arXiv subjects

Céline Péroux

Publications and source records attributed to Céline Péroux.

At least 19 recordsLinked to original sources

arXiv2026

MUSE-ALMA Haloes XIV: The ALMA Large Programme Data Release

The interactions between gas and galaxies are of paramount importance to our understanding of structure formation. A fundamental element of such baryon cycle studies is a complete census of the condensed matter (stars and cold gas) in both galaxies and their immediate surroundings, the so-called circumgalactic medium. Of particular importance are the processes of converting molecular gas into stars and deciphering whether this <100K gas is tracing gas flows. The MUSE-ALMA Haloes survey has assembled probes of the neutral atomic gas HI, ionised gas and stellar component for a sample of 79 $z\sim0.5$ galaxies. This is achieved by combining absorption line spectroscopy of background quasars with projected impact parameter as low as 5 kpc and up to 250 kpc to probe the low density circumgalactic gas with emission line tracers of both ionised gas and stars. This paper presents the Large Programme observational set-up and releases the data characterising the molecular phase of some of the MUSE-ALMA Haloes targets so as to reach a complete census of their condensed baryons. ALMA's unique millimetre coverage and high sensitivity is ideal to characterise the CO emission of these $z\sim0.5$ HI-selected galaxies. By measuring the molecular mass, kinematics, gas flows and gas fractions, this project then: i) quantifies the role of molecular gas in HI-rich galaxies, ii) characterises the molecular phase of gas flows from morpho-kinematics analyses, and iii) establishes a census of the condensed baryons in the interstellar and circumgalactic media. Ultimately, these results will provide unique insights into the baryon cycle - a crucial component of galaxy formation.

astro-ph.GA↗

arXiv2026

Stellar feedback drives the baryon deficiency in low-mass galaxies

Stellar feedback, as a key process regulating the baryon cycle, is thought to greatly redistribute baryonic material inside and outside the dark matter halos (DMHs), however the observational evidences are lacking. Through stacking analyses of ~400,000 galaxy spectra from Dark Energy Spectroscopic Instrument (DESI), we find star formation driven cool outflows in Mg II absorption line. Assuming only gravity acts on the launched gas, our calculations reveal that outflows from low mass galaxies ($M_*<10^{10}\,\rm M_\odot$) are capable of escaping beyond the DMHs, which aligns well with our finding in the circumgalactic medium (CGM) absorption along the minor-axes of galaxies using background quasars. This research offers indirect evidence that stellar feedback drives the low baryon retention rate in low-mass haloes, implicating that baryonic processes within galaxies are connected with the diffuse matter beyond the DMHs.

astro-ph.GA↗

arXiv2026

VLT Beyond 2030 and Call for White Papers

The VLT Beyond 2030 conference gathered participants from the community and ESO experts to present and discuss science and technological ideas for the future of both the Very Large Telescope (VLT) and its interferometer (VLTI). An effort was made to pair participants with science and engineering backgrounds so as to optimise cross-field fertilisation and initiate 'out-of-the-main-room' discussions. The well-attended conference reflected the continued interest within our community in developing new projects for the VLT/I and the will to use this facility to answer key science questions that are likely to be crucial in the decades to come. This article presents a summary of the overall points of focus during the conference and also serves as the opening of the call for White Papers with a deadline of 15 January 2027. Proposers are encouraged to fast-forward to the years beyond 2030 to identify essential areas of research so that together we can shape a long-term roadmap for the VLT/I.

astro-ph.IM↗

arXiv2026

High-S/N Quasar Observations with HST/COS: Deep Fields for Spectroscopy

Hubble is still in prime observing condition for making transformative discoveries in UV astronomy. In this white paper we describe the science case for a deep (S/N>30) UV spectroscopic survey with HST/COS targeting approximately 20 QSOs at 0.5<z<1.5 at good resolution (20 km/s). This survey would capitalize on our current UV capability, produce a legacy dataset enabling community science in many areas of galactic and extragalactic research, and pioneer a path for future UV science with the Habitable Worlds Observatory. Such high-S/N spectra are largely missing from the MAST archives, and would be analogous to the deep Hubble imaging fields (HDF, UDF, Frontier Fields) that have been enormously successful and far-reaching in their science impact. This legacy dataset would enable frontier science programs in several areas, including (1) studies of the CGM and IGM at unparalleled sensitivity, covering a wide range of UV metal lines and reaching very low H I column densities of log N=12.6 and low metallicities near [Z/H]=-2, enabling precision studies of the chemical abundances, ionization, temperature, and baryon and metal budgets of the CGM and IGM; (2) diffuse gas in the Milky Way and Local Group, including high-velocity clouds and gas streams from satellite mergers; (3) AGN outflows, which would be probed in the rest-frame extreme ultraviolet (EUV), covering continuum-generation mechanisms and diagnostics of gas in accretion-disk outflows.

astro-ph.GA↗

arXiv2026

The Baryon Budget of Galaxies across the First Billion Years

We provide a complete census of the baryons in early galaxies to investigate the phases in which gas and stars reside, their corresponding budgets, depletion times, and stellar return fraction as a function of redshift and stellar age. We use the ColdSIM hydrodynamical time-dependent non-equilibrium chemistry simulations and perform a detailed analysis of the cold, warm, hot, and stellar phases for both bound structures (galaxies/CGM) and the diffuse IGM. We investigate in depth the cold HI and H2 components, explicitly computed in our simulations, and their relations with host mass, SFR, metallicity and depletion times. We also provide observational insights and discuss the implications for stellar mass functions, PopIII star formation and changes in the IMF. We find that cosmic gas prior to reionisation is mostly cold, while at later epochs the warm phase becomes dominant due to enhanced star formation activity and increasing UV reionising radiation. Stellar return fractions at these times are ~0.15-0.20, a factor of two lower than the values usually adopted. Cold, warm, and hot gas masses as well as HI and H2 components show increasing trends with mass and SFR, while depletion times decrease down to 0.01-0.1 Gyr with a weak metallicity dependence. The resulting star formation efficiency remains at the level of a few per cent and gas-to-star fractions decline with mass, influenced by local feedback and environment. Our findings are consistent with ALMA, VLA and IRAM surveys at later epochs, including ALFALFA, xCOLDGASS, GASS, xGASS, EDGE-CALIFA, PHIBBS, and ASPECS. Gas phases are quantitatively related to the underlying stellar populations and can be used to infer unknown quantities. In the appendix we provide fit functions describing the trends of the stellar return fraction, the main sequence, phase mass relations, gas-to-star fractions and depletion times.

astro-ph.GA↗

arXiv2026

FEASTS and MHONGOOSE: HI Column Density Distribution at $z=0$ for $N_\mathrm{HI}>10^{17.8}\, \mathrm{cm}^{-2}$

We present the first $z=0$ HI column density distribution function, $f(N_\mathrm{HI})$, extending down to $\log (N_\mathrm{HI}/\mathrm{cm}^{-2})=17.8$. This was derived from high-sensitivity 21-cm emission-line imaging at $\sim$1 kpc resolution. At high-column-densities (19.8$< \log (N_\mathrm{HI}/\mathrm{cm}^{-2}) <$21.3), our results align with earlier $z=0$ studies but benefit from 100 times greater sensitivity. Comparisons with $z\sim3$ quasar absorption-line studies reveal that $f(N_\mathrm{HI})$ at $z=0$ is systematically lower by 0.1-0.4 dex for $19.2< \log (N_\mathrm{HI}/\mathrm{cm}^{-2}) <21$. However, the distributions become comparable at $17.8< \log (N_\mathrm{HI}/\mathrm{cm}^{-2}) <19.2$, suggesting weak evolution in this regime. Extrapolating the length incidence ($\mathrm{d}N/\mathrm{d}X$) for $\log (N_\mathrm{HI}/\mathrm{cm}^{-2}) >17.5$ implies a covering fraction ($f_\mathrm{cov}$) of $\sim0.7$ within 1-kpc-scale HI-detected pixels at $z=0$. Notably, for $17.8< \log (N_\mathrm{HI}/\mathrm{cm}^{-2}) <20$, impact parameters at a given $N_\mathrm{HI}$ are significantly lower than previous $z\sim0$ absorption-line results and TNG50 simulation predictions. This discrepancy indicates challenges in identifying galaxy counterparts for absorbers and in recovering low-column-density HI within cosmological simulations. Finally, we derive a covering fraction of 0.006 for $\log (N_\mathrm{HI}/\mathrm{cm}^{-2}) >17.8$ gas within the virial radius around Milky-Way-like galaxies. These findings provide new constraints on the baryonic flows and gaseous dynamics governing galaxy evolution.

astro-ph.GA↗

arXiv2026

Chemodynamical properties of gas-rich galaxies: a comparison of observations and simulations

We perform a comprehensive analysis of the chemical and dynamical properties of quasar-damped Lyman-α (DLA) galaxies and compare these to the GEAR chemodynamical simulations. Specifically, we aim to constrain the behavior of α-element enhancements with metallicity, the dependence of [α/Fe] on the specific star formation rate (sSFR), and the absorption-line velocity widths (Δv90) vs. stellar mass, Δv90 vs. metallicity, and mass-metallicity relations. For the comparison, we select five galaxies simulated with the chemodynamical Tree-SPH code GEAR with stellar masses in the range of log(M*/Msol) between 6.1 and 10.8, and at six different redshifts between 0.33 and 4.12. We find that the abundance ratios [α/Fe] and [M/H] observed in the interstellar medium (ISM) of DLA galaxies overlap with the abundance trends in gas of the simulated galaxies. Our findings corroborate a picture in which DLAs with Δv90 below and above 100 km/s trace galaxies with masses in the ranges of log M* 6 - 8 and 8 - 11 solar masses, respectively. We suggest that observations should be used with caution when constraining the theoretical [α/Fe] vs. sSFR relations because of systematics (if abundances are obtained from emission lines) or differences in the gas properties as probed by a DLA and its counterpart. So far, only the observations in absorption of inner gas of the LMC and SMC are in agreement with the simulated data. We confirm that DLAs detected at large impact parameters most likely probe the gas of satellite or other halo galaxies which are adjacent to the central galaxy. We further find that the velocity widths vs. stellar masses and mass-metallicity relations agree well with observations, while GEAR should be calibrated more carefully to reproduce the Δv90 vs. metallicity relation.

astro-ph.GA↗

arXiv2025

The First Large Absorption Survey in HI (FLASH): II. Pilot Survey data release and first results

The First Large Absorption Survey in HI (FLASH) is a large-area radio survey for neutral hydrogen in the redshift range 0.4 1$, and appear to be a mixture of intervening and associated systems. Interestingly, around two-thirds of the lines found in this untargeted sample are detected against sources with a peaked-spectrum radio continuum, which are only a minor (5-20%) fraction of the overall radio-source population. The overall detection rate for HI absorption lines in the Pilot Surveys (0.3 to 0.5 lines per ASKAP field) is a factor of two below the expected value. One possible reason for this is the presence of a range of spectral-line artefacts in the Pilot Survey data that have now been mitigated and are not expected to recur in the full FLASH survey. A future paper will discuss the host galaxies of the HI absorption systems identified here.

astro-ph.GA↗

arXiv2025

A Global Census of Metals in the Universe

We present a census of the mass density of metals and their evolution with cosmic time on a global scale throughout the Universe, synthesizing robust estimates of metals in stars, hot intra-cluster gas, and gaseous absorbers tracing neutral gas as well as ionized gas in the circumgalactic and intergalactic media. We observe an order of magnitude increase in the stellar metal mass density from z~2.5 to 0.7, over which time stars emerge as the most important metal reservoir at low redshifts, housing ~30% of the total expected metal density at z~0.1. Hot virialized intracluster/intragroup gas accounts for ~15% and 10% of metals at z~0.1 and 0.7, respectively. Using metallicity measurements from CCC, KODIAQ-Z, and HD-LLS surveys covering redshifts z<1 to z~2-3.5, we investigate the global distribution of metals in extragalactic cool ionized gas as a function of HI column density. During the period from z~3 to z<1, the global metal density of cool (T~10^{4-5} K) gas has doubled. However, the fractional contribution of the ionized gas to the total expected metal density decreased from ~20% at z~3 to ~4% at z<1. The cosmic metal density of all gas phases has increased with cosmic time, reflecting an ``inside-out'' metal dispersion by feedback mechanisms and galactic outflows.

astro-ph.GA↗

arXiv2025

FEASTS Combined with Interferometry. III. The Low Column Density HI Around M51 and Possibility of Turbulent-mixing Gas Accretion

With a new joint-deconvolution pipeline, we combine the single-dish and interferometric atomic hydrogen (HI) data of M51 observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) (FEASTS program) and the Very Large Array (VLA) (THINGS). The product data cube has a typical line width of $13\,\text{km}\,\text{s}^{-1}$ and a $2σ$ line-of-sight (LOS) sensitivity of HI column density $N_\text{HI}\sim3.2\times10^{18}\,\text{cm}^{-2}$ at a spatial resolution of ${\sim}18''$ (${\sim}0.7\,\text{kpc}$). Among the HI-detected LOSs extending to ${\sim}50\,\text{kpc}$, ${\sim}89\%$ consist of diffuse HI only, which is missed by previous VLA observations. The distribution of dense HI is reproduced by previous hydrodynamical simulations of this system, but the diffuse component is not, likely due to unresolved physics related to the interaction between the circumgalactic and interstellar media. With simple models, we find that these low-$N_\text{HI}$ structures could survive the background ultraviolet photoionization, but are susceptible to the thermal evaporation. We find a positive correlation between LOS velocity dispersion ($σ_v$) and $N_\text{HI}$ with a logarithmic index of ${\sim}0.5$. Based on existing turbulent mixing layer (TML) theories and simulations, we propose a scenario of hot gas cooling and accreting onto the disk through a TML, which could reproduce the observed power index of ${\sim}0.5$. We estimate the related cooling and accretion rates to be roughly one-third to two-thirds of the star-formation rate. A typical column density of diffuse HI (${\sim}10^{19}\,\text{cm}^{-2}$) can be accreted within $300\,\text{Myr}$, the interaction time scale previously estimated for the system. Such a gas accretion channel has been overlooked before, and may be important for gas-rich interacting systems and for high redshift galaxy evolution.

astro-ph.GA↗

arXiv2025

ALMACAL XIV: X-Shooter Spectroscopy, Infrared Properties and Radio SEDs of Calibrators

The ALMACAL-22 survey includes over 2700 hours of observations of ALMA phase and amplitude calibrators, spanning frequencies from 84 to 950 GHz across bands 3 to 10. In total, 687 out of the 1,047 calibrators have redshifts confirmed with spectroscopy and we find an additional 50 featureless blazars. The redshift distribution of the ALMACAL-22 sample peaks at $z \approx 1$ and spans a wide range, from the nuclei of nearby galaxies at $z \ll 0.01$ to quasars at $z = 3.742$. 70 new VLT/X-Shooter spectra of these sources covering UV to NIR wavelengths are also presented, which will be used in future stacking experiments to search for cold gas in the circumgalactic medium. Infrared magnitudes from WISE indicate that the majority of the sources are consistent with being quasars or blazars. After fitting the radio spectral energy distributions of the calibrators, we find that most ALMA calibrators exhibit peaked spectra or are re-triggered which is surprising given the large number of blazars in the sample. The peak frequencies span three orders of magnitude from 100 MHz to 170 GHz, corresponding to linear sizes ranging from sub-pc to $>$ 10 kpc. In the future, when combined with high-resolution radio imaging, these results will offer valuable constraints on the molecular gas content of the CGM, as well as the ages and duty cycles of AGN jets. The ever-growing ALMACAL data set will remain an indispensable resource for studying the various aspects of galaxy formation and evolution.

astro-ph.GA↗

arXiv2025

FEASTS Combined with Interferometry (IV): Mapping HI Emission to a limit of $N_{\text{HI}}=10^{17.7} \text{cm}^{-2}$ in Seven Edge-on Galaxies

We present a statistical study of the neutral atomic hydrogen (HI) gas extending into the circumgalactic medium perpendicular to the disk for 7 edge-on galaxies with inclinations above $85^{\circ}$ from the FEASTS program with a $3σ$ ($20\,\text{km}\,\text{s}^{-1}$) column density ($N_{\text{HI}}$) depth of $5\times10^{17} \text{cm}^{-2}$. We develop two photometric methods to separate the extraplanar HI from the disk component, based on existing interferometric data and parametric modeling of the disk flux distribution respectively. With both methods, the FEASTS data exhibit clear extended wings beyond the disk along the minor axis. The extraplanar HI accounts for 5% to 20% of the total HI mass and extends to $20\text{-}50$ kpc at $N_{\text{HI}}=10^{18} \text{cm}^{-2}$. We find a tight positive correlation between vertical extensions of the extraplanar HI and total HI mass $M_\text{HI}$. The iso-density shape of HI at $N_{\text{HI}}=10^{18} \text{cm}^{-2}$ has an average axis ratio of $0.56\pm0.11$. The off-disk $N_{\text{HI}}$ profiles of these edge-on galaxies well represent the lower envelop of previous Lyman-$α$ absorption measurements at low-redshift. Our results suggest that at $N_{\text{HI}}=5\times10^{17} \text{cm}^{-2}$, the HI extends considerably further than the known thin and thick disks in the vertical direction, but still remains much flattener than a spherical distribution, consistent with theoretical expectations that outflow, circulation, and accretion should have different impacts in these two directions. We show the tension of our results with Illustris and TNG predictions, highlighting the constraining power of our results for future simulations.

astro-ph.GA↗

arXiv2025

ALMACAL XIII. Evolution of the CO luminosity function and the molecular gas mass density out to $z$ ~ 6

Cold molecular gas, largely traced by CO emission, is the primary fuel for star formation, making it essential for understanding galaxy evolution. ALMA has made significant progress in the study of the cosmic evolution of cold molecular gas. Here, we exploit the ALMACAL survey to address issues relating to small sample sizes and cosmic variance, utilising calibration data from ALMA to compile a statistically significant and essentially unbiased sample of CO-selected galaxies. By employing a novel statistical approach to emission-line classification using semi-analytical models, we place strong constraints on the CO luminosity function and the cosmic evolution of molecular gas mass density ($ρ_{H_2}$) back to $z \sim 6$. The cosmic molecular gas mass density increases with redshift, peaking around $z \sim 1.5$, then slowly declines towards higher redshifts by $\sim 1$ dex. Our findings confirm the key role of molecular gas in fuelling star formation. The new $ρ_{H_2}$ estimates allow us to revisit the cosmic baryon cycle, showing that the ratio of molecular gas-to-stellar mass density is consistent with the so-called 'bathtub model' of baryons, which implies a continuous replenishment of gas. The cosmic gas depletion timescale, estimated on a global scale, is shown to be fairly constant at all redshifts. We emphasise the importance of surveys using multiple small fields rather than a single contiguous area to mitigate the effects of cosmic variance.

astro-ph.GA↗

arXiv2025

The cooler past of the intracluster medium in TNG-Cluster

The intracluster medium (ICM) today is comprised largely of hot gas with clouds of cooler gas of unknown origin and lifespan. We analyze the evolution of cool gas (temperatures $\lesssim10^{4.5}$ K) in the ICM of 352 galaxy clusters from the TNG-Cluster simulations, with present-day mass $\sim10^{14.3-15.4}\,{\rm M_\odot}$. We follow the main progenitors of these clusters over the past $\sim13$ billion years (since $z\lesssim7$) and find that, according to TNG-Cluster, the cool ICM mass increases with redshift at fixed cluster mass, implying that this cooler past of the ICM is due to more than just halo growth. The cool cluster gas at $z\lesssim0.5$ is mostly located in and around satellite galaxies, while at $z\gtrsim2$ cool gas can also accrete via filaments from the intergalactic medium. Lower-mass and higher-redshift clusters are more susceptible to cooling. The cool ICM mass correlates with the number of gaseous satellites and inversely with the central supermassive black hole (SMBH) mass. The average number of gaseous satellites decreases since $z=2$, correlating with the decline in the cool ICM mass over cosmic time, suggesting a link between the two. Concurrently, kinetic SMBH feedback shifts the ICM temperature distribution, decreasing the cool ICM mass inside-out. At $z\approx0.5$, the predicted \ion{Mg}{ii} column densities are in the ballpark of recent observations, where satellites and other halos contribute significantly to the total \ion{Mg}{ii} column density. Suggestively, a non-negligible amount of the ICM cool gas forms stars in-situ at early times, reaching $\sim10^{2}\,{\rm M_\odot}\,{\rm yr^{-1}}$ and an H$α$ surface brightness of $\sim10^{-17}\,{\rm erg\,s^{-1}\,cm^{-2}\,arcsec^{-2}}$ at $z\approx2$, detectable with Euclid and JWST.

astro-ph.GA↗

arXiv2025

FEASTS: Radial Distribution of HI surface densities down to 0.01 M$_{\odot}$ pc$^{-2}$ of 35 Nearby Galaxies

We present the HI surface density ($Σ_{\rm HI}$) radial distributions based on total-power HI images obtained by FAST in the FEASTS program, for 35 galaxies with inclinations lower than 72 degree. We derive the HI radius $R_{001}$, which is the radius for the 0.01 $\,M_{\odot}\,{\rm pc}^{-2}$ ($\sim10^{18.1}\,{\rm cm}^{-2}$) iso-density level, 100 times deeper than the 1 $\,M_{\odot}\,{\rm pc}^{-2}$ level previously commonly used to measure $R_1$. The profile shapes show a large diversity at a given radius in units of kpc, group virial radius, and $R_1$, but align more tightly with radius normalized by $R_{001}$. The universal HI profile has a scatter of $\sim0.2$ dex, and a scale-length of $\sim0.11R_{001}$ in the outer region. We derive a new $R_{001}$-$M_{\rm HI}$ relation, which has a scatter of 0.02 dex, and similar slope of $\sim$0.5 as the previously known $R_1$-$M_{\rm HI}$ relation. Excluding strongly tidal-interacting galaxies, the ratio $R_{001}/R_1$ (anti-)correlate strongly and significantly with the HI-to-stellar mass ratio and sSFR, but not with the stellar mass, $M_{\rm HI}$, dark matter mass, or SFR. The strongly tidal-interacting galaxies tend to show deviations from these trends, and have the most flattened profiles. These results imply that in absence of major tidal interactions, physical processes must cooperate so that $Σ_{\rm HI}$ distributes in a self-similar way in the outer region down to the 0.01$\,M_{\odot}\,{\rm pc}^{-2}$ level. Moreover, they may drive gas flows in such a way, that HI-richer galaxies have HI disks not only extend further, but also transport HI inward more efficiently from $R_{001}$ to $R_1$.

astro-ph.GA↗

arXiv2024

Baryonic Ecosystem in Galaxies (BEINGMgII). Host Galaxies of Ultra-strong MgII Absorbers in Subaru Hyper Suprime-Cam Survey

We study the galaxies hosting ultra-strong MgII (USMgII) absorbers at small impact parameters of $\sim$2" (5 - 20 kpc), spanning a redshift range of $0.4 \le z \le 1.7$, using deep, high-resolution images from Hyper Suprime-Cam Subaru Strategic Survey and spectra from SDSS survey. From a total of 418 USMgII absorbers with $W_{2796}\ \ge 3 \mathring{A}$, along 412 quasar sightlines, we detect 50 galaxies based on [O II] $λλ$3727,3729 nebular emission detected at $\ge 2σ$ level. Utilizing the [O II] emission from the stacked spectrum and employing the best-fit galaxy SED template, we further identify 86 galaxies, leading to a total of 136 bona fide USMgII galaxies. With a prerequisite of having a minimum of four HSC passbands available, we find a detection rate of $\sim$38% at an average impact parameter of 11.4 kpc. We find that galaxies hosting USMgII systems are typically star-forming main sequence galaxies, with 21% exhibiting a starburst nature. The non-zero [O II] emission along the `clear' sightlines, with no stellar counterpart, hints that the USMgII absorbers may likely emanate from the unseen faint galaxies near the quasar. The USMgII absorbers preferentially align along the major and minor axes of the galaxy, which suggests that they originate in the disk or large-scale wind. We show that the distribution of $W_{2796}$ as a function of impact parameter indicates a discernible radial dependence for the `disk' and `wind' subsets, with the observed large scatter in $W_{2796}$ potentially attributed to large-scale outflows. The quasar sightline hosting USMgII systems show a factor three higher galaxy surface density at impact parameters of $\lesssim 50$kpc, highlights the multiple pathways giving rise to USMgII absorption.

astro-ph.GA↗

arXiv2024

Atomic and molecular gas as traced by [C II] emission

The latest ALMA and JWST observations provide new information on the birth and evolution of galaxies in the early Universe, at the epoch of reionization. Of particular importance are measurements at redshift $ z > 5$ of their cold-gas budget, which is known to be the main fuel for star formation. A powerful tool for probing the physics characterising galaxies at high redshift is the \CII\ $158\,\rm μm$ emission line. Due to its low excitation potential, \CII\ emission can be produced in photodissociation regions, neutral atomic gas and molecular clouds. To properly capture the cold-gas processes taking place in such environments (molecule formation, self-shielding, dust grain catalysis, photoelectric and cosmic-ray heating), we make use of a new set of state-of-the-art hydrodynamic simulations (\coldsim) including time-dependent non-equilibrium chemistry, star formation, stellar evolution, metal spreading and feedback mechanisms. We are able to accurately track the evolution of \HI, \HII\ and H$_2$ in a cosmological context and predict the contribution of each gas phase to \CII\ luminosity. We provide formulas that can be used to estimate the mass of molecular and atomic gas from \CII\ detections. Furthermore, we analyse how conversion factors evolve with galactic properties, such as stellar metallicity, star formation rate and stellar mass. We demonstrate that \CII\ emission is dominated by \HI\ gas and most of the \CII\ luminosity is generated in warm, dense star-forming regions. Importantly, we conclude that, despite \CII\ tracing predominantly atomic rather than molecular gas, the \CII\ luminosity remains a robust indicator of the H$_2$ mass.

astro-ph.GA↗

arXiv2024

The MUSE Ultra Deep Field (MUDF). VI. The relationship between galaxy properties and metals in the circumgalactic medium

We present intial results associating galaxies in the MUSE Ultra Deep Field (MUDF) with gas seen in absorption along the line-of-sight to two bright quasars in this field, to explore the dependence of metals in the circumgalactic medium (CGM) on galaxy properties. The MUDF includes $\sim$140h of VLT/MUSE data and 90 orbits of HST/G141M grism observations alongside VLT/UVES spectroscopy of the two quasars and several bands of HST imaging. We compare the metal absorption around galaxies in this field as a function of impact parameter, azimuthal angle and galaxy metallicity across redshifts 0.5 $<$ z $<$ 3.2. Due to the depth of our data and a large field-of-view, our analysis extends to low stellar masses ($<$ $10^{7}$ M$_{\odot}$) and high impact parameters ($>$ 600 kpc). We find a correlation between absorber equivalent width and number of nearby galaxies, but do not detect a significant anti-correlation with impact parameter. Our full sample does not show any significant change in absorber incidence as a function of azimuthal angle. However, we do find a bimodality in the azimuthal angle distribution of absorption at small impact parameters ($<$2 r$_{vir}$) and around highly-star-forming galaxies, possibly indicating disk-like accretion and biconical outflows. Finally, we do not detect any systematic deviation from the fundamental metallicity relation (FMR) among galaxies with detected absorption. This work is limited by gaps in the wavelength coverage of our current data; broader-wavelength observations with JWST will allow us to unlock the full potential of the MUDF for studying the CGM.

astro-ph.GA↗