Search

We assess the impact of quasi-stellar objects (QSOs) on the high-redshift (⁠|$z\gt 4$|⁠) intergalactic medium using Monte Carlo realizations of QSO populations and the He  |$\rm \scriptstyle III$| regions they generate, applied to the Sherwood–Relics simulations, allowing for uncertainties in the QSO luminosity function, its evolution, and QSO spectra and ages. While QSO luminosity functions based on optical–infrared selection are unable to reproduce the broadening H  |$\rm \scriptstyle I$| Ly  |$\alpha$| optical depth distributions at |$z\gt 5$|⁠ , much broader distributions are found for the higher numbers of QSOs based on X-ray selection, suggesting a large QSO contribution to the ultraviolet background at |$z\gt 5$| may offer an alternative to late reionization models to account for the broad H  |$\rm \scriptstyle I$| Ly  |$\alpha$| optical depth distributions. Realizations using QSOs based on the higher QSO counts also much better recover the measured pixel flux autocorrelation function at |$z\gt 5$|⁠. The He  |$\rm \scriptstyle III$| regions from QSO sources according to both types of luminosity function suppress the pixel flux power spectrum on small scales, |$k\gt 0.02\, \mathrm{s\, km^{-1}}$|⁠ , while enhancing it on larger, both by amounts of up to tens of per cent at |$z\gt 4$|⁠ , with the magnitude increasing with the intergalactic He  |$\rm \scriptstyle III$| filling factor and the boost in temperature within the He  |$\rm \scriptstyle III$| regions. [ABSTRACT FROM AUTHOR]

A pulsar's pulse profile gets broadened at low frequencies due to dispersion along the line of sight or due to multipath propagation. The dynamic nature of the interstellar medium makes both of these effects time-dependent and introduces slowly varying time delays in the measured times-of-arrival similar to those introduced by passing gravitational waves. In this article, we present an improved method to correct for such delays by obtaining unbiased dispersion measure (DM) measurements by using low-frequency estimates of the scattering parameters. We evaluate this method by comparing the obtained DM estimates with those, where scatter-broadening is ignored using simulated data. A bias is seen in the estimated DMs for simulated data with pulse-broadening with a larger variability for a data set with a variable frequency scaling index, |$\alpha$|⁠ , as compared to that assuming a Kolmogorov turbulence. Application of the proposed method removes this bias robustly for data with band averaged signal-to-noise ratio larger than 100. We report the measurements of the scatter-broadening time and |$\alpha$| from analysis of PSR J1643 |$-$| 1224, observed with upgraded Giant Metrewave Radio Telescope as part of the Indian Pulsar Timing Array experiment. These scattering parameters were found to vary with epoch and |$\alpha$| was different from that expected for Kolmogorov turbulence. Finally, we present the DM time-series after application of this technique to PSR J1643 |$-$| 1224. [ABSTRACT FROM AUTHOR]

High-ionization iron coronal lines (CLs) are a rare phenomenon observed in galaxy and quasi-stellar object spectra that are thought to be created by high-energy emission from active galactic nuclei and certain types of transients. In cases known as extreme coronal line emitting galaxies (ECLEs), these CLs are strong and fade away on a time-scale of years. The most likely progenitors of these variable CLs are tidal disruption events (TDEs), which produce sufficient high-energy emission to create and sustain the CLs over these time-scales. To test the possible connection between ECLEs and TDEs, we present the most complete variable ECLE rate calculation to date and compare the results to TDE rates from the literature. To achieve this, we search for ECLEs in the Sloan Digital Sky Survey (SDSS). We detect sufficiently strong CLs in 16 galaxies, more than doubling the number previously found in SDSS. Using follow-up spectra from the Dark Energy Spectroscopic Instrument and Gemini Multi-Object Spectrograph, Wide-field Infrared Survey Explorer mid-infrared observations, and Liverpool Telescope optical photometry, we find that none of the nine new ECLEs evolve in a manner consistent with that of the five previously discovered variable ECLEs. Using this sample of five variable ECLEs, we calculate the galaxy-normalized rate of variable ECLEs in SDSS to be |$R_\mathrm{G}=3.6~^{+2.6}_{-1.8}~(\mathrm{statistical})~^{+5.1}_{-0.0}~(\mathrm{systematic})\times 10^{-6}~\mathrm{galaxy}^{-1}~\mathrm{yr}^{-1}$|⁠. The mass-normalized rate is |$R_\mathrm{M}=3.1~^{+2.3}_{-1.5}~(\mathrm{statistical})~^{+4.4}_{-0.0}~(\mathrm{systematic})\times 10^{-17}~\mathrm{M_\odot ^{-1}}~\mathrm{yr}^{-1}$| and the volumetric rate is |$R_\mathrm{V}=7~^{+20}_{-5}~(\mathrm{statistical})~^{+10}_{-0.0}~(\mathrm{systematic})\times 10^{-9}~\mathrm{Mpc}^{-3}~\mathrm{yr}^{-1}$|⁠. Our rates are one to two orders of magnitude lower than TDE rates from the literature, which suggests that only 10–40 per cent of all TDEs produce variable ECLEs. Additional uncertainties in the rates arising from the structure of the interstellar medium have yet to be included. [ABSTRACT FROM AUTHOR]

Accurate astrometric and photometric measurements from Gaia have led to the construction of 3D dust extinction maps which can now be used for estimating the integrated extinctions of Galactic sources located within 5 kpc. These maps based on optical observations may not be reliable for use in the ultraviolet (UV) which is more sensitive to reddening. Past studies have focussed on studying UV extinction using main-sequence stars but lack comparison with 3D dust maps. White dwarfs with well-modelled hydrogen-dominated (DA) atmospheres provide an advantage over main-sequence stars affected by magnetic activity. In this work, we study the variation of UV extinction with 3D dust maps utilizing Hubble Space Telescope (HST) and Galaxy Evolution Explorer (GALEX) observations of DA white dwarfs located within 300 pc. We used HST COS spectroscopic data of 76 sightlines to calculate the optical extinction from Si  ii column densities and validate our results with the kinematic model predictions of the local interstellar medium. Also, we combined GALEX and Gaia photometric observations of 1158 DA white dwarfs to study UV reddening by comparing observed and modelled colour–colour relations. We calculated GALEX non-linearity corrections and derived reddening coefficients [ |$R(NUV-G)=6.52\pm 1.53$| and |$R(FUV-G)=6.04\pm 2.41$| ] considering their variations with optical extinction (⁠|$\rm{A_{V}}\lt 0.1$|  mag), and found them to be in good agreement with known extinction laws. HST analysis suggests a positive bias of 0.01–0.02 mag in the optical extinction from 3D maps depending on the Galactic latitude. These results independently confirm the validity of 3D dust maps to de-redden the optical and UV observations of white dwarfs. [ABSTRACT FROM AUTHOR]

Being the most prominent H  i line, Ly |$\alpha$| permeates the cosmic web in emission. Despite its potential as a cosmological probe, its detection on large scales remains elusive. We present a new methodology to perform Ly |$\alpha$| intensity mapping with broad-band optical images, by cross-correlating them with Ly |$\alpha$| forest data using a custom one-parameter estimator. We also develop an analytical large-scale Ly |$\alpha$| emission model with two parameters (average luminosity |$\langle L_{\rm Ly\alpha } \rangle$| and bias |$b_{\rm e}$|⁠) that respects observational constraints from quasar (QSO) luminosity functions. We compute a forecast for Dark Energy Camera Legacy Survey (DECaLS)/Beijing–Arizona Sky Survey (BASS) g -band images cross-correlated with Dark Energy Spectroscopic Instrument (DESI) Ly |$\alpha$| forest data, setting guidelines for reducing images into Ly |$\alpha$| intensity maps. Given the transversal scales of our cross-correlation (26.4 arcmin, |$\sim$| 33 cMpc h−1), our study effectively integrates Ly |$\alpha$| emission over all the cosmic volume inside the DESI footprint at |$2.2 \lt z \lt 3.4$| (the g -band Ly |$\alpha$| redshift range). Over the parameter space (⁠|$\langle L_{\rm Ly\alpha } \rangle$|⁠ , |$b_{\rm e}$|⁠) sampled by our forecast, we find a 3 |$\sigma$| of large-scale structure in Ly |$\alpha$| likely, with a probability of detection of 23.95 per cent for DESI–DECaLS/BASS, and 54.93 per cent for a hypothetical DESI phase-II with twice as much Ly |$\alpha$| QSOs. Without a detection, we derive upper bounds on |$\langle L_{\rm Ly\alpha } \rangle$| competitive with optimistic literature estimates [ |$2.3 \pm 1 \times 10^{\rm 41}$| erg s−1 (cMpc |$^3$|⁠)−1 for DESI, and |$\sim$| 35  per cent lower for its hypothetical phase-II]. Extrapolation to the DESI-Rubin overlap shows that a detection of large-scale structure with Ly |$\alpha$| intensity mapping using next-generation imaging surveys is certain. Such detection would allow constraining |$\langle L_{\rm Ly\alpha } \rangle$|⁠ , and explore the constraining power of Ly |$\alpha$| intensity mapping as a cosmological probe. [ABSTRACT FROM AUTHOR]

We study the properties of long gamma-ray burst (GRB) host galaxies using a statistical modelling framework derived to model damped Lyman- |$\alpha$| absorbers (DLAs) in quasar spectra at high redshift. The distribution of |$N_{\rm H\, {\small I}}$| for GRB-DLAs is |$\sim$| 10 times higher than what is found for quasar-DLAs at similar impact parameters. We interpret this as a temporal selection effect due to the short-lived GRB progenitor probing its host at the onset of a starburst where the interstellar medium may exhibit multiple overdense regions. Owing to the larger |$N_{\rm H\, {\small I}}$|⁠ , the dust extinction is larger with 29 per cent of GRB-DLAs exhibiting |$A(V)\gt 1$|  mag in agreement with the fraction of 'dark bursts'. Despite the differences in |$N_{\rm H\, {\small I}}$| distributions, we find that high-redshift |$2 \lt z \lt 3$| quasar- and GRB-DLAs trace the luminosity function of star-forming host galaxies in the same way. We propose that their differences may arise from the fact that the galaxies are sampled at different times in their star formation histories, and that the absorption sightlines probe the galaxy haloes differently. Quasar-DLAs sample the full H  i cross-section, whereas GRB-DLAs sample only regions hosting cold neutral medium. Previous studies have found that GRBs avoid high-metallicity galaxies (⁠|$\sim$| 0.5  |$Z_{\odot }$|⁠). Since at these redshifts galaxies on average have lower metallicities, our sample is only weakly sensitive to such a threshold. Lastly, we find that the modest detection rate of cold gas (H |$_2$| or C  i) in GRB spectra can be explained mainly by a low volume filling factor of cold gas clouds and to a lesser degree by destruction from the GRB explosion itself. [ABSTRACT FROM AUTHOR]

Understanding the formation of carbonyl sulfide (OCS) in interstellar ices is key to constrain the sulfur chemistry in the interstellar medium (ISM), since it is the only ice S-bearing molecule securely detected thus far. Two general pathways for OCS formation have been proposed: sulfurization of CO (CO + S) and oxidation of CS (CS + O), but their relative contribution in interstellar ices remains unconstrained. We have evaluated the contribution of both pathways to OCS formation upon energetic processing in isotopically labelled CO |$_2$|⁠ :CS |$_2$| and CO:CS |$_2$| ice samples at 7 |$-$| 50 K. Our results indicated that formation of OCS through the CS + O pathway was more favourable than through the CO + S pathway, as previously suggested by theoretical calculations. In addition, its relative contribution increased at higher temperatures. Therefore, this pathway could play a role in the ice formation of OCS, especially in warm regions where CO is expected to be preferentially in the gas phase. At the same time, we have explored the chemistry of CS |$_2$| -bearing, CO |$_2$| -, CO-, and also H |$_2$| O-rich ices, that could be relevant to the sulfur interstellar chemistry. We observed formation of a variety of S-bearing products in addition to OCS, including SO |$_2$|⁠ , C |$_3$| S |$_2$|⁠ , and S |$_2$|⁠. However, a significant fraction of sulfur was not detected at the end of the experiments, and could be locked in long, undetectable sulfur allotropes, one of the potential carriers of the missing sulfur in the dense ISM. [ABSTRACT FROM AUTHOR]

Strong low-ionization transitions like the Mg  ii |$\lambda 2796,2804$|  Å doublet are believed to produce a detectable 'metal-line forest', if metals pollute the neutral intergalatic medium (IGM). We measure the autocorrelation of the Mg  ii forest transmission using 10 ground-based |$z \ge 6.80$| quasar spectra probing the redshift range |$5.96 \lt z_{\rm Mg\, {\small II}} \lt 7.42$| (⁠|$z_{\rm Mg\, {\small II}, median} = 6.47$|⁠). The correlation function exhibits strong small-scale clustering and a pronounced peak at the doublet velocity (⁠|$\Delta v = 768~{\rm km\, s^{-1}}$|⁠) arising from discrete absorbers in the circumgalactic medium of galaxies. After these strong absorbers are identified and masked the signal is consistent with noise. Our measurements are compared to a suite of models generated by combining a large hydrodynamical simulation with a seminumerical reionization topology, assuming a simple uniform enrichment model. We obtain a 95 per cent credibility upper limit of |$[{\rm Mg/H}] \lt -3.73$| at |$z_{\rm Mg\, {\small II},median} = 6.47$|⁠ , assuming uninformative priors on [Mg/H] and the IGM neutral fraction |$x_{\rm {H\, {\small I}}}$|⁠. Splitting the data into low- z (⁠|$5.96 \lt z_{\rm Mg\, {\small II}} \lt 6.47$|⁠ ; |$z_{\rm Mg\, {\small II},median} = 6.235$|⁠) and high- z (⁠|$6.47 \lt z_{\rm Mg\, {\small II}} \lt 7.42$|⁠ ; |$z_{\rm Mg\, {\small II},median} = 6.72$|⁠) subsamples again yields null detections and 95 per cent upper limits of |$[{\rm Mg/H}] \lt -3.75$| and |$\lt -3.45$|⁠ , respectively. These first measurements set the stage for making the Mg ii forest an emerging tool to precisely constrain the Universe reionization and enrichment history. [ABSTRACT FROM AUTHOR]

We present the largest Galactic neutral hydrogen H i absorption survey to date, utilizing the Australian SKA Pathfinder Telescope at an unprecedented spatial resolution of 30 arcsec. This survey, GASKAP-H i , unbiasedly targets 2714 continuum background sources over 250 square degrees in the direction of the Magellanic Clouds, a significant increase compared to a total of 373 sources observed by previous Galactic absorption surveys across the entire Milky Way. We aim to investigate the physical properties of cold (CNM) and warm (WNM) neutral atomic gas in the Milky Way foreground, characterized by two prominent filaments at high Galactic latitudes (between |$-45^{\circ }$| and |$-25^{\circ }$|⁠). We detected strong H i absorption along 462 lines of sight above the 3 |$\sigma$| threshold, achieving an absorption detection rate of 17 per cent. GASKAP-H i 's unprecedented angular resolution allows for simultaneous absorption and emission measurements to sample almost the same gas clouds along a line of sight. A joint Gaussian decomposition is then applied to absorption-emission spectra to provide direct estimates of H i optical depths, temperatures, and column densities for the CNM and WNM components. The thermal properties of CNM components are consistent with those previously observed along a wide range of Solar neighbourhood environments, indicating that cold H i properties are widely prevalent throughout the local interstellar medium. Across our region of interest, CNM accounts for |$\sim$| 30 per cent of the total H i gas, with the CNM fraction increasing with column density towards the two filaments. Our analysis reveals an anticorrelation between CNM temperature and its optical depth, which implies that CNM with lower optical depth leads to a higher temperature. [ABSTRACT FROM AUTHOR]

We explore the relations between the gas-phase metallicity radial profiles (few hundred inner parsec) and multiple galaxy properties for 15 Seyfert galaxies from the active galactic nuclei integral field spectroscopy sample using optical integral field unit observations from Gemini Multi-Object Spectrograph (GMOS) and Multi Unit Spectroscopic Explorer (MUSE) processed archival data. The data were selected at |$z \lesssim 0.013$| within black hole mass range |$\left[6\lt \log \left(M_{\rm BH}/{\rm M_\odot } \right)\lt 9\right]$| with moderate 14–150-keV X-ray luminosities |$\left[42\, \lesssim \, \log L_X (\rm erg\, s^{-1})\, \lesssim \, 44\right]$|⁠. We estimated the gas-phase metallicity using the strong-line methods and found mean values for the oxygen-dependent (⁠|$Z \sim 0.75\, \mathrm{Z}_\odot$|⁠) and nitrogen-dependent (⁠|$Z \sim 1.14\, \mathrm{Z}_\odot$|⁠) calibrations. These estimates show excellent agreement with |$\Delta Z \approx 0.19$| and 0.18 dex between the mean values from the two strong-line calibrations for GMOS and MUSE, respectively, consistent with the order of metallicity uncertainty via the strong-line methods. We contend that our findings align with a scenario wherein local Seyferts have undergone seamless gas accretion histories, resulting in positive metallicity profiles over an extended period of time, thereby providing insights into galaxy evolution and the chemical enrichment or depletion of the universe. Additionally, we argue that metal-poor gas inflow from the local interstellar medium and accreted through the circumgalactic medium on to the galaxy systems regulates the star formation processes by diluting their central metallicity and inverting their gas-phase metallicity radial gradients, producing a more prominent anticorrelation between gas-phase metallicity and Eddington ratio. [ABSTRACT FROM AUTHOR]

Cosmological information is usually extracted from the Lyman- |$\alpha$| (Ly  |$\alpha$|⁠) forest correlations using only either large-scale information interpreted through linear theory or using small-scale information interpreted by means of expensive hydrodynamical simulations. A complete cosmological interpretation of the three-dimensional (3D) correlations at all measurable scales is challenged by the need of more realistic models including the complex growth of non-linear small scales that can only be studied within large hydrodynamical simulations. Past works were often limited by the trade-off between the simulated cosmological volume and the resolution of the low-density intergalactic medium from which the Ly  |$\alpha$| signal originates. We conduct a suite of hydrodynamical simulations of the intergalactic medium, including one of the largest Ly  |$\alpha$| simulations ever performed in terms of volume (640 |$\, h^{-1}\, \mathrm{Mpc}$|⁠), alongside simulations in smaller volumes with resolutions up to 25 |$\, h^{-1}\, \mathrm{kpc}$|⁠ , which will be further improved to show resolution convergence in future studies. We compare the 3D Ly  |$\alpha$| power spectra (⁠|$P_{3\mathrm{D},\alpha }$|⁠) predicted by those simulations to different non-linear models. The inferred Ly  |$\alpha$| bias and redshift space distortion parameters, |$b_\alpha$| and |$\beta _\alpha$| are in remarkable agreement with those measured in SDSS (Sloan Digital Sky Survey) and DESI (Dark Energy Spectroscopic Instrument) data. We find that, contrary to intuition, the convergence of large-scale modes of the |$P_{3\mathrm{D},\alpha }$|⁠ , which determines |$\beta _\alpha$|⁠ , is primarily influenced by the resolution of the simulation box through mode coupling, rather than the box size itself. Finally, we study the Baryon Acoustic Oscillation (BAO) signal encoded in |$P_{3\mathrm{D},\alpha }$|⁠. For the first time with a hydrodynamical simulation, we clearly detect the BAO signal; however, we only marginally detect its damping, associated with the non-linear growth of the structures. [ABSTRACT FROM AUTHOR]

Neutral hydrogen (H i) bubbles and shells are common in the interstellar medium (ISM). Studying their properties provides insight into the characteristics of the local ISM as well as the galaxy in which the bubbles reside. We report the detection of magnetic fields associated with superbubbles in the nearby irregular galaxy, the Small Magellanic Cloud (SMC). Using the Polarisation Sky Survey of the Universe's Magnetism (POSSUM) pilot survey, we obtain a high-density grid (⁠|$\approx 25 \, \rm sources\, deg^{-2}$|⁠) of Faraday rotation measure (RM) from polarized sources behind the SMC. This provides a sufficiently large number of RM measurements to study the magnetic properties of three of the largest H i shells previously identified in the SMC. The RM profiles as a function of distance from the shell centre show characteristic patterns at angular scales comparable to the shell size. We demonstrate that this can be explained by magnetohydrodynamic simulation models of bubbles expanding in magnetized environments. From the observations, we estimate the line-of-sight magnetic field strength at the edges of the shells is enhanced by |$\sim 1\, \rm \mu G$| with respect to their centres. This is an order of magnitude larger than the field strength in the ambient medium (⁠|$\sim 0.1\, \rm \mu G$|⁠) estimated based on the expansion velocity of the shells. This paper highlights the power of densely mapped RM grids in studying the magnetic properties of galactic substructures beyond the Milky Way. [ABSTRACT FROM AUTHOR]

We investigate the numerical performance of a Discontinuous Galerkin (DG) hydrodynamics implementation when applied to the problem of driven, isothermal supersonic turbulence. While the high-order element-based spectral approach of DG is known to efficiently produce accurate results for smooth problems (exponential convergence with expansion order), physical discontinuities in solutions, like shocks, prove challenging and may significantly diminish DG's applicability to practical astrophysical applications. We consider whether DG is able to retain its accuracy and stability for highly supersonic turbulence, characterized by a network of shocks. We find that our new implementation, which regularizes shocks at subcell resolution with artificial viscosity, still performs well compared to standard second-order schemes for moderately high-Mach number turbulence, provided we also employ an additional projection of the primitive variables on to the polynomial basis to regularize the extrapolated values at cell interfaces. However, the accuracy advantage of DG diminishes significantly in the highly supersonic regime. Nevertheless, in turbulence simulations with a wide dynamic range that start with supersonic Mach numbers and can resolve the sonic point, the low-numerical dissipation of DG schemes still proves advantageous in the subsonic regime. Our results thus support the practical applicability of DG schemes for demanding astrophysical problems that involve strong shocks and turbulence, such as star formation in the interstellar medium. We also discuss the substantial computational cost of DG when going to high order, which needs to be weighted against the resulting accuracy gain. For problems containing shocks, this favours the use of comparatively low DG order. [ABSTRACT FROM AUTHOR]

The anions C |$_7$| N |$^-$| and C |$_{10}$| H |$^-$| are the two longest of the linear (C,N)-bearing and (C,H)-bearing chains that have so far been detected in the interstellar medium (ISM). In order to glean information on their collision-induced rotational state-changing processes, we analyse the general features of new ab initio potentials describing the interaction of both linear anions with H |$_2$|⁠ , one of the most abundant partners in their ISM environment. We employ an artificial neural network fit of the reduced-dimensionality potential energy surface for C |$_7$| N |$^-$|⁠...H |$_2$| interaction and discuss in detail the spatial features in terms of multipolar radial coefficients. For the C |$_{10}$| H |$^-$|⁠...H |$_2$| interaction, we use the initial grid of two-dimensional raw points to generate by quadrature the Legendre expansion directly, further including the long-range terms as discussed in the main text. Quantum scattering calculations are employed to obtain rotationally inelastic cross-sections, for collision energies in the range of 10 |$^{-4}$| to 400 cm |$^{-1}$|⁠. From them we generate the corresponding inelastic rate coefficients as a function of temperature covering the range from 10 to 50 K. The results for the rate coefficients for the longest cyanopolyyne are compared with the earlier results obtained for the smaller terms of the same series, also in collision with H |$_2$|⁠. We obtain that the inelastic rate coefficients for the long linear anions are all fairly large compared with the earlier systems. The consequences of such findings on their non-equilibrium rotational populations in interstellar environments are illustrated in our conclusions. [ABSTRACT FROM AUTHOR]

Cloud–cloud collisions in splash bridges produced in gas-rich disc galaxy collisions offer a brief but interesting environment to study the effects of shocks and turbulence on star formation rates in the diffuse intergalactic medium, far from the significant feedback effects of massive star formation and active galactic nucleus. Expanding on our earlier work, we describe simulated collisions between counter-rotating disc galaxies of relatively similar mass, focusing on the thermal and kinematic effects of relative inclination and disc offset at the closest approach. This includes essential heating and cooling signatures, which go some way towards explaining the luminous power in H |$_2$| and [C  ii ] emission in the Taffy bridge, as well as providing a partial explanation of the turbulent nature of the recently observed compact CO-emitting clouds observed in Taffy by the Atacama Large Millimeter Array (ALMA). The models show counter-rotating disc collisions result in swirling, shearing kinematics for the gas in much of the post-collision bridge. Gas with little specific angular momentum due to collisions between counter-rotating streams accumulates near the centre of mass. The disturbances and mixing in the bridge drive continuing cloud collisions, differential shock heating, and cooling throughout. A wide range of relative gas phases and line-of-sight velocity distributions are found in the bridges, depending sensitively on initial disc orientations, and the resulting variety of cloud collision histories. Most cloud collisions can occur promptly or persist for quite a long duration. Cold and hot phases can largely overlap throughout the bridge or can be separated into different parts of the bridge. [ABSTRACT FROM AUTHOR]

Phosphorous species are of great interest in interstellar chemistry since they are the basic blocks for building life here on Earth. Modelling the abundance and environment of recently detected PO |$^{+}$| under non-local thermodynamic equilibrium (LTE) requires rotational spectra of the molecule along with accurate collisional rates with the most abundant species, hydrogen and helium. A new 4D ab initio potential energy surface (PES) of PO |$^{+}$| – H |$_{2}$| collision is calculated using CCSD(T)/CBS(DTQ) methodology considering rigid rotor approximation. The region containing the minima of the PES is augmented using neural networks (NNs) model while very high potentials (⁠|$\gt 2500$| cm |$^{-1}$| ) and asymptotic region have been approximated using Slater and R |$^{-4}$| functions, respectively. The close coupling calculations have been performed using molscat software for both ortho and para -H |$_{2}$| . The rate coefficients have been reported for transitions |$j-j^{\prime }=$| |$1-0$|⁠ , |$2-1$|⁠ , |$3-2$|⁠ , and |$5-4$| through which PO |$^{+}$| has been experimentally detected in interstellar medium (ISM). The rate coefficients for even and odd transitions of PO |$^{+}$| with para -H |$_{2}$| are compared with that of helium and are found to be 1.1–2.0 times higher. For even transitions (|$\Delta j = 2$|), the ortho -H |$_{2}$| rates are 10 per cent higher than para -H |$_{2}$| rates. However, the trend reverses in the case of odd transitions (|$\Delta j = 1$|) when higher J transitions are considered at low temperatures. At higher temperatures, the ortho rates cross the para -H |$_{2}$| rates and become larger than the latter. The new rate coefficients with both ortho and para -H |$_{2}$| will enable accurate modelling of the PO |$^{+}$| abundance in the ISM under non-LTE conditions. [ABSTRACT FROM AUTHOR]

The anions C |$_7$| N |$^-$| and C |$_{10}$| H |$^-$| are the two longest of the linear (C,N)-bearing and (C,H)-bearing chains that have so far been detected in the interstellar medium (ISM). In order to glean information on their collision-induced rotational state-changing processes, we analyse the general features of new ab initio potentials describing the interaction of both linear anions with H |$_2$|⁠ , one of the most abundant partners in their ISM environment. We employ an artificial neural network fit of the reduced-dimensionality potential energy surface for C |$_7$| N |$^-$|⁠...H |$_2$| interaction and discuss in detail the spatial features in terms of multipolar radial coefficients. For the C |$_{10}$| H |$^-$|⁠...H |$_2$| interaction, we use the initial grid of two-dimensional raw points to generate by quadrature the Legendre expansion directly, further including the long-range terms as discussed in the main text. Quantum scattering calculations are employed to obtain rotationally inelastic cross-sections, for collision energies in the range of 10 |$^{-4}$| to 400 cm |$^{-1}$|⁠. From them we generate the corresponding inelastic rate coefficients as a function of temperature covering the range from 10 to 50 K. The results for the rate coefficients for the longest cyanopolyyne are compared with the earlier results obtained for the smaller terms of the same series, also in collision with H |$_2$|⁠. We obtain that the inelastic rate coefficients for the long linear anions are all fairly large compared with the earlier systems. The consequences of such findings on their non-equilibrium rotational populations in interstellar environments are illustrated in our conclusions. [ABSTRACT FROM AUTHOR]

We investigate galaxy sizes at redshift |$z\gtrsim 6$| with the cosmological radiation-magnetohydrodynamic simulation suite thesan(-hr). These simulations simultaneously capture reionization of the large-scale intergalactic medium and resolved galaxy properties. The intrinsic sizes (⁠|$r^{\ast }_{1/2}$|⁠) of simulated galaxies increase moderately with stellar mass at |$M_{\ast } \lesssim 10^{8}{\, \rm M_\odot}$| and decrease 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 outflows competing with the cold inflowing gas streams. In contrast, massive galaxies fit better with the disc formation model. They generally experience a phase of rapid compaction and gas depletion, likely driven by internal disc 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 ultraviolet 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 |$6 \lesssim z \lesssim 10$|⁠. The population of compact galaxies (⁠|$R^{\rm UV}_{\rm eff}\lesssim 300\, {\rm pc}$|⁠) galaxies at |$M_{\ast }\sim 10^{8}{\, \rm M_\odot}$| is missing in our simulations. This inconsistency persists across many other cosmological simulations with different galaxy formation models and demonstrates the potential of using galaxy morphology to constrain physics of galaxy formation at high redshifts. [ABSTRACT FROM AUTHOR]

Unveiling the thermal history of the intergalactic medium (IGM) at |$4 \le z \le 5$| holds the potential to reveal early onset He  ii reionization or lingering thermal fluctuations from H  i reionization. We set out to reconstruct the IGM gas properties along simulated Lyman-alpha (Lyα) forest data on pixel-by-pixel basis, employing deep neural networks. Our approach leverages the Sherwood-Relics simulation suite, consisting of diverse thermal histories, to generate mock spectra. Our convolutional and residual networks with likelihood metric predict the Ly |$\rm {\alpha }$| optical depth-weighted density or temperature for each pixel in the Ly |$\rm {\alpha }$| forest skewer. We find that our network can successfully reproduce IGM conditions with high fidelity across range of instrumental signal-to-noise ratio. These predictions are subsequently translated into the temperature–density plane, facilitating the derivation of reliable constraints on thermal parameters. This allows us to estimate temperature at mean cosmic density, |$T_{\rm 0}$|⁠ , with 1σ confidence, |$\delta {T_{\rm 0}} \lesssim 1000 \ {\rm K}$|⁠ , using only one |$20 \ h^{-1} \, {\rm cMpc}$| sightline (⁠|$\Delta z\simeq 0.04$|⁠) with a typical reionization history. Existing studies utilize redshift path-length comparable to |$\Delta z\simeq 4$| for similar constraints. We can also provide more stringent constraints on the slope (⁠|$1\sigma$| confidence interval, |$\delta {\rm \gamma } \lesssim 0.1$|⁠) of the IGM temperature–density relation as compared to other traditional approaches. We test the reconstruction on a single high signal-to-noise observed spectrum (⁠|$20 \ h^{-1}\,{\rm cMpc}$| segment) and recover thermal parameters consistent with current measurements. This machine learning approach has the potential to provide accurate yet robust measurements of IGM thermal history at the redshifts in question. [ABSTRACT FROM AUTHOR]

We use high-resolution magnetohydrodynamic simulations of isolated disc galaxies to investigate the co-evolution of magnetic fields with a self-regulated, star-forming interstellar medium (ISM). The simulations are conducted using the ramses adaptive mesh refinement code on the standard agora initial condition, with gas cooling, star formation, and feedback. We run galaxies with a variety of initial magnetic field strengths. The fields evolve and achieve approximate saturation within 500 Myr, but at different levels. The galaxies reach a quasi-steady state, with slowly declining star formation due to both gas consumption and increase in the field strength at intermediate ISM densities. We connect this behaviour to differences in the gas properties and overall structure of the galaxies. Stronger magnetic fields limit supernova bubble sizes. Different cases support the ISM using varying combinations of magnetic pressure, turbulence, and thermal energy. Initially, |$\gtrsim\!\! 1\ \mu \mathrm{ G}$| magnetic fields evolve modestly and dominate support at all radii. Conversely, initially weaker fields grow through feedback and turbulence but never dominate the support. This is reflected in the stability of the gas disc. This interplay determines the overall distribution of star formation in each case. We conclude that an initially weak field can grow to produce a realistic model of a local disc galaxy, but starting with typically assumed field strengths (⁠|$\gtrsim\!\! 1\ \mu \mathrm{ G}$|⁠) will not. [ABSTRACT FROM AUTHOR]

Modelling complex line emission in the interstellar medium (ISM) is a degenerate high-dimensional problem. Here, we present McFine , a tool for automated multicomponent fitting of emission lines with complex hyperfine structure, in a fully automated way. We use Markov chain Monte Carlo (MCMC) to efficiently explore the complex parameter space, allowing for characterizing model denegeracies. This tool allows for both local thermodynamic equilibrium (LTE) and radiative-transfer (RT) models. McFine can fit individual spectra and data cubes, and for cubes encourage spatial coherence between neighbouring pixels. It is also built to fit the minimum number of distinct components, to avoid overfitting. We have carried out tests on synthetic spectra, where in around 90 per cent of cases it fits the correct number of components, otherwise slightly fewer components. Typically, |$T_{\rm ex}$| is overestimated and |$\tau$| underestimated, but accurate within the estimated uncertainties. The velocity and line widths are recovered with extremely high accuracy, however. We verify McFine by applying to a large Atacama Large Millimeter/submillimeter Array (ALMA) N |$_2$| H |$^+$| mosaic of an high-mass star forming region, G316.75−00.00. We find a similar quality of fit to our synthetic tests, aside from in the active regions forming O-stars, where the assumptions of Gaussian line profiles or LTE may break down. To show the general applicability of this code, we fit CO(J = 2-1) observations of NGC 3627, a nearby star-forming galaxy, again obtaining excellent fit quality. McFine provides a fully automated way to analyse rich data sets from interferometric observations, is open source, and pip -installable. [ABSTRACT FROM AUTHOR]

Heterocycles have not been detected in the interstellar medium (ISM) yet. However, the direct involvement of some pentagonal heterocycles within the formation of key biomolecules for the origin of life makes the search for these systems in the ISM relevant for understanding whether some of the bricks of life could be formed in the ISM. We have explored the possible formation of the simple heterocycle furan (c-C |$_{4}$| H |$_{4}$| O) under interstellar conditions, through the reaction between two interstellar species, |$\mathrm{syn}$| -vinyl alcohol (⁠|$\mathrm{syn}$| -VA) and the CCH radical. We employed state-of-the-art quantum-chemical calculations to elucidate the reaction mechanism between the reaction of CCH radical and |$\mathrm{syn}$| -VA. Kinetic simulations were carried out aiming to quantitatively assess the viability of this reaction in the ISM. We have found a reaction pathway to furan where all energy barriers are submerged. However, the formation of this heterocycle is not feasible because the intermediates leading to furan can evolve through more favourable routes. In contrast, we have found viable pathways for the formation of the four isomers of 1-butenol-3-yne (HCCCHCHOH) (Z - |$\mathrm{syn}$|⁠ , E - |$\mathrm{syn}$|⁠ , E - |$\mathrm{anti}$|⁠ , and Z - |$\mathrm{anti}$|⁠), which thus are promising species to be detected in the ISM. Our theoretical work indicates that the four isomers of 1-butenol-3-yne should be present in the ISM because the precursors are known interstellar species, and the kinetic simulations indicate that their formation is very likely. We then encourage the observational search of these molecules in the ISM. [ABSTRACT FROM AUTHOR]

We present observations of mid- J (J = 4–3 or J = 5–4) carbon monoxide (CO) emission lines and continuum emission from a sample of ten of the most luminous (L bol |$\ge$| 10 |$^{14}$|  L |$\rm \odot$| ) Hot Dust-Obscured Galaxies (Hot DOGs) discovered by the Wide-field Infrared Survey Explorer (WISE) with redshifts up to 4.6. We uncover broad spectral lines (FWHM |$\ge$| 400 km s |$^{-1}$|⁠) in these objects, suggesting a turbulent molecular interstellar medium (ISM) may be ubiquitous in Hot DOGs. A halo of molecular gas, extending out to a radius of 5 kpc is observed in W2305–0039, likely supplied by 940 km s |$^{-1}$| molecular outflows. W0831+0140 is plausibly the host of a merger between at least two galaxies, consistent with observations made using ionized gas. These CO(4–3) observations contrast with previous CO(1–0) studies of the same sources: the CO(4–3) to CO(1–0) luminosity ratios exceed 300 in each source, suggesting that the lowest excited states of CO are underluminous. These findings show that the molecular gas in Hot DOGs is consistently turbulent, plausibly a consequence of AGN feedback, triggered by galactic mergers. [ABSTRACT FROM AUTHOR]

Most star formation in the local Universe occurs in spiral galaxies, but their origin remains an unanswered question. Various theories have been proposed to explain the development of spiral arms, each predicting different spatial distributions of the interstellar medium. This study maps the star formation rate (SFR) and gas-phase metallicity of nine spiral galaxies with the TYPHOON survey to test two dominating theories: density wave theory and dynamic spiral theory. We discuss the environmental effects on our galaxies, considering reported environments and merging events. Taking advantage of the large field of view covering the entire optical disc, we quantify the fluctuation of SFR and metallicity relative to the azimuthal distance from the spiral arms. We find higher SFR and metallicity in the trailing edge of NGC 1365 (by 0.117 and 0.068 dex, respectively) and NGC 1566 (by 0.119 and 0.037 dex, respectively), which is in line with density wave theory. NGC 2442 shows a different result with higher metallicity (0.093 dex) in the leading edge, possibly attributed to an ongoing merging. The other six spiral galaxies show no statistically significant offset in SFR or metallicity, consistent with dynamic spiral theory. We also compare the behaviour of metallicity inside and outside the corotation radius (CR) of NGC 1365 and NGC 1566. We find comparable metallicity fluctuations near and beyond the CR of NGC 1365, indicating gravitational perturbation. NGC 1566 shows the greatest fluctuation near the CR, in line with the analytic spiral arms. Our work highlights that a combination of mechanisms explains the origin of spiral features in the local Universe. [ABSTRACT FROM AUTHOR]

Observations of ionized H  |$\alpha$| gas in high-redshift disc galaxies have ubiquitously found significant line broadening, |$\sigma _{\rm H\,\alpha }\sim 10{\!-\!}100\, {\rm km\, s^{-1}}$|⁠. To understand whether this broadening reflects gas turbulence within the interstellar medium (ISM) of galactic discs, or arises from out-of-plane emission in mass-loaded outflows, we perform radiation hydrodynamic simulations of isolated Milky Way-mass disc galaxies in a gas-poor (low-redshift) and gas rich (high-redshift) condition and create mock H  |$\alpha$| emission line profiles. We find that the majority of the total (integrated) |${\rm H\,\alpha }$| emission is confined within the ISM, with extraplanar gas contributing |${\sim} 45~{{\ \rm per\ cent}}$| of the extended profile wings (⁠|$v_z\ge 200$| |${\, \rm {km\, s^{-1}} }$|⁠) in the gas-rich galaxy. This substantiates using the |${\rm H\,\alpha }$| emission line as a tracer of mid-plane disc dynamics. We investigate the relative contribution of diffuse and dense |${\rm H\,\alpha }$| emitting gas, corresponding to diffuse ionized gas (DIG; |$\rho \lesssim 0.1\, {\rm cm^{-3}}$|⁠ , |$T\sim 8\, 000$|  K) and H  ii regions (⁠|$\rho \gtrsim 10\, {\rm cm^{-3}}$|⁠ , |$T\sim 10\, 000$|  K), respectively, and find that DIG contributes |$f_{\rm DIG}\lesssim 10~{{\ \rm per\ cent}}$| of the total L |$_{\rm H\alpha }$|⁠. However, the DIG can reach upwards of |$\sigma _{\rm H\,\alpha } \sim 60{\!-\!}80\, {\rm km\, s^{-1}}$| while the H  ii regions are much less turbulent |$\sigma _{\rm H\,\alpha }\sim 10{\!-\!}40\, {\rm km\, s^{-1}}$|⁠. This implies that the |$\sigma _{\rm H\,\alpha }$| observed using the full |${\rm H\,\alpha }$| emission line is dependent on the relative |${\rm H\,\alpha }$| contribution from DIG/H  ii regions and a larger |$f_{\rm DIG}$| would shift |$\sigma _{\rm H\,\alpha }$| to higher values. Finally, we show that |$\sigma _{\rm H\,\alpha }$| evolves, in both the DIG and H  ii regions, with the galaxy gas fraction. Our high-redshift equivalent galaxy is roughly twice as turbulent, except for in the DIG which has a more shallow evolution. [ABSTRACT FROM AUTHOR]

We present an analysis of the cold gas phase in a low-metallicity starburst generated in a high-resolution hydrodynamical simulation of a gas-rich dwarf galaxy merger as part of the griffin project. The simulations resolve (4 M |$_\odot$| gas phase mass resolution, |$\sim$| 0.1 pc spatial resolution) the multiphase interstellar medium with a non-equilibrium chemical heating/cooling network at temperatures below 10 |$^4$|  K. Massive stars are sampled individually and interact with the interstellar medium (ISM) through the formation of H  ii regions and supernova explosions. In the extended starburst phase, the ISM is dominated by cold (⁠|$T_\mathrm{gas} < 300$|  K) filamentary clouds with self-similar internal structures. The clouds have masses of |$10^{2.6}$| – |$10^{5.6}$|  M |$_\odot$| with a power-law mass function, |$\mathrm{ d}N/\mathrm{ d}M \propto M^\alpha$| with |$\alpha = -1.78 (\,\pm \,0.08)$|⁠. They also follow the Larson relations, in good agreement with observations. We trace the lifecycle of the cold clouds and find that they follow an exponential lifetime distribution and an e-folding time of |$\sim$| 3.5 Myr. Clouds with peak masses below |$10^4$|  M |$_\odot$| follow a power-law relation with their average lifetime |$\tau _\mathrm{life} \propto M^{0.3}_\mathrm{max}$| which flattens out for higher cloud masses at |$< 10$|  Myr. A similar relation exists between cloud size at peak mass and lifetime. This simulation of the evolution of a realistic galactic cold cloud population supports the rapid formation and disruption of star-forming clouds by stellar radiation and supernovae on a time-scale less than 10 Myr. [ABSTRACT FROM AUTHOR]

We present a deep H  i survey at L band conducted with the Five-hundred-metre Aperture Spherical radio Telescope (FAST) over the COSMOS field. This survey is strategically designed to overlap with the MIGHTEE COSMOS field, aiming to combine the sensitivity of the FAST and high-resolution of the MeerKAT. We observed the field with FAST for approximately 11 hours covering |${\sim} 2$| square degrees, and reduced the raw data to H  i spectral cubes over the frequency range 1310–1420 MHz. The FAST-H  i data reach a median 3 |$\sigma$| column density of |$N_{\rm {H\,{{\small I}}}} \sim 2\times 10^{17}$|  cm |$^{-2}$| over a |${\sim} 5\, {\rm km}\, {\rm s}^{-1}$| channel width, allowing for studies of the distribution of H  i gas in various environments, such as in galaxies, the Circum-Galactic Medium (CGM) and Intergalactic Medium (IGM). We visually searched the spectral cubes for H  i sources, and found a total of 80 H  i detections, of which 56 have been cross-matched with the MIGHTEE-H  i catalogue. With the cross-matched sources, we compare their H  i masses and find that the total H  i mass fraction in the IGM and CGM surrounding the galaxy pairs is statistically higher than the H  i fraction surrounding the isolated galaxies by a difference of |${\sim} 13\pm 4$| per cent, indicating that the CGM and IGM associated with interacting systems are richer in neutral hydrogen compared to those around isolated galaxies in the local Universe. We also describe several FAST-MeerKAT synergy projects, highlighting the full potential of exploiting both single-dish and interferometric observations to study the distribution and evolution of the diffuse H  i gas. [ABSTRACT FROM AUTHOR]

We explore the potential of using the low-redshift Lyman |$\alpha$| (Ly  |$\alpha$|⁠) forest surrounding luminous red galaxies (LRGs) as a tool to constrain active galactic nuclei (AGNs) feedback models. Our analysis is based on snapshots from the Illustris and IllustrisTNG simulations at a redshift of |$z=0.1$|⁠. These simulations offer an ideal platform for studying the influence of AGN feedback on the gas surrounding galaxies, as they share the same initial conditions and underlying code but incorporate different feedback prescriptions. Both simulations show significant impacts of feedback on the temperature and density of the gas around massive haloes. Following our previous work, we adjusted the UV background in both simulations to align with the observed number density of Ly  |$\alpha$| lines (⁠|$\rm dN/dz$|⁠) in the intergalactic medium and study the Ly  |$\alpha$| forest around massive haloes hosting LRGs, at impact parameters (⁠|$r_{\perp }$|⁠) ranging from 0.1 to 100 pMpc. Our findings reveal that |$\rm dN/dz$|⁠ , as a function of |$r_{\perp }$|⁠ , is approximately 1.5 to 2 times higher in IllustrisTNG compared to Illustris up to |$r_{\perp }$| of |$\sim 10$| pMpc. To further assess whether existing data can effectively discern these differences, we search for archival data containing spectra of background quasars probing foreground LRGs. Through a feasibility analysis based on these data, we demonstrate that |${\rm dN/dz} (r_{\perp })$| measurements can distinguish between feedback models of IllustrisTNG and Illustris with a precision exceeding 16 |$\sigma$|⁠. This underscores the potential of |${\rm dN/dz} (r_{\perp })$| measurements around LRGs as a valuable benchmark observation for discriminating between different feedback models. [ABSTRACT FROM AUTHOR]

We present rest-frame optical data of the |$z\sim 4$| submillimetre galaxy GN20 obtained with the JWST Near Infrared Spectrograph (NIRSpec) in integral field spectroscopy mode. The H |$\alpha$| emission is asymmetric and clumpy and extends over a projected distance of >15 kpc. To first order, the large-scale ionized gas kinematics are consistent with a turbulent (⁠|$\sigma \sim 90$| km s |$^{-1}$|⁠), rotating disc (⁠|$v_{\rm rot}\sim 500$| km s |$^{-1}$|⁠), congruent with previous studies of its molecular and ionized gas kinematics. However, we also find clear evidence for non-circular motions in the H |$\alpha$| kinematics. We discuss their possible connection with various scenarios, such as external perturbations, accretion, or radial flows. In the centre of GN20, we find broad-line emission (full width at half-maximum |$\sim 1000{-}2000$| km s |$^{-1}$|⁠) in the H |$\alpha$|  + [N  ii ] complex, suggestive of fast, active galactic nucleus-driven winds or, alternatively, of the broad-line region of an active black hole. Elevated values of [N  ii ]  |$\lambda 6583$| /H |$\alpha \ \gt\ 0.4$| and of the Hα equivalent width EW(H |$\alpha)\ \gt\ 6$| Å throughout large parts of GN20 suggest that feedback from the active black hole is able to photoionize the interstellar medium. Our data corroborate that GN20 offers a unique opportunity to observe key processes in the evolution of the most massive present-day galaxies acting in concert, over 12 billion years ago. [ABSTRACT FROM AUTHOR]

We present initial results from the Polarization Sky Survey of the Universe's Magnetism (POSSUM), analysing 22 817 Faraday rotation measures (RMs) with median uncertainties of 1.2 rad m |$^{-2}$| across 1520 deg2 to study magnetized gas associated with 55 nearby galaxy groups (⁠|$z\lesssim 0.025$|⁠) with halo masses between |$10^{12.5}$| and |$10^{14.0}$| M |$_\odot$|⁠. We identify two distinct gas phases: the intragroup medium (IGrM) within 0–2 splashback radii and the warm-hot intergalactic medium (WHIM) extending from 2 to 7 splashback radii. These phases enhance the standard deviation of residual (i.e. Galactic foreground RM-subtracted) RMs by |$6.9\pm 1.8$| rad m |$^{-2}$| and |$4.2 \pm 1.2$| rad m |$^{-2}$|⁠ , respectively. Estimated magnetic field strengths are several μ G within the IGrM and 0.1–1 μ G in the WHIM. We estimate the plasma |$\beta$| in both phases, and show that magnetic pressure might be more dynamically important than in the ICM of more massive clusters or sparse cosmic web filaments. Our findings indicate that 'missing baryons' in the WHIM likely extend beyond the gravitational radii of group-mass haloes to Mpc scales, consistent with large-scale, outflow-driven 'magnetized bubbles' seen in cosmological simulations. We demonstrate that RM grids are an effective method for detecting magnetized thermal gas at galaxy group interfaces and within the cosmic web. This approach complements X-ray and Sunyaev-Zel'dovich effect methods, and when combined with fast radio burst dispersion measures, data from the full POSSUM survey – comprising approximately a million RMs – will allow direct magnetic field measurements to further our understanding of baryon circulation in these environments and the magnetized universe. [ABSTRACT FROM AUTHOR]

In order to understand galaxy growth evolution, it is critical to constrain the evolution of its building block: gas. Mostly comprised by Hydrogen in its neutral (H  i) and molecular (H |$_2$|⁠) phases, the latter is the one mostly directly associated to star formation, while the neutral phase is considered the long-term gas reservoir. In this work, we make use of an empirical relation between dust emission at millimetre wavelengths and total gas mass in the interstellar medium (M |$_{\rm HI}$| plus M |$_{\rm H_2}$|⁠) in order to retrieve the H  i content in galaxies. We assemble an heterogeneous sample of 335 galaxies at |$0.01\lt z\lt 6.4$| detected in both mm-continuum and carbon monoxide (CO), with special focus on a blindly selected sample to retrieve H  i cosmological content when the Universe was |$\sim 2-6\,$|  Gyr old (⁠|$1\lt z\lt 3$|⁠). We find no significant evolution with redshift of the M |$_{\rm HI}$| /M |$_{\rm H_2}$| ratio, which is about |$1-3$| (depending on the relation used to estimate M |$_{\rm HI}$|⁠). This also shows that M |$_{\rm H_2}$| -based gas depletion times are underestimated overall by a factor of |$2-4$|⁠. Compared to local Universe H  i mass functions, we find that the number density of galaxies with M |$_{\rm HI}\gtrsim 10^{10.5}\,$| M |$_\odot$| significantly decreased since 8–12 Gyr ago. The specific sample used for this analysis is associated to 20–50 per cent of the total cosmic H  i content as estimated via Damped Lyman- |$\alpha$| Absorbers. In IR luminous galaxies, H  i mass content decreases between |$z\sim 2.5$| and |$z\sim 1.5$|⁠ , while H |$_2$| seems to increase. We also show source detection expectations for SKA surveys. [ABSTRACT FROM AUTHOR]

We present new multifrequency Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations of the massive [ |$\log _{10}(M_\star /\mathrm{M}_\odot) = 10.3_{-0.2}^{+0.1}$| ], UV-luminous [ |$M_\mathrm{UV} = -21.7 \pm 0.2$| ] |$z=7.31$| galaxy REBELS-25 in Bands 3, 4, 5, and 9. Combining the new observations with previously taken data in Bands 6 and 8, we cover the dust continuum emission of the galaxy in six distinct bands – spanning rest-frame |$50-350\, \mu$| m – enabling simultaneous constraints on its dust mass (⁠|$M_\mathrm{dust}$|⁠), temperature (⁠|$T_\mathrm{dust}$|⁠), and emissivity index (⁠|$\beta _\mathrm{IR}$|⁠) via modified blackbody fitting. Given a fiducial model of optically thin emission, we infer a cold dust temperature of |$T_\mathrm{dust} = 32_{-6}^{+9}\,$|  K and a high dust mass of |$\log _{10}(M_\mathrm{dust}/\mathrm{M}_\odot) = 8.2_{-0.4}^{+0.6}$|⁠ , and moderately optically thick dust does not significantly alter these estimates. If we assume dust production is solely through supernovae (SNe), the inferred dust yield would be high, |$y = 0.7_{-0.4}^{+2.3}\, \mathrm{M}_\odot$| per SN. Consequently, we argue grain growth in the interstellar medium of REBELS-25 also contributes to its dust build-up. This is supported by the steep dust emissivity index |$\beta _\mathrm{IR} = 2.5 \pm 0.4$| we measure for REBELS-25, as well as by its high stellar mass, dense interstellar medium, and metal-rich nature. Our results suggest that constraining the dust emissivity indices of high-redshift galaxies is important not only to mitigate systematic uncertainties in their dust masses and obscured star formation rates, but also to assess if dust properties evolve across cosmic time. We present an efficient observing set-up to do so with ALMA, combining observations of the peak and Rayleigh–Jeans tail of the dust emission. [ABSTRACT FROM AUTHOR]

Reconstructing the intrinsic Ly  |$\alpha$| line flux from high- z QSOs can place constraints on the neutral hydrogen content of the intergalactic medium during reionization. There are now |$\gtrsim 10$| different Ly  |$\alpha$| reconstruction pipelines using different methodologies to predict the Ly  |$\alpha$| line flux from correlations with the spectral information redwards of Ly  |$\alpha$|⁠. However, there have been few attempts to directly compare the performance of these pipelines. Therefore, we devised a blind QSO challenge to compare these reconstruction pipelines on a uniform set of objects. Each author was provided de-identified, observed rest-frame QSO spectra with spectral information only redwards of 1260 Å rest-frame to ensure unbiased reconstruction. We constructed two samples of 30 QSOs, from X-Shooter and Sloan Digital Sky Survey (SDSS) both spanning |$3.5\lt z\lt 4.5$|⁠. Importantly, the purpose of this comparison study was not to champion a single, best-performing reconstruction pipeline but rather to explore the relative performance of these pipelines over a range of QSOs with broad observational characteristics to infer general trends. In summary, we find machine-learning approaches in general provide the strongest 'best guesses' but underestimate the accompanying statistical uncertainty, although these can be recalibrated, while pipelines that decompose the spectral information, for example principal component or factor analysis, generally perform better at predicting the Ly  |$\alpha$| profile. Further, we found that reconstruction pipelines trained on SDSS QSOs performed similarly on average for both the X-Shooter and SDSS samples indicating no discernible biases owing to differences in the observational characteristics of the training set or QSO being reconstructed, although the recovered distributions of reconstructions for X-Shooter were broader likely due to an increased fraction of outliers. [ABSTRACT FROM AUTHOR]

We present a new suite of late-end reionization simulations performed with aton-he , a revised version of the GPU-based radiative transfer code aton that includes helium. The simulations are able to reproduce the Ly  |$\alpha$| flux distribution of the E-XQR-30 sample of QSO absorption spectra at |$5 \lesssim z \lesssim 6.2$|⁠ , and show that a large variety of reionization models are consistent with these data. We explore a range of variations in source models and in the early-stage evolution of reionization. Our fiducial reionization history has a mid-point of reionization at |$z = 6.5$|⁠ , but we also explore an 'Early' reionization history with a mid-point at |$z = 7.5$| and an 'Extremely Early' reionization history with a mid-point at |$z = 9.5$|⁠. Haloes massive enough to host observed Ly  |$\alpha$| emitters are highly biased. The fraction of such haloes embedded in ionized bubbles that are large enough to allow high Ly  |$\alpha$| transmission becomes close to unity much before the volume filling factor of ionized regions. For our fiducial reionization history this happens at |$z = 8$|⁠ , probably too late to be consistent with the detection by JWST of abundant Ly  |$\alpha$| emission out to |$z = 11$|⁠. A reionization history in our 'Early' model or perhaps even our 'Extremely Early' model may be required, suggesting a Thomson scattering optical depth in tension with that reported by Planck, but consistent with recent suggestions of a significantly higher value. [ABSTRACT FROM AUTHOR]

During the epoch of reionization (EoR), the 21-cm signal allows direct observation of the neutral hydrogen (H  i) in the intergalactic medium (IGM). In the post-reionization era, this signal instead probes H  i in galaxies, which traces the dark matter density distribution. With new numerical simulations, we investigated the end stages of reionization to elucidate the transition of our Universe into the post-reionization era. Our models are consistent with the latest high-redshift measurements, including ultraviolet (UV) luminosity functions up to redshift |$\simeq$| 8. Notably, these models consistently reproduced the evolution of the UV photon background, which is constrained from Lyman- |$\alpha$| absorption spectra. We studied the dependence of this background on the nature of photon sinks in the IGM, requiring mean free path of UV photons to be |$\sim$| 10 comoving-megaparsecs (cMpc) during the EoR that increases gradually with time during late stages (⁠|$z\lesssim 6$|⁠). Our models revealed that the reionization of the IGM transitioned from an inside-out to an outside-in process when the Universe is less than 0.01 per cent neutral. During this epoch, the 21-cm signal also shifted from probing predominantly the H  i in the IGM to that in galaxies. Furthermore, we identified a statistically significant number of large neutral islands (with sizes up to 40 cMpc) persisting until very late stages (⁠|$5 \lesssim z \lesssim 6$|⁠) that can imprint features in Lyman- |$\alpha$| absorption spectra and also produce a knee-like feature in the 21-cm power spectrum. [ABSTRACT FROM AUTHOR]

Enlightening our understanding of the first galaxies responsible for driving reionization requires detecting the 21-cm signal from neutral hydrogen. Interpreting the wealth of information embedded in this signal requires Bayesian inference. Parameter inference from the 21-cm signal is primarily restricted to the spherically averaged power spectrum (1D PS) owing to its relatively straightforward derivation of an analytic likelihood function enabling traditional Monte Carlo Markov Chain approaches. However, in recent years, simulation-based inference (SBI) has become feasible which removes the necessity of having an analytic likelihood, enabling more complex summary statistics of the 21-cm signal to be used for Bayesian inference. In this work, we use SBI, specifically marginal neural ratio estimation to learn the likelihood-to-evidence ratio with swyft , to explore parameter inference using the cylindrically averaged 2D PS. Since the 21-cm signal is anisotropic, the 2D PS should yield more constraining information compared to the 1D PS which isotropically averages the signal. For this, we consider a mock 1000 h observation of the 21-cm signal using the Square Kilometre Array and compare the performance of the 2D PS relative to the 1D PS. Additionally, we explore two separate foreground mitigation strategies, perfect foreground removal and wedge avoidance. We find the 2D PS outperforms the 1D PS by improving the marginalized uncertainties on individual astrophysical parameters by up to |$\sim 30\!-\!40$|  per cent irrespective of the foreground mitigation strategy. Primarily, these improvements stem from how the 2D PS distinguishes between the transverse, |$k_{\perp }$|⁠ , and redshift-dependent, |$k_{\parallel }$|⁠ , information which enables greater sensitivity to the complex reionization morphology. [ABSTRACT FROM AUTHOR]

Detecting the 21-cm signal at |$z\gtrsim 6$| will reveal insights into the properties of the first galaxies responsible for driving reionization. To extract this information, we perform parameter inference with three-dimensional simulations of the 21-cm signal embedded within a Bayesian inference pipeline. Presently, when performing inference, we must choose which sources of uncertainty to sample and which to hold fixed. Since the astrophysics of galaxies is much more uncertain than that of the underlying halo-mass function (HMF), we typically parametrize and model the former while fixing the latter. However, doing so may bias our inference of the galaxy properties. In this work, we explore the consequences of assuming an incorrect HMF and quantify the relative biases on our inferred astrophysical model parameters when considering the wrong HMF. We then relax this assumption by constructing a generalized five parameter HMF model and simultaneously recover it with our underlying astrophysical model. For this, we use 21cmfast and perform simulation-based inference using marginal neural ratio estimation to learn the likelihood-to-evidence ratio with Swyft. Using a mock 1000-h observation of the 21-cm power spectrum from the forthcoming Square Kilometre Array, conservatively assuming foreground wedge avoidance, we find that assuming the incorrect HMF can bias the recovered astrophysical parameters by up to |$\sim 3{\!-\!}4\sigma$| even when including independent information from observed luminosity functions. Using our generalized HMF model, although we recover our astrophysical parameters with a factor of |$\sim 2{\!-\!}4$| larger marginalized uncertainties, the constraints are unbiased, agnostic to the underlying HMF and therefore more conservative. [ABSTRACT FROM AUTHOR]

Forsterite is a primary constituent of interstellar dust and planetary systems. It is believed to originate from the outflows of oxygen-rich stars and undergo further processing within the interstellar medium through the action of cosmic rays and shocks. Under these harsh conditions, point defects may form, such as MgO Schottky vacancies. These vacancies can then undergo atom reconstruction as part of a chemical process to maintain the system's crystalline structure. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously observed interstellar molecules and are thought to form through gas-phase reactions akin to sooting flames. However, their role and impact on dust stability remain unknown. In this study, we employ an atomistic artificial-intelligence-based method, surrogate machine learning trained directly by density functional theory. Specifically, we utilize gofee (global optimization with first-principles energy expressions) to predict possible reconstructions of MgO vacancies on a crystalline forsterite (010) surface as an important component of interstellar dust and planetary systems. We identify nine possible reconstructions involving the formation of unbound Si and O atoms. We investigate their energy stability and find that the reconstruction of Si–O atoms stabilizes the vacancy by about 0.54 eV. Additionally, if PAHs bind with the unbound O and Si atoms of the vacancy, the vacancy is stabilized by approximately 1.76 eV. We demonstrate that PAHs, along with the reconstruction of unbound atoms on the dust surface, affect the stability of the dust, which might open up avenues for diverse chemistry. [ABSTRACT FROM AUTHOR]

Multiple observations now suggest that the hydrogen reionization may have ended well below redshift six. While there has previously been no conclusive proof of extended neutral islands in the |$z \lt 6$| intergalactic medium, it is possible that such islands give rise to the giant Ly  |$\alpha$| absorption troughs seen in the spectra of high-redshift quasars. Here, we present evidence that the deepest and longest known Ly  |$\alpha$| trough at |$z \,\lt\, 6$|⁠ , towards ULAS J0148 + 0600 (J0148), is associated with damping wing absorption. The evidence comes from a window of strong Ly  |$\alpha$| transmission at the edge of the J0148 proximity zone. We show that the relatively smooth profile of this transmission window is highly unlikely to arise from resonant absorption alone, but is consistent with the presence of a damping wing. We further argue that the damping wing is unlikely to arise from a compact source due to the lack of associated metal lines, and is more likely to arise from an extended neutral island associated with the giant Ly  |$\alpha$| trough. We investigate the physical conditions that may give rise to the strong transmission window, and speculate that it may signal an usually deep void, nearby ionizing sources, and/or the recent passage of an ionization front. [ABSTRACT FROM AUTHOR]

We study the radio continuum emission of four galaxies experiencing ram-pressure stripping in four clusters of the Shapley Supercluster at redshift |$z\sim 0.05$|⁠. Multiband (235–1367 MHz) radio data, complemented by integral-field spectroscopy, allow us to detect and analyse in detail the non-thermal component both in the galaxy discs and the radio continuum tails. Three galaxies present radio continuum tails that are tens of kiloparsecs long. By deriving the radio spectral index in the inner and outer tails and comparing our findings with the distribution of the extraplanar ionized gas and the results of N -body/hydrodynamical simulations, we demonstrate that these tails are caused by the ram pressure, which, together with the ionized gas, sweeps the magnetic field from the galaxy discs. We suggest that the radio continuum emission in these tails can be differently powered by (i) in situ star formation, (ii) relativistic electrons stripped from the disc, and (iii) shock excitation or a combination of them. All the ram-pressure-stripped galaxies are found in environments where cluster–cluster interactions occurred and/or are ongoing, thus strongly supporting the thesis that cluster and group collisions and mergers may locally increase the ram pressure and trigger hydrodynamical interactions between the intracluster medium and the interstellar medium of galaxies. [ABSTRACT FROM AUTHOR]

We studied the physical conditions in the local interstellar medium (ISM) and at high redshift by fitting observed column densities of CO and H2 rotational levels and C  i fine-structure levels using photodissociation models calculated with the Meudon PDR code. We analysed CO absorption systems in 28 sight lines in the local ISM and seven damped Lyman-α absorption systems at high redshift, covering |$N({\rm H_2})=10^{19}\!-\!10^{21.5}\,{\rm cm}^{-2}$| and |$N({\rm CO})=10^{13}\!-\!10^{18}\,{\rm cm}^{-2}$|⁠. We constructed a method to accurately calculate CO excitation, incorporating the effects of photon trapping. Our findings indicate that in the local ISM, CO excitation is primarily driven by collisions and excitation due to the CMB radiation. We demonstrated that an increase in CO excitation observed near |$N({\rm CO})\simeq 10^{15}~{\rm cm^{-2}}$|⁠ , is attributed to an increase in gas densities from |${\simeq}100\,{\rm cm}^{-3}$| to |${\simeq}300\!-\!1000\,{\rm cm}^{-3}$|⁠. CO absorption systems in the local ISM are characterized by a gas number density of about 10–1000 cm−3, a kinetic temperature of 10–100 K, and an intensity of external UV field ranging from 0.1 to 10 units of Mathis field. Compared to the average gas probed by C  i absorption, the gas detected in CO is denser and colder, while the external UV field remains nearly constant. We observed a negative correlation between the kinetic temperature and both N (CO) and N (H2), with power-law slopes of |$-0.21\pm 0.02$| and |$-0.65\pm 0.05$|⁠ , respectively. At the same time, the gas number density exhibits a positive correlation with N (CO) and N (H2) with slopes of |$0.38\pm 0.02$| and |$1.15\pm 0.05$|⁠ , respectively. [ABSTRACT FROM AUTHOR]

Small-scale winds driven from accretion discs surrounding active galactic nuclei (AGN) are expected to launch kpc-scale outflows into their host galaxies. However, the ways in which the structure of the interstellar medium (ISM) affects the multiphase content and impact of the outflow remain uncertain. We present a series of numerical experiments featuring a realistic small-scale AGN wind with velocity |$5\times 10^3 \!-\! 10^4\rm {\ km\ s^{-1}}$| interacting with an isolated galaxy disc with a manually controlled clumpy ISM, followed at sub-pc resolution. Our simulations are performed with arepo and probe a wide range of AGN luminosities (⁠|$L_{\rm {AGN}}{=} 10^{43-47}\rm {\ erg\ s^{-1}}$|⁠) and ISM substructures. In homogeneous discs, the AGN wind sweeps up an outflowing, cooling shell, where the emerging cold phase dominates the mass and kinetic energy budgets, reaching a momentum flux |$\dot{p} \approx 7\ L/c$|⁠. However, when the ISM is clumpy, outflow properties are profoundly different. They contain small, long-lived (⁠|$\gtrsim 5\ \rm {Myr}$|⁠), cold (⁠|$T{\lesssim }10^{4.5}{\rm {\ K}}$|⁠) cloudlets entrained in the faster, hot outflow phase, which are only present in the outflow if radiative cooling is included in the simulation. While the cold phase dominates the mass of the outflow, most of the kinetic luminosity is now carried by a tenuous, hot phase with |$T \gtrsim 10^7 \, \rm K$|⁠. While the hot phases reach momentum fluxes |$\dot{p} \approx (1 - 5)\ L/c$|⁠ , energy-driven bubbles couple to the cold phase inefficiently, producing modest momentum fluxes |$\dot{p} \lesssim L/c$| in the fast-outflowing cold gas. These low momentum fluxes could lead to the outflows being misclassified as momentum-driven using common observational diagnostics. We also show predictions for scaling relations between outflow properties and AGN luminosity and discuss the challenges in constraining outflow driving mechanisms and kinetic coupling efficiencies using observed quantities. [ABSTRACT FROM AUTHOR]

Hot, |$\log (T/\mathrm{K})$| |$\sim$| 7.5, gas was recently discovered in the Milky Way in extragalactic sightlines. In order to determine its location, here we present sightlines to Galactic X-ray binaries (XRBs) passing through the Interstellar Medium (ISM). In this pilot study, we investigate absorption features of S |$_{\mathrm{XVI}}$|⁠ , Si |$_{\mathrm{XIV}}$|⁠ , and Ne |$_{\mathrm{X}}$| in the spectra of three XRBs, namely 4U 1735–44, 4U 1820–30, and Cyg X-2, using Chandra High Energy Transmission Grating archival observations. We do not detect any of these lines. We determine the 2 |$\sigma$| upper limit for the equivalent widths of the undetected absorption lines and the column densities of the corresponding ions. We note that the 2 |$\sigma$| upper limits for S |$_{\mathrm{XVI}}$| K |$\alpha$| and Si |$_{\mathrm{XIV}}$| K |$\alpha$| are an order of magnitude smaller than those previously detected in the extragalactic sightlines. Our finding suggests that if any gas at |$\log (T/\mathrm{K})$| |$\gt\ 7$| is present in the Galactic ISM, it is unlikely to be ubiquitous. This is an important result because it implies that S |$_{\mathrm{XVI}}$|⁠ , Si |$_{\mathrm{XIV}}$|⁠ , and Ne |$_{\mathrm{X}}$| absorption detected in extragalactic sightlines is not from the ISM, but is likely from a hot gas phase in the extraplanar region beyond the ISM or in the extended Circumgalactic Medium. [ABSTRACT FROM AUTHOR]

The identification of complex pre-biotic molecules using millimetre and submillimetre telescopes allows us to understand how the basic building blocks of life are formed in the universe. In the interstellar medium, ethylene glycol (⁠|$({\rm CH}_2{\rm OH})_{2}$|⁠) is the simplest sugar alcohol molecule, and it is the reduced alcohol of the simplest sugar-like molecule, glycolaldehyde (⁠|${\rm CH}_{2}{\rm OHCHO}$|⁠). We present the detection of the rotational emission lines of |$aGg^{\prime }$| conformer of ethylene glycol (⁠|$({\rm CH}_2{\rm OH})_{2}$|⁠) towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array. The estimated column density of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| towards the G358.93–0.03 MM1 is (4.5 |$\pm 0.1)\times 10^{16}$| cm |$^{-2}$| with an excitation temperature of 155 |$\pm$| 35 K. The abundance of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with respect to |${\rm H}_{2}$| is (1.4 |$\pm 0.5)\times 10^{-8}$|⁠. Similarly, the abundances of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with respect to |${\rm CH}_{2}{\rm OHCHO}$| and |${\rm CH}_{3}{\rm OH}$| are 3.1 |$\pm$| 0.5 and (6.1 |$\pm 0.3)\times 10^{-3}$|⁠. We compare the estimated abundance of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| with the existing three-phase warm-up chemical model abundance of |$({\rm CH}_2{\rm OH})_{2}$|⁠ , and we notice the observed abundance and modelled abundance are nearly similar. We discuss the possible formation pathways of |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| towards the hot molecular cores, and we find that |$aGg^{\prime }$| - |$({\rm CH}_2{\rm OH})_{2}$| is probably created via the recombination of two |${\rm CH}_{2}{\rm OH}$| radicals on the grain surface of G358.93–0.03 MM1. [ABSTRACT FROM AUTHOR]

The recent detection of ethanolamine (EtA, HOCH |$_2$| CH |$_2$| NH |$_2$|⁠), a key component of phospholipids, i.e. the building blocks of cell membranes, in the interstellar medium is in line with an exogenous origin of life-relevant molecules. However, the stability and survivability of EtA molecules under inter/circumstellar and Solar System conditions have yet to be demonstrated. Starting from the assumption that EtA mainly forms on interstellar ice grains, we have systematically exposed EtA, pure and mixed with amorphous water (H |$_2$| O) ice, to electron, ion, and thermal processing, representing 'energetic' mechanisms that are known to induce physicochemical changes within the ice material under controlled laboratory conditions. Using infrared (IR) spectroscopy, we have found that heating of pure EtA ice causes a phase change from amorphous to crystalline at 180 K, and further temperature increase of the ice results in sublimation-induced losses until full desorption occurs at about 225 K. IR and vacuum ultraviolet (VUV) spectra of EtA-containing ices deposited and irradiated at 20 K with 1 keV electrons as well as IR spectra of H |$_2$| O:EtA mixed ice obtained after 1 MeV He |$^+$| ion irradiation have been collected at different doses. The main radiolysis products, including H |$_2$| O, CO, CO |$_2$|⁠ , NH |$_3$|⁠ , and CH |$_3$| OH, have been identified and their formation pathways are discussed. The measured column density of EtA is demonstrated to undergo exponential decay upon electron and ion bombardment. The half-life doses for electron and He |$^+$| ion irradiation of pure EtA and H |$_2$| O:EtA mixed ice are derived to range between |$10.8\!-\!26.3$|  eV/16u. Extrapolating these results to space conditions, we conclude that EtA mixed in H |$_2$| O ice is more stable than in pure form and it should survive throughout the star and planet formation process. [ABSTRACT FROM AUTHOR]

Ram pressure stripping is perhaps the most efficient mechanism for removing gas and quenching galaxies in dense environments, as they move through the intergalactic medium. Extreme examples of on-going ram pressure stripping are known as jellyfish galaxies, characterized by a tail of stripped material that can be directly observed in multiple wavelengths. Using the largest homogeneous broad-band optical jellyfish candidate sample in local clusters known to date, we measure the angle between the direction of the tails visible in the galaxies, and the direction towards the host cluster centre. We find that 33 per cent of the galaxy tails point away from the cluster centre, 18  per cent point towards the cluster centre, and 49  per cent point elsewhere. Moreover, we find stronger signatures of ram pressure stripping happening on galaxies with a tail pointing away and towards the cluster centre, and larger velocity dispersion profiles for galaxies with tails pointing away. These results are consistent with a scenario where ram pressure stripping has a stronger effect for galaxies following radial orbits on first infall. The results also suggest that in many cases, radially infalling galaxies are able to retain their tails after pericenter and continue to experience significant on-going ram pressure stripping. We further constrain the lifespan of the optical tails from the moment they first appear to the moment they disappear, by comparing the observed tail directions with matched N -body simulations through Bayesian parameter estimation. We obtain that galaxy tails appear for the first time at |$\sim 1.16$| R |$_{200}$| and disappear |$\sim 660$| Myr after pericenter. [ABSTRACT FROM AUTHOR]

Making use of the APOGEE DR17 catalogue with high quality data for 143 509 red giant branch stars we explore the strength of different mechanisms that causes a star to radially migrate in the Milky Way stellar disc. At any position in the disc we find stars that are more metal-rich than the local interstellar medium. This is surprising and normally attributed to the migration of these stars after their formation inside their current Galactocentric radius. Such stars are prime candidates for studying the strength of different migratory processes. We specifically select two types of metal-rich stars: (i) super metal-rich stars (⁠|$\mathrm{[Fe/H]}\gt 0.2$|⁠) and (ii) stars that are more metal-rich than their local environment. For both, we explore the distribution of orbital parameters and ages as evidence of their migration history. We find that most super metal-rich stars have experienced some amount of churning as they have orbits with |$R_g\gtrsim 5 \,{\rm kpc}$|⁠. Furthermore, about half of the super metal-rich stars are on non-circular orbits (⁠|$\mathrm{ecc} \gt 0.15$|⁠) and therefore also have experienced blurring. The metallicity of young stars in our sample is generally the same as the metallicity of the interstellar medium, suggesting they have not radially migrated yet. Stars with lower metallicity than the local environment have intermediate to old ages. We further find that super metal-rich stars have approximately the same age distribution at all Galactocentric radii, which suggests that radial migration is a key mechanism responsible for the chemical compositions of stellar populations in the Milky Way. [ABSTRACT FROM AUTHOR]

Measurements of the mean free path of Lyman-continuum photons in the intergalactic medium during the epoch of reionization can help constrain the nature of the sources as well as sinks of hydrogen-ionizing radiation. A recent approach to this measurement has been to utilize composite spectra of multiple quasars at |$z\sim 6$|⁠ , and infer the mean free path after correcting the spectra for the presence of quasar proximity zones. This has revealed not only a steep drop in the mean free path from |$z=5$| to |$z=6$|⁠ , but also potentially a mild tension with reionization simulations. We critically examine such direct measurements of the mean free path for biases due to quasar environment, incomplete reionization, and quasar proximity zones. Using cosmological radiative transfer simulations of reionization combined with one-dimensional radiative transfer calculations of quasar proximity zones, we find that the bias in the mean free path due to overdensities around quasars is minimal at |$z\sim 6$|⁠. Patchiness of reionization at this redshift also does not affect the measurements significantly. Fitting our model to the data results in a mean free path of |$\lambda _{\mathrm{mfp}}=1.49^{+0.47}_{-0.52}$|  pMpc at |$z=6$|⁠ , which is consistent with the recent measurements in the literature, indicating robustness with respect to the modelling of quasar proximity zones. We also compare various ways in which the mean free path has been defined in simulations before the end of reionization. Overall, our finding is that recent measurements of the mean free path appear to be robust relative to several sources of potential bias. [ABSTRACT FROM AUTHOR]

The intergalactic medium in the vicinity of galaxy protoclusters are interesting testbeds to study complex baryonic effects such as gravitational shocks and feedback. Here, we utilize hydrodynamical simulations from the SIMBA and The Three Hundred suites to study the mechanisms influencing large-scale Lyman- |$\alpha$| transmission in |$2\lt z\lt 2.5$| protoclusters. We focus on the matter overdensity-Lyman- |$\alpha$| transmission relation |$(\delta _m-\delta _F)$| on Megaparsec-scales in these protoclusters, which is hypothesized to be sensitive to the feedback implementations. The lower density regions represented by the SIMBA-100 cosmological volume trace the power-law |$\delta _m-\delta _F$| relationship often known as the fluctuating Gunn–Peterson approximation. This trend is continued into higher density regions covered by simulations that implement stellar feedback only. Simulations with active galactic nucleus (AGN) thermal and AGN jet feedback, however, exhibit progressively more Lyman- |$\alpha$| transmission at fixed matter overdensity. Compared with the seven protoclusters observed in the COSMOS field, only two display the excess absorption expected from protoclusters. The others exhibit deviations: four show some increased transparency suggested by AGN X-ray thermal feedback models while the highly transparent COSTCO-I protocluster appears to reflect intense jet feedback. Discrepancies with the stellar-feedback-only model suggests processes at play beyond gravitational heating and/or stellar feedback as the cause of the protocluster transparencies. Some form of AGN feedback is likely at play in the observed protoclusters, and possibly long-ranged AGN jets in the case of COSTCO-I. While more detailed and resolved simulations are required to move forward, our findings open new avenues for probing AGN feedback at Cosmic Noon. [ABSTRACT FROM AUTHOR]

We present determinations of the gas-phase and stellar metallicities of a sample of 65 star-forming galaxies at |$z \simeq 3.5$| using rest-frame far-ultraviolet (FUV) spectroscopy from the VANDELS survey in combination with follow-up rest-frame optical spectroscopy from VLT /KMOS and Keck/MOSFIRE. We infer gas-phase oxygen abundances (⁠|$Z_{\mathrm{g}}$|⁠ ; tracing O/H) via strong optical nebular lines and stellar iron abundances (⁠|$Z_{\star }$|⁠ ; tracing Fe/H) from full spectral fitting to the FUV continuum. Our sample spans the stellar mass range |$8.5 \lt \mathrm{log}(M_{\star }/\mathrm{M}_{\odot }) \lt 10.5$| and shows clear evidence for both a stellar and gas-phase mass-metallicity relation (MZR). We find that our O and Fe abundance estimates both exhibit a similar mass-dependence, such that |$\mathrm{Fe/H}\propto M_{\star }^{0.30\pm 0.11}$| and |$\mathrm{O/H}\propto M_{\star }^{0.32\pm 0.09}$|⁠. At fixed |$M_{\star }$| we find that, relative to their solar values, O abundances are systematically larger than Fe abundances (i.e. α-enhancement). We estimate an average enhancement of |$\mathrm{(O/Fe)} = 2.65 \pm 0.16 \times \mathrm{(O/Fe)_\odot }$| which appears to be independent of |$M_{\star }$|⁠. We employ analytic chemical evolution models to place a constraint on the strength of galactic-level outflows via the mass-outflow factor (⁠|$\eta$|⁠). We show that outflow efficiencies that scale as |$\eta \propto M_{\star }^{-0.32}$| can simultaneously explain the functional form of of the stellar and gas-phase MZR, as well as the degree of α-enhancement at fixed Fe/H. Our results add further evidence to support a picture in which α-enhanced abundance ratios are ubiquitous in high-redshift star-forming galaxies, as expected for young systems whose interstellar medium is primarily enriched by core-collapse supernovae. [ABSTRACT FROM AUTHOR]