Papers for Thursday, Feb 15 2024

The most distant galaxies detected by JWST are assembling in a Universe that is less than 5\% of its present age. At these times, the progenitors of galaxies like the Milky Way are expected to be about 10,000 times less massive than they are now, with masses quite comparable to that of massive globular clusters seen in the local Universe. Composed today primarily of old stars and correlating with the properties of their parent dark matter halos, the first globular clusters are thought to have formed during the earliest stages of galaxy assembly. In this article we explore the connection between star clusters and galaxy assembly by showing JWST observations of a strongly lensed galaxy at zspec = 8.304, exhibiting a network of massive star clusters (the 'Firefly Sparkle') cocooned in a diffuse arc. The Firefly Sparkle exhibits the hallmarks expected of a future Milky Way-type galaxy captured during its earliest and most gas-rich stage of formation. The mass distribution of the galaxy seems to be concentrated in ten distinct clusters, with individual cluster masses that straddle the boundary between low-mass galaxies and high-mass globular clusters. The cluster ages suggest that they are gravitationally bound with star formation histories showing a recent starburst possibly triggered by the interaction with a companion galaxy at the same redshift at a projected distance of $\sim$2 kpc away from the Firefly Sparkle. The central star cluster shows nebular-dominated spectra consistent with high temperatures and a top-heavy initial mass function, the product of formation in a very metal poor environment. Combined with abundance matching that suggests that this is likely to be a progenitor of galaxies like our own, the Firefly Sparkle provides an unprecedented case study of a Milky Way-like galaxy in the earliest stages of its assembly in only a 600 million year old Universe.

The upcoming NASA SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) all-sky 0.7 to 5.0 um spectral survey, to be conducted from 2025 to 2027, provides a unique space-based opportunity to detect, spectrally categorize, and catalog hundreds of thousands of solar system objects at WISE/NEOWISE sensitivities. This paper discusses the unique near-infrared capabilities of SPHEREx, its potential applications in Planetary Defense, (PD), and the implications for risk mitigation associated with Potentially Hazardous Objects (PHOs). By leveraging SPHEREx data, scientists and decision-makers can enhance our ability to track and characterize PHOs, ultimately contributing to the protection of our planet.

We investigate galaxy sizes at redshift $z\gtrsim 6$ with the cosmological radiation-magneto-hydrodynamic simulation suite THESAN(-HR). These simulations simultaneously capture the reionization of the large-scale intergalactic medium and resolved galaxy properties. The intrinsic size ($r^{\ast}_{1/2}$) of simulated galaxies increases moderately with stellar mass at $M_{\ast} \lesssim 10^{8}\,{\rm M}_{\odot}$ and decreases fast at larger masses, resulting in a hump feature at $M_{\ast}\sim 10^{8}\,{\rm M}_{\odot}$ that is insensitive to redshift. Low-mass galaxies are in the initial phase of size growth and are better described by a spherical shell model with feedback-driven gas outflows competing with the cold inflows. In contrast, massive galaxies fit better with the disk formation model. They generally experience a phase of rapid compaction and gas depletion, likely driven by internal disk instability rather than external processes. We identify four compact quenched galaxies in the $(95.5\,{\rm cMpc})^{3}$ volume of THESAN-1 at $z\simeq 6$, and their quenching follows reaching a characteristic stellar surface density akin to the massive compact galaxies at cosmic noon. Compared to observations, we find that the median UV effective radius ($R^{\rm UV}_{\rm eff}$) of simulated galaxies is at least three times larger than the observed ones at $M_{\ast}\lesssim 10^{9}\,{\rm M}_{\odot}$ or $M_{\rm UV}\gtrsim -20$ at $6 \lesssim z \lesssim 10$. This inconsistency, related to the hump feature of the intrinsic size--mass relation, persists across many other cosmological simulations with different galaxy formation models and numerical resolutions, demonstrating the potential of using galaxy morphology to constrain galaxy formation models at high redshifts.

Quasi-Periodic Eruptions (QPEs) are luminous X-ray outbursts recurring on hour timescales, observed from the nuclei of a growing handful of nearby low-mass galaxies. Their physical origin is still debated, and usually modeled as (a) accretion disk instabilities or (b) interaction of a supermassive black hole (SMBH) with a lower mass companion in an extreme mass-ratio inspiral (EMRI). EMRI models can be tested with several predictions related to the short- and long-term behavior of QPEs. In this study, we report on the ongoing 3.5-year NICER and XMM-Newton monitoring campaign of eRO-QPE1, which is known to exhibit erratic QPEs that have been challenging for the simplest EMRI models to explain. We report 1) complex, non-monotonic evolution in the long-term trends of QPE energy output and inferred emitting area; 2) the disappearance of the QPEs (within NICER detectability) in October 2023, then reappearance by January 2024 at a luminosity $\sim$100x fainter (and temperature $\sim$3x cooler) than initial discovery; 3) radio non-detections with MeerKAT and VLA observations partly contemporaneous with our NICER campaign (though not during outbursts); and 4) the presence of a possible $\sim$6-day modulation of the QPE timing residuals, which aligns with the expected nodal precession timescale of the underlying accretion disk. Our results tentatively support EMRI-disk collision models powering the QPEs, and we demonstrate that the timing modulation of QPEs may be used to jointly constrain the SMBH spin and disk density profile.

We present STARRED, a Point Spread Function (PSF) reconstruction, two-channel deconvolution, and light curve extraction method designed for high-precision photometric measurements in imaging time series. An improved resolution of the data is targeted rather than an infinite one, thereby minimizing deconvolution artifacts. In addition, STARRED performs a joint deconvolution of all available data, accounting for epoch-to-epoch variations of the PSF and decomposing the resulting deconvolved image into a point source and an extended source channel. The output is a deep sharp frame combining all data, and the photometry of all point sources in the field of view as a function of time. Of note, STARRED also provides exquisite PSF models for each data frame. We showcase three applications of STARRED in the context of the imminent LSST survey and of JWST imaging: i) the extraction of supernovae light curves and the scene representation of their host galaxy, ii) the extraction of lensed quasar light curves for time-delay cosmography, and iii) the measurement of the spectral energy distribution of globular clusters in the "Sparkler", a galaxy at redshift z=1.378 strongly lensed by the galaxy cluster SMACS J0723.3-7327. STARRED is implemented in JAX, leveraging automatic differentiation and GPU acceleration. This enables rapid processing of large time-domain datasets, positioning the method as a powerful tool for extracting light curves from the multitude of lensed or unlensed variable and transient objects in the Rubin-LSST data, even when blended with intervening objects.

We examine the nature, origin, and fate of early ($z\geq 2$) massive ($M_\star>10^{10}M_\odot$) quenched galaxies (EQGs) in a new $(100h^{-1}{\rm Mpc}^3)$ run of the Simba-C galaxy formation model. We define ``quenched'' to be $>4\sigma$ below an iterative polynomial fit to the star-forming sequence (SFS), and find that Simba-C produces EQGs as early as $z\sim 5$ and number densities agreeing with observations at $z\leq 3$ (though slightly low at $z\geq 4$). Using a photometric-based EQG selection or a fixed sSFR cut of $10^{-10}$yr$^{-1}$ yields similar results. EQGs predominantly arise in central galaxies with stellar mass $M_\star\sim 10^{10.5-11.3}M_\odot$, not necessarily the most massive systems. A UMAP projection shows that quenched galaxies have notably large black hole-to-stellar mass ratios, lower rotational support, and less dust, but are not atypical versus similar-mass non-EQGs in their environments, halo mass, or halo gas temperatures at the time of quenching. However, via galaxy tracking we show that the progenitor environments of EQGs are significantly more overdense than that of non-EQGs, which drives higher black hole mass fractions and stellar-to-halo mass ratios. This results in the Eddington ratio dropping sufficiently low for Simba-C's jet mode feedback to turn on, which quickly quenches the host galaxies. EQGs thus seem to be galaxies that grow their black holes quickly within highly dense environments, but end up in moderately-dense environments where black hole feedback can quench effectively. We find that $\geq 30\%$ of EQGs rejuvenate, but the rejuvenating fraction drops quickly at $z\leq 2$. By $z=0$ it is difficult to distinguish the descendants of EQGs vs. non-EQGs.

We present deep Hubble Space Telescope (HST) photometry of ten targets from Treasury Program GO-14734, including six confirmed ultra-faint dwarf galaxies (UFDs), three UFD candidates, and one likely globular cluster. Six of these targets are satellites of, or have interacted with, the Large Magellanic Cloud (LMC). We determine their structural parameters using a maximum-likelihood technique. Using our newly derived half-light radius ($r_h$) and $V$-band magnitude ($M_V$) values in addition to literature values for other UFDs, we find that UFDs associated with the LMC do not show any systematic differences from Milky Way UFDs in the magnitude-size plane. Additionally, we convert simulated UFD properties from the literature into the $M_V-r_h$ observational space to examine the abilities of current dark matter (DM) and baryonic simulations to reproduce observed UFDs. Some of these simulations adopt alternative DM models, thus allowing us to also explore whether the $M_V-r_h$ plane could be used to constrain the nature of DM. We find no differences in the magnitude-size plane between UFDs simulated with cold, warm, and self-interacting dark matter, but note that the sample of UFDs simulated with alternative DM models is quite limited at present. As more deep, wide-field survey data become available, we will have further opportunities to discover and characterize these ultra-faint stellar systems and the greater low surface-brightness universe.

Quasars at redshifts $z>6$ are an excellent probe of the formation and evolution of supermassive black holes in the early Universe. The population of radio-luminous quasars is of particular interest, as such quasars could potentially be used to study the neutral intergalactic medium during cosmic reionisation via H$\,$I 21$\,$cm absorption studies. However, the lack of deep radio observations of $z>6$ quasars leaves the population poorly constrained, and suitable candidates for an H$\,$I 21$\,$cm absorption study have yet to be found. In this work, we present Jansky Very Large Array (VLA) 1$-$2 GHz radio continuum observations of 138 quasars at redshifts $6.0 \leq z<7.6$. We detect the radio continuum emission of the $z=6.1$ quasar J1034-1425, with a 1.6 GHz flux density of $170\pm 36\,\mu$Jy. This quasar is radio-quiet with radio-loudness, $R \equiv f_{5\text{~GHz}}/f_{\nu,\text{4400 A}} = 2.4\pm0.5$. In addition, we detect 7 other quasars at z>6, which have previously been characterised in the literature at these frequencies. Using the full sample, we estimate the radio-loud fraction to be $3.8^{+6.2}_{-2.4}\%$, where the uncertainties are 95% confidence intervals. This is lower than recent estimates of the radio-loud fraction in the literature, but is still marginally consistent with no redshift evolution of the radio-loud fraction. We explore the undetected quasar population by stacking their continuum images at their optical positions and obtain a median stacked flux density of $13.8\pm 3.9~\mu$Jy and luminosity of $\log{L_{5~\mathrm{GHz}}/(\mathrm{W~Hz}^{-1})}=24.2\pm0.1$.

Reconstructions of the paleoclimate indicate that ancient climatic fluctuations on Earth are often correlated with variations in its orbital elements. However, the chaos inherent in the solar system's orbital evolution prevents numerical simulations from confidently predicting Earth's past orbital evolution beyond 50-100 Myrs. Gravitational interactions among the Sun's planets and asteroids are believed to set this limiting time horizon, but most prior works approximate the solar system as an isolated system and neglect our surrounding Galaxy. Here we present simulations that include the Sun's nearby stellar population, and we find that close-passing field stars alter our entire planetary system's orbital evolution via their gravitational perturbations on the giant planets. This shortens the timespan over which Earth's orbital evolution can be definitively known by a further ~10%. In particular, in simulations that include an exceptionally close passage of the Sun-like star HD 7977 2.8 Myrs ago, new sequences of Earth's orbital evolution become possible in epochs before ~50 Myrs ago, which includes the Paleocene-Eocene Thermal Maximum. Thus, simulations predicting Earth's past orbital evolution before ~50 Myrs ago must consider the additional uncertainty from passing stars, which can open new regimes of past orbital evolution not seen in previous modeling efforts.

The compact object in quasar 3C 186 is one of the most promising recoiling black-hole candidates, exhibiting both an astrometric displacement between the quasar and the host galaxy as well as a spectroscopic shift between broad and narrow lines. 3C 186 also presents a radio jet which, when projected onto the plane of the sky, appears to be perpendicular to the quasar/galaxy displacement. Assuming a gravitational-wave kick is indeed responsible for the properties of 3C 186 and using state-of-the-art relativistic modeling, we show that current observations allow for exquisite modeling of the recoiling black hole. Most notably, we find that the kick velocity, the black-hole spin, and the line of sight are almost collinear and the former appear perpendicular to each other only because of a strong projection effect. The targeted configuration requires substantial fine-tuning: while there exists a region in the black-hole binary parameter space that is compatible with 3C 186, the observed system appears to be a rare occurrence. Using archival radio observations, we explore different strategies that could potentially confirm or rule out our interpretation. In particular, we develop two observational tests that rely on the brightness ratio between the approaching and receding jet as well as the asymmetry of the jet lobes. While the available radio data provide loose constraints, deeper observations have the unique potential of unveiling the nature of 3C 186.

Stellar-driven galactic winds regulate the mass and energy content of star-forming galaxies. Emission- and absorption-line spectroscopy shows that these outflows are multiphase and comprised of dense gas clouds embedded in much hotter winds. Explaining the presence of cold gas in such environments is a challenging endeavour that requires numerical modelling. In this paper we report a set of 3D hydrodynamical simulations of supersonic winds interacting with radiative and adiabatic multicloud systems, in which clouds are placed along a stream and separated by different distances. As a complement to previous adiabatic, subsonic studies, we demonstrate that hydrodynamic shielding is also triggered in supersonic winds and operates differently in adiabatic and radiative regimes. We find that the condensation of warm, mixed gas in between clouds facilitates hydrodynamic shielding by replenishing dense gas along the stream, provided that its cooling length is shorter than the cloud radius. Small separation distances between clouds also favour hydrodynamic shielding by reducing drag forces and the extent of the mixing region around the clouds. In contrast, large separation distances promote mixing and dense gas destruction via dynamical instabilities. The transition between shielding and no-shielding scenarios across different cloud separation distances is smooth in radiative supersonic models, as opposed to their adiabatic counterparts for which clouds need to be in close proximity. Overall, hydrodynamic shielding and re-condensation are effective mechanisms for preserving cold gas in multiphase flows for several cloud-crushing times, and thus can help understand cold gas survival in galactic winds.

The existence of cosmic dark matter and neutrino properties are long-standing problems in cosmology and particle physics. These problems have been investigated by using radiation detectors. We will discuss the application of inorganic crystal scintillators to studies on dark matter and neutrino properties. A large volume and high-purity inorganic crystal is a promising detector for investigating dark matter and neutrino.

Noble gases provide tracers of cosmic provenance that are accessible to a future Uranus Atmospheric Probe. Argon and krypton are expected to be well-mixed on Uranus with respect to H$_2$ and He, although condensation at the winter pole may be possible. The Ar/H$_2$ and Ar/Kr ratios address whether the materials accreted by Uranus resembled the extremely cold materials accreted by Jupiter's atmosphere, or whether they were warmer like comet 67P/Churyumov-Gerasimenko, or whether Uranus is like neither. Xenon condenses as an ice, probably on methane ice, in Uranus's upper troposphere. Condensation may complicate interpretation of Xe/H$_2$, but it also presents an opportunity to collect concentrated xenon samples suitable for measuring isotopes. Solar System Xe tracks three distinct nucleosynthetic xenon reservoirs, one evident in the Sun and in chondritic meteorites, a second in refractory presolar grains, and a third evident in comet 67P/C-G and in Earth's air. The first and third reservoirs appear to have been captured from different clouds of gas. The two gases do not appear to have been well-mixed; moreover, the high $^{129}$Xe/$^{132}$Xe ratio in 67P/C-G implies that the gas was captured before the initial nucleosynthetic complement of $^{129}$I (15.7 Myr half-life) had decayed. Xenon's isotopic peculiarities, if seen in Uranus, could usefully upset our understanding of planetary origins. Krypton's isotopic anomalies are more subtle and may prove hard to measure. There is a slight chance that neon and helium fractionations can be used to constrain how Uranus acquired its nebular envelope.

We present a new technique to identify associations of HI emission in the Magellanic Stream (MS) and ultraviolet (UV) absorbers from 92 QSO sight lines near the MS. We quantify the level of associations of individual HI elements to the main HI body of the Stream using Wasserstein distance-based models, and derive characteristic spatial and kinematic distances of the HI emission in the MS. With the emission-based model, we further develop a comparison metric, which identifies the dominant associations of individual UV absorbers with respective to the MS and nearby galaxies. For ionized gas associated with the MS probed by CII, CIV, SiII, SiIII, SiIV, we find that the ion column densities are generally $\sim$0.5 dex higher than those that are not associated, and that the gas is more ionized toward the tail of the MS as indicated by the spatial trend of the CII/CIV ratios. For nearby galaxies, we identify potential new absorbers associated with the CGM of M33 and NGC300, and affirm the associations of absorbers with IC1613 and WLM. For M31, we find the previously identified gradient in column densities as a function of impact parameter, and that absorbers with higher column densities beyond M31's virial radius are more likely to be associated with the MS. Our analysis of absorbers associated with the Magellanic Clouds reveals the presence of continuous and blended diffuse ionized gas between the Stream and the Clouds. Our technique can be applied to future applications of identifying associations within physically complex gaseous structures.

The main aim of this work is to explore the possibility that cold dark matter (CDM) and early dark energy (EDE) can be described by canonical scalar fields that are coupled at the level of its conservation equations. The formalism covers dynamical aspects at the background and linear perturbation levels for an arbitrary coupling function, followed by an example of it. We emphasize the impact of this model on the Matter Power Spectrum and the Cosmic Microwave Background (CMB) spectra, with or without direct interaction. Our findings indicate that the presence of a scalar field can partially counteract the known effects of the other, opening the possibility to avoid some undesired aspects, such as the increase in $\Omega_{m}$ that usually is needed in the case of a purely EDE scalar field scenario, in order to fit the CMB spectra. This opens up the possibility to analyzing whether the interaction can help to ameliorate the cosmological tensions.

This book chapter explores key aspects of neutron stars, pulsar glitches, tidal deformability, fast pulsars, the equation of state, and strange quark matter stars. Challenges in directly measuring neutron star radius have led to reliance on spectroscopic and timing techniques, with uncertainties addressed through careful source selection and theoretical modeling. Pulsar glitches reveal insights into the equation of state through angular momentum transfer within the neutron star. Tidal deformability is crucial in gravitational-wave astronomy, exemplified by the GW170817 event. Fast pulsars, instrumental in astrophysical testing, are classified into ordinary pulsars, millisecond pulsars, and magnetars. The EOS is vital for understanding neutron star internal structure, explored through various models. The chapter delves into the theoretical framework for rotating neutron stars, addressing uniform and differential rotation scenarios and their impacts on mass and radius. Additionally, the intriguing concept of quark stars and strange dwarfs is investigated. The various topics discussed in this book chapter contribute to a broader understanding of dense matter physics, astrophysical phenomena, and the potential for transformative discoveries through advanced observational techniques and technologies like gravitational wave detectors, radio telescopes, and X-ray telescopes.

We present a comprehensive catalog of 2824 RR Lyrae stars (RRLs) residing in 115 Galactic globular clusters (GCs). Our catalog includes 1594 fundamental-mode (RRab), 824 first-overtone (RRc), and 28 double-mode (RRd) RRLs, as well as 378 RRLs of an unknown pulsation mode. We cross-matched 481349 RRLs reported in the third data release (DR3) of the ESA mission Gaia and the literature to 170 known GCs. Membership probabilities were computed as the products of a position and shape-dependent prior and a likelihood was computed using parallaxes, proper motions, and, where available, radial velocities from Gaia. Membership likelihoods of RRLs were computed by comparing cluster average parameters based on known member stars and the cross-matched RRLs. We determined empirical RRL instability strip (IS) boundaries based on our catalog and detected three new cluster RRLs inside this region via their excess Gaia G-band photometric uncertainties. We find that 77% of RRLs in GCs are included in the Gaia DR3 Specific Object Study, and 82% were classified as RRLs by the Gaia DR3 classifier, with the majority of the missing sources being located at the crowded GC centers. Surprisingly, we find that 25% of cluster member stars located within the empirical IS are not RRLs and appear to be non-variable. Additionally, we find that 80% of RRab, 84% of RRc, and 100% of the RRd stars are located within theoretical IS boundaries predicted using MESA models with Z = 0.0003, M = 0.7 (M_\odot), and Y = 0.290. Unexpectedly, a higher Y = 0.357 is required to fully match the location of RRc stars, and lower Y = 0.220 is needed to match the location of RRab stars. Lastly, our catalog does not exhibit an Oosterhoff dichotomy, with at least 22 GCs located inside the Oosterhoff "gap," which is close to the mode of the distribution of mean RRL periods in GCs.

To create early warning capabilities for upcoming Space Weather disturbances, we have selected a dataset of 61 emerging active regions, which allows us to identify characteristic features in the evolution of acoustic power density to predict continuum intensity emergence. For our study, we have utilized Doppler shift and continuum intensity observations from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The local tracking of 30.66 x 30.66-degree patches in the vicinity of active regions allowed us to trace the evolution of active regions starting from the pre-emergence state. We have developed a machine learning model to capture the acoustic power flux density variations associated with upcoming magnetic flux emergence. The trained Long Short-Term Memory (LSTM) model is able to predict 5 hours ahead whether, in a given area of the solar surface, continuum intensity values will decrease. The performed study allows us to investigate the potential of the machine learning approach to predict the emergence of active regions using acoustic power maps as input.

Geostatistical methods are powerful tools for understanding the spatial structure of the metallicity distribution of galaxies, and enable construction of accurate predictive models of the 2D metallicity distribution. However, so far these methods have only been applied to very high spatial resolution metallicity maps, leaving it uncertain if they will work on lower quality data. In this study, we apply geostatistical techniques to high-resolution spectroscopic maps of three local galaxies convolved to eight different spatial resolutions ranging from ~40pc to ~1 kpc per pixel. We fit a geostatistical model to the data at all resolutions, and find that for metallicity maps where small scale structure is visible by eye (with > ~10 resolution elements per Re), all parameters, including the metallicity correlation scale, can be recovered accurately. At all resolutions tested, we find that point metallicity predictions from such a geostatistical model outperform a circularly symmetric metallicity gradient model. We also explore dependence on the number of data points, and find that N > ~100 spatially resolved metallicity values are sufficient to train a geostatistical model that yields more accurate metallicity predictions than a radial gradient model. Finally, we investigate the potential detrimental effects of having spaxels smaller than an individual Hii region by repeating our analysis with metallicities integrated over Hii regions. We see that spaxel-based measurements have more noise, as expected, but the underlying spatial metallicity distribution can be recovered regardless of whether spaxels or integrated regions are used.

Recent JWST observations with superb angular resolution have revealed the existence of clumpy galaxies at high redshift through the detection of rest-frame optical emission lines. We use the FirstLight simulation to study the properties of (sub-)galactic clumps that are bright in [OIII] 5007$\mathrm{\mathring{A}}$ line with flux greater than $\sim 10^{-18} \, {\rm erg\, s^{-1}\, cm^{-2}}$, to be detected by JWST. For 62 simulated galaxies that have stellar masses of $(0.5-6) \times 10^{10} \, M_\odot$ at $z=5$, we find clumps in 1828 snapshots in the redshift range $z = 9.5-5.5$. The clumps are identified by the surface density of star formation rate. About one-tenth of the snapshots show the existence of clumpy systems with two or more components. Most of the clumps are formed by mergers and can be characterized by their ages; central clumps dominated by stellar populations older than 50 Myr, and off-centered clumps dominated by younger stellar populations with specific star formation rates of $\sim 50 \, {\rm Gyr^{-1}}$. The latter type of young clumps is formed from gas debris in the tidal tails of major mergers with baryonic mass ratios of $1 \leq q < 4$. The merger-induced clumps are short-lived, and merge within a dynamical time of several tens million years. The number density of the clumpy systems is estimated to be $\sim 10^{-5}\, {\rm cMpc^{-3}}$, which is large enough to be detected in recent JWST surveys.

Radio emission from pulsars can be used to map out their distances through dispersion measure (DM), which quantifies the amount of radio pulse dispersion. However, this method relies on accurately modeling the free electron density in the line of sight. Here, we present a detailed study of the multi-wavelength emission from PSR J1720-0534, a black widow compact binary millisecond pulsar discovered in 2021, which the latest electron density model of the Galaxy (YMW16; Yao et al. 2017) places at only 191 pc. We obtained and analyzed deep multi-wavelength observations in the $\gamma$-ray (Fermi-LAT, 2008-2022), optical (LCO, 2.7-h), near-infrared (NOT, 3.5-h) and X-ray (Swift-XRT, 10 ksec) bands. We found no significant detection of $\gamma$-ray, optical, near-infrared, or X-ray counterparts around the radio-timing position of PSR J1720-0534, which we thus nickname 'the invisible black widow'. Employing the most constraining near-infrared limit ($J>23.4$ mag), we established a lower limit on the source distance, $d>1.1$ kpc, assuming conservative properties for the black widow companion star. This distance lower limit differs drastically (by a factor of more than five) from the YMW16 DM distance estimate. We attribute this difference to the inclusion in the YMW16 model of a large and dense component towards the North Polar Spur. Considering our results and recent parallax distances to other pulsars in this direction, we argue that such a local and large component in the electron density model of the Galaxy is unnecessary.

Asgard/NOTT (previously Hi-5) is a European Research Council (ERC)-funded project hosted at KU Leuven and a new visitor instrument for the Very Large Telescope Interferometer (VLTI). Its primary goal is to image the snow line region around young stars using nulling interferometry in the L-band (3.5 to 4.0)$\mu$m, where the contrast between exoplanets and their host stars is advantageous. The breakthrough is the use of a photonic beam combiner, which only recently allowed the required theoretical raw contrast of $10^{-3}$ in this spectral range. Nulling interferometry observations of exoplanets also require a high degree of balancing between the four pupils of the VLTI in terms of intensity, phase, and polarization. The injection into the beam combiner and the requirements of nulling interferometry are driving the design of the warm optics and the injection system. The optical design up to the beam combiner is presented. It offers a technical solution to efficiently couple the light from the VLTI into the beam combiner. During the coupling, the objective is to limit throughput losses to 5% of the best expected efficiency for the injection. To achieve this, a list of different loss sources is considered with their respective impact on the injection efficiency. Solutions are also proposed to meet the requirements on beam balancing for intensity, phase, and polarization. The different properties of the design are listed, including the optics used, their alignment and tolerances, and their impact on the instrumental performances in terms of throughput and null depth. The performance evaluation gives an expected throughput loss of less than <6.4% of the best efficiency for the injection and a null depth of $\sim2.10^{-3}$, mainly from optical path delay errors outside the scope of this work.

The age, evolution, and chemical properties of the Galactic disk can be effectively ascertained using open clusters. Within the large program Stellar Populations Astrophysics at the Telescopio Nazionale Galileo, we specifically focused on stars in open clusters, to investigate various astrophysical topics, from the chemical content of very young systems to the abundance patterns of lesser studied intermediate-age and old open clusters. We investigate the astrophysically interesting element fluorine (F), which has an uncertain and intriguing cosmic origin. We also determine the abundance of cerium (Ce), as F abundance is expected to correlate with the s-process elements. High-resolution near-infrared spectra were obtained using the GIANO-B spectrograph. The Python version of Spectroscopy Made Easy (PySME), was used to derive atmospheric parameters and abundances. The stellar parameters were determined using OH, CN, and CO molecular lines along with Fe I lines. This paper presents the first F Galactic radial abundance gradient. Our results are also compared with literature estimates and with Galactic chemical evolution models that have been generated using different F production channels. Our results indicate a constant, solar pattern in the [F/Fe] ratios across clusters of different ages, supporting the latest findings that fluorine levels do not exhibit any secondary behavior for stars with solar or above-solar metallicity. By comparing our sample stars with the predictions of Galactic chemical evolution models, we came to the conclusion that both asymptotic giant branch stars and massive stars, including a fraction of fast rotators that increase with decreasing metallicity, are needed to explain the cosmic origin of F.

Recent observations of galaxy mergers inside galaxy cluster environments report high star formation rates in the ejected tidal tails, which point towards currently developing tidal dwarf galaxies. We test whether these dwarf objects could get stripped from the galaxy potential by the galaxy cluster and thus populate it with dwarf galaxies. To this end, we perform three high-resolution hydrodynamical simulations of mergers between spiral galaxies in a cluster environment, varying the initial orbit of the infalling galaxies with respect to the cluster center. We demonstrate that cluster environments are indeed capable of stripping tidal dwarf galaxies from the host potential in all tested setups. In the three orbit scenarios, we find 3, 7, and 8 tidal dwarf galaxies per merger, respectively, which survive longer than 1 Gyr after the merger event. Exposed to ram pressure, these gas dominated dwarf galaxies exhibit high star formation rates while also losing gas to the environment. Experiencing a strong headwind due to their motion through the intracluster medium, they quickly lose momentum and start spiraling towards the cluster center, reaching distances on the order of ~Mpc from their progenitor. About 4 Gyr after the merger event, we still find several intact dwarf galaxies, demonstrating that such objects can prevail for a significant fraction of the Hubble time. Comparing their contribution to the observed galaxy mass function in clusters, our results indicate that ~30% of dwarf galaxies in clusters could have been formed by stripping from galaxy mergers.

High resolution optical spectra (R = 60 000) of the LBV star P Cyg beyond outburst were obtained on the 6-meter BTA telescope in the wavelength range 477-780 nm. We perform a detailed identification of different types lines (photospheric absorptions, permitted and forbidden emissions, components of lines with P Cyg type profiles), and studied the variability of their profiles and radial velocities. The average radial velocity from positions of forbidden emissions ([NII] 5754.64, [FeII] 5261.62, [FeII] 7155.14 and [NiII] 7377.83 \r{A}) is accepted as the system velocity Vsys=$-34\pm1.4$ km/s. About a dozen photospheric absorptions of CNO triad ions and SiIII are found, their stable position, Vr(abs)=$-73.8$ km/s, shifted relative to at $-40$ km/s, indicates that these absorbtions are formed in the pseudophotosphere region. The high-excitation emissions ([OI] 5577, 6300, 6363 \r{A}, [OIII] 4959 and 5007 \r{A}, as well as HeII 4686 \r{A}) are absent in the spectra. The radial velocity Vr(DIBs)=$-11.8$ km/s according to the position of numerous DIBs is consistent with the position of the interstellar components of the D-lines NaI and KI forming in the galactic Perseus arm. A color excess E(B-V)=0.34+/-0.03 mag and interstellar absorption Av=1.09 mag were determined by measurements of equivalent widths of nine DIBs.

A number of pulsars are known to have profile evolution on timescales of months, often correlated with spin-down rate changes. Here, we present the first result from 3 years of monitoring observations from MeerKAT as part of the Thousand Pulsar Array programme. This programme obtains high-fidelity pulse profiles for $\sim$ 500 pulsars, which enabled the detection of subtle changes in seven sources not previously known to exhibit long-term profile evolution. A 2D Gaussian convolution is used to highlight correlated emission variability in both the pulse phase and observing epoch direction. Simulations show that for one additional source the observed profile variability is likely to originate from stochastic single-pulse shape variability (jitter). We find that it is common for long-term profile variability to be associated with changes in polarization fractions, but not with polarisation position angle (PA) changes. PA changes are expected if emission height changes or precession is responsible for the profile variability. PSR J1741$-$3927 is the only pulsar in our sample that shows correlated PA variability, and this is associated with orthogonal polarization mode activity. For the six %the rest, without correlated PA variability, other pulsars limits on possible emission height changes and impact angle changes are derived. These limits are consistent with the small changes in the total intensity profile shape. None of the sources show detectable spin-down variability correlated with the emission changes, which are thought to be driven by magnetospheric current fluctuations. Therefore the absence of correlated spin-down rate variability allows upper limits to be placed on changes in the magnetospheric charge density.

Dynamical masses of young planets aged between 10 and 200 Myr detected in imaging play a crucial role in shaping models of giant planet formation. Regrettably, only a few such objects possess these characteristics. Furthermore, the evolutionary pattern of young sub-stellar companions in near-infrared colour-magnitude diagrams might diverge from free-floating objects, possibly due to differing formation processes. The recent identification of a giant planet around AF Lep, part of the beta Pic moving group (BPMG), encouraged us to re-examine these points. We considered updated dynamical masses and luminosities for the sub-stellar objects in the BPMG. In addition, we compared the properties of sub-stellar companions and free-floating objects in the BPMG and other young associations remapping the positions of the objects in the colour-magnitude diagram into a dustiness-temperature plane. We found that cold-start evolutionary models do not reproduce the mass-luminosity relation for sub-stellar companions in the BPMG. This aligns rather closely with predictions from 'hot start' scenarios and is consistent with recent planet formation models. We obtain rather good agreement with masses from photometry and the remapping approach compared to actual dynamical masses. We also found a strong suggestion that the near-infrared colour-magnitude diagram for young companions is different from that of free-floating objects belonging to the same young associations. If confirmed by further data, this last result would imply that cloud settling - which likely causes the transition between L and T spectral type - occurs at a lower effective temperature in young companions than in free-floating objects. This might tentatively be explained with a different chemical composition.

KM3NeT/ARCA is a Cherenkov neutrino telescope under construction in the Mediterranean sea, optimised for the detection of astrophysical neutrinos with energies above $\sim$1~TeV. In this work, using Monte Carlo simulations including all-flavour neutrinos, the integrated and differential sensitivities for KM3NeT/ARCA are presented considering the case of a diffuse neutrino flux as well as extended and point-like neutrino sources. This analysis is applied to Starburst Galaxies demonstrating that the detector has the capability of tracing TeV neutrinos from these sources. Remarkably, after eight years, a hard power-law spectrum from the nearby Small Magellanic Cloud can be constrained. The sensitivity and discovery potential for NGC 1068 is also evaluated showing that KM3NeT/ARCA will discriminate between different astrophysical components of the measured neutrino flux after 3 years of data taking.

The gaseous envelope of an accreting rocky planet becomes hot enough to sublimate silicates and other refractory minerals. % aims heading (mandatory) For this work, we studied the effect of the resulting envelope enrichment with a heavy vapor species on the composition and temperature of the envelope. For simplification, we used the gas-phase molecule SiO to represent the sublimation of silicate material. We solved the equilibrium structure equations in 1D for planets in the mass range of $0.1$ to $3\,M_\oplus$. The convective stability criterion was extended to take the stabilizing effect of the condensation of SiO clouds into account. We assumed that the envelope is both in hydrostatic equilibrium and in vapor equilibrium with the underlying magma ocean. This means that pebbles do not undergo sublimation in the envelope and therefore survive until they plunge into the magma ocean. We find that the emergence of an inner radiative region, where SiO condensation suppresses convection, increases the pressure and temperature in the inner envelope compared to pure H$_2$/He envelopes once $M_\mathrm{pl} \gtrsim 0.3\,M_\oplus$. For $M_\mathrm{pl}>0.75\,M_\oplus$, the temperature and pressure close to the surface reach the supercritical point of SiO. The amount of SiO stored in the envelope is lower than the total planet mass for low mass planets. However, for $M_\mathrm{pl}>2.0\,M_\oplus$, all accreted pebble material must contribute to maintain the vapor equilibrium in the envelope. Therefore, the non-vapor mass of the planet ceases to increase beyond this threshold. Overall, our vapor equilibrium model of the planetary envelope allows for direct core growth by pebble accretion up to much higher masses than previously thought.

A six-night optical turbulence monitoring campaign has been carried at Cerro Paranal observatory in February and March, 2023 to facilitate the development and characterisation of two novel atmospheric site monitoring instruments - the ring-image next generation scintillation sensor (RINGSS) and 24-hour Shack Hartmann image motion monitor (24hSHIMM) in the context of providing optical turbulence monitoring support for upcoming 20-40m telescopes. Alongside these two instruments, the well-characterised Stereo-SCIDAR and 2016-MASS-DIMM were operated throughout the campaign to provide data for comparison. All instruments obtain estimates of optical turbulence profiles through statistical analysis of intensity and wavefront angle-of-arrival fluctuations from observations of stars. Contemporaneous measurements of the integrated turbulence parameters are compared and the ratios, bias, unbiased root mean square error and correlation of results from each instrument assessed. Strong agreement was observed in measurements of seeing, free atmosphere seeing and coherence time. Less correlation is seen for isoplanatic angle, although the median values agree well. Median turbulence parameters are further compared against long-term monitoring data from Paranal instruments. Profiles from the three small-telescope instruments are compared with the 100-layer profile from the stereo-SCIDAR. It is found that the RINGSS and SHIMM offer improved accuracy in characterisation of the vertical optical turbulence profile over the MASS-DIMM. Finally, the first results of continuous optical turbulence monitoring at Paranal are presented which show a strong diurnal variation and predictable trend in the seeing. A value of 2.65" is found for the median daytime seeing.

Alfv\'enic fluctuations, as modelled by the non-linear interactions of Alfv\'en waves of various scales, are seen to dominate solar wind turbulence. However, there is also a non-negligible component of non-Alfv\'enic fluctuations. The Els\"asser formalism, which is central to the study of Alfv\'enic turbulence due to its ability to differentiate between parallel and anti-parallel Alfv\'en waves, cannot strictly separate wavemodes in the presence of compressive magnetoacoustic waves. In this study, we analyse the deviations generated in the Els\"asser formalism as density fluctuations are naturally generated through the propagation of a linearly polarised Alfv\'en wave. The study was performed in the context of a coronal mass ejection (CME) propagating through the solar wind, which enables the creation of two solar wind regimes, pristine wind and a shocked CME sheath, where the Els\"asser formalism can be evaluated. In these two regimes we studied the deviations of the Els\"asser formalism in separating parallel and anti-parallel components of Alfv\'enic solar wind perturbations generated by small-amplitude density fluctuations. We used an ideal 2.5D magnetohydrodynamic (MHD) model with an adiabatic equation of state. An Alfv\'en pump wave was injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components. This wave subsequently generates density fluctuations through the ponderomotive force. A CME was injected by inserting a flux-rope modelled as a magnetic island into the quasi-steady solar wind. The presence of density perturbations creates an approximately 10% deviation in the Els\"asser variables and reflection coefficient for the Alfv\'en waves as well as a deviation of approximately 0.1 in the cross helicity in regions containing both parallel and anti-parallel fluctuations.

The McNish and Lincoln (ML) method, introduced in 1949, was one of the first attempts to produce mid-term forecasts of solar activity, up to 12 months ahead. However, it has been poorly described and evaluated in the past literature, in particular its actual operational implementation by NOAA. Here, we reconstruct the exact formulation of the method, as it was applied since the early 1970s, and we provide a full mathematical derivation of the prediction errors. For bench-marking the method, we also produce monthly predictions over the past 190 years, from 1833 (Cycle 8) to 2023 (Cycle 25), and develop statistics of the differences between the predictions and the observed 13-month smoothed sunspot number (SSN) time series, according to the phase in the solar cycle. Our analysis shows that the ML method is heavily constrained because it is primarily based on the mean of all past cycles, which imposes a fixed amplitude and length and suffers from a temporal smearing that grows towards the end of the solar cycle. We find that predictions are completely unreliable in the first 12 months of the cycle, and over the last two years preceding the ending minimum (around 130 months), and beyond this minimum. By contrast, in the course of the cycle (months 18 to 65), ML predictions prove to be reliable over a time range of up to 50 months (4.2 years), thus much longer than the 12-month conventional range used so far. However, we find that predictions then suffer from systematic under-(over-)estimates for cycles that have a higher (lower) amplitude than the base mean cycle. Overall, we conclude that although the ML method provides valid prediction errors, it suffers from strong limitations, with very little room for improvement, as it indifferently merges all past cycles into a single fixed statistics.

Neutrino evolution, of great importance in environments such as neutron star mergers (NSMs) because of their impact on explosive nucleosynthesis, is still poorly understood due to the high complexity and variety of possible flavor conversion mechanisms. In this study, we focus on so-called "fast flavor oscillations", which can occur on timescales of nanoseconds and are connected to the existence of a crossing between the angular distributions of electron (anti)neutrinos. Based on the neutrino radiation field drawn from a three dimensional neutron star merger simulation, we use an extension of the two-moment formalism of neutrino quantum kinetics, and perform a linear stability analysis to determine the characteristics of fast flavor instabilities across the simulation. We compare the results to local (centimeter-scale) three-dimensional two-flavor simulations using either a moment method or a particle-in-cell architecture. We get generally good agreement in the instability growth rate and typical instability lengthscale, although the imperfections of the closure used in moment methods remain to be better understood.

Aims. We explore different scenarios to explain the chemical difference found in the remarkable giant-giant binary system HD 138202 + CD-30 12303. For the first time, we suggest how to distinguish these scenarios by taking advantage of the extensive convective envelopes of giant stars. Methods. We carried out a high-precision determination of stellar parameters and abundances by applying a full line-by-line differential analysis on GHOST high-resolution spectra. Results. We found a significant chemical difference between the two stars (0.08 dex), which is largely unexpected considering the insensitivity of giant stars to planetary ingestion and diffusion effects. We tested the possibility of engulfment events by using several different combinations of stellar mass, ingested mass, metallicity of the engulfed object and different convective envelopes. However, the planetary ingestion scenario does not seem to explain the observed differences. For the first time, we distinguished the source of chemical differences using a giant-giant binary system. By ruling out other possible scenarios such as planet formation and evolutionary effects between the two stars, we suggest that primordial inhomogeneities might explain the observed differences. This remarkable result implies that the metallicity differences that were observed in at least some main-sequence binary systems might be related to primordial inhomogeneities rather than engulfment events. We also discuss the important implications of finding primordial inhomogeneities, which affect chemical tagging and other fields such as planet formation. We strongly encourage the use of giant-giant pairs. They are a relevant complement to main-sequence pairs for determining the origin of the observed chemical differences in multiple systems. [abridged]

Magnetars are neutron stars with extremely high magnetic fields that exhibit various X-ray phenomena such as sporadic sub-second bursts, long-term persistent flux enhancements, and variable rates of rotation period change. In 2020, a fast radio burst (FRB), akin to cosmological millisecond-duration radio bursts, was detected from the Galactic magnetar SGR 1935+2154, confirming the long-suspected association between some FRBs and magnetars. However, the mechanism for FRB generation in magnetars remains unclear. Here we report the X-ray discovery of an unprecedented double glitch in SGR 1935+2154 within a time interval of approximately nine hours, bracketing an FRB that occurred on October 14, 2022. Each glitch involved a significant increase in the magnetar's spin frequency, being among the largest abrupt changes in neutron star rotation ever observed. Between the glitches, the magnetar exhibited a rapid spin-down phase, accompanied by a profound increase and subsequent decline in its persistent X-ray emission and burst rate. We postulate that a strong, ephemeral, magnetospheric wind provides the torque that rapidly slows the star's rotation. The trigger for the first glitch couples the star's crust to its magnetosphere, enhances the various X-ray signals, and spawns the wind that alters magnetospheric conditions that might produce the FRB.

We investigate the first-order phase transition catalyzed by primordial black holes~(PBHs) in the early Universe. We find that super-horizon curvature perturbations generated in this scenario lead to the production of gravitational waves when the scalar modes re-enter the horizon. If PBHs with masses about $10^{-13}M_{\odot}$ constitute all dark matter, the first-order electroweak phase transition catalyzed by PBHs can explain the gravitational wave signal observed by pulsar timing array collaborations without the overproduction of PBHs.

Ultra-short period planets have orbital periods of less than one day. Since their masses and radii can be determined to a higher precision than long-period planets, they are the preferred targets to determine the density of planets which constrains their composition. The K2-106 system is particularly interesting because it contains two planets of nearly identical masses. One is a high density USP, the other is a low-density planet that has an orbital period of 13 days. Combining the Gaia DR3 results with new ESPRESSO data allows us to determine the masses and radii of the two planets more precisely than before. We find that the USP K2-106b has a density consistent with an Earth-like composition, and K2-106c is a low-density planet that presumably has an extended atmosphere. We measure a radius of Rp=1.676-0.037+0.037 REarth, a mass of Mp=7.80-0.70+0.71 MEarth and a density of rho=9.09-0.98+0.98 gcm-3 for K2-106b. For K2-106c, we derive Rp=2.84-0.08+0.10 REarth, Mp=7.3-2.4+2.5 MEarth, and a density of rho= 1.72-0.58+0.66 gcm-3. We finally discuss the possible structures of the two planets with respect to other low-mass planets.

The chemical evolution of protoplanetary discs is not fully understood, several factors influence the final distribution of disc material. One such factor are inward drifting and evaporating pebbles that enrich the inner disc with vapour. In particular, it is first enriched with water vapour, resulting in a low C/O ratio, before carbon-rich gas from the outer disc is transported inwards elevating the C/O ratio again. However, it is unclear how internal photoevaporation, which carries away gas and opens gaps that block inward drifting pebbles, affects the chemical composition of the disc. We aim to study these effects in discs around solar-like stars, where we especially focus on the C/O ratio and the water content. The simulations are carried out using a semi-analytical 1D disc model. Our code chemcomp includes viscous evolution and heating, pebble growth and drift, pebble evaporation and condensation, and a simple chemical partitioning model. We show that internal photoevaporation plays a major role in the (chemical) evolution of protoplanetary discs: As it opens a gap, inward drifting pebbles are stopped and cannot contribute to the volatile content any more. In addition, gas from the outer disc is carried away by photoevaporative winds. Consequently, the C/O ratio in the inner disc is low. In contrast, gaps opened by giant planets allow the gas to pass, resulting in an elevated C/O ratio, similar to viscous discs without internal photoevaporation. This will enable us to distinguish observationally between these two scenarios when measuring the C/O ratio, implying that we can infer the cause of gap structures in disc observations. In the case of a photoevaporative disc, we additionally find an elevated water content in the inner disc as the water vapour and ice undergo a cycle of evaporation/re-condensation, preventing its inward accretion onto the star.

We have searched for radio pulsations towards 49 Fermi Large Area Telescope (LAT) 1FGL Catalog $\gamma$-ray sources using the Green Bank Telescope at 350 MHz. We detected 18 millisecond pulsars (MSPs) in blind searches of the data; 10 of these were discoveries unique to our survey. Sixteen are binaries, with eight having short orbital periods $P_B < 1$ day. No radio pulsations from young pulsars were detected, although three targets are coincident with apparently radio-quiet $\gamma$-ray pulsars discovered in LAT data. Here, we give an overview of the survey and present radio and $\gamma$-ray timing results for the 10 MSPs discovered. These include the only isolated MSP discovered in our survey and six short-$P_B$ binary MSPs. Of these, three have very low-mass companions ($M_c$ $\ll$ 0.1M$_{\odot}$) and hence belong to the class of black widow pulsars. Two have more massive, non-degenerate companions with extensive radio eclipses and orbitally modulated X-ray emission consistent with the redback class. Significant $\gamma$-ray pulsations have been detected from nine of the discoveries. This survey and similar efforts suggest that the majority of Galactic $\gamma$-ray sources at high Galactic latitudes are either MSPs or relatively nearby non-recycled pulsars, with the latter having on average a much smaller radio/$\gamma$-ray beaming ratio as compared to MSPs. It also confirms that past surveys suffered from an observational bias against finding short-$P_B$ MSP systems.

The current major challenge to reconstruct the chronology of the Milky Way (MW) is the difficulty to derive precise stellar ages. CMD-fitting offers an alternative to individual age determinations to derive the star formation history (SFH). We present CMDft.Gaia and use it to analyse the CMD of the Gaia Catalogue of Nearby Stars (GCNS), which contains a census of the stars within 100 pc of the Sun. The result is an unprecedented detailed view of the evolution of the MW disk. The bulk of star formation started 11-10.5 Gyr ago at [Fe/H]~solar and continued with a slightly decreasing metallicity trend until 6 Gyr ago. Between 6-4 Gyr ago, a break in the age-metallicity distribution is observed, with 3 stellar populations with distinct metallicities (sub-solar, solar, and super-solar), possibly indicating some dramatic event in the Galaxy. Star formation resumed 4 Gyr ago with a bursty behaviour, metallicity near solar and higher average SFR. The derived metallicity distribution closely matches precise spectroscopic data, which also show stellar populations deviating from solar metallicity. Interestingly, our results reveal the presence of intermediate-age populations with both a metallicity typical of the thick disk and supersolar metallicity. Our many tests indicate that, with high precision Gaia photometric and distance data, CMDft.Gaia can achieve a precision ~10% and an accuracy better than 6% in the dating of even old stellar populations. The comparison with independent spectroscopic data shows that metallicity distributions are determined with high precision, without imposing a-priory metallicity information. This opens the door to obtaining detailed and robust information on the evolution of the stellar populations of the MW over cosmic time. As an example we provide an unprecedented detailed view of the age and metallicity distributions of the stars within 100 pc of the Sun.

Recent work suggested that the variation of the initial mass function (IMF) of stars depends on the physical conditions, notably, the metallicity and gas density. We investigated the properties of two clusters, namely the main cluster (MC) and the subcluster (SC), in the low-metallicity HII region Sh 2-209 (S209) based on recently derived IMFs. We tested three previously published correlations using previous observations: the top-heaviness of the IMF in dependence on metallicity, the half-mass radius, and the most massive star in dependence on the stellar mass of the embedded clusters. For this region, two different galactocentric distances, namely 10.5 kpc and 18 kpc, were considered, where an age-distance-degeneracy was found for the previously determined IMF to be consistent with other formulated metallicity and density dependent IMFs. The determined half-mass radius (0.080 +/- 0.005) pc and the embedded cluster density (0.2 +/- 0.1) 10^6 Msun pc^-3 for the MC with an age of 0.5 Myr in S209 assuming a galactocentric distance of 18 kpc support the assumption that a low-metallicity environment results in a denser cluster, which leads to a top-heavy IMF. Thus, all three tests are consistent with the previously published correlations. The results for S209 are placed in the context with the IMF determination within the metal-poor cluster in the star-forming region NGC 346 in the Small Magellanic Cloud.

The origin and nature of dark energy is one of the most significant challenges in modern science. This research aims to investigate dark energy on astrophysical scales and provide a cosmology-independent method to measure its equation-of-state parameter $w$. To accomplish this, we introduce the concept of a perfect fluid in any static, curved spacetime, and express the energy-momentum tensor of the perfect fluid in a general isotropic form, namely Weinberg's isotropic form. This enables us to define an equation-of-state parameter in a physical and global manner. Within this theoretical framework, we demonstrate that the energy-momentum tensor of dark energy on different scales can take the general isotropic form. Furthermore, we explore the SdS$_{w}$ spacetime and establish its connection with dark energy in cosmology through the equation-of-state parameter $w$. In the SdS$_{w}$ spacetime, a repulsive dark force can be induced by dark energy locally. We then apply the concept of the dark force to realistic astrophysical systems using the Poisson equation. Finally, we find that an anomaly in the Milky Way rotation curve can be quantitatively interpreted by the dark force. By fitting the galactic curve, we are able to obtain the value of the equation-of-state parameter of dark energy, independently of specific dark energy models.

We study a cosmological model in Rastall's theory of gravity in the framework of flat FLRW metric. We formulate the value of the Hubble parameter which contains two model parameters $ \alpha $ and $ j $. Employing the Markov Chain Monte Carlo (MCMC) sampling technique, we constrain the magnitude of the model parameters with their uncertainties. Moreover, we reconstruct the effective equation-of-state (EoS) parameter, which converges around the quintessence region. We perform a dynamical system analysis using the linearization technique to validate the results independently. Also, we discuss various physical properties of the model which shows the transition to acceleration and the violation of the Strong energy condition (SEC) in late times evolution. Finally, we conclude that our model mimics the behavior of a dark matter fluid during the past epoch and transitions into a quintessence dark energy model in later times.

We propose a new mechanism to produce axion dark matter from inflationary fluctuations. Quantum fluctuations during inflation are strengthened by a coupling of the axion kinetic term to the inflaton, which we parametrize as an effective curvature $\kappa$ in the axion equation of motion. A nonvanishing curvature breaks the scale invariance of the axion power spectrum, driving a quantum phase transition with $\kappa$ as the order parameter. The axion power spectrum is proportional to the inverse comoving horizon to the power of $\kappa$. For positive $\kappa$ the spectrum gets a red tilt, leading to an exponential enhancement of the axion abundance as the comoving horizon shrinks during inflation. This enhancement allows sufficient axion production to comprise the entire dark matter relic abundance despite the ultralight mass. Our mechanism predicts a significantly different parameter space from the usual misalignment mechanism. It allows for axion-like particle dark matter with a much lower decay constant and thus a larger coupling to Standard Model particles. Much of the parameter space can be probed by future experiments including haloscopes, nuclear clocks, and CMB-S4. We can also generate heavier QCD axion dark matter than the misalignment mechanism.

We constrain the neutrino-dark matter cross section using properties of the dark matter density profiles of Milky Way dwarf spheroidal galaxies. The constraint arises from core-collapse supernova neutrinos scattering on dark matter as a form of energy injection, allowing the transformation of the dark matter density profile from a cusped profile to a flatter profile. We assume $\mathrm{\Lambda}$CDM, collisionless and non-self-interacting dark matter, and by requiring that the dark matter cores do not overshoot constraints from stellar kinematics, we place an upper limit on the cross section of $\sigma_{\nu-\mathrm{DM}}(E_\nu{=}15 \, \mathrm{MeV}, m_\chi{=}1\;\mathrm{GeV}) \approx 3.2 \times 10^{-27} \, \mathrm{cm^2}$, which is stronger than existing ones by several orders of magnitude. Consideration of baryonic feedback or host galaxy effects on the dark matter profile can strengthen this constraint.

We calculated cross sections for the dielectronic recombination (DR) satellite lines of Fe XVII and benchmarked our predictions with experimental cross sections of Fe XVII resonances that were mono-energetically excited in an electron beam ion trap. We extend the benchmark to all resolved DR and direct electron-impact excitation (DE) channels in the experimental dataset, specifically the $n\geq4$ DR resonances of Fe XVII, complementing earlier investigations of $n=3$ channels. Our predictions overestimate by 20-25$\%$ the DR and DE absolute cross sections for the higher $n$ complexes when using the same methods as in previous works. However, we achieve agreement within $\sim$10$\%$ of the experimental results by an approach in which we "forward fold" the predicted cross sections with the spread of the electron-beam energy and the photon-energy resolution of our experiment. We then calculated rate coefficients from the experimental and theoretical cross sections, finding departures of $10-20\%$ from the rates found in the OPEN-ADAS atomic database.

Searches for dark matter with liquid xenon time projection chamber experiments have traditionally focused on the region of the parameter space that is characteristic of weakly interacting massive particles, ranging from a few GeV/$c^2$ to a few TeV/$c^2$. Models of dark matter with a mass much heavier than this are well motivated by early production mechanisms different from the standard thermal freeze-out, but they have generally been less explored experimentally. In this work, we present a re-analysis of the first science run (SR1) of the LZ experiment, with an exposure of $0.9$ tonne$\times$year, to search for ultraheavy particle dark matter. The signal topology consists of multiple energy deposits in the active region of the detector forming a straight line, from which the velocity of the incoming particle can be reconstructed on an event-by-event basis. Zero events with this topology were observed after applying the data selection calibrated on a simulated sample of signal-like events. New experimental constraints are derived, which rule out previously unexplored regions of the dark matter parameter space of spin-independent interactions beyond a mass of 10$^{17}$ GeV/$c^2$.

The axion-photon coupling allows the existence of a magnetically and electrically charged black hole (BH) solution endowed with a pseudo-scalar hair. For the Reissner-Nordstr\"om BH with a given total charge and mass, it is known that the quasinormal modes (QNMs) are independent of the mixture between the magnetic and electric charges due to the presence of electric-magnetic duality. We show that the BH with an axion hair breaks this degeneracy by realizing nontrivial QNMs that depend on the ratio between the magnetic and total charges. Thus, the upcoming observations of BH QNMs through gravitational waves offer an exciting possibility for probing the existence of both magnetic monopoles and the axion coupled to photons.

Flavor ergodicity implies that angular crossings are necessary and sufficient for fast instability.

Ultralight bosons with masses in the range from $\sim 10^{-22}$ eV to $\sim 1$ eV, are well-motivated, wave-like dark matter candidates. Particles on the lower-mass end are less explored in experiments due to their vanishingly small mass and weak coupling to the Standard Model. We propose to search for U(1)$_{B\!-\!L}$ gauge boson dark matter using a Torsion Pendulum Dual Oscillator (TorPeDO), a sensor originally designed to detect Newtonian gravitational field fluctuations with an enhanced differential torque sensitivity in a frequency band of $\sim 10^{-2}$-$10$ Hz. We describe the experiment setup of a modified TorPeDO sensor, equipped with four 5-kg end test masses (two made from beryllium and two from aluminium). We present the estimated sensitivity to an ultralight dark matter field coupled to baryon minus lepton ($B\!-\!L$) number, in a mass range of $\sim 10^{-17}$-$10^{-13}$ eV. The projected constraints on the coupling constant $g_{B\!-\!L} (\hbar c)^{-1/2}$ can reach $\sim 10^{-29}$ for a boson mass of $\sim 10^{-15}$ eV in the most sensitive frequency band.

Studies in Physics Education Research show that interdisciplinary approaches in education foster students' motivation, creativity, curiosity, and interest in physics. We discuss their features and potential role in bringing contemporary physics topics to high school, and how to use them to integrate formal educational programs. We make an explicit example of the use of storytelling and theatrical techniques to introduce secondary school students to black holes and gravitational waves topics. The activity has been designed by the Educational Division of the Physics Department at the University of Cagliari. Participants were 200 high-school students (17 to 19 years old) from five schools (scientific, humanities) in Sardinia. A measure of the efficacy in the use of artistic tools to communicate and teach the proposed subjects has been done utilizing a research questionnaire. We collected 76 answers. Results show that our methodology is useful to introduce students to contemporary physics themes, fostering their interest and learning of such contents. Students from humanities significantly appreciated more the use of poetry and artistic tools than their scientific peers. Finally, we discuss the potentiality of our approach in orientating students towards a STEAM (STEM and Arts) career.

Radiolarians are significant contributors to the oceanic primary productivity and the global silica cycle in the last 500 Myr. Their diversity throughout the Phanerozoic shows periodic fluctuations. We identify a possible abiotic candidate for driving these patterns which seems to potentially influence radiolarian diversity changes during this period at a significance level of $\sim 2.2 \sigma$. Our finding suggests a significant correlation between the origination of new radiolaria species and maximum excursions of the Solar system from the Galactic plane, where the magnetic shielding of cosmic rays is expected to be weaker. We connect the particularly strong radiolaria blooming during the Middle Triassic to the so-called Mesozoic dipole-low of the geomagnetic field, which was in its deepest state when radiolarias were blooming. According to the scenario, high-energy cosmic rays presumably implied particular damage to the DNA during the maximum excursions which may trigger large chromosomal abnormalities leading to the appearance of a large number of new genera and species during these periods.