arXiv subjects

Guinevere Kauffmann

Publications and source records attributed to Guinevere Kauffmann.

At least 19 recordsLinked to original sources

arXiv2026

Galaxies in the first two billion years: Earlier formation and quenching with surface-density modulated star formation and feedback

JWST has revealed massive, UV-bright, compact, and in some cases quenched galaxies in the first two billion years of cosmic history, challenging current galaxy formation models. We develop an extended L-Galaxies semi-analytic model, run on the MillenniumTNG dark-matter-only simulation, and follow galaxy evolution over $0 \le z \lesssim 15$. The model ties the star formation efficiency and the coupling of stellar feedback energy to the local cold gas surface density, making star formation efficient and feedback ineffective in dense gas. We include dissipative gas-rich mergers and disc instabilities in stellar and gaseous discs. All parameters are calibrated simultaneously against stellar mass functions and quenched fractions at $z\simeq0-4$ and UV luminosity functions at $z\simeq11-12$ with a new parallelised Markov chain Monte Carlo framework. The model reproduces the stellar mass function up to $z\approx 11$ and increases the abundance of massive and UV-bright galaxies at $z\gtrsim9$ by up to two orders of magnitude over the legacy version. Although the AGN feedback prescription is unchanged, the enhanced bulge growth and black hole fuelling make massive quenched galaxies at $z\simeq3-8$ two orders of magnitude more abundant, while dissipative mergers produce compact remnants with UV size-luminosity relations matching observations at $z\simeq10-13$. At low redshift, galaxy sizes, cold-gas content, metallicities, radial profiles, and morphologies remain consistent with observations. Our results indicate that the tension between models and JWST observations at cosmic dawn can be substantially reduced by regulating star formation and feedback through the local gas surface density, without a modified initial mass function, non-standard cosmology, or new AGN physics.

astro-ph.GA↗

arXiv2026

A Spatially Resolved Evolutionary Sequence of Multi-wavelength AGN Host Galaxies

We study the spatially resolved star formation, gas ionisation, and outflow properties of 1813 active galactic nuclei (AGNs) from the MaNGA survey, which we classify into infrared (IR), broad-line (BL), narrow-line (NL), and radio (RD) AGNs based on their mid-infrared colours, optical spectra, and/or radio photometry. We also provide estimations of AGN power at different wavelengths. AGN incidence is found to increase with stellar mass following a power-law, with the high-mass end dominated by RDAGNs and the low-mass end dominated by NLAGNs. Compared to their mass-matched non-AGN counterparts, we find that IRAGNs, BLAGNs, and NLAGNs on average show enhanced specific star formation rates, younger stellar populations, and harder ionisation towards the centre. RDAGNs, in contrast, show radial profiles similar to quiescent galaxies. [OIII] outflows are more common and stronger in BL/IRAGNs, while RDAGNs on average show no outflow features. The outflow incidence increases with [OIII] luminosity, and the features in BL/IRAGNs on average extend to ~2 kpc from the nuclei. We further discuss a possible evolutionary sequence of AGNs and their host galaxies, where AGNs with strong emission lines or dust tori are present in star-forming galaxies. Later, young compact radio jets emerge, the host galaxies gradually quench, and the AGN hosts eventually evolve into globally quiescent systems with larger radio jets that prevent further gas cooling.

astro-ph.GA↗

arXiv2025

Unveiling the small-scale web around galaxies with miniJPAS and DESI

We present the first statistical observational study detecting filaments in the immediate surroundings of galaxies, i.e. the local web of galaxies. Simulations predict that cold gas, the fuel for star formation, is channeled through filamentary structures into galaxies. Yet, direct observational evidence for this process has been limited by the challenge of mapping the cosmic web at small scales. Using miniJPAS spectro-photometric data combined with spectroscopic DESI redshifts when available, we construct a high-density observational galaxy sample spanning 0.2 10^(10) Msun using all nearby galaxies as tracers, combined with a probabilistic adaptation of the DisPerSE algorithm designed to overcome limitations due to photometric redshift uncertainties. Our methodology is tested and validated using mock catalogues built with random forest models applied to a simulated lightcone. Besides recovering the expected increase in galaxy connectivity (defined as the number of filaments attached to a galaxy) with stellar mass, we show that our connectivity measurements agree with 3D reference estimates from the mock galaxies. Thanks to these filament reconstructions, we explore the relation between small-scale connectivity and galaxy star formation rate, finding a mild positive trend which needs to be confirmed by follow up studies with larger sample sizes. We propose galaxy connectivity to local filaments as a powerful and physically motivated metric of environment, offering new insights into the role of cosmic structure in galaxy evolution.

astro-ph.CO↗

arXiv2025

FEASTS Compared with Simulations: Abnormally Irregular and Extended HI Morphologies at a Column Density of $10^{18}\,\text{cm}^{-2}$ in TNG50 and Auriga

With new atomic-hydrogen (HI) observations of FAST Extended Atlas of Selected Targets Survey (FEASTS), we present the first statistical comparison of HI morphology between observations and cosmological simulations, focusing on low-column density ($10^{18}\,\text{cm}^{-2}$) regions of Milky Way-like central galaxies. We select a 330-galaxy sample from IllustrisTNG50 (TNG50) matched to 33 FEASTS galaxies by stellar and HI masses, and mock observe them to the FAST resolution and depth at corresponding inclinations and distances for a fair comparison. In contrast to FEASTS, abnormally irregular and extended morphology is found in more than one-third of TNG50 galaxies, especially those massive and HI poor. Stellar feedback is the property that most significantly correlates with the HI morphological deviation from observations, although these deviations mostly occur at a high stellar or black-hole mass. These results indicate that in TNG50, stellar feedback significantly influences the HI morphology at $10^{18}\,\text{cm}^{-2}$, while active galactic nucleus (AGN) feedback has not so direct a role as expected. With an additional sample from Auriga, we find that the magnetic field may help HI to be more regular in its morphology, while improving the mass resolution does not alleviate the discrepancy from observation. This study reveals the potential of constraining future simulations of galaxies by observing low-column density HI.

astro-ph.GA↗

arXiv2025

The origin of double-peaked narrow emission-line galaxies in MaNGA Survey

We select 36 double-peaked narrow emission-line galaxies (DPGs) from 10,010 unique galaxies in MaNGA survey. These DPGs show double-peaked Balmer lines and forbidden lines in the spectra. We use a double Gaussian model to separate the double-peaked profiles of each emission line into blue and red components ($λ_\text{blue}$ < $λ_\text{red}$), and analyze the spatially resolved kinematics and ionization mechanisms of each component. We find that in 35 out of 36 DPGs, the flux ratio between the blue and red components varies systematically along the major axes, while it keeps roughly a constant along the minor axes. The blue and red components of these DPGs exhibit similar distributions in both the value of line-of-sight velocity and the velocity dispersion. Additionally, 83.3% DPGs have both blue and red components located in the same ionization region in the [SII]-BPT diagram. Combining all these observational results, we suggest that the double-peaked emission line profiles in these 35 DPGs primarily originate from rotating discs. The remaining one galaxy shows clear outflow features. 8 out of 35 DPGs show symmetric line profiles that indicate undisturbed rotating discs, and the other 27 DPGs exhibit asymmetric profiles, suggesting dynamic disturbances in the rotating discs. Furthermore, we find that 58.3% DPGs experienced external processes, characterized by tidal features, companion galaxies, as well as gas-star misalignments. This fraction is about twice as much as that of the control sample, suggesting the origin of double-peaked emission line profiles is associated with external processes.

astro-ph.GA↗

arXiv2025

QSO MUSEUM III: the circumgalactic medium in Ly$α$ emission around 120 $z\sim3$ quasars covering the SDSS parameter space. Witnessing the instantaneous AGN feedback on halo scales

Recent surveys show that $z>2$ quasars are surrounded by Hydrogen Lyman-$α$ (Ly$α$) glows with diverse emission levels and extents. These seem to depend on the activity of embedded quasars, the number of active galactic nucleus (AGN) photons able to reach the halo gas or circumgalactic medium (CGM) and the physical properties of the CGM. In this framework, we present VLT/MUSE snapshot observations (45 min/source) of 59 $z\sim3$ quasars extending the long-term QSO MUSEUM campaign to fainter SDSS sources. The whole survey now targets 120 quasars with a median redshift of $z$=3.13, and bolometric luminosities, black hole masses and Eddington ratios of $45.1<\log(L_{\rm bol}/[{\rm erg\,s^{-1}]})<48.7$, $7.9<\log(M_{\rm BH}/[{\rm M_{\odot}]})<10.3 $ and $0.01<λ_{\rm Edd}<1.8$, respectively. We detect extended Ly$α$ emission in 110/120 systems, with all non-detections in the new fainter sample. Stacking non-detections unveils emission below our individual detection limit. The Ly$α$ surface brightness (SB$_{\rm Lyα}$) of the CGM increases with quasar luminosity. Moreover, the Ly$α$ linewidth increases in the central regions (projected radius $R<40$ kpc or $\sim$40% $R_{\rm vir}$) of the CGM around brighter quasars. These trends indicate that we are witnessing the instantaneous AGN feedback in action on CGM scales. Assuming that all targeted quasars sit in halos of $M_{\rm DM}\sim10^{12.5}\,M_\odot$, as found in clustering studies, the trend in SB$_{\rm Lyα}$ can be explained by larger fractions of cool gas mass illuminated, implying that brighter quasars have larger ionization cone opening angles. Similarly, brighter AGNs seem to perturb the cool ($T\sim10^4$ K) gas more strongly. We show that QSO MUSEUM now has enough statistics to study the instantaneous AGN feedback while controlling for black hole properties, which are key to constraining AGN models.

astro-ph.GA↗

arXiv2025

An integral field spectroscopic study of stellar and ionized gas properties around edge-on disk galaxies in the stellar mass range 9<log M*<11

We analyze the stellar light, 4000 Angstrom break and emission line profiles of 82 edge-on disk galaxies from the MaNGA survey. We characterize the stellar light profiles perpendicular to the disk plane using two parameters: a) the power law slope of the thick disk component, 2) the transition radius where the profile flattens. The 4000 Angstrom break profiles perpendicular to the plane are characterized by the number of significant changes in slope (breaks) and by the change in D_n(4000) from inner to outer disk. The slope correlates tightly with the stellar mass of the galaxy over the stellar mass range 10^9<log M*<10^10 M_sun. More massive galaxies have more extended thick disks. The slope and transition radius exhibit large scatter for galaxies more massive than 10^{10} M_sun. Half the sample have older stellar populations in their thick disks, a third have flat D$_n$(4000) profiles and 15% have younger thick disks. The D$_n$(4000) profiles exhibit as many as 4 separate breaks. There are more breaks in massive galaxies with bulges and more extended thick disks. This may indicate that the breaks are produced by more frequent accretion events in such systems. The extra-planar Halpha EQW correlates most strongly with the specific star formation rate of the galaxy, and the [OII]/Halpha ratio increases with distance from the disk plane. This increase is most apparent for massive galaxies with extended thick disk components and low SFR/M* These findings support the hypothesis that the larger [OII]/Halpha ratios may be caused by ionization from evolved stars.

astro-ph.GA↗

arXiv2025

Misaligned external gas acquisition boosts central black hole activities

One important question in active galactic nucleus (AGN) is how gas is brought down to the galaxy center. Both internal secular evolution (torque induced by non-axisymmetric galactic structures such as bars) and external processes (e.g. mergers or interactions) are expected to redistribute the angular momentum (AM) and transport gas inward. However, it is still under debate whether these processes can significantly affect AGN activities. Here we for the first time report that AGN fraction increases with the difference of kinematic position angles ($ΔPA\equiv|PA_{\mathrm{gas}}-PA_{\mathrm{star}}|$) between ionized gas ($PA_{\mathrm{gas}}$) and stellar disks ($PA_{\mathrm{star}}$) in blue and green galaxies, meanwhile this fraction remains roughly constant for red galaxies. Also the high luminosity AGN fraction increases with $ΔPA$ while the low luminosity AGN fraction is independent with $ΔPA$. These observational results support a scenario in which the interaction between accreted and pre-existing gas provides the AM loss mechanism, thereby the gas inflow fuels the central BH activities, and the AM loss efficiency is positively correlated with the $ΔPA$.

astro-ph.GA↗

arXiv2025

DIISC -- VI (COS-DIISC): UV Metal Absorption Relative to the H I disk of Galaxies

As part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we present the UV metal absorption features in the Circumgalactic Medium (CGM) near the H I gas disk ($<$4.5$R_\mathrm{HI}$) of 31 nearby galaxies through quasar absorption line spectroscopy. Of the ions under study, Si III $\lambda1206$ was most frequently detected (18 of 31 sight lines), while C II $\lambda1334$ and Si II $\lambda1260$ were detected in 17 and 15 of 31 sight lines, respectively. Many components were consistent with photoionization equilibrium models, most of the cold and cool gas phase clouds were found to have lengths smaller than 2 kpc. Sight lines with smaller impact parameters ($ρ$) normalized by the galaxy's virial radius ($R_\mathrm{vir}$) and H I radius ($R_\mathrm{HI}$) tend to have more components and larger rest-frame equivalent widths ($W_r$) than those that probe the CGM at larger radii. In particular, we find that the location of metals are better traced by $ρ$ / $R_\mathrm{HI}$ rather than the traditional $ρ$ / $R_\mathrm{vir}$. Larger covering fractions are found closer to galaxies, with a radial decline that depends on the $W_r$ limit used. Our results provide new insights into the spatial distribution of metals around the H I disks of low-redshift galaxies.

astro-ph.GA↗

arXiv2025

The Host Galaxies of Radio AGN: New Views from Combining LoTSS and MaNGA Observations

We utilize a combination of radio continuum observations and optical integral field spectroscopic (IFS) data to explore the impact of radio AGN on the evolution of their host galaxies at both global and sub-galactic scales. We construct a comprehensive radio-IFS sample comprising 5548 galaxies with redshift z<0.15 by cross-matching the LoTSS with the MaNGA survey. We revisit the tight linear radio continuum - star formation relation and quantify its intrinsic scatter, then use the relation to classify 616 radio-excess AGN with excessive radio luminosities over that expected from their star formation rate. Massive radio AGN host galaxies are predominantly quiescent systems, but the quenching level shows no correlation with the jet luminosity. The mass assembly histories derived from the stellar population synthesis model fitting agree with the cosmological simulations incorporating radio-mode AGN feedback models. We observe that radio AGN hosts grow faster than a control sample of galaxies matched in stellar mass, and the quenching age ($\sim$5 Gyr) is at larger lookback times than the typical radio jet age (<1 Gyr). By stacking the spectra in different radial bins and comparing results for radio AGN hosts and their controls, we find emission line excess features in the nuclear region of radio AGN hosts. This excess is more prominent in low-luminosity, low-mass, and compact radio AGN. The [NII]/H$α$ ratios of the excessive emission line indicate that radio AGN or related jets are ionizing the surrounding interstellar medium in the vicinity of the nucleus. Our results support the scenario that the observed present-day radio AGN activity may help their host galaxies maintain quiescence through gas ionization and heating, but it is not responsible for the past quenching of their hosts.

astro-ph.GA↗

arXiv2024

Probing galaxy evolution from $z=0$ to $z\simeq10$ through galaxy scaling relations in three L-Galaxies flavours

We present a comprehensive examination of the three latest versions of the L-Galaxies semi-analytic galaxy formation model, focusing on the evolution of galaxy properties across a broad stellar mass range ($10^7\:{\rm M}_{\odot}\lesssim{M_\star}\lesssim10^{12}\:{\rm M}_{\odot}$) from $z=0$ to $z\simeq10$. This study is the first to compare predictions of L-Galaxies with high-redshift observations well outside the original calibration regime, utilising multiband data from surveys such as SDSS, CANDELS, COSMOS, HST, JWST, and ALMA. We assess the models' ability to reproduce various time-dependent galaxy scaling relations for star-forming and quenched galaxies. Key focus areas include global galaxy properties such as stellar mass functions, cosmic star formation rate density, and the evolution of the main sequence of star-forming galaxies. Additionally, we examine resolved morphological properties such as the galaxy mass-size relation, alongside core $(R<1\,{\rm{kpc}})$ and effective $(R<R_{\rm{e}})$ stellar-mass surface densities as a function of stellar mass. This analysis reveals that the L-Galaxies models are in qualitatively good agreement with observed global scaling relations up to $z\simeq10$. However, significant discrepancies exist at both low and high redshifts in accurately reproducing the number density, size, and surface density evolution of quenched galaxies. These issues are most pronounced for massive central galaxies, where the simulations underpredict the abundance of quenched systems at $z\geq1.5$, reaching a discrepancy of a factor of 60 by $z\approx3$, with sizes several times larger than observed. Therefore, we propose that the physical prescriptions governing galaxy quenching, such as AGN feedback and processes related to merging, require improvement to be more consistent with observational data.

astro-ph.GA↗

arXiv2024

QSO MUSEUM II: Search for extended Ly$α$ emission around eight $z \sim 3$ quasar pairs

Extended Ly$α$ emission is routinely found around single quasars (QSO) across cosmic time. However, few studies have investigated how such emission changes in fields with physically associated QSO pairs, which should reside in dense environments and are predicted to be linked through intergalactic filaments. We present VLT/MUSE snapshot observations (45 min./source) to unveil extended Ly$α$ emission on scales of the circumgalactic medium (CGM) around the largest sample of physically associated QSO pairs to date, encompassing 8 pairs (14 observed QSOs) at $z$~3 with $i$-band magnitude between 18 and 22.75. The pairs are either at close (~50-100 kpc, 5 pairs) or wide (~450-500 kpc, 3 pairs) separation with velocity differences of $Δ$v < 2000 km s$^{-1}$. We detect extended emission around 12 of the 14 targeted QSOs and investigate the luminosity, size, kinematics and morphology of these Ly$α$ nebulae. On average, they span 90 kpc and are 2.8 $\times 10^{43}$ erg s$^{-1}$ bright. Irrespective of the QSOs' projected distance, the nebulae often (~45 %) extend toward the other QSO in the pair, leading to asymmetric emission whose flux-weighted centroid is at an offset position from any QSO location. We show that large nebulae are preferentially aligned with the large-scale structure as traced by the two QSOs, and conclude that the cool gas (10$^4$ K) in the CGM traces well the direction of cosmic web filaments. Additionally, the radial profile of the Ly$α$ surface brightness around QSO pairs can be described by a power law with a shallower slope (~$-1.6$) with respect to single QSOs (~$-2$), indicative of increased CGM densities out to large radii and/or enhanced contribution from the intergalactic medium (IGM). The sample presented in this study contains excellent targets for ultra-deep observations to directly study filamentary IGM structures in emission.

astro-ph.GA↗

arXiv2024

FEASTS Combined with Interferometry (I): Overall Properties of Diffuse HI and Implications for Gas Accretion in Nearby Galaxies

We present a statistical study of the properties of diffuse HI in ten nearby galaxies, comparing the HI detected by the single-dish telescope FAST (FEASTS program) and the interferometer VLA (THINGS program), respectively. The THINGS' observation missed HI with a median of 23% due to the short-spacing problem of interferometry and limited sensitivity. We extract the diffuse HI by subtracting the dense HI, which is obtained from the THINGS data with a uniform flux-density threshold, from the total HI detected by FAST. Among the sample, the median diffuse-HI fraction is 34%, and more diffuse HI is found in galaxies exhibiting more prominent tidal-interaction signatures. The diffuse HI we detected seems to be distributed in disk-like layers within a typical thickness of $1\,\text{kpc}$, different from the more halo-like diffuse HI detected around NGC 4631 in a previous study. Most of the diffuse HI is cospatial with the dense HI and has a typical column density of $10^{17.7}$-$10^{20.1}\,\text{cm}^{-2}$. The diffuse and dense HI exhibits a similar rotational motion, but the former lags by a median of 25% in at least the inner disks, and its velocity dispersions are typically twice as high. Based on a simplified estimation of circum-galactic medium properties and assuming pressure equilibrium, the volume density of diffuse HI appears to be constant within each individual galaxy, implying its role as a cooling interface. Comparing with existing models, these results are consistent with a possible link between tidal interactions, the formation of diffuse HI, and gas accretion.

astro-ph.GA↗

arXiv2023

DIISC-III: Signatures of Stellar Disk Growth in Nearby Galaxies

We explore the growth of the stellar disks in 14 nearby spiral galaxies as part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey. We study the radial distribution of specific star formation rates (sSFR) and investigate the ratio of the difference in the outer and inner sSFR ($Δ_{sSFR}~={\rm sSFR}_{out}-{\rm sSFR}_{in}$) of the disk and the total sSFR, $Δ_{sSFR}$/sSFR to quantify disk growth. We find $Δ_{sSFR}$/sSFR and the HI gas fraction to show a mild correlation of Spearman's $ρ=0.30$, indicating that star formation and disk growth are likely to proceed outward in galactic disks with high HI gas fractions. The HI gas fractions and $Δ_{sSFR}$/sSFR of the galaxies also increase with the distance to the nearest L$_\star$ neighbor, suggesting that galaxies are likely to sustain their ISM cold gas and exhibit inside-out growth in isolated environments. However, the HI content in their circumgalactic medium, probed by the Ly$α$ equivalent width (W$_{Lyα}$) excess, is observed to be suppressed in isolated environments, apparent from the strong anti-correlation between the W$_{Lyα}$ excess and the distance to the 5$^{\rm th}$ nearest L$_\star$ neighbor (Spearman's $ρ=-0.62$). As expected, W$_{Lyα}$ is also found to be suppressed in cluster galaxies. We find no relation between the W$_{Lyα}$ excess of the detected CGM absorber and $Δ_{sSFR}$/sSFR implying that the enhancement and suppression of the circumgalactic HI gas does not affect the direction in which star formation proceeds in a galactic disk or vice-versa.

astro-ph.GA↗

arXiv2023

A resolved study of the inner regions of nearby galaxies with an excess of young massive stars: missing link in the AGN-starburst connection?

We have selected galaxies with very high levels of H$α$ emission (EQW(H$α$)$>$700 Å.) in their central regions from the final data release of the MaNGA survey . Our study focuses on 14 very well-resolved nearby galaxies with stellar masses in the range $9.5 < \log M_*/(M_{\odot}) < 11.5$. We investigate a variety of procedures for selecting galaxy regions that are likely to harbour excess populations of young massive stars, finding that selection in the 2-dimensional space of extinction-corrected H$α$ EQW and [SIII]/[SII] line ratio produces the best results. By comparing stacked spectra covering these regions with stacked spectra covering normal starburst regions with 100Å$<$EQW(H$α$)$<$200Å, we obtain the following main results: 1) Clear signatures of excess Wolf Rayet stars are found in half of the H$α$ excess regions, 2) Galaxy regions containing excess Wolf Rayet stars are more often associated with the presence of high-ionization emission lines characteristic of accreting black holes. Excess [NeIII] is detected in 4 out of 8 of the WR regions and there are tentative [FeX] detections in 2 galaxies. 3) Regions of the galaxy with excess Wolf Rayet stars are located where the interstellar medium has larger ionized gas turbulent velocities and higher neutral gas overdensities. We make a first attempt to constrain changes in the high mass end of the stellar initial mass function (IMF) using the HR-pyPopStar evolutionary population synthesis models that include high wavelength-resolution theoretical atmosphere libraries for Wolf Rayet stars.

astro-ph.GA↗

arXiv2023

Circumgalactic Ly$α$ emission around submillimeter-bright galaxies with different quasar contributions

We present VLT/MUSE observations targeting the extended Lyman-$α$ (Ly$α$) emission of five high-redshift ($z\sim$3-4) submillimeter galaxies (SMGs) with increasing quasar (QSO) radiation: two SMGs, two SMGs hosting a QSO, and one SMG hosting a QSO with a SMG companion (QSO+SMG). These sources should be located in dark matter halos of comparable masses (average mass of $M_{\rm DM}\sim10^{12.2}\,{\rm M}_\odot$). We quantify the luminosity and extent of the Ly$α$ emission, together with its kinematics, and examine four Ly$α$ powering mechanisms: photoionization from QSOs/star formation, shocks by galactic/QSO outflows, gravitational cooling radiation, and Ly$α$ photons resonant scattering. We find a variety of Ly$α$ luminosities and extents, with the QSO+SMG system displaying the most extended and bright nebula, followed by the SMGs hosting a QSO, and finally the undetected circumgalactic medium (CGM) of SMGs. This diversity implies that gravitational cooling is unlikely to be the main powering mechanism. We show that photoionization from the QSO and QSO outflows can contribute to power the emission for average densities $n_{\rm H}>0.5\,$cm$^{-3}$. Moreover, the observed Ly$α$ luminosities scale with the QSO's budget of Ly$α$ photons modulo the dust content in each galaxy, highlighting a possible contribution from resonant scattering of QSO's radiation in powering the nebulae. We find larger Ly$α$ linewidths (FWHM$\gtrsim 1200\,$km$\,$s$^{-1}$) than usually reported around radio-quiet systems, pointing to large-scale outflows. A statistical survey targeting similar high-redshift massive systems with known host properties is needed to confirm our findings.

astro-ph.GA↗

arXiv2023

Flows around galaxies. I. The dependency of galaxy connectivity on cosmic environments and effects on the star-formation rate

With the aim of bringing substantial insight to the fundamental question of how galaxies acquire their material for star-formation, we present the first comprehensive characterisation of the galaxy connectivity (i.e. the number of small-scale filamentary streams connected to a galaxy) in relation with the cosmic environment, and a statistical exploration of the impact of connectivity on the star-formation rate at z=2. We detect kpc-scale filaments directly connected to galaxies by applying the DisPerSE filament finder to the DM density around 2942 central galaxies ($M_* > 10^{8}$ $\mathrm{M}_\odot / h$) of the TNG50-1 simulation. Our results demonstrate that galaxy connectivity spans a broad range (from 0 to 9), with more than half of the galaxies connected to two or three streams. We examine a variety of factors that could influence the connectivity finding out that it increases with mass, decreases with local density for low mass galaxies, and does not depend on local environment, estimated by the Delaunay tessellation, for high mass galaxies. We further classify galaxies according to their location in different cosmic web environments, and we highlight the influence of the large-scale structure on the number of connected streams. Our results reflect the different strengths of the cosmic tides, which can prevent the formation of coherent streams feeding the galaxies, or even disconnect the galaxy from its local web. Finally, we show that, at fixed local density, the star-formation rate (SFR) of low mass galaxies is up to $5.9σ$ enhanced due to connectivity. This SFR boost is even more significant ($6.3σ$) for galaxies embedded in cosmic filaments, where the available matter reservoirs are large. A milder impact is found for high mass galaxies, hinting at different relative efficiencies of matter inflow via small-scale streams in galaxies of different masses.

astro-ph.GA↗

arXiv2023

Formation of star clusters and enrichment by massive stars in simulations of low-metallicity galaxies with a fully sampled initial stellar mass function

We present new GRIFFIN project hydrodynamical simulations that model the formation of galactic star cluster populations in low-metallicity ($Z=0.00021$) dwarf galaxies, including radiation, supernova and stellar wind feedback of individual massive stars. In the simulations, stars are sampled from the stellar initial mass function (IMF) down to the hydrogen burning limit of $0.08$ M$_\odot$. Mass conservation is enforced within a radius of $1$ pc for the formation of massive stars. We find that massive stars are preferentially found in star clusters and follow a correlation set at birth between the highest initial stellar mass and the star cluster mass that differs from pure stochastic IMF sampling. With a fully sampled IMF, star clusters lose mass in the galactic tidal field according to mass-loss rates observed in nearby galaxies. Of the released stellar feedback, $60\%$ of the supernova material and up to $35\%$ of the wind material reside either in the hot interstellar medium (ISM) or in gaseous, metal enriched outflows. While stellar winds (instantaneously) and supernovae (delayed) start enriching the ISM right after the first massive stars form, the formation of supernova-enriched stars and star clusters is significantly delayed (by $>50$ Myr) compared to the formation of stars and star clusters enriched by stellar winds. Overall, supernova ejecta dominate the enrichment by mass, while the number of enriched stars is determined by continuous stellar winds. These results present a concept for the formation of chemically distinct populations of stars in bound star clusters, reminiscent of multiple populations in globular clusters.

astro-ph.GA↗