arXiv subjects

Sebastian Lopez

Publications and source records attributed to Sebastian Lopez.

At least 19 recordsLinked to original sources

arXiv2026

The Cosmic Ultraviolet Baryon Survey X: Density and Pressure Profiles of Clumpy Circumgalactic Gas at $z=0.4-0.7$

The thermodynamic state and turbulent properties of the cool circumgalactic medium (CGM) are investigated for 23 galaxies and galaxy groups at intermediate redshift ($z=0.4$--0.7) in the Cosmic Ultraviolet Baryon Survey (CUBS) midz sample using background QSOs within the virial radius. Kinematically resolved absorption-line measurements from Hubble Space Telescope/COS and STIS spectra, combined with photoionization modeling, yield gas densities of $n_\mathrm{H}\approx10^{-4}$--$10^{-2} \ \mathrm{cm}^{-3}$, temperatures of $T\approx(1$--$5) \times 10^4\,\mathrm{K}$, and non-thermal line broadening of $b_\mathrm{NT}\approx2$--$30 \ \mathrm{km \ s^{-1}}$ for individual cool clumps. Combined with published samples at similar redshifts, the results indicate that photoionization equilibrium accurately describes the cool CGM and that turbulent motions are predominantly subsonic. At fixed projected distance, cool-gas density decreases systematically with halo mass, while inferred cool-gas pressures in $M_h\approx10^{12}$--$10^{13}\,\mathrm{M}_\odot$ halos are consistent with hot-gas pressures inferred from stacked X-ray observations. The analysis uncovers a near constant total cool gas mass across a broad halo mass range, which directly translates to a declining baryon mass fraction in the cool phase from $\approx 6$--$19\%$ in halos of $M_h \approx 10^{12}\, \mathrm{M}_\odot$ to $\approx 0.6$--$1.5\%$ in halos of $M_h \approx 10^{13}\, \mathrm{M}_\odot$. Finally, several CUBS galaxies exhibit kinematically aligned low- and high-ionization species spanning up to two orders of magnitude in density, reflecting local fluctuations in the halo gas pressure.

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arXiv2026

JWST Observations of Starbursts: The motion of dust - PAH kinematics of M82 and NGC 253 with JWST/MIRI spectroscopy

We present an analysis of dust kinematics in the local starburst galaxies M82 (NGC 3034) and NGC 253 using Polycyclic Aromatic Hydrocarbon (PAH) features observed with JWST/MIRI spectroscopy. We are able to produce high-quality velocity maps of the 5.2 $μ$m, 6.2 $μ$m, and 11.3 $μ$m PAH features, as well as numerous lines of molecular gas via H$_2$ rotational transitions and ionized gas from [NeII] and H recombination lines. Given the field of view and inclination, we trace a rotating disk in M82 where we observe a steep rise in the velocities followed by flattening, typical of galaxy rotation curves. In NGC 253, however, the 6.2 $μ$m and 11.3 $μ$m PAH features trace the launching region of the outflow, firmly within the starburst region. We find the ionized gas also shows outflow contributions in NGC 253 while the warm molecular gas is dominated by rotation. Additionally, the molecular gas outflow velocities are lower than the ionized gas, with the 11.3 $μ$m PAH feature consistent with the ionized gas rather than the molecular gas. We therefore suggest that PAHs are more closely associated with the ionized gas rather than the molecular at the base of the galaxy outflow, where larger scale imaging shows comparable morphology between PAHs and HI. The 6.2 $μ$m PAH feature has an even higher outflow velocity for both galaxies, possibly suggesting preferential ionization of the PAHs within the faster-moving hot phase of the base of the outflow.

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arXiv2026

JWST Observations of Starbursts: A Young Bubble in NGC 253's Central Starburst

We present a multi-wavelength analysis of a young bubble in the nuclear starburst of NGC 253 using new JWST MIRI-MRS observations together with archival ALMA (100, 350, 690 GHz) and Chandra data. The MIRI maps reveal a prominent bubble-like structure in both ionized and molecular emission lines. The bubble is spatially coincident with one of the least embedded massive young clusters detected with ALMA, suggesting that the cluster is driving the expansion. We measure a radius of $\sim 11.5 \pm 3.4$ pc and an expansion velocity of $\sim 90 \pm 44$ km s$^{-1}$, implying a dynamical age of $\sim 0.1 \pm 0.1$ Myr. Using RADEX modeling of multiple CO transitions, we infer a molecular mass in the range of $(1.3 \pm 0.3) \times 10^4$ to $(2.8 \pm 0.8) \times 10^5$ $M_\odot$. We derive a kinetic energy of order $10^{51}$-$10^{52}$ erg, consistent with mechanical input from Wolf-Rayet stellar winds or supernovae in a $\sim 10^6$ $M_\odot$ cluster. The existence of a large population of Wolf-Rayet stars or past supernovae is supported by the presence of coincident X-ray emission. Our results provide direct evidence that individual clusters in a nuclear environment can carve out coherent structures on parsec scales and inject significant energy and momentum into the surrounding interstellar medium, which can contribute to the nuclear outflow in NGC 253.

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arXiv2026

The Small-scale Structures in the Wind of Messier 82

Small-scale multiphase structure plays a central role in galactic-wind evolution, yet the parsec-scale morphology and excitation of the warm ionised gas remain poorly constrained. We present deep HST narrow-band imaging of the southern wind of Messier~82 (M82) in Halpha, [OIII], [SII], and [NII], designed to resolve the warm ionised phase on parsec scales. The Halpha emission is detected to 2.1 kpc above the disk, while the fainter emission lines are detected over smaller radial extents, with [OIII] reaching 1.5kpc. We develop a filament-finding pipeline for the Halpha image and construct a quantitative catalogue of the filamentary structures. The wind forms a highly connected network of strands and knots, dominated by compact filaments with typical projected widths of 5.3pc and lengths of 9.5pc. Both the projected covering fraction and the line-flux contribution of the filamentary component decline with height, showing that the outer wind becomes increasingly dominated by diffuse emission. Optical line-ratio diagnostics indicate that the warm ionised gas occupies an intermediate excitation regime: photoionisation by the central starburst can energetically power the observed Halpha luminosity, while the systematic separation between filamentary and diffuse emission, together with the evolution of the line ratios with vertical distance, suggests an increasing contribution from shocks or other similar heating in the diffuse outer wind. These results show that separating filamentary and diffuse emission in high-resolution imaging provides a powerful way to connect the morphology, excitation, and multiphase structure of galactic winds.

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arXiv2026

Illuminating M82: Simulating X-ray Emission from Galactic Winds in a Starburst Galaxy

We generate mock X-ray observations from a suite of idealized high-resolution ($\sim 4$ pc), tall-box ($\sim 2 \times 2 \times 8$ kpc$^3$) simulations of star formation driven galactic winds in an M82-like system, varying the spatial resolution as well as the strength and distribution of supernova (SN) energy injection. We compare our mock X-ray observations with deep Chandra observations of the hot plasma around M82. While the simulated total X-ray luminosity, $L_X$, increases with resolution and when SNe feedback is spatially distributed, even in the best case scenario, our simulated $L_X$ is a factor of $\sim 50-100$ lower than observed and the surface brightness profiles of X-ray emission, $S_X(z)$, fall off too quickly with distance from the galaxy. Past results were able to reproduce these observables and we discuss potential simulation differences that could explain this discrepancy. We make the first comparison of the X-ray spectrum of our simulations to observations and find that our simulated spectrum is too soft, with a deficit of hard X-ray photons at $\gtrsim 1$ keV. We discuss how physical processes missing from our simulations and prior work (e.g., thermal conduction and cosmic rays) could help resolve this discrepancy.

astro-ph.GA↗

arXiv2026

The Synthetic Absorption Line Spectral Almanac (SALSA)

We create the first large-scale mock spectroscopic survey of gas absorption sightlines traversing the interstellar medium (ISM), circumgalactic medium (CGM), and intergalactic medium (IGM) surrounding galaxies of virtual Universes. That is, we create mock, or synthetic, absorption spectra by drawing lines-of-sight through cosmological hydrodynamical simulations, using a new mesh-free Voronoi ray-tracing algorithm. The result is the Synthetic Absorption Line Spectral Almanac (SALSA), which is publicly released on a feature-rich online science platform (www.tng-project.org/spectra). It spans a range of ions, transitions, instruments, observational characteristics, assumptions, redshifts, and simulations. These include, but are not limited to: (ions) HI, OI, CI, MgI, MgII, FeII, SiII, CaII, ZnII, SiIII, SiIV, NV, CII, CIV, OVI; (instruments) SDSS-BOSS, KECK-HIRES, UVES, COS, DESI, 4MOST, WEAVE, XSHOOTER; (model choices) with/without dust depletion, noise, quasar continua, foregrounds; (redshift) from z=0 to z~6; (ancillary data) integrated equivalent widths, column densities, distances and properties of nearby galaxies; (simulations) IllustrisTNG including TNG50, TNG-Cluster, EAGLE, and SIMBA. This scope is not fixed, and will grow and evolve with community interest and requests over time -- suggestions are welcome. The resulting dataset is generic and broadly applicable, enabling diverse science goals such as: (i) studies of the underlying physical gas structures giving rise to particular absorption signatures, (ii) galaxy-absorber and halo-absorber correlations, (iii) virtual surveys and survey strategy optimization, (iv) stacking experiments and the identification of faint absorption features, (v) assessment of data reduction methods and completeness calculations, (vi) inference of physical properties from observables, and (vii) apples-to-apples comparisons between simulations and data.

astro-ph.GA↗

arXiv2026

JWST Observations of Starbursts: Dust Processing in the M82 Superwind

We present JWST MIRI and NIRCam imaging of the inner ~5 kpc of the M82 superwind at 0.05-0.375'' (~0.9-6.5 pc) resolution. Targeted filters probe emission from polycyclic aromatic hydrocarbons (PAHs; F335M, F360M, F770W, F1130W) and continuum (F250M, F360M). The images reveal a network of cool wind filaments traced by PAHs. PAH surface brightness declines with the inverse square of distance to the midplane, suggesting that the incident radiation field from the starburst drives the observed PAH intensity out to 2.5 kpc. The 3.3/11.3 and 3.3/7.7 band ratios show uniformity with distance from the starburst, though comparisons with mid-IR dust emission models indicate a modest shift toward larger PAHs. Outside the disk, 11.3/7.7 increases moderately, reflecting that PAHs become more neutral with distance from the starburst as they are exposed to a declining radiation field and ionization parameter. Overall, PAHs in the wind are consistent with standard-to-large sizes and standard-to-high ionization states. Including Spitzer and Herschel data, PAH abundance (qPAH) is set at ~1% in the starburst and remains unchanging out to 5 kpc off the disk. This flat qPAH profile suggests that PAHs are shielded from the hot wind, perhaps residing in the surface layers of cool clouds, with possible replenishment from cloud interiors and enrichment of the halo from previous bursts. In this picture, clouds are not dense enough to promote PAH growth, and they likely undergo radiative cooling and mixing with the hot phase to survive the gauntlet for at least ~20 Myr.

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arXiv2026

The Qz5 Survey (II): Metallicity Evolution of Damped Lyα Systems Out to z$\sim$5

Damped Ly$α$ absorbers (DLAs) are the highest \HI\ column density (\NHI) absorption line systems detected in the spectra of background quasars. DLAs dominate the neutral gas content of the Universe ($Ω_{\rm HI}$) and are used to measure the metallicity evolution of \HI\ gas. In this work, we introduce a sample of five recently detected DLAs at $z > 4.7$, found in mid to high-resolution spectroscopy from VLT/X-shooter and Keck/HIRES. These DLAs were not pre-selected based on metallicity, enabling an unbiased study of the metallicity of HI gas at $z \sim 5$. We also search for DLAs unbiased in metallicity at $0<z<5.5$ from the literature, we apply a combined correction for dust depletion and $α$-enhancement (assuming no depletion of S, Si, and Zn) to Fe abundances, and we measure the cosmic metallicity evolution of $α$-elements using a linear fit with a slope of$-0.22 \pm 0.05$ dex per unit redshift. For the highest redshift bin, we find an \NHI weighted average of $\langle Z \rangle = -2.00$. This value is $4.4σ$ deviant from the trend recovered at $z < 4.7$ and a K-S test comparison gives a $2.4 σ$ difference. We conclude that the metallicity of HI gas sharply decreases at $z \sim 5$, in agreement with previous tentative evidence. This sharp decrease may be connected with the onset of the enrichment of galaxies' circumgalactic media or with the end of cosmic reionization, though we cannot exclude that it is driven by small sample statistics.

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arXiv2026

The Spatially Resolved Hot Gas Properties of NGC 1266's AGN-Driven Outflow

Galactic winds play a critical role in galaxy evolution, yet their structure and driving mechanisms remain poorly understood, especially in low-luminosity AGN (LLAGN) systems. NGC~1266 hosts one such LLAGN, embedded in a massive molecular gas reservoir that is not forming stars, likely due to AGN feedback. We analyze deep archival \textit{Chandra} data to constrain the properties of its hot gas and compare them to other wind systems. We find temperatures of $0.25-1.8$~keV and notably high electron densities of $0.33-4.2$~cm$^{-3}$, suggesting significant mass loading, further supported by charge exchange emission in the southern lobe, one of the few AGN systems where it has been detected. We measure pressures and thermal energies of $10^6-10^8$~K cm$^{-3}$ and $10^{54}-10^{56}$~erg, exceeding the minimum energy needed for the radio jet to power the outflow and implying the hot phase comprises a large fraction of the energy budget. Archival MUSE data reveal a cavity-like feature in the southern outflow, potentially associated with the far side of the outflow cone. At the maximum outflow extent, the warm and hot phases appear to be in pressure equilibrium. Coupled with short cooling timescales of $\sim$1~Myr, comparable to the advection time, this suggests the outflow is undergoing radiative cooling and may have stalled. Finally, we compare NGC~1266 to other local AGN and starburst galaxies, finding NGC~1266 to be the densest wind in the sample.

astro-ph.GA↗

arXiv2026

Constraining the Sub-Galactic Relationship Between Star Formation and the Hot Interstellar Medium in NGC 4254

We investigate the relationship between star formation and X-ray emission from the hot interstellar medium (ISM) on $\sim$kpc scales in NGC 4254 (M99) by combining spatially resolved star formation histories (SFHs) and Bayesian X-ray spectral fitting. We measure sub-galactic star formation rates (SFR) by modeling spectrophotometric UV-IR data with flexible SFHs, and we produce point-source-subtracted maps of the diffuse X-ray emission using Chandra data. We extract and fit the spectra of 5 regions selected by their SFR density $Σ_{\rm SFR}$, deriving hot gas luminosities and plasma temperatures. We examine the sub-galactic $kT-Σ_{\rm SFR}$ and $L^{\rm gas}_X-Σ_{\rm SFR}$ scaling relations in NGC 4254, and compare to predictions from simple models of the feedback into the ISM from core collapse supernovae (CCSNe). The hot gas emission from NGC 4254 is consistent with thermalization of $\approx 40-50\%$ of the energy from CCSNe in the ISM, and mass-loading of the CCSNe ejecta which decreases as $Σ_{\rm SFR}^{-1/3}$. Our optimized model implies a temperature and X-ray production efficiency that scale as $kT = (0.72^{+0.26}_{-0.18}~{\rm keV}) Σ_{\rm SFR}^{0.34\pm0.10}$ and $η= (0.03^{+0.02}_{-0.01}) Σ_{\rm SFR}^{0.34\pm0.18}$, respectively, for $Σ_{\rm SFR} = 0.01-0.13~{\rm M_{\odot}~yr^{-1}~kpc^{-2}}$. We also compare the properties of the hot ISM to other ISM phases using data from the PHANGS program. The diffuse X-ray emission of a given region is on average 200 times fainter than the H$α$ emission, and we see evidence that the hot ISM is over-pressurized compared to the large-scale dynamical equilibrium pressure of the galaxy, consistent with expansion of the hot ISM into the ambient medium.

astro-ph.GA↗

arXiv2026

JWST Observations of Starbursts: PAHs Closely Trace the Cool Phase of M82's Galactic Wind

Stellar feedback drives multiphase gas outflows from starburst galaxies, but the interpretation of dust emission in these winds remains uncertain. To investigate this, we analyze new JWST mid-infrared images tracing polycyclic aromatic hydrocarbon (PAH) emission at 7.7 and 11.3~$μ$m from the outflow of the prototypical starburst M82 out to $3.2$ kpc. We find that PAH emission shows significant correlations with CO, H$α$, and X-ray emission within the outflow, though the strengths and behaviors of these correlations vary with gas phase and distance from the starburst. PAH emission correlates strongly with cold molecular gas, with PAH--CO scaling relations in the wind nearly identical to those in galaxy disks despite the very different conditions. The H$α$--PAH correlation indicates that H$α$ traces the surfaces of PAH-bearing clouds, consistent with arising from ionized layers produced by shocks. Meanwhile the PAH--X-ray correlation disappears once distance effects are controlled for past 2~kpc, suggesting that PAHs are decoupled from the hot gas and the global correlation merely reflects the large-scale structure of the outflow. The PAH-to-neutral gas ratio remains nearly flat to 2~kpc, with variations following changes in the radiation field. This implies that the product of PAH abundance and dust-to-gas ratio does not change significantly over the inner portion of the outflow. Together, these results demonstrate that PAHs robustly trace the cold phase of M82's wind, surviving well beyond the starburst and providing a powerful, high-resolution proxy for mapping the life cycle of entrained cold material in galactic outflows.

astro-ph.GA↗

arXiv2025

Clumpy, dense gas in the outflow of NGC 1266

Outflows are one of the most spectacular mechanisms through which active galactic nuclei (AGN) impact their host galaxy, though the role of AGN-driven outflows in global star formation regulation across the galaxy population is unclear. NGC 1266 is an excellent case study for investigating the outflows and star formation quenching because it is a nearby (D\sim30 Mpc) AGN host galaxy with an outflow driving shocks through the interstellar medium (ISM) and has recently quenched its star formation outside the nucleus. While previous works have studied the molecular outflow from its CO emission, to fully characterize the impact the outflow has on the ISM observations probing the dense, cold gas are necessary. Our ALMA cycle 0 observations do not detect a molecular outflow in 13CO(2-1) and yield a lower limit 12CO/13CO \geq 250, suggesting a highly optically thin CO outflow with low 13CO abundance. In contrast, we detect substantial HCN(1-0) emission in the outflow, with an HCN(1-0)/12CO(1-0) ratio of 0.09, consistent with global measurements of many star-forming galaxies and Luminous InfraRed Galaxies (LIRGs). We conclude that the CO emission traces a diffuse component of the molecular gas with a low optical depth, whereas the HCN(1-0) traces dense clumps of gas entrained in the outflow. We measure an upper limit molecular outflow rate of < 85 Msun/yr. Assuming the ongoing nuclear star formation and outflow continue at the same rates, NGC 1266 will deplete its gas reservoirs in 450 Myr or longer, indicating that relatively low-level AGN feedback is capable of gradually expelling the molecular gas reservoir after a rapid quenching event.

astro-ph.GA↗

arXiv2025

From the Intergalactic to the Interstellar Scales -- EQUALS: a High-resolution Legacy Survey of Gas in the Distant Universe Using ESPRESSO

Understanding how the Universe evolved from diffuse primordial gas into the rich cosmic web we observe today is one of the great challenges of modern astrophysics. Quasar absorption lines - the imprints left by intervening gas on the light from distant quasars - provide key diagnostics of many aspects of this investigation, ranging from fundamental physics to cosmology and galaxy formation. The unprecedented combination of extremely precise wavelength calibration, high spectral resolution and high sensitivity of the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) has finally enabled observations that will further constrain both state-of-the-art cosmological simulations of galaxy evolution and theoretical stellar nucleosynthetic yields. In this article, we present the ESPRESSO Quasar Absorption Line Survey (EQUALS), an ESO Large Programme, designed to tackle several outstanding questions from constraining the properties of dark matter at the smallest scales probed by the Lyman-alpha forest to determining the temperature of the intergalactic medium at z ~ 4 and precisely quantifying the chemical contributions of stellar populations in the early Universe. EQUALS will provide a legacy sample of deep spectra to showcase ESPRESSO capabilities to the quasar absorption line community whilst providing epoch measurements for the key science goals of upcoming spectroscopic instrumentation on the next generations of telescopes.

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arXiv2025

Taming the Tarantula: How Stellar Wind Feedback Shapes Gas and Dust in 30 Doradus

Observations of massive star-forming regions show that classical stellar wind models over-predict the luminosity of the X-ray emitting gas, indicating a significant fraction of wind energy is lost. In this paper, we present a multi-wavelength analysis of the giant HII region 30 Doradus and its central star cluster R136 using 2 Ms of Chandra X-ray Observatory data, combined with James Webb Space Telescope and Hubble Space Telescope imaging and Spitzer spectral-energy distributions, to investigate how the hot gas energy is lost through turbulent mixing, radiative cooling, and physical leakage. We compare the spatial and spectral properties of the hot gas with those of the warm ionized gas and dust. We find no significant correlation between the dust and hot gas temperatures, suggesting they are not directly coupled and that the dust resides in the swept-up shells where it is heated radiatively. H$α$ and X-ray surface brightness profiles show that the X-rays peak interior to the H$α$ shells, demonstrating partial confinement of the hot gas. The fragmented shell structure and bright X-ray interior that declines near the H$α$ shell reflect efficient cooling from turbulent mixing at the hot-cold interface. We compare against recent simulations of stellar-feedback driven bubbles which have broad agreement with the morphology of the X-ray and H$α$ emission, but the simulations produce a dip in the interior X-ray surface brightness and a lack of hard X-rays compared to the observations. These differences may suggest thermal conduction is important as mass-loading of the hot bubble could reproduce the X-ray observables.

astro-ph.HE↗

arXiv2025

The role of supercluster filaments in shaping galaxy clusters

In a hierarchical $Λ$CDM Universe, cosmic filaments serve as the primary channels for matter accretion into galaxy clusters, influencing the shape of their dark matter halos. We investigate whether the elongation of galaxy clusters correlates with the orientation of surrounding filaments, providing the first observational test of this relationship in large supercluster regions. We identified and characterized cosmic filaments in two dimensions within the two superclusters that are part of the low-redshift sub-survey of the Chilean Cluster Galaxy Evolution Survey (CHANCES): the Shapley supercluster and the Horologium-Reticulum supercluster. We analyzed the alignment between filament directions -- traced by galaxy distributions -- and the triaxiality of cluster gravitational potentials -- traced by X-ray emission- using publicly available optical and X-ray data. We have found that most (82%) of the X-ray clusters are associated with and interconnected by the optically detected filaments. The clusters-filaments alignment analysis shows that the elongation of most clusters is well aligned with nearby filaments, providing observational confirmation of theoretical predictions, with the alignment progressively reducing at larger cluster-centric distances ($> 1.6 r_{200}$). Overall, our results support the notion that filaments are the main source of galaxy accretion at redshift below 0.1 and additionally provide evidence that matter accretion through filaments shapes the gravitational potential of galaxy clusters. We propose this measurement as a simple observational proxy to determine the direction of accretion in clusters, which is key to understanding both galaxy evolution and the merger history of galaxy clusters.

astro-ph.CO↗

arXiv2025

How far have metals reached? Reconciling statistical constraints and enrichment models at reionization

The incidence of quasar absorption systems and the space density of their galaxies are proportional, the proportionality factor being the mean absorbing cross section. In this paper we use redshift parameterizations of these two statistics to predict the cosmic evolution of an equivalent-width ($W_r$) radial profile model, tailored for the low-ionization species Mg II and O I. Our model provides an excellent match with well-sampled, low-redshift Mg II equivalent-width/impact-parameter pairs from the literature. We then focus on the evolution of various quantities between the Reionization and Cosmic Noon eras. Our findings are: (1) The extent of Mg II and hence the amount of cool ($T\sim 10^4$ K), enriched gas in the average halo decreases continuously with cosmic time after $z \approx 6$--$8$. This effect is more pronounced in $W_r^{2796}\lesssim 0.3$ Å systems (outermost layers of the model) and, in general, affects O I more than Mg II, probably due to the onset of photoionization by the UV background. (2) The line density of $W_r^{2796}\gtrsim 1$ Å systems (model inner layers) constantly increases in synchrony with the star formation rate density until it reaches a peak at Cosmic Noon. The line density of $W_r^{2796}\lesssim 0.3$ Å systems, on the other hand, remains constant or decreases over the same period. (3) At the end of Reionization, the filling factor is low enough that the winds have not yet reached neighboring halos. This implies that the halos are self-enriched, as suggested by semi-analytic models. We discuss how these statistical predictions can be reconciled with early metal enrichment models and offer a practical comparison point for future analyses of quasar absorption lines at $z>6$.

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arXiv2025

The Diversity of Metal-Enrichment and Abundance Patterns at High Redshift: A Magellan Survey of Gas-rich Galaxies Traced by Damped Lyman-alpha Absorbers at z~5

A powerful technique to trace the signatures of the first stars is through the metal enrichment in concentrated reservoirs of hydrogen, such as the damped Lyman-alpha absorbers (DLAs) in the early universe. We conducted a survey aimed at discovering DLAs along sight lines to high-z quasars in order to measure element abundances at z>4. Here we report our first results from this survey for 10 DLAs with redshifts of ~4.2-5.0. We determine abundances of C, O, Si, S, and Fe, and thereby the metallicities and dust depletions. We find that DLA metallicities at z>4.5 show a wide diversity spanning ~3 orders of magnitude. The metallicities of DLAs at 3.7 =30% Pop-III contribution). Combining our sample and the literature, we find the dust depletion strength and dust-to-metal ratios to correlate positively with the total (gas+solid phase) metallicity, confirming the presence of metal-rich, dusty DLAs even at ~1 billion years after the Big Bang.

astro-ph.GA↗

arXiv2025

Unmixed metals: Variations in the enrichment of z~4 sub-damped Lyman alpha systems

The chemical abundance patterns of near-pristine objects provide important constraints on the properties of the first generations of stars in the Universe. We present the chemical abundances of five very metal-poor ([M/H]<-2.5) sub damped Lyman alpha systems (subDLAs) covering the redshift range $3.6<z<4.3$, identified with the XQ-100 survey. We find that the subDLAs in our sample show consistent chemical abundance patterns (in particular [C/O], [Al/O], and [Fe/O]) with those of very metal-poor DLAs. Based on Voigt profile fitting, the chemical abundance ratios [C/O], [Al/O], and [Si/O] of individual velocity components in at least three of the subDLAs shows some intrinsic scatter. In order to verify these chemical inhomogeneities in absorption components, we present a novel method for computing ionization corrections (ICs) on a component-by-component basis and show that ICs alone cannot explain the variations in [C/O], [Al/O], and [Si/O] between components of the same absorber at ~2 sigma significance. Comparing the observed abundance ratios to the simulated core-collapse supernovae yields of early stellar populations, we find that all individual components of the subDLAs appears to be enriched by progenitor masses of <30 M_sol. The observed inhomogeneities between components can be reproduced by differences in the progenitor mass or supernova explosion energy. As such, the observed chemical inhomogeneities between components can be explained by poorly mixed gas from different nucleosynthetic events.

astro-ph.GA↗