Metal abundance and its evolution are studied for Mg II quasar absorption line systems from their weak, unsaturated spectral lines using stacked spectra from the archived data of Sloan Digital Sky Survey. They show an abundance pattern that resembles that of Galactic halo or Small Magellanic Cloud, with metallicity [Z/H] showing an evolution from redshift z=2 to 0.5: metallicity becomes approximately solar or even larger at z~0. We show that the evolution of the metal abundance traces the cumulative amount of the hydrogen fuel consumed in star formation in galaxies. With the aid of a spectroscopic simulation code, we infer the median gas density of the cloud to be roughly 0.3 $\rm cm^{-3}$, with which the elemental abundance in various ionization stages, in particular C I, is consistently explained. This gas density implies that the size of the Mg II clouds is of the order of 0.03 kpc, which suggests that individual Mg II clouds around a galaxy are of a baryonic mass typically $\rm 10^{3} \, M_{\odot}$. This means that Mg II clouds are numerous and `foamy', rather than the large entity that covers a sizable fraction of galaxies with a single cloud.
The bimodal absorption system imaging campaign (BASIC) aims to characterize the galaxy environments of a sample of 36 HI-selected partial Lyman limit systems (pLLSs) and Lyman limit systems (LLSs) in 23 QSO fields at $z \lesssim 1$. These pLLSs/LLSs provide a unique sample of absorbers with unbiased and well-constrained metallicities, allowing us to explore the origins of metal-rich and low-metallicity circumgalactic medium (CGM) at $z<1$. Here we present Keck/KCWI and VLT/MUSE observations of 11 of these QSO fields (19 pLLSs) that we combine with HST/ACS imaging to identify and characterize t…
We present 13 new 2175 Å dust absorbers at z_abs = 1.0 - 2.2 towards background quasars from the Sloan Digital Sky Survey. These absorbers are examined in detail using data from the Echelle Spectrograph and Imager (ESI) on the Keck II telescope. Many low-ionization lines including Fe II, Zn II, Mg II, Si II, Al II, Ni II, Mn II, Cr II, Ti II, and Ca II are present in the same absorber which gives rise to the 2175 Å bump. The relative metal abundances (with respect to Zn) demonstrate that the depletion patterns of our 2175 Å dust absorbers resemble that of the Milky Way clouds although some are…
We present an analysis of the metallicity distribution of the dense circumgalactic medium (CGM) of galaxies at 0.1 < z < 1.1 as probed by partial Lyman limit systems (pLLSs, 16.1 < log N(H I) < 17.2) and LLSs (17.2 < log N(H I) < 17.7 in our sample). The new H I-selected sample, drawn from our HST COS G140L snapshot survey of 61 QSOs, has 20 pLLSs and 10 LLSs. Combined with our previous survey, we have a total of 44 pLLSs and 11 LLSs. We find that the metallicity distribution of the pLLSs is bimodal at z < 1, with a minimum at [X/H] = -1. The low-metallicity peak comprises (57 +/- 8)% of the p…
We characterize the metallicities and physical properties of cool, photoionized gas in a sample of 152 z<1 strong Lya forest systems (SLFSs, absorbers with 15<log N(HI)<16.2). The sample is drawn from our COS circumgalactic medium (CGM) compendium (CCC), an ultraviolet survey of HI-selected circumgalactic gas around z<1 galaxies that targets 262 absorbers with 15<log N(HI)<19. We show that the metallicity probability distribution function of the SLFSs at z<1 is unimodal, skewed to low metallicities with a mean and median of [X/H]=-1.47$ and -1.18 dex. Very metal-poor gas with [X/H]<-1.4 repres…
We present the detection and analysis of a weak low-ionization absorber at $z = 0.12122$ along the blazar sightline PG~$1424+240$, using spectroscopic data from both $HST$/COS and STIS. The absorber is a weak Mg II analogue, with incidence of weak C II and Si II, along with multi-component C IV and O VI. The low ions are tracing a dense ($n_{H} \sim 10^{-3}$ cm$^{-3}$) parsec scale cloud of solar or higher metallicity. The kinematically coincident higher ions are either from a more diffuse ($n_{H} \sim 10^{-5} - 10^{-4}$ cm$^{-3}$) photoionized phase of kiloparsec scale dimensions, or are trac…
We report the discovery of a massive $\log(M/M_\odot)=10.74^{+0.18}_{-0.16}$ galaxy at the same redshift as a carbon-monoxide-bearing sub-damped Lyman $α$ absorber (sub-DLA) seen in the spectrum of QSO J1439+1117. The galaxy, J1439B, is located 4\farcs7 from the QSO sightline, a projected distance of 38 physical kpc at $z=2.4189$, and exhibits broad optical emission lines ($σ_{\rm{[O III]}}=303 \pm 12$~\kms) with ratios characteristic of excitation by an active galactic nucleus (AGN). The galaxy has a factor of $\sim$9 lower star formation than is typical of star-forming galaxies of the same m…
The damped and sub-damped Lyman alpha systems (DLAs and sub-DLAs) traced in absorption against bright background quasars represent the main reserve of neutral hydrogen at high redshifts. We used the archival Very Large Telescope (VLT) instrument Ultraviolet and Visual Echelle Spectrograph (UVES) high-resolution data of Q0338-0005 (zem = 3.049) to study abundances of the DLA (zabs = 2.2298) and sub-DLA (zabs =2.7457) along the line of sight. We estimated column densities of HI and various elements present in the DLA and sub-DLA through Voigt profile fitting. The DLA trough shows the Lyman alpha…
Metallicity estimates of circumgalactic gas based on absorption line measurements typically require photoionization modeling to account for unseen ionization states. We explore the impact of uncertainties in the extreme ultraviolet background (EUVB) radiation on such metallicity determinations for the z < 1 circumgalactic medium (CGM). In particular, we study how uncertainties in the power-law slope of the EUV radiation, $\mathrm{α_{EUVB}}$, from active galactic nuclei affect metallicity estimates in a sample of 34 absorbers with HI column densities between 15.25 < log ($\mathrm{N_{HI}}$ / $\m…
We report Keck/ESI and VLT/UVES observations of three super-damped Lyman-alpha quasar absorbers with H I column densities log N(HI) >= 21.7 at redshifts z=2-2.5. All three absorbers show similar metallicities (-1.3 to -1.5 dex), and dust depletion of Fe, Ni, and Mn. Two of the absorbers show supersolar [S/Zn] and [Si/Zn]. We combine our results with those for other DLAs to examine trends between N(HI), metallicity, dust depletion. A larger fraction of the super-DLAs lie close to or above the line [X/H]=20.59-log N(HI) in the metallicity vs. N(HI) plot, compared to the less gas-rich DLAs, sugge…
Ne VIII absorbers seen in QSO spectra are useful tracers of warm ionized gas, when collisional ionization is the dominant ionization process. While photoionization by the ultraviolet background (UVB) is a viable option, it tends to predict large line-of-sight thickness for the absorbing gas. Here, we study the implications of the recently updated UVB at low-z to understand the ionization mechanisms of intervening Ne VIII absorbers. With the updated UVB, one typically needs higher density and metallicity to reproduce the observed ionic column densities under photoionization. Both reduce the inf…
We present results of the MUSE-ALMA Halos, an ongoing study of the Circum-Galactic Medium (CGM) of low redshift galaxies (z < 1.4), currently comprising 14 strong HI absorbers in five quasar fields. We detect 43 galaxies associated with absorbers down to star formation rate (SFR) limits of 0.01-0.1 solar masses/yr, found within impact parameters (b) of 250 kpc from the quasar sightline. Excluding the targeted absorbers, we report a high detection rate of 89 per cent and find that most absorption systems are associated with pairs or groups of galaxies (three to eleven members). We note that gal…
We aim at assessing what are the most dominant dust species or types, including silicate and iron oxide grains present in the ISM, by using recent observations of dust depletion of galaxies at various evolutionary stages. We use the observed elemental abundances in dust of several metals (O, S, Si, Mg, and Fe) in different environments, considering systems with different metallicities and dust content, namely damped Lyman-α absorbers (DLAs) towards quasars and the Galaxy. We derive a possible dust composition by computationally finding the statistically expected elemental abundances in dust as…
Observed and simulated galaxies exhibit correlations between stellar mass, metallicity and morphology. We use the EAGLE cosmological simulation to examine the origin of these correlations for galaxies in the stellar mass range $10^9~\rm{M_\odot} \leqslant\ M_\star \leqslant 10^{10}~\rm{M_\odot}$, and the extent to which they contribute to the scatter in the mass-metallicity relation. We find that rotationally supported disc galaxies have lower metallicity than dispersion supported spheroidal galaxies at a given mass, in agreement with previous findings. In EAGLE, this correlation arises becaus…
We consider the questions of whether the damped Lyman-alpha (DLA) and sub-DLA absorbers in quasar spectra differ intrinsically in metallicity, and whether they could arise in galaxies of different masses. Using the recent measurements of the robust metallicity indicators Zn and S in DLAs and sub-DLAs, we confirm that sub-DLAs have higher mean metallicities than DLAs, especially at $z \lesssim 2$. We find that the intercept of the metallicity-redshift relation derived from Zn and S is higher than that derived from Fe by 0.5-0.6 dex. We also show that, while there is a correlation between the me…
We present abundance measurements of elements O, C, Si and Fe for three gas-rich galaxies at z~5 using observations from the Very Large Telescope (VLT) and the Keck telescope in order to better constrain the early chemical enrichment of gas-rich galaxies. These galaxies show strong Lyman-α absorption in the spectra of background quasars, with neutral hydrogen column densities log N${_H{}_I}$(cm$^{-2}$)=20.10$\pm$0.15, 20.10$\pm$0.15, and 20.80$\pm$0.15. Using the undepleted element O, we find the metallicities [O/H] to be in the range of -2.51 to -2.05 dex. Our study has doubled the existing s…
The Velocity Map Asymmetry of Ionized Gas in MaNGA II. Correlation between Velocity Map Morphology, Star Formation, and Metallicity in Regular Disk Galaxies
We present the cold neutral content (H I and C I gas) of 13 quasar 2175 Å$ $ dust absorbers (2DAs) at $z$ = 1.6 - 2.5 to investigate the correlation between the presence of the UV extinction bump with other physical characteristics. These 2DAs were initially selected from the Sloan Digital Sky Surveys I - III and followed up with the Keck-II telescope and the Multiple Mirror Telescope as detailed in our Paper I. We perform a correlation analysis between metallicity, redshift, depletion level, velocity width, and explore relationships between 2DAs and other absorption line systems. The 2DAs on …
The cosmic chemical enrichment as measured from damped Ly$α$ absorbers (DLAs) will be underestimated if dusty and metal-rich absorbers have evaded identification. Here we report the discovery and present the spectroscopic observations of a quasar, KV-RQ\,1500-0031, at $z=2.520$ reddened by a likely dusty DLA at $z=2.428$ and a strong MgII absorber at $z=1.603$. This quasar was identified as part of the KiDS-VIKING Red Quasar (KV-RQ) survey, specifically aimed at targeting dusty absorbers which may cause the background quasars to escape the optical selection of e.g. the SDSS quasar survey. For …
We report on a sensitive search for redshifted H$α$ line-emission from three high-metallicity damped Ly$α$ absorbers (DLAs) at $z \approx 2.4$ with the Near-infrared Integral Field Spectrometer (NIFS) on the Gemini-North telescope, assisted by the ALTtitude conjugate Adaptive optics for the InfraRed (ALTAIR) system with a laser guide star. Within the NIFS field-of-view, $\approx 3.22" \times 2.92"$ corresponding to $\approx 25$ kpc $ \times 23$ kpc at $z=2.4$, we detect no statistically significant line-emission at the expected redshifted H$α$ wavelengths. The measured root-mean-square noise f…
We present results from the analysis of a multiphase O VI - broad Ly-alpha absorber at z = 0.19236 in the HST/COS spectrum of PG 1121+422. The low and intermediate ionization metal lines in this absorber have a single narrow component, whereas the Ly-alpha has a possible broad component with b(HI) $\sim 71$ km/s. Ionization models favor the low and intermediate ions coming from a $T \sim 8,500$ K, moderately dense photoionized gas with near solar metallicities. The weak O VI requires a separate gas phase that is collisionally ionized. The O VI coupled with BLA suggests $T \sim 3.2 \times 10^5$…
MUSEQuBES: Investigating the Physical and Chemical Properties of Circumgalactic Gas Around Ly$α$ Emitters at $z \approx 3.3$
IUCAA（印度天体物理研究与教育中心）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Department of Astronomy, University of Michigan（密歇根大学天文学系）；Department of Physics, University of Milan Bicocca（米兰比可卡大学物理学系）
We use N-body chemo-dynamic simulations to study the coupling between morphology, kinematics and metallicity of the bar/bulge region of our Galaxy. We make qualitative comparisons of our results with available observations and find very good agreement. We conclude that this region is complex, since it comprises several stellar components with different properties -- i.e. a boxy/peanut bulge, thin and thick disc components, and, to lesser extents, a disky pseudobulge, a stellar halo and a small classical bulge -- all cohabiting in dynamical equilibrium. Our models show strong links between kine…
The BRIDGE Survey. I. Metallicities and Physical Properties of Gas Probing the Circumgalactic Medium at Cosmic Noon
University of Notre Dame（圣母大学）；W.M. Keck Observatory（W.M.凯克天文台）；European Southern Observatory（欧洲南方天文台）；Aix Marseille Université（艾克斯-马赛大学）；CNRS（法国国家科学研究中心）；Laboratoire d’Astrophysique de Marseille（马赛天体物理学实验室）；University of California（加利福尼亚大学）；UCO/Lick Observatory（加州大学/利克天文台）；Kavli Institute for the Physics and Mathematics of the Universe（Kavli宇宙物理与数学研究所）；National Astronomical Observatory of Japan（日本国立天文台）
Context. Absorbing galaxies are selected via the detection of characteristic absorption lines which their gas-rich media imprint in the spectra of distant light-beacons. The proximity of the typically faint foreground absorbing galaxies to bright background sources makes it challenging to robustly identify these in emission, and hence to characterise their relation to the general galaxy population. Aims. We search for emission to confirm and characterise ten galaxies hosting damped, metal-rich quasar absorbers at redshift z < 1. Methods. We identify the absorbing galaxies by matching spectrosc…
In this paper, we present a new method to constrain the metallicities of high redshift damped Ly$α$ (DLA) absorbers using observed extinction curves. This is the first time such an approach is employed to constrain the metallicities of extragalactic absorbers. To demonstrate our method, we use the spectra of 13 quasars and one GRB with DLA absorbers detected along their sightlines. By using the Kramers-Kronig (KK) relation, which relates the wavelength-integrated extinction to the total volume occupied by dust per hydrogen nucleon, we set some robust lower limits on the metallicity of the DLAs…
We present the Voigt profile analysis of 132 intervening CIV+CIII components associated with optically-thin HI absorbers at 2.1 < z < 3.4 in the 19 high-quality UVES/VLT and HIRES/Keck QSO spectra. For log N(CIV) = [11.7, 14.1], N(CIII) is proportional to N(CIV) with an exponent (1.42 +- 0.11) and < N(CIII)/N(CIV) > = 1.0 +- 0.3 with a negligible redshift evolution. For 54 CIV components tied (aligned) with HI at log N(HI) = [12.2, 16.0] and log N(CIV) = [11.8, 13.8], the gas temperature T_b estimated from absorption line widths is well-approximated to a Gaussian peaking at log T_b ~ 4.4 +- 0.…
Albeit radial migration must be a ubiquitous process in disc galaxies, its significance in the evolution of stellar discs is not always reflected through global trends. However, there are other key observables, such as the metallicity distribution function (MDF), that may shed some light in this matter. We argue that the shape of the MDF not only tells us whether the stellar disc experienced radial migration, but it also contains important clues on the structure that triggered it. Specifically, the MDF contains information about the dynamics and morphology of the spiral pattern. To constrain t…
A Partial Lyman Limit Absorber in the Halo of a Galaxy Pair: A Possible Signature of Gas Inflow
Indian Institute of Space Science and Technology（印度空间科学与技术学院）；Inter-University Centre for Astronomy and Astrophysics (IUCAA)（大学天体物理与天文中心）；The Pennsylvania State University（宾夕法尼亚州立大学）；University of Milano-Bicocca（米兰比可卡大学）
We use fossil record techniques on the CALIFA sample to study how galaxies in the local universe have evolved in terms of their chemical content. We show how the metallicity and the mass-metallicity relation (MZR) evolve through time for the galaxies in our sample and how this evolution varies when we divide them based on their mass, morphology and star-forming status. We also check the impact of measuring the metallicity at the centre or the outskirts. We find the expected results that the most massive galaxies got enriched faster, with the MZR getting steeper at higher redshifts. However, on…
The production and distribution of metals in the diffuse intergalactic medium (IGM) have implications for galaxy formation models and the baryon (re)cycling process. The relative abundance of metals in high versus low-ionization states has also been argued to be sensitive to the Universe's reionization history. However, measurements of the background metallicity of the IGM at z~4 are sparse and in poor agreement with one another, and reduced sensitivity in the near-IR renders detecting individual metal absorbers nearly impossible. We present a new clustering-based technique that enables the de…
We report observations of four sub-damped Lyman-alpha (sub-DLA) quasar absorbers at z<0.5 obtained with the Hubble Space Telescope Cosmic Origins Spectrograph. We measure the available neutrals or ions of C, N, O, Si, P, S, Ar, Mn, Fe, and/or Ni. Our data have doubled the sub-DLA metallicity samples at z<0.5 and improved constraints on sub-DLA chemical evolution. All four of our sub-DLAs are consistent with near-solar or super-solar metallicities and relatively modest ionization corrections; observations of more lines and detailed modeling will help to verify this. Combining our data with meas…
We study metal depletion due to dust in the interstellar medium (ISM) to infer the properties of dust grains and characterize the metal and dust content of galaxies, down to low metallicity and intermediate redshift z. We provide metal column densities and abundances of a sample of 70 damped Lyman-α absorbers (DLAs) towards quasars, observed at high spectral resolution with the Very Large Telescope (VLT) Ultraviolet and Visual Echelle Spectrograph (UVES). This is the largest sample of phosphorus abundances measured in DLAs so far. We use literature measurements for Galactic clouds to cover the…
The visibility of LyA emitting galaxies during the Epoch of Reionization is controlled by both diffuse HI patches in large-scale bubble morphology and small-scale absorbers. To investigate the impact on LyA photons, we apply a novel combination of analytic and numerical calculations to three scenarios: (i) the `bubble' model, where only diffuse HI outside ionized bubbles is present; (ii) the `web' model, where HI exists only in overdense self-shielded gas; and (iii) the more realistic 'web-bubble' model, which contains both. Our analysis confirms that there is a degeneracy between the ionizati…
We present a sample of 34 weak metal line absorbers at $z< 0.3$ complied via the simultaneous detections ($3σ$) of the SiII$\lambda1260$ and CII$\lambda1334$ absorption lines, with $W_{r}$(SiII)$<0.2$ Å and $W_{r}$(CII)$<0.3$ Å, in archival HST/COS spectra. Our sample increases the number of known low-$z$ "weak absorbers" by a factor of $>5$. The column densities of HI and low-ionization metal lines obtained from Voigt profile fitting are used to build simple photoionization models using CLOUDY. The inferred densities and total hydrogen column densities are in the ranges of $-3.3 < \log n_{\rm…
We present the KODIAQ-Z survey aimed to characterize the cool, photoionized gas at 2.2<z<3.6 in 202 HI-selected absorbers with 14.6<log N(HI)<20, i.e., the gaseous interface between galaxies and the intergalactic medium (IGM). We find that the 14.6<log N(HI)<20 gas at 2.2<z<3.6 can be metal-rich gas (-1.6<[X/H]<-0.2) as seen in damped Ly-alpha absorbers (DLAs); it can also be very metal-poor ([X/H]<-2.4) or even pristine gas ([X/H]<-3.8) not observed in DLAs, but commonly observed in the IGM. For 16<log N(HI)<20 absorbers, the frequency of pristine absorbers is about 1%-10%, while for 14.6<log…
To fully exploit the potential of quasars as probes of cosmic chemical evolution and the internal gas dynamics of galaxies it is important to understand the selection effects behind the quasar samples and in particular if the selection criteria exclude foreground galaxies with certain properties (most importantly a high dust content). Here we present spectroscopic follow-up from the 10.4-m GTC telescope of a dust-reddened quasar, eHAQ0111+0641, from the extended High A_V Quasar (HAQ) survey. We find that the z=3.21 quasar has a foreground Damped Lyman-alpha Absorber (DLA) at z=2.027 along the …
We present seven new abundance measurements of the elements O, C and Si at z > 4.5, doubling the existing sample of weakly depleted elements in gas-rich galaxies, in order to constrain the first ~1 billion years of cosmic metal evolution. These measurements are based on quasar spectra of damped Lyman-alpha absorbers (DLAs) and sub-DLAs obtained with the Magellan Inamori Kyocera Echelle (MIKE) and Magellan Echellette (MagE) spectrographs on Magellan-South, and the X-Shooter spectrograph on the Very Large Telescope. We combine these new measurements with those drawn from the literature to estima…
We present a neutral hydrogen-selected absorption-line survey of gas with HI column densities 15<log N(HI)<19 at z<1 using the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our main aim is to determine the metallicity distribution of these absorbers. Our sample consists of 224 absorbers selected on the basis of their HI absorption strength. Here we discuss the properties of our survey and the immediate empirical results. We find singly and doubly ionized metal species and HI typically have similar velocity profiles, implying they probe gas in the same or similar environments. The …
Element abundances in high-redshift quasar absorbers offer excellent probes of the chemical enrichment of distant galaxies, and can constrain models for population III and early population II stars. Recent observations indicate that the sub-damped Lyman-alpha (sub-DLA) absorbers are more metal-rich than DLA absorbers at redshifts 0$<$$z$$<$3. It has also been suggested that the DLA metallicity drops suddenly at $z$$>$4.7. However, only 3 DLAs at $z$$>$4.5 and none at $z$$>$3.5 have "dust-free" metallicity measurements of undepleted elements. We report the first quasar sub-DLA metallicity measu…
We present the results from our COS circumgalactic medium (CGM) compendium (CCC), a survey of the CGM at z<1 using HI-selected absorbers with 15<log N(HI) <19. We focus here on 82 partial Lyman limit systems (pLLSs, 16.2<log N(HI) <17.2) and 29 LLSs (17.2<log N(HI) <19). Using Bayesian techniques and Markov-chain Monte Carlo sampling of a grid of photoionization models, we derive the posterior probability distribution functions (PDFs) for the metallicity of each absorber in CCC. We show that the combined pLLS metallicity PDF at z<1 has two main peaks at [X/H]=-1.7 and -0.4, with a strong dip a…
Damped Lyman-α Absorbers (DLAs) as a class of QSO absorption-line systems are currently our most important source of detailed information on the cosmic chemical evolution of galaxies. However, the degree to which this information is biased by dust remains to be understood. One strategy is to specifically search for QSOs reddened by metal-rich and dusty foreground absorbers. In this Letter we present the discovery of a z=2.60 QSO strongly reddened by dust in an intervening extremely-strong DLA at z=2.226. This QSO was identified through a novel selection combining the astrometric measurements f…
We present the first results from our KODIAQ Z survey aimed to determine the metallicity distribution and physical properties of the z>2 partial and full Lyman limit systems (pLLSs and LLSs; 16.2<log N(HI)<19), which are probed of the interface regions between the intergalactic medium (IGM) and galaxies. We study 31 HI-selected pLLSs and LLSs at 2.3<z<3.3 observed with Keck/HIRES in absorption against background QSOs. We compare the column densities of metal-ions to HI and use photoionization models to assess the metallicity. The metallicity distribution of the pLLSs/LLSs at 2.3<z<3.3 is consi…
The distribution of gas and metals in the circumgalactic medium (CGM) plays a critical role in how galaxies evolve. The MUSE-ALMA Halos survey combines MUSE, ALMA and HST observations to constrain the properties of the multi-phase gas in the CGM and the galaxies associated with the gas probed in absorption. In this paper, we analyse the properties of galaxies associated with 32 strong \ion{H}{i} Ly-$α$ absorbers at redshift $0.2 \lesssim z \lesssim 1.4$. We detect 79 galaxies within $\pm 500$ \kms \!of the absorbers in our 19 MUSE fields. These associated galaxies are found at physical distanc…
The distribution of stellar metallicities within and across galaxies is an excellent relic of the chemical evolution across cosmic time. We present a detailed analysis of spatially resolved stellar populations based on $>2.6$ million spatial bins from 7439 nearby galaxies in the SDSS-IV MaNGA survey. To account for accurate inclination corrections, we derive an equation for morphology dependent determination of galaxy inclinations. Our study goes beyond the well-known global mass-metallicity relation and radial metallicity gradients by providing a statistically sound exploration of local relat…
To explore the role of titanium- and calcium-dust depletion in gas in and around galaxies we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope and spectroscopically analyze 34 absorption-line systems at z<=0.5 to measure column densities (or limits) for CaII and TiII. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z~3.8. Our absorber sample contains 110 absorbers (DLAs, …
We show that the ultraviolet absorption features, newly discovered in HST spectra, are consistent with being formed in a layer that extends a few kpc above the disk of the Milky Way. In this interface between the disk and the Galactic corona, high-metallicity gas ejected from the disk by supernova feedback can mix efficiently with the virial-temperature coronal material. The mixing process triggers the cooling of the lower corona down to temperatures encompassing the characteristic range of the observed absorption features, producing a net supernova-driven gas accretion onto the disk at a rate…
Using the Atacama Large Millimeter/sub-millimeter Array, we have detected CO(3-2) line and far-infrared continuum emission from a galaxy associated with a high-metallicity ([M/H] = -0.27) damped Ly-alpha absorber (DLA) at z =2.19289. The galaxy is located 3.5" away from the quasar sightline, corresponding to a large impact parameter of 30 kpc at the DLA redshift. We use archival Very Large Telescope-SINFONI data to detect Halpha emission from the associated galaxy, and find that the object is dusty, with a dust-corrected star formation rate of 110 +60 -30 Msun/yr. The galaxy's molecular mass i…
The horizontal branch (HB) morphology of globular clusters (GCs) is mainly described by metallicity. The fact that some clusters with almost the same metallicity exhibit different HB demonstrates that other parameters are at work. We present results from the analysis of the CMD of 72 GCs obtained with the Advanced Camera for Survey (ACS) of the Hubble Space Telescope (HST). We find a significant correlation between the HB color extension and the mass of the hosting cluster, while the color distance between the HB and the red-giant branch (RGB) depends on metallicity and age. We suggest that ag…
We present a detailed analysis of 99 optically thin C III absorption systems at redshift, $0.2 \le z \le 0.9$ associated with neutral hydrogen column densities in the range, $15 \le {\rm log}$ $N_{\rm H\,I}$ ($cm^{-2}$) $\le 16.2$. Using photoionization models, we infer the number density ($n_{\rm H}$), C-abundance ($[C/H]$) and line-of-sight thickness ($L$) of these systems in the ranges, $-3.4 \le$ log $n_{\rm H}$ (in $cm^{-3}$) $\le -1.6$, $-1.6 \le [C/H] \le 0.4$, and 1.3 pc $\le L \le$ 10 kpc, respectively with most of the systems having sub-kpc scale thickness. We combine the low$-z$ and…
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
本研究通过 Magellan 巡天分析10个 z≈4.2–5.0 的 DLA 元素丰度，揭示高红移金属丰度的显著离散、C/α元素增丰及 Pop III 贡献，并证实早期富金属多尘埃系统的存在。
In this study we present high-resolution VIsible Multi-Object Spectrograph integral field unit spectroscopy (VIMOS-IFU) of the extremely metal-poor HII/blue compact dwarf (BCD) galaxy Tol 65. The optical appearance of this galaxy shows clearly a cometary morphology with a bright main body and an extended and diffuse stellar tail. We focus on the detection of metallicity gradients or inhomogeneities as expected if the ongoing star-formation activity is sustained by the infall/accretion of metal-poor gas. No evidences of significant spatial variations of abundances were found within our uncertai…
We assess the metal content of the cool (10^4 K) circumgalactic medium (CGM) about galaxies at z<1 using an H I-selected sample of 28 Lyman limit systems (LLS, defined here as absorbers with 16.2<log N(H I)<18.5) observed in absorption against background QSOs by the Cosmic Origins Spectrograph on-board the Hubble Space Telescope. The N(H I) selection avoids metallicity biases inherent in many previous studies of the low-redshift CGM. We compare the column densities of weakly ionized metal species (e.g., O II, Si II, Mg II) to N(H I) in the strongest H I component of each absorber. We find that…
We present analysis on three intervening H I-C IV absorption systems tracing gas within galaxy group/cluster environments, identified in the $HST$/COS far-UV spectra of the background quasars PG $1148+549$ ($z_{abs}=0.00346$), SBS~$1122+594$ ($z_{abs}=0.00402$) and RXJ~$1230.8+0115$ ($z_{abs}=0.00574$). The ionization models are consistent with the origin of metal lines and H I from a cool and diffuse photoionized gas phase with $T \lesssim 4 \times 10^{4}$ K and $n_{\mathrm{H}} \lesssim 5 \times 10^{-4}$ cm$^{-3}$. The three absorbers have $89$, $51$ and $17$ galaxies detected within $1$ Mpc …
It is believed that, except for metallicity, some other parameters are needed to explain the horizontal branch (HB) morphology of globular clusters (GCs). Furthermore, these parameters are considered to be correlated with the mass loss of the red giant branch (RGB) stars. In our previous work, we proposed that tidally enhanced stellar wind during binary evolution may affect the HB morphology by enhancing the mass loss of the red giant primary. As a further study, we now investigate the effects of metallicity and age on HB morphology by considering tidally enhanced stellar winds during binary e…
We demonstrate that failure to properly account for stellar evolution can bias results in determinations of the spatial morphology of Galactic bulge stars, focusing on the question of whether or not the X-shape is more pronounced among the more metal-rich stars than among the metal-poor stars. We argue that this trend, a result recently claimed by three separate groups, may have been overestimated as it is relatively easier to detect a bimodality in the distance distribution function at higher metallicities. This is due to three factors. First, the intrinsic colour of red clump and red giant s…
With the goal of a thorough investigation of the ionised gas and its origin in early-type group-dominant galaxies, we present archival MUSE data for 18 galaxies from the Complete Local-Volume Groups Sample (CLoGS). This data allowed us to study the spatially-resolved warm gas properties, including the morphology of the ionised gas, EW(H$α$) and kinematics as well as the gas-phase metallicity (12 + log(O/H)) of these systems. In order to distinguish between different ionisation mechanisms, we used the emission-line ratios [O III]/H$β$ and [N II]/H$α$ in the BPT diagrams and EW(H$α$). We find th…
We report Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet and Arecibo Telescope H{\sc i} 21cm spectroscopic studies of six damped and sub-damped Lyman-$α$ absorbers (DLAs and sub-DLAs, respectively) at $z \lesssim 0.1$, that have yielded estimates of their H{\sc i} column density, metallicity and atomic gas mass. This significantly increases the number of DLAs with gas mass estimates, allowing the first comparison between the gas masses of DLAs and local galaxies. Including three absorbers from the literature, we obtain H{\sc i} masses $\approx (0.24 - 5.2) \times 10^9 \: {\…
We present optical spectroscopic and milli-arcsecond scale radio continuum observations of the quasar M1540-1453 ($z_{em}$ = 2.104$\pm$0.002) that shows associated HI 21-cm absorption at $z_{abs}$ = 2.1139. At sub-kpc scales, the powerful radio source with 1.4 GHz luminosity of $5.9\times10^{27}$ WHz$^{-1}$ shows Fanaroff-Riley (FR) class I morphology caused by the interaction with dense gas within 70 pc from the AGN. Interestingly, while there are indications for the presence of absorption from low-ionization species like FeII, SiII and SiIII in the optical spectrum, the expected strong dampe…
