We utilize the hydrodynamic and N-body code {\small GIZMO} coupled with our newly developed sub-grid Population~III (Pop~III) Legacy model, designed specifically for cosmological volume simulations, to study the baseline metal enrichment from Pop~III star formation at $z>7$. In this idealized numerical experiment, we only consider Pop~III star formation. We find that our model Pop~III star formation rate density (SFRD), which peaks at $\sim 10^{-3}\ {\rm M_\odot yr^{-1} Mpc^{-1}}$ near $z\sim10$, agrees well with previous numerical studies and is consistent with the observed estimates for Pop~II SFRDs. The mean Pop~III metallicity rises smoothly from $z=25-7$, but does not reach the critical metallicity value, $Z_{\rm crit}=10^{-4}\ Z_\odot$, required for the Pop~III to Pop~II transition in star formation mode until $z\simeq7$. This suggests that, while individual halos can suppress in-situ Pop~III star formation, the external enrichment is insufficient to globally terminate Pop~III star formation. The maximum enrichment from Pop~III star formation in star forming dark matter halos is $Z\sim10^{-2}\ Z_\odot$, whereas the minimum found in externally enriched haloes is $Z\gtrsim10^{-7}\ Z_\odot$. Finally, mock observations of our simulated IGM enriched with Pop~III metals produce equivalent widths similar to observations of an extremely metal poor damped Lyman alpha (DLA) system at $z=7.04$, which is thought to be enriched by Pop~III star formation only.
We develop a model for stochastic pre-enrichment and self-enrichment in globular clusters (GCs) during their formation process. GCs beginning their formation have an initial metallicity determined by the pre-enrichment of their surrounding protocloud, but can also undergo internal self-enrichment during formation. Stochastic variations in metallicity arise because of the finite numbers of supernova. We construct an analytic formulation of the combined effects of pre-enrichment and self-enrichment and use Monte Carlo models to verify that the model accurately encapsulates the mean metallicity a…
Quasars are powerful systems whose spectrum is rich of metal features that allow us to investigate the chemical evolution of galaxies at very high redshift, even close to the reionization epoch. I review the main observational constraints on the metallicity of quasars host galaxies at high redshift and discuss the implications and issues for models of galaxy evolution in the early universe.
We demonstrate that high abundances of water vapor could have existed in extremely low metallicity ($10^{-3}$ solar) partially shielded gas, during the epoch of first metal enrichment of the interstellar medium of galaxies at high redshifts.
Metals from Population III (Pop III) supernovae led to the formation of less massive Pop II stars in the early universe, altering the course of evolution of primeval galaxies and cosmological reionization. There are a variety of scenarios in which heavy elements from the first supernovae were taken up into second-generation stars, but cosmological simulations only model them on the largest scales. We present small-scale, high-resolution simulations of the chemical enrichment of a primordial halo by a nearby supernova after partial evaporation by the progenitor star. We find that ejecta from th…
We propose a semi-analytic model that is developed to understand the cosmological evolution of the mean metallicity in the Universe. In particular, we study the contributions of Population III (Pop III) and Population II (Pop II) stars to the production of $\mathrm{Fe,~Si,~Zn, ~Ni,~P, ~Mg, ~Al, ~S, ~C, ~N}$, and $\mathrm{~O}$. We aim to quantify the roles of two different models in the chemical enrichment of the Universe. The first model (A) considers both stars with Pop III and Pop II yields. For the second model (B), the yields involved are only for Pop II stars. We start by describing the c…
On the relative CNO underabundance in quasar absorption systems at $z \sim 3$ arising from Population III enrichment and attenuation by intermediate-mass black holes and primordial baryon accretion
National Institute for Space Research (INPE), Instituto Nacional de Pesquisas Espaciais（国家空间研究所）
The emergence of the first sources of light at redshifts of z ~ 10-30 signaled the transition from the simple initial state of the Universe to one of increasing complexity. We review recent progress in our understanding of the formation of the first stars and galaxies, starting with cosmological initial conditions, primordial gas cooling, and subsequent collapse and fragmentation. We emphasize the important open question of how the pristine gas was enriched with heavy chemical elements in the wake of the first supernovae. We conclude by discussing how the chemical abundance patterns conceivabl…
Aim: We establish the mean metallicity from high-resolution spectroscopy for the recently found dwarf spheroidal galaxy Bootes I and test whether it is a common feature for ultra-faint dwarf spheroidal galaxies to show signs of inhomogeneous chemical evolution (e.g. as found in the Hercules dwarf spheroidal galaxy). Methods: We analyse high-resolution, moderate signal-to-noise spectra for seven red giant stars in the Bootes I dSph galaxy using standard abundance analysis techniques. In particular, we assume local thermodynamic equilibrium and employ spherical model atmospheres and codes that t…
Star clusters are known to have smaller intrinsic metallicity spreads than dwarf galaxies due to their shorter star formation timescales. Here we use individual spectroscopic [Fe/H] measurements of stars in 19 Local Group dwarf galaxies, 13 Galactic open clusters, and 49 globular clusters to show that star cluster and dwarf galaxy linear metallicity distributions are binomial in form, with all objects showing strong correlations between their mean linear metallicity $\bar{Z}$ and intrinsic spread in metallicity $σ(Z)^{2}$. A plot of $σ(Z)^{2}$ versus $\bar{Z}$ shows that the correlated relatio…
A study of the IGM metal enrichment using a series of SPH simulations is presented, employing metal cooling and turbulent diffusion of metals and thermal energy. An adiabatic feedback mechanism was adopted where gas cooling was prevented to generate galactic winds without explicit wind particles. The simulations produced a cosmic star formation history (SFH) that is broadly consistent with observations until z $\sim$ 0.5, and a steady evolution of the universal neutral hydrogen fraction ($Ω_{\rm H I}$). At z=0, about 40% of the baryons are in the warm-hot intergalactic medium (WHIM), but most …
Stellar winds from fast-rotating Population III (Pop III) stars have long been suspected to make important contributions to early metal enrichment, as features in the nucleosynthesis of such `spinstars' are consistent with the chemical abundance patterns of some metal-poor stars in the local Universe. Particularly, stellar winds rich in light elements can provide another pathway towards explaining the carbon enhancement in carbon-enhanced metal-poor (CEMP) stars. In this work, we focus on the feedback of Pop III stellar winds combined with supernovae (SNe), and derive the resulting chemical si…
Recent high-resolution simulations of early structure formation have shown that externally enriched halos may form some of the first metal enriched stars. This study utilizes a 1 comoving Mpc$^3$ high-resolution simulation to study the enrichment process of metal-enriched halos down to $z=9.3$. Our simulation uniquely tracks the metals ejected from Population III stars, and we use this information to identify the origin of metals within metal-enriched halos. These halos show a wide range of metallicities, but we find that the source of metals for $\gtrsim$ 50\% of metal-enriched halos is super…
We investigate signatures of population III (PopIII) stars in the metal-enriched environment of GRBs originating from population II-I (PopII/I) stars by using abundance ratios derived from numerical simulations that follow stellar evolution and chemical enrichment. We find that at $z>10$ more than $10%$ of PopII/I GRBs explode in a medium previously enriched by PopIII stars (we refer to them as GRBII$\rightarrow$III). Although the formation of GRBII$\rightarrow$III is more frequent than that of pristine PopIII GRBs (GRBIIIs), we find that the expected GRBII$\rightarrow$III observed rate is com…
The epoch of reionization and formation of first stars are inter-linked topics that are of considerable interest. We use a simplified approach for studying formation of stars in collapsed haloes, and the resulting ionization of the inter-galactic medium (IGM). We consider a set of LCDM models allowed by observations of CMB temperature and polarization anisotropies for this study. We constrain parameters related to star formation with the help of observations. We constrain subsets of these parameters independently by using the observed metallicity of the inter-galactic medium at z ~ 5 and the r…
The fate of metals ejected by young OB associations into the Interstellar Medium (ISM) is investigated numerically. In particular, we study the enrichment of the cold gas phase, which is the material that forms molecular clouds. Following previous work, the expansion and collision of two supershells in a diffuse ISM is simulated, in this case also introducing an advected quantity which represents the metals expelled by the young stars. We adopt the simplest possible approach, not differentiating between metals coming from stellar winds and those coming from supernovae. Even though the hot, dif…
We investigate the formation of extremely metal-poor (EMP) stars that are observed in the Galactic halo and neighboring ultra-faint dwarf galaxies. Their low metal abundances (${\rm [Fe/H]} < -3$) indicate that their parent clouds were enriched by a single or several supernovae (SNe) from the first (Pop III) stars. In this study, we perform numerical simulations of the entire formation sequence of a EMP star through the feedback effects of photo-ionization and metal-enrichment by a Pop III SN. We for the first time employ a metal/dust properties calculated consistently with the progenitor mode…
Metal enrichment by the first-generation (Pop III) stars is the very first step of the matter cycle in the structure formation and it is followed by the formation of extremely metal-poor (EMP) stars. To investigate the enrichment process by the Pop III stars, we carry out a series of numerical simulations including the feedback effects of photoionization and supernovae (SNe) of Pop III stars with a range of masses of minihaloes (MHs), M_halo , and Pop III stars, M_PopIII . We find that the metal-rich ejecta reaches neighbouring haloes and external enrichment (EE) occurs when the halo binding e…
We present the simulation of a $2\times10^9 M_\odot$ halo mass cosmological dwarf galaxy run to $z=0$ at 4 solar mass gas resolution with resolved supernova feedback. We compare three simple subgrid implementations for the inhomogeneous chemical enrichment from Population III stars and compare them to constraints from Local Group dwarf galaxies. The employed model, LYRA, is a novel high resolution galaxy formation model built for the moving mesh code AREPO, which is marked by a resolved multi-phase interstellar medium, single stars and individual supernova events. The resulting reionization re…
The fate of metals after they are released in starburst episodes is still unclear. What phases of the interstellar medium are involved, in which timescales? Evidence has grown over the past few years that the neutral phase of blue compact dwarf (BCD) galaxies may be metal- deficient as compared to the ionized gas of their HII regions. These results have strong implications for our understanding of the chemical evolution of galaxies. We review here the main results and the main caveats in the abundance determination from far-UV absorption-lines. We also discuss possible scenarios concerning the…
Using the Eris zoom-in cosmological simulation of assembly of a Milky Way analog, we study chemical enrichment of stars due to accretion of metal-enriched gas from the interstellar medium during the Galaxy's development. We consider metal-poor and old stars in both Galactic halo and bulge and make use of stellar orbits, gas density and metallicity distributions in Eris. Assuming spherically symmetric Bondi-Hoyle accretion, we find that halo and bulge stars accrete metals at the rate of about 10^-24 solar mass per year and 10^-22 solar mass per year, respectively, at redshifts z < 3, but this a…
The distribution of metals in the intracluster medium (ICM) of galaxy clusters provides valuable information on their formation and evolution, on the connection with the cosmic star formation and on the effects of different gas processes. By analyzing a sample of simulated galaxy clusters, we study the chemical enrichment of the ICM, its evolution, and its relation with the physical processes included in the simulation and with the thermal properties of the core. These simulations, consisting of re-simulations of 29 Lagrangian regions performed with an upgraded version of the SPH GADGET-3 code…
The distribution of chemical elements in the hot intracluster medium (ICM) retains valuable information about the enrichment and star formation histories of galaxy clusters, and on the feedback and dynamical processes driving the evolution of the cosmic baryons. In the present study we review the progresses made so far in the modelling of the ICM chemical enrichment in a cosmological context, focusing in particular on cosmological hydrodynamical simulations. We will review the key aspects of embedding chemical evolution models into hydrodynamical simulations, with special attention to the cruc…
We study the evolution of the stellar component and the metallicity of both the intracluster medium and of stars in massive ($M_{\rm vir}\approx 6\times 10^{14}$ M$_{\odot}/h$) simulated galaxy clusters from the Rhapsody-G suite in detail and compare them to observational results. The simulations were performed with the AMR code RAMSES and include the effect of AGN feedback at the sub-grid level. AGN feedback is required to produce realistic galaxy and cluster properties and plays a role in mixing material in the central regions and regulating star formation in the central galaxy. In both our …
We present a new semi-analytic model of the formation of the first stars. Our method takes dark matter halo merger trees (including 3-dimensional spatial information) from cosmological N-body simulations as input and applies analytic prescriptions to compute both the Population III (Pop III) and metal-enriched star formation histories. We have developed a novel method to accurately compute the major feedback processes affecting Pop III star formation: H$_2$ photodissociation from Lyman-Werner (LW) radiation, suppression of star formation due to inhomogeneous reionization, and metal enrichment …
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…
The star formation and metal enrichment histories of galaxies - at any epoch - constitute one of the key properties of galaxies, and their measurement is a core aim of observational extragalactic astronomy. The lack of deep rest-frame optical coverage at high-redshift has made robust constraints elusive, but this is now changing thanks to the \emph{James Webb Space Telescope (JWST)}. In preparation for the constraints provided by \emph{JWST} we explore the star formation and metal enrichment histories of galaxies at $z=5-13$ using the First Light And Reionisation Epoch Simulations (FLARES) sui…
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…
Gas flows play a fundamental role in galaxy formation and evolution, providing the fuel for the star formation process. These mechanisms leave an imprint in the amount of heavy elements. Thus, the analysis of this metallicity signature provides additional constraint on the galaxy formation scenario. We aim to discriminate between four different galaxy formation models based on two accretion scenarios and two different star formation recipes. We address the impact of a bimodal accretion scenario and a strongly regulated star formation recipe. We present a new extension of the eGalICS model, whi…
The first stars, known as Population III (PopIII), produced the first heavy elements, thereby enriching their surrounding pristine gas. Previous detections of metals in intergalactic gas clouds, however, find a heavy element enrichment larger than $1/1000$ times that of the solar environment, higher than expected for PopIII remnants. In this letter we report the discovery of a Lyman limit system (LLS) at $z=3.53$ with the lowest metallicity seen in gas with discernable metals, $10^{-3.41\pm0.26}$ times the solar value, at a level expected for PopIII remnants. We make the first relative abundan…
The most metal-poor, high redshift damped Lyman-alpha systems (DLAs) provide a window to study some of the first few generations of stars. In this paper, we present a novel model to investigate the chemical enrichment of the near-pristine DLA population. This model accounts for the mass distribution of the enriching stellar population, the typical explosion energy of their supernovae, and the average number of stars that contribute to the enrichment of these DLAs. We conduct a maximum likelihood analysis of these model parameters using the observed relative element abundances ([C/O], [Si/O], a…
We investigate the colour-magnitude relation of metal-poor globular clusters, the 'blue tilt', in the Hydra and Centaurus galaxy clusters and constrain the primordial conditions for star cluster self-enrichment. We analyse U,I photometry for about 2500 globular clusters in the central regions of Hydra and Centaurus, based on FORS1@VLT data. We convert the measured colour-magnitude relations into mass-metallicity space and obtain a scaling of Z \propto M^{0.27 \pm 0.05} for Centaurus GCs and Z \propto M^{0.40 \pm 0.06} for Hydra GCs, consistent with results in other environments. We find that t…
We incorporate new scale-intelligent models of metal-enriched star formation (\starss) with surrogate models of primordial stellar feedback (\starnet) into the astrophysics simulation code \enzo to analyze the impact of heterogeneous metal enrichment on the first galaxies. Our study includes the earliest generations of stars and the protogalaxies ($10^6 \lesssim M_v/M_\odot \lesssim 10^8$) containing them. We compare results obtained with the new methods to two common paradigms of metallicity initial conditions in simulations: ignoring the metallicity initial condition and assuming a uniform m…
In-Situ Star Formation in a Thick Disk: A Model for Metal Enrichment of Mrk 573
JILA, University of Colorado and National Institute of Standards and Technology（科罗拉多大学JILA研究所与美国国家标准与技术研究院）；Columbia Astrophysics Laboratory, Columbia University（哥伦比亚大学哥伦比亚天体物理实验室）；Department of Physics and Astronomy, Michigan State University（密歇根州立大学物理与天文系）；Center for Computational Astrophysics, Flatiron Institute（平顿研究所计算天体物理学中心）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森尼天体物理中心）；Astronomical Observatory of the Jagiellonian University（雅盖隆大学天文台）
We focus on exploring the metal enrichment of the intergalactic medium (IGM) in Cold and Warm (1.5 and 3 keV) Dark Matter (DM) cosmologies, and the constraints this yields on the DM particle mass, using a semi-analytic model, Delphi, that jointly tracks the Dark Matter and baryonic assembly of galaxies at $z \simeq 4-20$ including both Supernova and (a range of) reionization feedback (models). We find that while ${\rm M_{UV}} \geq -15$ galaxies contribute half of all IGM metals in the Cold Dark Matter model by $z \simeq 4.5$, given the suppression of low-mass halos, larger halos with ${\rm M_{…
We present the first measurements of the abundances of $α$-elements (Mg, Si, and S) extending out to beyond the virial radius of a cluster of galaxies. Our results, based on Suzaku Key Project observations of the Virgo Cluster, show that the chemical composition of the intra-cluster medium is consistent with being constant on large scales, with a flat distribution of the Si/Fe, S/Fe, and Mg/Fe ratios as a function of radius and azimuth out to 1.4 Mpc (1.3 $r_{200}$). Chemical enrichment of the intergalactic medium due solely to core collapse supernovae (SNcc) is excluded with very high signifi…
We use numerical N-body hydrodynamical simulations with varying PopIII stellar models to investigate the possibility of detecting first star signatures with observations of high-redshift damped Ly$α$ absorbers (DLAs). The simulations include atomic and molecular cooling, star formation, energy feedback and metal spreading due to the evolution of stars with a range of masses and metallicities. Different initial mass functions (IMFs) and corresponding metal-dependent yields and lifetimes are adopted to model primordial stellar populations. The DLAs in the simulations are selected according to ei…
Centre for Space Research, North-West University（西北大学空间研究中心）；National Centre for Radio Astrophysics (NCRA), Tata Institute of Fundamental Research (TIFR)（塔塔基础研究院国家射电天文学中心）；National Institute for Theoretical and Computational Sciences (NITheCS)（理论与计算科学国立研究所）；Dayanand Science College（戴亚南德理学院）
The combination of gas-phase oxygen abundances and stellar metallicities can provide us with unique insights into the metal enrichment histories of galaxies. In this work, we compare the stellar and gas-phase metallicities measured within a 1$R_{e}$ aperture for a representative sample of 472 star-forming galaxies extracted from the SAMI Galaxy Survey. We confirm that the stellar and interstellar medium (ISM) metallicities are strongly correlated, with scatter $\sim$3 times smaller than that found in previous works, and that integrated stellar populations are generally more metal-poor than the…
One-zone models constructed to match observed stellar abundance patterns have been used extensively to constrain the sites of nucleosynthesis with sophisticated libraries of stellar evolution and stellar yields. The metal mixing included in these models is usually highly simplified, although it is likely to be a significant driver of abundance evolution. In this work we use high-resolution hydrodynamics simulations to investigate how metals from individual enrichment events with varying source energies $E_{\rm ej}$ mix throughout the multi-phase interstellar medium (ISM) of a low-mass ($M_{\rm…
The presence of elements heavier than helium ("metals") is of fundamental importance for a large number of astrophysical processes occurring in planet, star and galaxy formation; it also affects cosmic structure formation and evolution in several ways. Even a small amount of heavy elements can dramatically alter the chemistry of the gas, opening the path to complex molecules. Metals might enhance the ability of the gas to radiate away its thermal energy, thus favoring the formation of gravitationally bound objects; they can also condensate in a solid phase (dust grains), partly or totally bloc…
The heaviest iron-peak element, Zn has been used as an important tracer of cosmic chemical evolution. Spectroscopic observations of the metal-poor stars in Local Group galaxies show that an increasing trend of [Zn/Fe] ratios toward lower metallicity. However, enrichment of Zn in galaxies is not well understood due to the poor knowledge of astrophysical sites of Zn as well as metal mixing in galaxies. Here we show possible explanations for the observed trend by taking into account electron-capture supernovae (ECSNe) as one of the sources of Zn in our chemodynamical simulations of dwarf galaxies…
We investigate the role of supernova (SN)-driven galactic winds in the chemical enrichment of the intracluster medium (ICM). Such outflows on galactic scales have their origin in huge star forming regions and expel metal enriched material out of the galaxies into their surroundings as observed, for example, in the nearby starburst galaxy NGC 253. As massive stars in OB-associations explode sequentially, shock waves are driven into the interstellar medium (ISM) of a galaxy and merge, forming a superbubble (SB). These SBs expand in a direction perpendicular to the disk plane following the densit…
Metal-Poor Stars as Metal-Rich Impostors via Planet Engulfment
Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；University of Chinese Academy of Sciences（中国科学院大学）；International Centre of Supernovae, Yunnan Key Laboratory of Supernova Research, Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台超新星研究中心（国际超新星中心、云南省超新星研究重点实验室））；School of Physics and Astronomy, Sun Yat-sen University（中山大学物理学院）
Deep observations have detected extended Ly$α$ emission nebulae surrounding tens of quasars at redshift 2 to 6. However, the metallicity of such extended haloes is still poorly understood. We perform a detailed analysis on a large sample of 80 quasars at $z\sim3$ based on MUSE-VLT data. We find clear evidence of extended emission of the UV nebular lines such as CIV or HeII for about 20$\%$ of the sample, while CIII] is only marginally detected in a few objects. By stacking the cubes we detect emission of CIV, HeII and CIII] out to a radius of about 45 kpc. CIV and HeII show a radial decline mu…
Detailed observations of globular clusters (GCs) have revealed evidence of self-enrichment: some of the heavy elements that we see in stars today were produced by cluster stars themselves. Moreover, GCs have internal subpopulations with different elemental abundances, including, in some cases, in elements such as iron that are produced by supernovae. This paper presents a theoretical model for GC formation motivated by observations of Milky Way star forming regions and simulations of star formation, where giant molecular clouds fragment into multiple clumps which undergo star formation at slig…
We measure the red giant branch bump (RGBB) of the Galactic bulge, the most metal-rich RGBB ever detected. The RGBB luminosity functions peaks at the expected brightness, but its number density is very low relative to Galactic globular cluster calibrations, implying the Galactic bulge has a higher helium enrichment parameter ΔY/ΔZ $\ge$ 4.0 for Y~0.35 rather than the standard 2.0 with Y=0.27. The RGBB is (0.71 +/- 0.02) mag fainter than the red clump (RC) in I toward the densest stellar regions imaged by the OGLE-III Galactic bulge photometric survey, (|l| $\le$ 4, 2 <~ |b| $\le$ 4). The numbe…
The chemical composition of gas in galaxies can be measured in detail from absorption spectroscopy. By studying gas in galaxies in this way, it is possible to investigate the small and faint galaxies, which are the most numerous in the universe. In particular, the chemical distribution of gas in absorbing systems gives us insight into cycles of gas in and around galaxies. Here we study chemical enrichment within 64 Damped Lyman-alpha Absorption (DLA) systems between $1.7 < z < 4.2$. We use high-resolution spectra from VLT/UVES to infer dust depletion from relative abundances of several metals.…
We present the Atacama Large Millimeter/submillimeter Array (ALMA) detection of the [O III] 88 $μ$m line and rest-frame 90 $μ$m dust continuum emission in a Y-dropout Lyman break galaxy (LBG), MACS0416_Y1, lying behind the Frontier Field cluster MACS J0416.1-2403. This [O III] detection confirms the LBG with a spectroscopic redshift of $z = 8.3118 \pm 0.0003$, making this object one of the furthest galaxies ever identified spectroscopically. The observed 850 $μ$m flux density of $137 \pm 26$ $μ$Jy corresponds to a de-lensed total infrared (IR) luminosity of $L_{\rm IR} = (1.7 \pm 0.3) \times 1…
