solar-like young stellar objects (YSOs), particularly within protostellar disks, are of significant interest due to their potential connection to prebiotic chemistry in emerging planetary systems. We report the discovery of a rotating feature enriched in COMs, including CH3OH, CH3CHO, and NH2CHO, in the protostellar core G192.12-11.10. By constructing a YSO model, we find that the COM-rich feature is likely located within or near the boundary of the Keplerian disk. The image synthesis results suggest that additional heating mechanisms leading to a warm ring or a warm inner disk are required to reproduce the observed emission. We discuss possible origins of the COM-rich feature, particularly accretion shocks as a plausible cause for a warm ring. Additionally, molecules such as C18O, H2CO, DCS, H2S, and OCS exhibit distinct behavior compared to CH3OH, indicating a range of physical and chemical conditions within the region. The observed kinematics of H2S and OCS suggest that OCS resides in regions closer to the central protostar than H2S, consistent with previous experimental studies.

Classical novae are common cataclysmic events involving a binary system of a white dwarf and a main sequence or red giant companion star. In metal-poor environments, these explosions produce ejecta different from their solar counterparts due to the accretion of sub-solar metallicity material onto the white dwarf. In particular, it has been suggested that the nucleosynthesis flow in such low-metallicity nova explosions extends up to the Cu-Zn region, much beyond the expected endpoint, around Ca, predicted for solar-metallicity classical novae. This behavior resembles a weak rp-process, and such nuclear activity has never been observed in accreting white dwarf binaries with typical accretion flows. In this work, we study the characteristics of the weak rp-process for four nova models with metallicities $Z= 2\times 10^{-9}$, $10^{-7}$, $2\times 10^{-6}$, and $2\times 10^{-5}$, and explore the impact of the nuclear physics uncertainties via a Monte Carlo sensitivity study. We identify nuclear reactions whose uncertainties affect the production of intermediate-mass nuclei under these conditions. These reactions and relevant nuclear quantities are targets for measurements at stable or radioactive beam facilities to reduce their rate uncertainties.

We present a detailed analysis of the light curves and pulsation properties of First Overtone (FO) Cepheids in the Magellanic Clouds (MCs) obtained using observations and predictions from stellar pulsation models. Multiwavelength observational light curves were compiled from the literature (OGLE-IV, Gaia and VMC). We investigate the period-amplitude (PA), period-colour (PC), period-luminosity (PL), and amplitude-colour (AC) relations for FO Cepheids at multiwavelengths. We find that the PA distribution of FO Cepheids in the MCs modelled using a Gaussian Mixture Model shows that the SMC consists of higher amplitude stars than the LMC. We find multiple break-points in the PC/PL/AC relations for FO/FU Cepheids in the optical and near-infrared bands including the one near to P = 2.5 d in the MCs using piecewise regression analysis and F- test statistics. Similarly, for the LMC FO Cepheids, we find a break-point in the PC/PL/AC relations near P = 0.58 d. The slopes of the PC relations for LMC FO Cepheids are found to be shallow for 0.58 < P(d) < 2.5 but steeper for P < 0.58 d and P > 2.5 d. We complemented the observed relations using theoretical models for FO Cepheids with chemical compositions Z = 0.008 and Z = 0.004, appropriate for the LMC and SMC, respectively computed with MESA-RSP. Our results show that the pulsation properties of FO Cepheids in PC/PL/AC relations and colour-magnitude diagram are strongly correlated and their connections can provide stringent constraints for the theoretical pulsation models.

We establish significant upper limits to the current star formation rate in two samples of post starburst galaxies by measuring the rate of Type II supernovae from the Zwicky Transient Factory Bright Transient Survey. No Type II supernovae are observed within the Petrosian radii of $z < 0.05$ post starburst galaxies during this supernova search survey. We calculate that at 95\% confidence level the star formation rate in these galaxies is $< 0.8$ M$_{\odot}$ yr$^{-1}$.

The cluster R136 in the LMC contains a population of stars in excess of 100 M$_\odot$, including R136a1, the most massive star known. Very Massive Stars (VMSs) play an influential role in feedback processes and may potentially produce exotic supernova types and black holes of tens of solar masses. The evolutionary history and final fate of the three most luminous stars, R136a1, R136a2, and R136a3, has been a puzzling issue. We aim to resolve this by rotating single-star MESA models. We produce interpolated model grids and apply a Markov-Chain Monte Carlo analysis to compare our models with observations. The nature of supernova progenitors strongly depends on mass loss and the AM coupling schemes. We predict no pair-instability and no GRB progenitors from our fiducial model grid at LMC metallicity. The onset of Wolf-Rayet-type mass-loss rates on the main sequence leads to a rapid decrease in stellar mass and luminosity. The mass turnover implies that the evolutionary history can only be inferred if additional constraints are available. We utilise the surface helium abundance, which poses a conundrum: R136a1, the most luminous star, is less enriched in helium than R136a2 and R136a3. We propose that this can be explained if both R136a2 and R136a3 were initially more massive than R136a1. From a rigorous confrontation of our models to spectroscopically-derived observables, we estimate an initial mass of 346$\pm41$ M$_\odot$ for R136a1, and $\gtrsim$500 M$_\odot$ for R136a2 and R136a3. Even though VMSs are only present in the youngest clusters below 2 Myr of age, our study strengthens their role in local and galaxy evolution. At LMC metallicity, they will be observable as helium-enriched massive stars after their drastic mass loss, produced via single-star evolution. If the core collapse leads to a supernova, it will be of Type Ib/c. [abridged]

Flares and associated Coronal Mass Ejections (CMEs) are energetic stellar phenomena that shape the space weather around planets. Close-in exoplanets orbiting active cool stars are likely exposed to extreme space weather whose effects on the planets are not understood well enough. The terrestrial Trappist-1 exoplanets are excellent targets to study the impact of CMEs on close-in planets and their atmospheres. We study the role of planetary magnetic fields in shielding the planet from external forcing. We expand on recent studies of CME-induced Joule heating of planetary interiors and atmospheres by including a magnetohydrodynamic (MHD) model of the interaction. We study the interaction of CMEs with Tr-1b & e using MHD simulations. We consider magnetic flux rope and density pulse CMEs. We calculate induction heating in the planetary interior and ionospheric Joule heating for various intrinsic magnetic field strengths and CME energies. Magnetospheric compression is the main driver of magnetic variability. Planetary magnetic fields enhance induction heating in the interior although the effect is weaker with flux rope CMEs. Single event dissipation rates with 1-hour CMEs amount to 20 TW and 1 TW for Trappist-1b and e, respectively. Taking CME occurrence rates into account, annual average heating rates are ~10 TW (b) and ~1 TW (e), which are placed near the lower end of previous estimates. Within the range of studied planetary magnetic field strengths $B_p$, magnetospheric Poynting fluxes scale with $B_p^3$. Thus, stronger magnetic fields increase CME energy absorption. Ionospheric Joule heating rates amount to $10^{3-4}$ TW and decrease for stronger magnetic fields $B_p$. These heating rates exceed the average stellar XUV input by 1-2 orders of magnitude and might severely impact atmospheric erosion. In a steady state stellar wind ionospheric Joule heating amounts to ~$10^2$ TW.

Correlations of fluctuations of the flux in Lyman-$\alpha$ forests of high-redshift quasars have been observed by the Baryonic Acoustic Oscillation Spectroscopy Survey (BOSS) and the Dark Energy Spectroscopy Instrument (DESI) survey where they have revealed the effects of baryon acoustic oscillations (BAO). In order to fit the correlation functions to a physical model and thereby constrain cosmological parameters, it is necessary to take into account the effects of fitting the observed spectra to a template about which the fluctuations are measured. In this paper we use mock spectra to test the distortion matrix technique that has been used since the final BOSS data release to appropriately distort the models. We show that while percent-level effects on the derived forest bias parameters may be present, the technique works sufficiently well that the determination of the BAO peak position is not affected at the percent level. We introduce modifications in the technique used by DESI that were not in the original applications and suggest further possibilities for improvements.

Dwarf-dwarf galaxy mergers are among the least explored aspects of dwarf galaxy pre-processing as they fall into clusters. We present the first case study of a coalesced late-type dwarf major merger (VCC 479; stellar mass $\sim\,8\,\times\,10^7\,\rm M_\odot$) that has undergone significant environmental influence, with the aim of exploring dwarf galaxy evolution under the combined effects of galaxy interactions and environmental processes, and understanding its relevance to the diversity of dwarf galaxies in cluster environments. Our analysis is based on VLA and FAST HI emission line mapping from the Atomic gas in Virgo Interacting Dwarf galaxies (AVID) survey. We also perform idealized hydrodynamical simulations of dwarf-dwarf mergers to help interpret the observations. We identify symmetric stellar shell structures in VCC 479, indicative of a coalesced major merger of dwarf galaxies. The galaxy features a central starburst, initiated $\sim$600 Myr ago, embedded within an exponential disk quenched $\sim$1 Gyr ago. The starburst contributes only 2.9$\pm$0.5\% of the total stellar mass, and VCC 479's global star formation rate is 0.3 dex lower than typical dwarfs of similar mass. The galaxy is highly HI deficient, with most HI gas concentrated within the central 1 kpc and little extended HI envelope. The misalignment of the HI velocity field with the stellar body is best explained by merger-triggered gas inflow, as seen in our simulations. Our analysis is consistent with a scenario that the majority of HI gas of the progenitor galaxies was removed by the cluster environment prior to the final coalescence. The merger concentrates the remaining gas toward the galaxy center, triggering a central starburst. The combined effect of environment stripping and galaxy merger has transformed VCC 479 into a blue-core dwarf undergoing morphological transition from a late-type to an early-type galaxy.

Context. It is crucial to understand the interaction between globular clusters (GCs) and the Oort cloud, as close flybys of such massive objects can significantly disturb the cloud's structure and redirect comets towards the inner Solar System. This increases the risk of impacts on Earth. Studying such events can teach us about the evolution and stability of the Solar System, as well as the effect of external gravitational forces on its dynamics over time. Aims. In our study of the gravitational effects of the flyby of the NGC 7078 or M 15 GC on the Oort cloud, we focus on two types of approximation. First, we investigate the impact on the Sun's orbit during close passages, treating the GC as a point mass. At the second stage, we use a complete N-body system representation of the GC comprising over one million particles. Methods. We carried out a dynamical study of the gravitational interaction between Oort cloud particles and galactic GCs within the time-varying galactic external potential. Initially, the GCs are represented as point masses orbiting the Galaxy alongside the Sun and the Oort cloud system. Results. Our study reveals significant variations in the impact of NGC 7078 on the Oort cloud, depending on whether it is modelled as a point mass or a complete N-body system. The N-body system results in much greater stripping of Oort cloud particles, with over 52% stripped during a close pass, compared to a few percent in the point mass model for a flyby at a large distance (>200 pc) and 36% for a closer 10 pc point mass flyby. The N-body system also causes substantial expansion, with particles spreading over 50 pc from the Sun within 30 Myr after the GC's crossing. This creates a twisted and flattened cloud structure with extended outer tails. These stripped cloud particles (more than 10%) spread across the galaxy, reaching distances of up to 16 kpc from the Sun.

We present a kinematical study of the ionized and molecular gas in the central region (~7-14"~100-200pc) of the nearby radio galaxy Cen A. We used JWST/MIRI MRS 5-28$\mu$m observations taken as part of the MIR Characterization of Nearby Iconic galaxy Centers (MICONIC) of the MIRI EC. The two gas phases present contrasting morphologies and kinematics. The brightest emission from the ionized gas, traced with a range of IP lines ([Fe II] to [Ne VI]), is extended along the direction of the radio jet. We also detected emission from low IP emission lines and H$_2$ transitions in the galaxy disk. Both gas phases present rotational motions but also complex kinematics. The observations reveal several ionized gas kinematical features that are consistent with simulation predictions of a jet-driven bubble and outflow interacting with the galaxy ISM. These include broad components in the nuclear line profiles ($\sigma$~600km/s), high velocities (~ +1000, -1400km/s) confined within the nuclear region, velocities of hundreds of km/s in several directions in the central 2", and enhanced velocity dispersions perpendicular to the radio jet. Moreover, we find evidence of shock excitation in the nuclear region based on MIR line ratios. We compared the ionized gas mass outflow rate with Cen A's AGN luminosity and radio jet power and demonstrate that both mechanisms provide sufficient energy to launch the outflow. The noncircular motions observed in the H$_2$ lines can be reproduced with either a warped rotating disk model or a radial component. The latter might be to related to gas streamers detected in cold molecular gas. There is no clear indication of a fast nuclear H$_2$ outflow, only a weak blueshifted component. This could be due to a relatively low nuclear warm H$_2$ column density and/or the limited geometrical coupling of Cen A's inner radio jet with the circumnuclear disk of the galaxy. (Abridged)

As part of the N2CLS Survey, we have identified a remarkable overdensity of ten bright dusty star-forming galaxies at z$\sim$5.2 in the GOODS-N field. Three of these galaxies, N2GN_1_01, 06, and 23 (known as GN10, HDF850.1, and S3, respectively), had previously been spectroscopically confirmed as members of the exceptional large-scale structure at z$\sim$5.1-5.3, which is notably elongated along the line of sight, spanning 30 cMpc. We present the spectroscopic confirmation of N2GN_1_13 at z$_{\rm spec}$=5.182, a massive dusty star-forming galaxy identified through targeted NOEMA observations, and N2GN_1_61 at z$_{\rm spec}$=5.201, revealed using JWST/FRESCO data. In addition to these five spectroscopically confirmed members, we identify five further candidates with photometric redshifts consistent with the overdense structure. These galaxies are massive (with a median stellar mass of 10$^{11}$ M$_{\odot}$) and highly obscured (with a median A$_V$ of 2.9), caught in a short-lived yet extreme starburst phase at z$\sim$5.2. Their high SFRs (with a median of 680 M$_{\odot}$ yr$^{-1}$), efficient baryon to stellar mass conversion ($\epsilon_{\star}>$20%), substantial gas reservoir and dust content, suggest rapid evolution and imminent quenching. Six of these galaxies reside in overdense filaments, while the remaining four may trace new distinct structures which will have to be spectroscopically confirmed. These few dusty galaxies dominate the star formation within the overdensity, contributing more than the numerous H$_{\alpha}$ emitters, and surpassing the cosmic average star formation rate density for this epoch. Their properties suggest an accelerated evolution that current models and simulations have difficulty reproducing.

We present the first statistical observational study detecting small-scale filaments in the immediate surroundings of galaxies, i.e. the local web of galaxies. Simulations predict that cold gas, the fuel for star formation, is channeled through filamentary structures into galaxies. Yet, direct observational evidence for this process has been limited by the challenge of mapping the cosmic web at small scales. Using miniJPAS spectro-photometric data combined with spectroscopic DESI redshifts when available, we construct a high-density observational galaxy sample spanning 0.2<z<0.8. Local filaments are detected within a 3 Mpc physical radius of each galaxy with stellar mass M* $> 10^9$ $\mathrm{M}_\odot$, using other nearby galaxies as tracers and a probabilistic adaptation of the DisPerSE algorithm, designed to overcome limitations due to photometric redshift uncertainties. Our methodology is tested and validated using mock catalogues built with random forest models and reference lightcone simulations. We recover the expected increase in galaxy connectivity, defined as the number of filaments attached to a galaxy, with stellar mass. Interestingly, we find a persistent correlation between connectivity and star formation in medium mass galaxies (M* $= 10^{10-11}$ $\mathrm{M}_\odot$) in the low redshift bins. These results are consistent with the cosmic web detachment scenario, suggesting that reduced connectivity to local filaments hinders the inflow of star-forming material. We propose galaxy connectivity to local (small-scale) filaments as a powerful and physically motivated metric of environment, offering new insights into the role of cosmic structure in galaxy evolution.

The standard nonlocal thermodynamic equilibrium (non-LTE) multi-level radiative transfer problem only takes into account the deviation of the radiation field and atomic populations from their equilibrium distribution. We aim to show how to solve for the full non-LTE (FNLTE) multi-level radiative transfer problem, also accounting for deviation of the velocity distribution of the massive particles from Maxwellian. We considered, as a first step, a three-level atom with zero natural broadening. In this work, we present a new numerical scheme. Its initialisation relies on the classic, multi-level approximate Lambda-iteration (MALI) method for the standard non-LTE problem. The radiative transfer equations, the kinetic equilibrium equations for atomic populations, and the Boltzmann equations for the velocity distribution functions were simultaneously iterated in order to obtain self-consistent particle distributions. During the process, the observer's frame absorption and emission profiles were re-computed at every iterative step by convolving the atomic frame quantities with the relevant velocity distribution function. We validate our numerical strategy by comparing our results with the standard non-LTE solutions in the limit of a two-level atom with Hummer's partial redistribution in frequency, and with a three-level atom with complete redistribution. In this work, we considered the so-called cross-redistribution problem. We then show new FNLTE results for a simple three-level atom while evaluating the assumptions made for the emission and absorption profiles of the standard non-LTE problem with partial and cross-redistribution.

We present a comprehensive analysis of inflationary models in light of projected sensitivities from forthcoming CMB and gravitational wave experiments, incorporating data from recent ACT DR6, DESI DR2, CMB-S4, LiteBIRD, and SPHEREx. Focusing on precise predictions in the $(n_s, \alpha_s, \beta_s)$ parameter space, we evaluate a broad class of inflationary scenarios -- including canonical single-field models, non-minimally coupled theories, and string-inspired constructions such as Starobinsky, Higgs, Hilltop, $\alpha$-attractors, and D-brane models. Our results show that next-generation observations will sharply constrain the scale dependence of the scalar power spectrum, elevating $\alpha_s$ and $\beta_s$ as key discriminants between large-field and small-field dynamics. Strikingly, several widely studied models -- such as quartic Hilltop inflation and specific DBI variants -- are forecast to be excluded at high significance. We further demonstrate that the combined measurement of $\beta_s$ and the field excursion $\Delta\phi$ offers a novel diagnostic of kinetic structure and UV sensitivity. These findings underscore the power of upcoming precision cosmology to probe the microphysical origin of inflation and decisively test broad classes of theoretical models.

Accurate distance measurements to supernova remnants (SNRs) are essential for determining their physical parameters, such as size, age, explosion energy, and for constraining the properties of associated neutron stars (NSs). We present an extinction--distance method that combines precise Gaia DR3 photometry, parallax, and stellar parameters from the SHBoost catalog to homogeneously construct extinction--distance profiles for 44 NS-associated Galactic SNRs. Applying a statistical model, we identify clear extinction jumps along each sightline, corresponding to probable SNR distances. We classify the results into three reliability levels (A, B, and C), primarily based on comparisons with previously reported kinematic distances, supplemented by independent estimates from other methods. Our results show that the majority of reliable distances (17 Level A and 8 Level B) are located within 5 kpc, predominantly in the Local Arm. This study presents an independent and effective method for determining distances to SNRs, particularly for those with small angular sizes or located in the second and third Galactic quadrants. Although the current method is limited to within 5 kpc due to the precision constraints of Gaia parallax and photometry, the upcoming Gaia DR4 release, combined with complementary infrared data, will extend its applicability to more distant and heavily obscured SNRs, and help resolve kinematic distance ambiguities.

We compare the radii derived from the asteroseismic scaling relations with those from surface brightness-colour relations (SBCRs) combined with the Gaia DR3 parallaxes for main-sequence (MS) stars. The atmospheric and asteroseismic parameters were sourced from the recently released KEYSTONE catalogue and matched to Gaia DR3 and TESS Input Catalog v8.2. We computed SBCR-based radii using two different SBCRs, and estimated their relative differences with respect to radius estimates from asteroseismic grid-based methods. We find a good agreement between SBCR and asteroseismic radii, with mean relative differences in radii ($E_g$) in the range 2% to 3% and a standard deviation of about 3%. We find no dependence on parallax, and a mild dependence on [Fe/H] for one of the SBCRs tested. We find a negative correlation between $E_g$ and the stellar mass, with a slope varying from $-0.051\pm0.016$ to $-0.039\pm0.014$ per solar mass. This change in slope led to a roughly 1.5% larger discrepancy in the $E_g$ estimates for stars with masses below 1.0 $M_{\odot}$. This larger discrepancy at the low-mass end supports conclusions drawn from giant star studies. This result is independently corroborated by the LEGACY sample, which uses Kepler photometry. For the LEGACY sample we measure a mean relative offset in $E_g$ of -1.4% with a standard deviation of 2.3%, and a dependence of $E_g$ on mass with a slope of $-0.052\pm0.011$ per mass unit, both fully consistent with the KEYSTONE analysis. The [...] apparent mass dependence still requires closer examination. This result is reassuring as it demonstrates the great accuracy and reliability of the radius estimates obtained through SBCRs, which, moreover, offer the significant advantage of being applicable to a large sample of stars with substantially lower time and costs compared to what is required by asteroseismology.

One crucial aspect of planning any large scale astronomical survey is constructing an observing strategy that maximizes reduced data quality. This is especially important for surveys that are rather heterogeneous and broad-ranging in their science goals. The Sloan Digital Sky Survey V (SDSS-V), which now utilizes the Focal Plane System (FPS) to robotically place fibers that feed the spectrographs, certainly meets these criteria. The addition of the FPS facilities an increase in survey efficiency, number of targets and target diversity, but also means the positions of fibers must be constrained to allow for simultaneous observations of sometimes competing programs. The constraints on the positions of the fibers are clearly driven by properties of the science targets e.g., the type of target, brightness of the target, position of the target relative to others in the field, etc. The parameters used to describe these constraints will also depend on the intended science goal of the observation, which will vary with the types of objects requested for the particular observation and the planned sky conditions for the observation. In this work, we detail the SDSS-V data collection scenarios, which consist of sets of parameters that serve as the framework for constraining fiber placements. The numerical values of these parameters were set based on either past experiences or from a series of new tests, which we describe in detail here. These parameters allow a survey like SDSS-V to be algorithmically planned to maximize the science output, while guaranteeing data quality throughout its operation.

Turbulence governs the fragmentation of molecular clouds and plays a pivotal role in star formation. The persistence of observed cloud turbulence suggests it does not decay significantly within the turnover timescale, implying a recurrent driving mechanism. Although ubiquitous self-gravity is a plausible driver, MHD simulations by \citet{ostriker2001density} demonstrated that self-gravity alone does not modify the global turbulence decay rate. In this study, we demonstrate that the dominant diffuse volume of a cloud dictates its overall decay rate, while individual dense cores can maintain near-zero decay rates. Crucially, this phenomenon is absent in control simulations excluding self-gravity. This discrepancy cannot be attributed to contamination of turbulent velocities by core contraction, as most cores in our simulations remain in a quasi-equilibrium state. Our analysis reveals that the gravitational potential energy released during core formation\textemdash not necessarily driven by self-gravity but also by turbulent compression\textemdash is sufficient to sustain the observed turbulence levels within cores.

Observations of the cosmic velocity field could become an important cosmological probe in the near future. To take advantage of future velocity-flow surveys we must however have the theoretical predictions under control. In many respects, the velocity field is easier to simulate than the density field because it is less severely affected by small-scale clustering. Therefore, as we also show in this paper, a particle-mesh (PM) based simulation approach is usually sufficient, yielding results within a few percent of a corresponding P$^3$M simulation in which short-range forces are properly accounted for, but which also carry a much larger computational cost. However, in other respects the velocity field is much more challenging to deal with than the density field: Interpolating the velocity field onto a grid is significantly more complicated, and the vorticity field (the curl-part of the velocity field) is severely affected by both sample variance and discretisation effects. While the former can be dealt with using fixed amplitude initial conditions, the former makes it infeasible to run fully converged simulations in a cosmological volume. However, using the $N$-body code CONCEPT we show that one can robustly extrapolate the cosmic vorticity power spectrum from just 4 simulations with different number of particles. We expect our extrapolated vorticity power spectra to be correct within 5\% of the fully converged result across three orders of magnitude in $k$.

A subclass of early impulsive solar flares, cold flares, was proposed to represent a clean case, where the release of the free magnetic energy (almost) entirely goes to acceleration of the nonthermal electrons, while the observed thermal response is entirely driven by the nonthermal energy deposition to the ambient plasma. This paper studies one more example of a cold flare, which was observed by a unique combination of instruments. In particular, this is the first cold flare observed with the Expanded Owens Valley Solar Array and, thus, for which the dynamical measurement of the coronal magnetic field and other parameters at the flare site is possible. With these new data, we quantified the coronal magnetic field at the flare site, but did not find statistically significant variations of the magnetic field within the measurement uncertainties. We estimated that the uncertainty in the corresponding magnetic energy exceeds the thermal and nonthermal energies by an order of magnitude; thus, there should be sufficient free energy to drive the flare. We discovered a very prominent soft-hard-soft spectral evolution of the microwave-producing nonthermal electrons. We computed energy partitions and concluded that the nonthermal energy deposition is likely sufficient to drive the flare thermal response similarly to other cold flares.

At the moment, one of the main ways to infer the disk mass is to use a combination of CO isotopologue line observations. A number of theoretical studies have concluded that CO must be a reliable gas tracer as its relative abundance depends on disk parameters only weakly. However, the observed line fluxes cannot always be easily used to infer the column density, much less the abundance of CO. The aim of this work is to study the dependence of the CO isotopologue millimeter line fluxes on the astrochemical model parameters of a standard protoplanetary disk around a T Tauri star and to conclude whether they or their combinations can be reliably used to determine disk parameters. Our case is set apart from earlier studies in the literature by the usage of a comprehensive chemical network with grain surface chemistry together with line radiative transfer. We use the astrochemical model ANDES together with the radiative transfer code RADMC-3D to simulate CO isotopologue line fluxes from a set of disks with varying key parameters (disk mass, disk radius, stellar mass, and inclination). We study how these values change with one parameter varying and others fixed and approximate the dependences log-linearly. We describe the dependences of CO isotopologue fluxes on all chosen disk parameters. Physical and chemical processes responsible for these dependences are analyzed and explained for each parameter. We show that using a combination of the $^{13}$CO and C$^{18}$O line fluxes, the mass can be estimated only within two orders of magnitude uncertainty and characteristic radius within one order of magnitude uncertainty. We find that inclusion of grain surface chemistry reduces $^{13}$CO and C$^{18}$O fluxes which can explain the underestimation of disk mass in the previous studies.

In the interstellar medium (ISM), polycylic aromatic hydrocarbons (PAHs) are believed to be an important carbon reservoir, accounting for up to a quarter of all interstellar carbon in our galaxy. This makes the investigation of their potential formation precursors highly relevant in the context of ISM chemistry. This, in turn, includes knowing the abundance of the precursor species. One of the possible precursor molecules for PAHs is the recently detected cyanocyclopentadiene, c-C$_5$H$_5$CN. Given the physical conditions of the dense dark molecular cloud TMC-1 where the cyclic species was detected, it is crucial to consider that local thermodynamic equilibrium conditions may not be satisfied. In such case an accurate estimation of the molecular abundance involves taking into account the competition between the radiative and collisional processes, which requires the knowledge of rotational excitation data for collisions with the most abundant interstellar species - He or H$_2$. In this paper the first potential energy surface (PES) for the interaction of the most stable isomer of cyanocyclopentadiene (1-cyano-1,3-cyclopentadiene) with He atoms is computed using the explicitly correlated coupled-cluster theory [CCSD(T)-F12]. The obtained PES demonstrates a high anisotropy and is characterized by a global potential well of -101.8 cm$^{-1}$. Scattering calculations of the rotational (de-)excitation of 1-cyano-cyclopentadiene induced by He atoms are performed with the quantum mechanical close-coupling method for total energies up to 125 cm$^{-1}$. The resulting rotational state-to-state cross sections are used to compute the corresponding rate coefficients for temperatures up to 20 K. A propensity favoring the transitions with $\Delta k_a=0$ is observed.

Chemical clocks offer a powerful tool for estimating stellar ages from spectroscopic surveys. We present a new detailed spectroscopic analysis of 68 Kepler red giant stars to provide a suite of high-precision abundances along with asteroseismic ages with better than 10 percent precision from individual mode frequencies. We obtained several chemical clocks as ratios between s-process elements (Y, Zr, Ba, La, Ce) and alpha-elements (Mg, Ca, Si, Al, Ti). Our data show that [Ce/Mg] and [Zr/Ti] display a remarkably tight correlation with stellar ages, with abundance dispersions of 0.08 and 0.01 dex respectively and below 3 Gyr in ages, across the entire Galactic chronochemical history. While improving the precision floor of spectroscopic surveys is critical for broadening the scope and applicability of chemical clocks, the intrinsic accuracy of our relations -- enabled by high-resolution chemical abundances and stellar ages in our sample -- allows us to draw meaningful conclusions about age trends across stellar populations. By applying our relations to the APOGEE and Gaia-ESO surveys, we are able to differentiate the low- and high-alpha sequences in age, recover the age-metallicity relation, observe the disc flaring of the Milky Way, and identify a population of old metal-rich stars.

A recent study announced the detection of three bands in the ultraviolet emission spectra of more than a dozen comets, assigning two of them to pentacene (C$_{22}$H$_{14}$) and the third one to toluene (C$_7$H$_8$). The comparison of the spectra with the results of exploitable laboratorymeasurements on rare-gas-matrix-isolated pentacene and on jet-cooled toluene does not reveal elements that would justify the assignment, which is therefore unsubstantiated. The study also claimed the detection of an Fe II line in the gas of all but one comet. Yet, spectroscopic data on Fe II do not corroborate the attribution. Because spectroscopic measurements on the ultraviolet emission of pentacene in the gas phase are not available, this work also presents a synthetic spectrum of the S$_5$ $\rightarrow$ S$_0$ transition relevant to the wavelength range of the observations. Calculated using density functional theory and its time-dependent extension, the synthetic spectrum may facilitate the search for pentacene fluorescence in cometary spectra until laboratory measurements are accessible.

We report the discovery of an unusual z=1.14 object, dubbed the $\infty$ galaxy, in JWST imaging of the COSMOS field. Its rest-frame near-IR light is dominated by two compact nuclei with stellar masses of $\sim 10^{11}$ Msun and a projected separation of 10 kpc. Both nuclei have a prominent ring or shell around them, giving the galaxy the appearance of a figure eight or an $\infty$ symbol. The morphology resembles that of the nearby system II Hz 4, where the head-on collision of two galaxies with parallel disks led to the formation of collisional rings around both of their bulges. Keck spectroscopy, VLA radio data, and Chandra X-ray data show that the $\infty$ galaxy hosts an actively accreting supermassive black hole (SMBH), with quasar-like radio and X-ray luminosity. Remarkably, the SMBH is not associated with either of the two nuclei, but is in between them in both position and radial velocity. Furthermore, from excess emission in the NIRCAM F150W filter we infer that the SMBH is embedded in an extended distribution of H$\alpha$-emitting gas, with a rest-frame equivalent width ranging from 400 - 2000 Angstrom. The gas spans the entire width of the system and was likely shocked and compressed at the collision site, in a galaxy-scale equivalent of what happened in the bullet cluster. We suggest that the SMBH formed within this gas in the immediate aftermath of the collision, when it was dense and highly turbulent. If corroborated with simulations and follow-up JWST spectroscopy, this would demonstrate that `direct' SMBH formation by a runaway gravitational collapse is possible in extreme conditions.

The z=1.14 $\infty$ galaxy consists of two ringed nuclei with an active supermassive black hole (SMBH) in between them. The system is likely the result of a nearly face-on collision between two disk galaxies with massive bulges. In van Dokkum et al. (2025) we suggested that the SMBH may have formed from shocked and compressed gas at the collision site, in a runaway gravitational collapse. Here we test this hypothesis using newly obtained NIRSpec IFU observations. We first confirm that the system has a cloud of gas in between the nuclei that is photo-ionized by an AGN-like object near its center. Next, we constrain the origin of the SMBH from its radial velocity. If it formed in the cloud its velocity should be similar to the surrounding gas, whereas it would be offset if the SMBH had escaped from one of the nuclei or were associated with a faint galaxy. We find that the radial velocity of the SMBH is within $\sim 50$ km/s of that of the surrounding gas, as expected if the SMBH formed within the cloud. Unexpectedly, we find that both nuclei have active SMBHs as well, as inferred from very broad H$\alpha$ emission with FWHM $\sim 3000$ km/s. This rules out scenarios where the central SMBH was ejected from one of the nuclei in a gravitational recoil. Taken together, these results strengthen the hypothesis that the object at the center of the $\infty$ galaxy is a newly formed SMBH.

Candidate Dark Galaxy-2 (CDG-2) is a potential dark galaxy consisting of four globular clusters (GCs) in the Perseus cluster, first identified in Li et al. (2025) through a sophisticated statistical method. The method searched for over-densities of GCs from a \textit{Hubble Space Telescope} (\textit{HST}) survey targeting Perseus. Using the same \textit{HST} images and the new imaging data from the \textit{Euclid} survey, we report the detection of extremely faint but significant diffuse emission around the four GCs of CDG-2. We thus have exceptionally strong evidence that CDG-2 is a galaxy. This is the first galaxy detected purely through its GC population. Under the conservative assumption that the four GCs make up the entire GC population, preliminary analysis shows that CDG-2 has a total luminosity of $L_{V, \mathrm{gal}}= 6.2\pm{3.0} \times 10^6 L_{\odot}$ and a minimum GC luminosity of $L_{V, \mathrm{GC}}= 1.03\pm{0.2}\times 10^6 L_{\odot}$. Our results indicate that CDG-2 is one of the faintest galaxies having associated GCs, while at least $\sim 16.6\%$ of its light is contained in its GC population. This ratio is likely to be much higher ($\sim 33\%$) if CDG-2 has a canonical GC luminosity function (GCLF). In addition, if the previously observed GC-to-halo mass relations apply to CDG-2, it would have a minimum dark matter halo mass fraction of $99.94\%$ to $99.98\%$. If it has a canonical GCLF, then the dark matter halo mass fraction is $\gtrsim 99.99\%$. Therefore, CDG-2 may be the most GC dominated galaxy and potentially one of the most dark matter dominated galaxies ever discovered.

We present the first high-resolution abundance study of ESO 280-SC06, one of the least luminous and most metal-poor gravitationally bound Milky Way globular clusters. Using Magellan/MIKE spectroscopy for ten stars, we confirm the cluster's low metallicity as [Fe/H] = $-2.54 \pm 0.06$ and the presence of a nitrogen-enhanced star enriched by binary mass transfer. We determine abundances or abundance upper limits for 21 additional elements from the light, alpha, odd-Z, iron peak, and neutron-capture groups for all ten stars. We find no spread in neutron-capture elements, unlike previous trends identified in some metal-poor globular clusters such as M15 and M92. Eight of the ten stars have light-element abundance patterns consistent with second-population globular cluster stars, which is a significantly larger second-population fraction than would be expected from the low present-day mass of $10^{4.1}$ Msun. We estimate the initial mass of the cluster as $10^{5.4 - 5.7}$ Msun based on its orbit in the Milky Way. A preferential loss of first-population stars could explain the high fraction of second-population stars at the present time. Our results emphasize the importance of considering mass loss when studying globular clusters and their enrichment patterns.

We present a general and automated approach for computing model gradients for PDE solvers built on sparse spectral methods, and implement this capability in the widely used open-source Dedalus framework. We apply reverse-mode automatic differentiation to symbolic graph representations of PDEs, efficiently constructing adjoint solvers that retain the speed and memory efficiency of this important class of modern numerical methods. This approach enables users to compute gradients and perform optimization for a wide range of time-dependent and nonlinear systems without writing additional code. The framework supports a broad class of equations, geometries, and boundary conditions, and runs efficiently in parallel using MPI. We demonstrate the flexibility and capabilities of this system using canonical problems from the literature, showing both strong performance and practical utility for a wide variety of inverse problems. By integrating automatic adjoints into a flexible high-level solver, our approach enables researchers to perform gradient-based optimization and sensitivity analyses in spectral simulations with ease and efficiency.

Titan's atmosphere possesses thick haze layers, but their formation mechanisms remain poorly understood, including the influence of oxygen-containing gas components on organic matter synthesis. As the most abundant oxygen-containing gas, the presence of CO has been found to exert a significant impact on the generation of oxygen-containing organic compounds. Therefore, investigating the influence of CO on the production and composition of Tholins through laboratory simulations, holds profound scientific significance in the context of Titan. The work presented here is an experimental simulation designed to evaluate the impact of CO on the atmospheric chemistry of Titan. To this end, CO was introduced into the standard N2/CH4 mixture at varying mixing ratios from 0.2% to 9%, and exposed to Electron Cyclotron Resonance (ECR) plasma to initiate photochemical reactions. Optical emission spectroscopy was employed for gas-phase in situ characterization, while infrared spectroscopy and high-resolution mass spectrometry were used to analyze the resulting solid products (tholins). Our results demonstrate that the addition of CO enriches the complexity of the chemical system. CO not only supplies oxygen to the system, but also enhances nitrogen's reactivity and incorporation, enhancing the number and quantity of the organic products.

We study gravitational waves from a stellar-mass binary orbiting a spinning supermassive black hole, a system referred to as a binary extreme mass ratio inspiral (b-EMRI). We use Dixon's formalism to describe the stellar-mass binary as a particle with internal structure, and keep terms up to quadrupole order to capture the generation of gravitational waves by the inner motion of the stellar-mass binary. The problem of emission and propagation of waves is treated from first principles using black hole perturbation theory. In the gravitational waveform at future null infinity, we identify for the first time Doppler shifts and beaming due to the motion of the center of mass, as well as helicity breaking gravitational lensing, and resonances with ringdown modes of the supermassive black hole. We establish that previously proposed phenomenological models inadequately capture these effects.

The influence of a possible low gravity scale, concretely through the presence of extra dimensions or additional species, on radiation properties of micro black holes is investigated. In particular, the suppression of evaporation through the so-called memory-burden effect is shown to be stronger, occurs earlier and with sharper transition compared to the canonical Planck-scale regime. It is furthermore shown how this affects the possibility of light primordial black hole dark matter, constraints on which may weaken substantially and allow them to be as light as $10^{-5}\,M_{\rm P}$, thereby lying in the particle regime.

We revisit well-established mechanisms for primordial black hole (PBH) production, namely inflation, phase transitions, and cosmic strings, in the context of the Dark Dimension Scenario, which is motivated by Swampland principles. Applying quantum gravity constraints, we demonstrate that any viable mechanism, barring exotic new physics at low energies, inevitably leads to the formation of five-dimensional PBHs. We further show that PBHs formed from cosmic strings can have lifetimes comparable to the age of the universe. We comment on the observational implications of this result, including a potential connection to the recent detection of a high-energy neutrino by KM3NeT, whose energy is intriguingly close to the five-dimensional Planck scale in the Dark Dimension Scenario.

We provide a new perspective on the cosmological constant by exploring the background-independent Wheeler-DeWitt quantization of general relativity. The Chern-Simons-Kodama state of quantum gravity, a generalization of the Hartle-Hawking and Vilenkin states, has a striking structural similarity to the topological field theory of the quantum Hall effect. As a result, we study the gravitational topological $\theta$-sectors in analogy to Yang-Mills theory. We find that the cosmological constant $\Lambda$ is intimately linked to the $\theta$-parameter by $\theta=12\pi^2/(\Lambda \ell^2_{\rm Pl}) \mod 2\pi$ due to the fact that Chern-Simons-Kodama state must live in a particular $\theta$-sector. This result is shown in the canonical, non-perturbative formalism. Furthermore, we explain how the physics of the Hamiltonian constraint is analogous to the quantum Hall effect, with the cosmological constant playing the role of a quantum gravitational Hall resistivity. These relations suggest that $\Lambda$ is topologically protected against perturbative graviton loop corrections, analogous to the robustness of quantized Hall conductance against disorder in a metal.

We investigate limitations of causality arguments from flat-spacetime amplitudes, based on the eikonal limit of gravitational scattering, to place constraints on modified gravity. We show that causality constraints are only valid in the weak-gravity regime even for transplanckian scattering, and that such constraints are much less stringent than astrophysical ones, obtained for example from gravitational waves emitted in black hole coalescence. Special attention is given to the weakness of causality constraints on dynamical Chern-Simons gravity, but our results apply to other modified gravity theories as well. In the context of that theory, we also discuss how to obtain a time-delay formula from black hole, neutron stars, and shockwave solutions. For scattering with compact objects, we explicitly show that time delays are greatly suppressed by the ratio of the object's mass to the impact parameter, so time advances only occur greatly outside the cut off of the theory. For the shockwave solution, we find that the time delay is always positive within the regime of validity of the solution. We also comment on the impact of graviton nonlinearities for time-delay calculations in the nonlinear, strong gravity regime. We conclude that amplitude-based causality constraints on modified gravity are typically not stringent relative to other experimental and observational bounds.

We study the dynamical and thermal roles of internal gravity waves generated in the troposphere and above using the Coupled Middle Atmosphere Thermosphere-2 General Circulation Model. This model incorporates the whole atmosphere nonlinear gravity wave parameterization and its extension to include non-tropospheric sources. We conducted model experiments for northern summer solstice conditions, first including only tropospheric sources, then including sources localized at 50 and 90 km, and uniformly distributed over all heights. The simulated differences in mean temperature and horizontal winds demonstrate that gravity waves produce the greatest dynamical and thermal changes in the latter case compared to the localized sources. While the gravity wave drag is longitudinally uniform in the lower thermosphere, it is more localized in the upper thermosphere in all the simulations. Waves from uniformly distributed sources increase the longitudinal variability of zonal winds in the thermosphere up to $\sim$150 km. Gravity wave effects exhibit different local time variations in the lower thermosphere (100--140 km) than in the upper thermosphere. In the upper thermosphere, gravity wave effects are stronger during the day than at night. In contrast, nighttime gravity wave effects are stronger than the daytime ones in the lower thermosphere. Finally, a comparison with ICON-MIGHTI observations shows that the model reproduces the basic structure of thermospheric winds, performing better with zonal winds than with meridional winds. Adding non-tropospheric wave sources modifies wind structures in wave-breaking regions, but does not improve the global statistical comparison.

Supernova-neutrino-boosted dark matter (SN$\nu$ BDM) has emerged as a promising portal for probing sub-GeV dark matter. In this work, we investigate the behavior of BDM signatures originating from core-collapse supernovae (CCSNe) within the Milky Way (MW) over the past one hundred thousand years, examining both their temporal evolution and present-day spatial distributions. We show that while the MW BDM signature is approximately diffuse in the nonrelativistic regime, it exhibits significant temporal variation and spatial localization when the BDM is relativistic. Importantly, we compare these local MW signatures with the previously proposed diffuse SN$\nu$ BDM (DBDM), which arises from the accumulated flux of all past SNe in the Universe [Y.-H. Lin and M.-R. Wu, Phys. Rev. Lett. 133, 111004 (2024)]. In the nonrelativistic limit, DBDM consistently dominates over the local diffuse MW BDM signature. Only when the MW BDM becomes ultrarelativistic and transitions into a transient, highly-localized signal, it can potentially surpass the DBDM background. This work thus reinforces the importance of DBDM for SN$\nu$ BDM searches until the next galactic SN offers new opportunities.