CLEAR: The Gas-Phase Metallicity Gradients of Star-Forming Galaxies at 0.6 < z < 2.6
Raymond C. Simons, Casey Papovich, Ivelina Momcheva, Jonathan R. Trump, Gabriel Brammer, Vicente Estrada-Carpenter, Bren E. Backhaus, Nikko J. Cleri, Steven L. … 展开作者
Raymond C. Simons, Casey Papovich, Ivelina Momcheva, Jonathan R. Trump, Gabriel Brammer, Vicente Estrada-Carpenter, Bren E. Backhaus, Nikko J. Cleri, Steven L. Finkelstein, Mauro Giavalisco, Zhiyuan Ji, Intae Jung, Jasleen Matharu, Benjamin Weiner
备注：
19 pages, 10 figures (v2: typo fixed in Figure 10 label); submitted to ApJ
We report on the gas-phase metallicity gradients of a sample of 264 star-forming galaxies at 0.6 < z < 2.6, measured through deep near-infrared Hubble Space Telescope slitless spectroscopy. The observations include 12-orbit depth Hubble/WFC3 G102 grism spectra taken as a part of the CANDELS Lya Emission at Reionization (CLEAR) survey, and archival WFC3 G102+G141 grism spectra overlapping the CLEAR footprint. The majority of galaxies (84%) in this sample are consistent with a zero or slightly positive metallicity gradient across the full mass range probed (8.5 < log M_*/M_sun < 10.5). We measure the intrinsic population scatter of the metallicity gradients, and show that it increases with decreasing stellar mass---consistent with previous reports in the literature, but confirmed here with a much larger sample. To understand the physical mechanisms governing this scatter, we search for correlations between the observed gradient and various stellar population properties at fixed mass. However, we find no evidence for a correlation with the galaxy properties we consider---including star-formation rates, sizes, star-formation rate surface densities, and star-formation rates per gravitational potential energy. We use the observed weakness of these correlations to provide material constraints for predicted intrinsic correlations from theoretical models.
Spiral star-forming galaxies are complex astrophysical objects whose baryonic component is dominated by the disk, where most of the star formation resides. The metallicity in the disk is not uniform, and it usually decreases with the distance to the galaxy center, in the so-called radial metallicity gradient. Radial metallicity gradients have been successfully used to set important constraints on galaxy formation and their chemical evolution. This paper focuses on the implications of radial metallicity gradients measured with different probes for a variety of galaxies, and on the foreseen adva…
We derive new empirical calibrations for strong-line diagnostics of gas phase metallicity in local star forming galaxies by uniformly applying the Te method over the full metallicity range probed by the Sloan Digital Sky Survey (SDSS). To measure electron temperatures at high metallicity, where the auroral lines needed are not detected in single galaxies, we stacked spectra of more than 110,000 galaxies from the SDSS in bins of log[O II]/H$β$ and log[O III]/H$β$. This stacking scheme does not assume any dependence of metallicity on mass or star formation rate, but only that galaxies with the s…
The origin of nebular HeII emission, which is frequently observed in low-metallicity (O/H) star-forming galaxies, remains largely an unsolved question. Using the observed anticorrelation of the integrated X-ray luminosity per unit of star formation rate ($L_X/{\rm SFR}$) of an X-ray binary population with metallicity and other empirical data from the well-studied galaxy I Zw 18, we show that the observed HeII 4686 intensity and its trend with metallicity is naturally reproduced if the bulk of He$^+$ ionizing photons are emitted by the X-ray sources. We also show that a combination of X-ray bin…
We present metallicity gradients in 49 local field star-forming galaxies. We derive gas-phase oxygen abundances using two widely adopted metallicity calibrations based on the [OIII]/Hbeta, [NII]/Halpha and [NII]/[OII] line ratios. The two derived metallicity gradients are usually in good agreement within +/-0.14 dex/R25 (R25 is the B-band iso-photoal radius), but the metallicity gradients can differ significantly when the ionisation parameters change systematically with radius. We investigate the metallicity gradients as a function of stellar mass (8<log(M*/Msun)<11) and absolute B-band lumino…
We study the relations between gas-phase metallicity ($Z$), local stellar mass surface density ($Σ_*$), and the local star formation surface density ($Σ_{\rm SFR}$) in a sample of 1120 star-forming galaxies from the MaNGA survey. At fixed $Σ_{*}$ the local metallicity increases as decreasing of $Σ_{\rm SFR}$ or vice versa for metallicity calibrators of N2 and O3N2. Alternatively, at fixed $Σ_{\rm SFR}$ metallicity increases as increasing of $Σ_{*}$, but at high mass region, the trend is flatter. However, the dependence of metallicity on $Σ_{\rm SFR}$ is nearly disappeared for N2O2 and N2S2 cal…
Gas inflow feeds galaxies with low metallicity gas from the cosmic web, sustaining star formation across the Hubble time. We make a connection between these inflows and metallicity inhomogeneities in star-forming galaxies, by using synthetic narrow-band images of the Halpha emission line from zoom-in AMR cosmological simulations of galaxies with stellar masses of $M \simeq 10^9 $Msun at redshifts z=2-7. In $\sim$50\% of the cases at redshifts lower than 4, the gas inflow gives rise to star-forming, Halpha-bright, off-centre clumps. Most of these clumps have gas metallicities, weighted by Halph…
Star-forming galaxies display a close relation among stellar mass, metallicity and star-formation rate (or molecular-gas mass). This is known as the fundamental metallicity relation (FMR) (or molecular-gas FMR), and it has a profound implication on models of galaxy evolution. However, there still remains a significant residual scatter around the FMR. We show here that a fourth parameter, the surface density of stellar mass, reduces the dispersion around the molecular-gas FMR. In a principal component analysis of 29 physical parameters of 41,338 star-forming galaxies, the surface density of ste…
We use the newest generation of the Starburst99/Mappings code to generate an extensive suite of models to facilitate detailed studies of star-forming galaxies and their ISM properties, particularly at low metallicities. The new models used include a rigorous treatment of metal opacities in the population synthesis modeling and more detailed dust physics in the photoionization code. These models span a wide range of physical parameters including metallicity, ionization parameter, and the adoption of both a instantaneous burst and continuous star formation history. We examine the agreement betwe…
We derive data of 4615 star-forming early-type galaxies (ETGs), which come from cross-match of the $Galaxy~Zoo~1$ and the catalogue of the MPA-JHU emission-line measurements for the Sloan Digital Sky Survey Data Release 7. Our sample distributes mainly at $\rm -0.7<log(SFR[M_{\sun}yr^{-1}])<1.2$, and the median value of our SFRs is slightly higher than that shown in Davis \& Young. We display a significant trend of lower/higher stellar mass ETGs to have lower/higher SFR, and obtain our sample best fit of log(SFR)=$ (0.74\pm0.01)$log$(M_{*}/M_{\sun})-(7.64\pm0.10)$, finding the same slope as th…
We present a sample of low-redshift (z<0.133) candidates for extremely low-metallicity star-forming galaxies with oxygen abundances 12+logO/H<7.4 selected from the Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS). Three methods are used to derive their oxygen abundances. Among these methods two are based on strong [OII]3727, [OIII]4959, and [OIII]5007 emission lines, which we call strong-line and semi-empirical methods. These were applied for all galaxies. We have developed one of these methods, the strong-line method, in this paper. This method is specifically focused on the accu…
We study the direct gas-phase oxygen abundance using the well-detected auroral [OIII]4363 line in the stacked spectra of a sample of local analogs of high-redshift galaxies. These local analogs share the same location as $z\sim2$ star-forming galaxies on the Baldwin-Phillips-Terlevich diagram. This type of analog has the same ionized interstellar medium (ISM) properties as high-redshift galaxies. We establish empirical metallicity calibrations between the direct gas-phase oxygen abundances ($7.8<12+\log(\rm{O/H})<8.4$) and the N2/O3N2 indices in our local analogs. We find significant systemati…
Recent observations of galaxies in a cluster at z=0.35 show that their integrated gas-phase metallicities increase with decreasing cluster-centric distance. To test if ram pressure stripping (RPS) is the underlying cause, we use a semi-analytic model to quantify the "observational bias" that RPS introduces into the aperture-based metallicity measurements. We take integral field spectroscopy of local galaxies, remove gas from their outer galactic disks via RPS, and then conduct mock slit observations of cluster galaxies at z=0.35. Our RPS model predicts a typical cluster-scale metallicity gradi…
A large sample of MgII emitting star-forming galaxies with low metallicity [O/H] = log(O/H)-log(O/H)sun between -0.2 and -1.2 dex is constructed from Data Release 14 of the Sloan Digital Sky Survey. We selected 4189 galaxies with MgII 2797, 2803 emission lines in the redshift range z~0.3-1.0 or 35% of the total Sloan Digital Sky Survey star-forming sample with redshift z>0.3. We study the dependence of the magnesium-to-oxygen and magnesium-to-neon abundance ratios on metallicity. Extrapolating this dependence to [Mg/Ne]=0 and to solar metallicity we derive a magnesium depletion of [Mg/Ne]~-0.4…
Using idealised N-body simulations of a Milky Way-sized disc galaxy, we qualitatively study how the metallicity distributions of the thin disc star particles are modified by the formation of the bar and spiral arm structures. The thin disc in our numerical experiments initially has a tight negative radial metallicity gradient and a constant vertical scale-height. We show that the radial mixing of stars drives a positive vertical metallicity gradient in the thin disc. On the other hand, if the initial thin disc is flared, with vertical scale-height increasing with galactocentric radius, the met…
We present near-infrared spectroscopy of the host galaxy of dark GRB 080325 using Subaru/MOIRCS. The obtained spectrum provides a clear detection of H$α$ emission and marginal [NII]$λ$6584. The host is a massive (M$_{*}\sim10^{11}$M$_{\odot}$), dusty ($A_{V}\sim 1.2$) star-forming galaxy at z=1.78. The star formation rate calculated from the H$α$ luminosity (35.6-47.0 M$_{\odot}$ yr$^{-1}$) is typical among GRB host galaxies (and star-forming galaxies generally) at z $>$1; however, the specific star formation rate is lower than normal star-forming galaxies at redshift $\sim$ 1.6, in contrast t…
The MASSIV (Mass Assembly Survey with SINFONI in VVDS) project aims at finding constraints on the different processes involved in galaxy evolution. This study proposes to improve the understanding of the galaxy mass assembly through chemical evolution using the metallicity as a tracer of the star formation and interaction history. Methods. We analyse the full sample of MASSIV galaxies for which a metallicity estimate has been possible, that is 48 star-forming galaxies at $z\sim 0.9-1.8$, and compute the integrated values of some fundamental parameters, such as the stellar mass, the metallicity…
The exploration of the spatial distribution of chemical abundances in star-forming regions in galactic discs provides clues to understand the complex interplay of physical processes that regulate the star formation activity and the chemical enrichment across a galaxy. We study the azimuthal variations of the normalized oxygen abundance profiles in the highest numerical resolution run of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) Project at $z=0$. We use young stellar populations to trace the abundances of star-forming regions. Oxygen profiles are estimated along diff…
We present observations of CO(3-2) in 13 main-sequence $z=2.0-2.5$ star-forming galaxies at $\log(M_*/M_{\odot})=10.2-10.6$ that span a wide range in metallicity (O/H) based on rest-optical spectroscopy. We find that CO(3-2)/SFR decreases with decreasing metallicity, implying that the CO luminosity per unit gas mass is lower in low-metallicity galaxies at $z\sim2$. We constrain the CO-to-H$_2$ conversion factor ($α_{\text{CO}}$) and find that $α_{\text{CO}}$ inversely correlates with metallicity at $z\sim2$. We derive molecular gas masses ($M_{\text{mol}}$) and characterize the relations among…
The stellar mass-metallicity relation ($M_* - Z$, MZR) indicates that the metallicities of galaxies increase with increasing stellar masses. The fundamental metallicity relation (FMR) suggests that the galaxies with higher star formation rates (SFRs) tend to have lower metallicities for a given stellar mass. To examine whether the MZR and FMR still hold at poorer metallicities and higher redshifts, we compile a sample of 35 star-forming galaxies (SFGs) at $0.6<z<0.9$ using the public spectral database ($\rm v5\_10\_0$) of emission-line galaxies from the extended Baryon Oscillation Spectroscopi…
While all models for the evolution of galaxies require the accretion of gas to sustain their growth via on-going star formation, it has proven difficult to directly detect this inflowing material. In this paper we use data of nearby star-forming galaxies in the SDSS IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to search for evidence of accretion imprinted in the chemical composition of the interstellar medium. We measure both the O/H and N/O abundance ratios in regions previously identified as having anomalously low values of O/H. We show that the unusual locations of …
Using a representative sample of 14 star-forming dwarf galaxies in the local Universe, we show the existence of a spaxel-to-spaxel anti-correlation between the index N2 (log([NII]6583/Halpha)) and the Halpha flux. These two quantities are commonly employed as proxies for gas-phase metallicity and star formation rate (SFR), respectively. Thus, the observed N2 to Halpha relation may reflect the existence of an anti-correlation between the metallicity of the gas forming stars and the SFR it induces. Such an anti-correlation is to be expected if variable external metal-poor gas fuels the star-form…
We present an analysis of the chemical abundance properties of $\approx$650 star-forming galaxies at $z \approx0.6-1.8$. Using integral-field observations from the $K$-band Multi-Object Spectrograph (KMOS), we quantify the [NII]/H$α$ emission-line ratio, a proxy for the gas-phase Oxygen abundance within the interstellar medium. We define the stellar mass-metallicity relation at $z \approx0.6-1.0$ and $z \approx1.2-1.8$ and analyse the correlation between the scatter in the relation and fundamental galaxy properties (e.g. H$α$ star-formation rate, H$α$ specific star-formation rate, rotation dom…
We present updated metallicity relations for the spectral database of star-forming galaxies (SFGs) found in the KPNO International Spectroscopic Survey (KISS). New spectral observations of emission-line galaxies (ELGs) obtained from a variety of telescope facilities provide oxygen abundance information. A nearly four-fold increase in the number of KISS objects with robust metallicities relative to our previous analysis provides for an empirical abundance calibration to compute self-consistent metallicity estimates for all SFGs in the sample with adequate spectral data. In addition, a sophistic…
We use data from 1222 late-type star-forming galaxies in the SDSS IV MaNGA survey to identify regions in which the gas-phase metallicity is anomalously-low compared to expectations from the tight empirical relation between metallicity and stellar surface mass-density at a given stellar mass. We find anomalously low metallicity (ALM) gas in 10% of the star-forming spaxels, and in 25% of the galaxies in the sample. The incidence rate of ALM gas increases strongly with both global and local measures of the specific star-formation rate, and is higher in lower mass galaxies and in the outer regions…
Metallicity is one of the crucial factors that determine stellar evolution. To characterize the properties of stellar populations one needs to know the fraction of stars forming at different metallicities. Knowing how this fraction evolves over time is necessary e.g. to estimate the rates of occurrence of any stellar evolution related phenomena (e.g. double compact object mergers, gamma ray bursts). Such theoretical estimates can be confronted with observational limits to validate the assumptions about the evolution of the progenitor system leading to a certain transient. However, to perform t…
We study the relationship between stellar mass, star formation rate (SFR),ionization state, and gas-phase metallicity for a sample of 41 normal star-forming galaxies at $3 \lesssim z \lesssim 3.7$. The gas-phase oxygen abundance, ionization parameter, and electron density of ionized gas are derived from rest-frame optical strong emission lines measured on near-infrared spectra obtained with Keck/MOSFIRE. We remove the effect of these strong emission lines in the broad-band fluxes to compute stellar masses via spectral energy distribution fitting, while the SFR is derived from the dust-correcte…
The outer Galaxy is an environment with metallicity lower than the Solar one and, because of this, the formation and survival of molecules in star-forming regions located in the inner and outer Galaxy is expected to be different. To gain understanding on how chemistry changes throughout the Milky Way, it is crucial to observe outer Galaxy star-forming regions to constrain models adapted for lower metallicity environments. The project "chemical complexity in star-forming regions of the outer Galaxy" (CHEMOUT) aims to address this problem observing a sample of 35 high-mass star-forming cores at …
We present a comprehensive study of the relations between gas kinematics, metallicity, and stellar mass in a sample of 82 GRB-selected galaxies using absorption and emission methods. We find the velocity widths of both emission and absorption profiles to be a proxy of stellar mass. We also investigate the velocity-metallicity correlation and its evolution with redshift and find the correlation derived from emission lines to have a significantly smaller scatter compared to that found using absorption lines. Using 33 GRB hosts with measured stellar mass and metallicitiy, we study the mass-metall…
For the same stellar mass, physically smaller star-forming galaxies are also metal richer (Ellison et al. 2008). What causes the relation remains unclear. The central star-forming galaxies in the EAGLE cosmological numerical simulation reproduce the observed trend. We use them to explore the origin of the relation assuming that the physical mechanism responsible for the anti-correlation between size and gas-phase metallicity is the same in the simulated and the observed galaxies. We consider the three most likely causes: (1) metal-poor gas inflows feeding the star-formation process, (2) metal-…
We present integral field spectroscopy observations of two star-forming dwarf galaxies in the Virgo cluster (VCC135 and VCC324) obtained with PMAS/PPak at the Calar Alto 3.5 meter telescope. We derive metallicity maps using the N2 empirical calibrator. The galaxies show positive gas metallicity gradients, contrarily to what is usually found in other dwarfs or in spiral galaxies. We measure gradient slopes of 0.20 $\pm$ 0.06 and 0.15 $\pm$ 0.03 dex/$R_e$ for VCC135 and VCC324, respectively. Such a trend has been only observed in few, very isolated galaxies, or at higher redshifts ($z >$ 1). It …
We present a study of the consequences of an initial mass function that is stochastically sampled on the main emission lines used for gas-phase metallicity estimates in extra-galactic sources. We use the stochastic stellar population code SLUG and the photoionisation code Cloudy to show that the stochastic sampling of the massive end of the mass function can lead to clear variations in the relative production of energetic emission lines such as [OIII] relative to that of Balmer lines. We use this to study the impact on the Te, N2O2, R23 and O3N2 metallicity calibrators. We find that stochastic…
We report the first spatially resolved measurements of gas-phase metallicity radial gradients in star-forming galaxies in overdense environments at $z\gtrsim2$. The spectroscopic data are acquired by the \mg\ survey, a Hubble Space Telescope (HST) cycle-28 medium program. This program is obtaining 45 orbits of WFC3/IR grism spectroscopy in the density peak regions of three massive galaxy protoclusters (BOSS 1244, BOSS 1542 and BOSS 1441) at $z=2-3$. Our sample in the BOSS 1244 field consists of 20 galaxies with stellar-mass ranging from $10^{9.0}$ to $10^{10.3}$ \Msun\ , star formation rate (S…
We have observed a sample of 14 nearby ($z \sim 0.03$) star-forming blue compact galaxies in the rest-frame far-UV ($\sim1150-2200 Å$) using the Cosmic Origins Spectrograph on the Hubble Space Telescope. We have also generated a grid of stellar population synthesis models using the Starburst99 evolutionary synthesis code, allowing us to compare observations and theoretical predictions for the SiIV_1400 and CIV_1550 UV indices; both are comprised of a blend of stellar wind and interstellar lines and have been proposed as metallicity diagnostics in the UV. Our models and observations both demons…
We present a comparative study of the relation between the aperture-based gas-phase metallicity and three structural parameters of star-forming galaxies: mass ($\mathrm{M \equiv M_*}$), average potential ($Φ\equiv \mathrm{M_*/R_e}$) and average surface mass density ($Σ\equiv \mathrm{M_*/R_e^2}$; where $\mathrm{R_e}$ is the effective radius). We use a volume-limited sample drawn from the publicly available SDSS DR7, and base our analysis on aperture-matched sampling by selecting sets of galaxies where the SDSS fibre probes a fixed fraction of $\mathrm{R_e}$. We find that between 0.5 and 1.5 $\m…
An analytical chemical evolution model is constructed to investigate the radial distribution of gas-phase and stellar metallicity for star-forming galaxies. By means of the model, the gas-phase and stellar metallicity can be obtained from the stellar-to-gas mass ratio. Both the gas inflow and outflow processes play an important role in building the final gas-phase metallicity, and there exists degeneracy effect between the gas inflow and outflow rates for star-forming galaxies. On the other hand, stellar metallicity is more sensitive to the gas outflow rate than to the gas inflow rate, and thi…
The fundamental metallicity relation (FMR) of galaxies is a 3D relation between the gas-phase metallicity, stellar mass and star-formation rate (SFR). It has been studied so far only for galaxies identified as star-forming (SF) on the BPT diagrams (BPT-SF), but not for galaxies with LI(N)ER/AGN classification (BPT-non-SF), mainly due to the lack of diagnostics for estimating their gas-phase metallicities in the latter cases. We extend the FMR to BPT-non-SF galaxies. To this end, we exploit the recent nebular line empirical calibrations derived specifically for galaxies classified as non-SF in …
The predictions of the multiple burst accretion model of chemical evolution are compared to the observations of the stellar masses and metallicities of star-forming galaxies. With the addition of one parameter, the model can account for the observations of the star-forming galaxies if the observations of the galaxies are identified with the star bursting behaviour of the model. This consistency with the model holds only if galaxy downsizing is assumed to occur.
We investigate the variation in the mid-infrared spectral energy distributions of 373 low-redshift ($z<0.4$) star-forming galaxies, which reflects a variety of polycyclic aromatic hydrocarbon (PAH) emission features. The relative strength of PAH emission is parameterized as $q_\mathrm{PAH}$, which is defined as the mass fraction of PAH particles in the total dust mass. With the aid of continuous mid-infrared photometric data points covering 7-24$μ$m and far-infrared flux densities, $q_\mathrm{PAH}$ values are derived through spectral energy distribution fitting. The correlation between $q_\mat…
We discuss spatially resolved emission line spectroscopy secured for a total sample of 15 gravitationally lensed star-forming galaxies at a mean redshift of $z\simeq2$ based on Keck laser-assisted adaptive optics observations undertaken with the recently-improved OSIRIS integral field unit (IFU) spectrograph. By exploiting gravitationally lensed sources drawn primarily from the CASSOWARY survey, we sample these sub-L$^{\ast}$ galaxies with source-plane resolutions of a few hundred parsecs ensuring well-sampled 2-D velocity data and resolved variations in the gas-phase metallicity. Such high sp…
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…
We analyse the evolution of the oxygen abundance gradient of star-forming galaxies with stellar mass Mstar > 10^9 Mo in the EAGK simulation over the redshift range z=[0, 2.5]. We find that the median metallicity gradient of the simulated galaxies is close to zero at all z, whereas the scatter around the median increases with z. The metallicity gradients of individual galaxies can evolve from strong to weak and vice-versa, since mostly low-metallicity gas accretes onto the galaxy, resulting in enhanced star formation and ejection of metal enriched gas by energy feedback. Such episodes of enhanc…
We present hitherto the largest sample of gas-phase metallicity radial gradients measured at sub-kiloparsec resolution in star-forming galaxies in the redshift range of $z\in[1.2, 2.3]$. These measurements are enabled by the synergy of slitless spectroscopy from the Hubble Space Telescope near-infrared channels and the lensing magnification from foreground galaxy clusters. Our sample consists of 76 galaxies with stellar mass ranging from 10$^7$ to 10$^{10}$ $M_\odot$, instantaneous star-formation rate in the range of [1, 100] $M_\odot$/yr, and global metallicity [$\frac{1}{12}$, 2] solar. At 2…
In this work, we investigate how the central stellar metallicity ([Z/H]) of 1363 galaxies from the SAMI galaxy survey is related to their stellar mass and a proxy for the gravitational potential, $Φ$ = log10(M/M*) - log10($r_e$/kpc). In agreement with previous studies, we find that passive and star-forming galaxies occupy different areas of the [Z/H]-M* plane, with passive galaxies having higher [Z/H] than star-forming galaxies at fixed mass (a difference of 0.23 dex at log10(M/M*)=10.3). We show for the first time that all galaxies lie on the same relation between [Z/H] and $Φ$, and show that…
Utilizing low-luminosity star-forming systems discovered in the H$α$ Dots survey, we present spectroscopic observations undertaken using the KPNO 4m telescope for twenty-six sources. With determinations of robust, "direct"-method metal abundances, we examine the properties of these dwarf systems, exploring their utility in characterizing starburst galaxies at low luminosities and stellar masses. We find that the H$α$ Dots survey provides an effective new avenue for identifying star-forming galaxies in these regimes. In addition, we examine abundance characteristics and metallicity scaling rela…
Context. The xGASS and xCOLD GASS surveys have measured the atomic (HI) and molecular gas (H2) content of a large and representative sample of nearby galaxies (redshift range of 0.01 $\lt$ z $\lt$ 0.05). Aims. We present optical longslit spectra for a subset of the xGASS and xCOLD GASS galaxies to investigate the correlation between radial metallicity profiles and cold gas content. In addition to data from Moran et al. (2012), this paper presents new optical spectra for 27 galaxies in the stellar mass range of 9.0 $\leq$ log Mstar/Msun $\leq$ 10.0. Methods. The longslit spectra were taken alon…
We present radial gas-phase metallicity profiles, gradients, and break radii at redshift $z = 0 - 3$ from the TNG50-1 star-forming galaxy population. These metallicity profiles are characterized by an emphasis on identifying the steep inner gradient and flat outer gradient. From this, the break radius, $r_{\rm Break}$, is defined as the region where the transition occurs. We observe the break radius having a positive trend with mass that weakens with redshift. When normalized by the stellar half-mass radius, the break radius has a weaker relation with both mass and redshift. To test if our res…
We measured gas-phase metallicity, ionisation parameter and dust extinction for 1795 representative local star-forming galaxies using integral field spectroscopy from the SDSS-IV MaNGA survey. We self-consistently derive these quantities by comparing observed line fluxes with photoionisation models using a Bayesian framework. We also present the first comprehensive study of the [SIII]$λλ$9069,9532 nebular lines, which have long been predicted to be ideal tracers of the ionisation parameter. Unfortunately, we find that current photoionisation models substantially over-predict [SIII] lines inten…
Aligned and misaligned metallicity gradients in young stars and star-forming regions in the EAGLE discs
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；Instituto de Astrofísica, Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学天体物理研究所）；Centro de Astro-Ingeniería, Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学天文工程学院）
The Star Formation Factory revisited I. The impact of metallicity on collapsing star-forming clouds
Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Faculty of Mathematics and Physics, Charles University（查理大学数学物理学院）；Instituto Nacional de Astrofísica Óptica y Electrónica（国家天体物理学、光学和电子研究所）
The nature of the sources powering nebular HeII emission in star-forming galaxies remains debated, and various types of objects have been considered, including Wolf-Rayet stars, X-ray binaries, and Population III stars. Modern X-ray observations show the ubiquitous presence of hot gas filling star-forming galaxies. We use a collisional ionization plasma code to compute the specific HeII ionizing flux produced by hot gas and show that if its temperature is not too high (less than 2.5 MK), then the observed levels of soft diffuse X-ray radiation could explain HeII ionization in galaxies. To gain…
Analytical models of chemical evolution, including inflow and outflow of gas, are important tools to study how the metal content in galaxies evolves as a function of time. In this work, we present new analytical solutions for the evolution of the gas mass, total mass and metallicity of a galactic system, when a decaying exponential infall rate of gas and galactic winds are assumed. We apply our model to characterize a sample of local star-forming and passive galaxies from the Sloan Digital Sky Survey data, with the aim of reproducing their observed mass-metallicity relation; in this way, we ca…
We explore the evolution of the Stellar Mass-Star Formation Rate-Metallicity Relation using a set of 256 COSMOS and GOODS galaxies in the redshift range 1.90 < z < 2.35. We present the galaxies' rest-frame optical emission-line fluxes derived from IR-grism spectroscopy with the Hubble Space Telescope and combine these data with star formation rates and stellar masses obtained from deep, multi-wavelength (rest-frame UV to IR) photometry. We then compare these measurements to those for a local sample of galaxies carefully matched in stellar mass (7.5 < log(M*/Msol) < 10.5) and star formation rat…
DIISC-VII: Linking Radial Gas Motions to Anomalously Low Metallicity Star-forming Regions in the XUV Disk of NGC 3344
Arizona State University（亚利桑那州立大学）；Università di Firenze（佛罗伦萨大学）；INAF - Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Inter-University Centre for Astronomy and Astrophysics（大学间天文与天体物理中心）；University of California, San Diego（加州大学圣地亚哥分校）；Eureka Scientific Inc.（尤里卡科学公司）；National Radio Astronomy Observatory（美国国家射电天文台）
