We present a first study based on the analysis of the DEep Spectra of Ionized REgions Database (DESIRED). This is a compilation of 190 high signal-to-noise ratio optical spectra of HII regions and ...other photoionized nebulae, mostly observed with 8-10m telescopes and containing \(\sim\)29380 emission lines. We find that the electron density --\(n_{\rm e}\)-- of the objects is underestimated when SII \(\lambda6731/\lambda6716\) and/or OII \(\lambda3726/\lambda3729\) are the only density indicators available. This is produced by the non-linear density dependence of the indicators in the presence of density inhomogeneities. The average underestimate is \(\sim 300\) cm\(^{-3}\) in extragalactic HII regions, introducing systematic overestimates of \(T_{\rm e}\)(OII) and \(T_{\rm e}\)(SII) compared to \(T_{\rm e}\)(NII). The high-sensitivity of OII \(\lambda\lambda7319+20+30+31/\lambda\lambda3726+29\) and SII \(\lambda\lambda4069+76/\lambda\lambda6716+31\) to density makes them more suitable for the diagnosis of the presence of high-density clumps. If \(T_{\rm e}\)(NII) is adopted, the density underestimate has a small impact in the ionic abundances derived from optical spectra, being limited to up to \(\sim\)0.1 dex when auroral SII and/or OII lines are used. However, these density effects are critical for the analysis of infrared fine structure lines, such as those observed by the JWST in local star forming regions, implying strong underestimates of the ionic abundances. We present temperature relations between \(T_{\rm e}\)(OIII), \(T_{\rm e}\)(ArIII), \(T_{\rm e}\)(SIII) and \(T_{\rm e}\)(NII) for the extragalactic HII regions. We confirm a non-linear dependence between \(T_{\rm e}\)(OIII)-\(T_{\rm e}\)(NII) due to a more rapid increase of \(T_{\rm e}\)(OIII) at lower metallicities.
In this paper we discuss and confront recent results on metallicity variations in the local interstellar medium, obtained from observations of HII regions and neutral clouds of the Galactic thin ...disk, and compare them with recent high-quality metallicity determinations of other tracers of the chemical composition of the interstellar medium as B-type stars, classical Cepheids and young clusters. We find that the metallicity variations obtained for these last kinds of objects are consistent with each other and with that obtained for HII regions but significantly smaller than those obtained for neutral clouds. We also discuss the presence of a large population of low-metallicity clouds as the possible origin for large metallicity variations in the local Galactic thin disk. We find that such hypothesis does not seem compatible with: (a) what is predicted by theoretical studies of gas mixing in galactic disks, and (b) the models and observations on the metallicity of high-velocity clouds and its evolution as they mix with the surrounding medium in their fall onto the Galactic plane. We conclude that that most of the evidence favors that the chemical composition of the interstellar medium in the solar neighborhood is highly homogeneous.
For the first time, a calibration between the HeI \(\lambda5876\)/H\(\beta\) emission line ratio and the helium abundance \(y\)=12+log(He/H) for Narrow line regions (NLRs) of Seyfert~2 Active ...Galactic Nuclei (AGN) is proposed. In this context, observational data (taken from the SDSS-DR15 and from the literature) and direct abundance estimates (via the \(T_{\rm e}\)-method) for a sample of 65 local (\(z \: < \: 0.2\)) Seyfert~2 nuclei are considered. The resulting calibration estimates the \(y\) abundance with an average uncertainty of 0.02 dex. Applying our calibration to spectroscopic data containing only strong emission lines, it yields a helium abundance distribution similar to that obtained via the \(T_{\rm e}\)-method. Some cautions must be considered to apply our calibration for Seyfert~2 nuclei with high values of electron temperature (\(\gtrsim\: 20\,000\) K) or ionization parameter (\(\log U > -2.0\)).
We derive the nitrogen and oxygen abundances in the Narrow Line Regions (NLRs) of a sample of 38 local (\(z \: < \: 0.4\)) Seyfert~2 nuclei. For that, we consider narrow optical emission line ...intensities and direct estimates of the electron temperatures (\(T_{\rm e}\)-method). We find nitrogen abundances in the range \(7.6 \: < \: \rm 12+log(N/H) \: < \: 8.6\) (mean value \(8.06\pm0.22\)) or \(\rm 0.4 \: < \: (N/N_{\odot}) \: < 4.7\), in the metallicity regime \(8.3 \: < \: \rm 12+log(O/H) \: < \: 9.0\). Our results indicate that the dispersion in N/H abundance for a fixed O/H value in AGNs is in agreement with that for disc \ion{H}{ii} regions with similar metallicity. We show that Seyfert~2 nuclei follow a similar (N/O)-(O/H) relation to the one followed by star-forming objects. Finally, we find that active galaxies called as 'nitrogen-loud' observed at very high redshift (\(z \: > \: 5\)) show N/O values in consonance with those derived for local NLRs. This result indicates that the main star-formation event is completed in the early evolution stages of active galaxies.
We present a reassessment of the radial abundance gradients of He, C, N, O, Ne, S, Cl, and Ar in the Milky Way using the deep optical spectra of 42 HII regions presented in Arellano-Córdova et al. ...(2020, 2021) and Méndez-Delgado et al. (2020) exploring the impact of: (1) new distance determinations based on Gaia EDR3 parallaxes and (2) the use of Peimbert's temperature fluctuations paradigm (\(t ^ 2> 0\)) for deriving ionic abundances. We find that distances based on Gaia EDR3 data are more consistent with kinematic ones based on Galactic rotation curves calibrated with radio parallaxes, which give less dispersion and uncertainties than those calibrated with spectrophotometric stellar distances. The distances based on the Gaia parallaxes --DR2 or EDR3-- eliminate the internal flattening observed in previous determinations of the Galactic gradients at smaller distances than \(\sim 7\) kpc. Abundances and gradients determined assuming \( t ^ 2> 0 \) -- not only for O but also for the rest of elements -- are not affected by the abundance discrepancy problem and give elemental abundances much consistent with the solar ones for most elements. We find that our radial abundance gradient of He is consistent with the most accurate estimates of the primordial He abundance. We do not find evidence of azimuthal variations in the chemical abundances of our sample. Moreover, the small dispersion in the O gradient -- indicator of metallicity in photoionized regions -- indicate that the gas of the HII regions is well mixed in the sampled areas of the Galaxy.
We present determinations of the gas-phase and stellar metallicities of a sample of 65 star-forming galaxies at \(z \simeq 3.5\) using rest-frame far-ultraviolet (FUV) spectroscopy from the VANDELS ...survey in combination with follow-up rest-frame optical spectroscopy from VLT/KMOS and Keck/MOSFIRE. We infer gas-phase oxygen abundances (\(Z_{\mathrm{g}}\); tracing O/H) via strong optical nebular lines and stellar iron abundances (\(Z_{\star}\); tracing Fe/H) from full spectral fitting to the FUV continuum. Our sample spans the stellar mass range \(8.5 < \mathrm{log}(M_{\star}/\mathrm{M}_{\odot}) < 10.5\) and shows clear evidence for both a stellar and gas-phase mass-metallicity relation (MZR). We find that our O and Fe abundance estimates both exhibit a similar mass-dependence, such that \(\mathrm{Fe/H}\propto M_{\star}^{0.30\pm0.11}\) and \(\mathrm{O/H}\propto M_{\star}^{0.32\pm0.09}\). At fixed \(M_{\star}\) we find that, relative to their solar values, O abundances are systematically larger than Fe abundances (i.e., \(\alpha\)-enhancement).We estimate an average enhancement of \(\mathrm{(O/Fe)} = 2.65 \pm 0.16 \times \mathrm{(O/Fe)_\odot}\) which appears to be independent of \(M_{\star}\). We employ analytic chemical evolution models to place a constraint on the strength of galactic-level outflows via the mass-outflow factor (\(\eta\)). We show that outflow efficiencies that scale as \(\eta \propto M_{\star}^{-0.32}\) can simultaneously explain the functional form of of the stellar and gas-phase MZR, as well as the degree of \(\alpha\)-enhancement at fixed Fe/H. Our results add further evidence to support a picture in which \(\alpha\)-enhanced abundance ratios are ubiquitous in high-redshift star-forming galaxies, as expected for young systems whose interstellar medium is primarily enriched by core-collapse supernovae.
We report ultra-deep, medium-resolution spectroscopic observations for 4 quiescent galaxies with log\(_{10}(M_*/\mathrm{M_\odot})>11\) at \(3 < z < 5\). These data were obtained with JWST NIRSpec as ...part of the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey, which we introduce in this work. The first pair of galaxies are newly selected from PRIMER UDS imaging, both at \(z=4.62\) and separated by \(860\) pkpc on the sky, within a larger structure for which we confirm several other members. These galaxies formed at \(z\simeq8-10\), and, despite their similar stellar masses, ages, and their proximity, they exhibit very different stellar metallicities, hinting at different formation pathways. These systems could plausibly merge by the present day to produce a local massive elliptical galaxy. The other 2 ultra-massive quiescent galaxies are previously known at \(z=3.99\) and \(3.19\), with the latter (ZF-UDS-7329) having been the subject of debate as potentially too old and too massive to be accommodated by the \(\Lambda\)-CDM halo-mass function. Both exhibit high stellar metallicities, and for ZF-UDS-7329 we are able to measure the \(\alpha-\)enhancement, obtaining Mg/Fe = \(0.42^{+0.19}_{-0.17}\). We finally evaluate whether these 4 galaxies are consistent with the \(\Lambda\)-CDM halo-mass function using an extreme value statistics approach. We find that the \(z=4.62\) objects and the \(z=3.19\) object are unlikely within our area under the assumption of standard stellar fractions (\(f_*\simeq0.1-0.2\)). However, these objects roughly align with the most massive galaxies expected under the assumption of 100 per cent conversion of baryons to stars (\(f_*\)=1). Our results suggest extreme galaxy formation physics during the first billion years, but no conflict with \(\Lambda\)-CDM cosmology.
Binary systems constitute a valuable astrophysics tool for testing our understanding of stellar structure and evolution. Systems containing a oscillating component are interesting as asteroseismology ...offers independent parameters for the oscillating component that aid the analysis. About 150 of such systems are known in the literature. To enlarge the sample of these benchmark objects, we crossmatch the Two-Body-Orbit Catalogue (TBO) of Gaia DR3, with catalogs of confirmed solar-like oscillators on the main-sequence and red-giant phase from NASA Kepler and TESS. We obtain 954 new binary system candidates hosting solar-like oscillators, of which 45 and 909 stars are on the main sequence and red-giant, resp., including 2 new red giants in eclipsing systems. 918 oscillators in potentially long-periodic systems are reported. We increase the sample size of known solar-like oscillators in binary systems by an order of magnitude. We present the seismic properties of the full sample and conclude that the grand majority of the orbital elements in the TBO is physically reasonable. 82% of all TBO binary candidates with multiple times with APOGEE are confirmed from radial-velocity measurement. However, we suggest that due to instrumental noise of the TESS satellite the seismically inferred masses and radii of stars with $\nu_\textrm{max}$$\lesssim\(30\)\mu$Hz could be significantly overestimated. For 146 giants the seismically inferred evolutionary state has been determined and shows clear differences in their distribution in the orbital parameters, which are accounted the accumulative effect of the equilibrium tide acting in these evolved binary systems. For other 146 systems hosting oscillating stars values for the orbital inclination were found in the TBO. From testing the TBO on the SB9 catalogue, we obtain a completeness factor of 1/3.
We present preliminary results of the O, Ne, S and Cl abundance gradients of the Milky Way. We analyze in a homogenous way the physical conditions and chemical abundances of a sample of 35 H II ...regions with deep spectra observed mainly with the GTC and VLT telescopes. The sample covers a range in Galactocentric distances from 5 to 17 kpc. We reanalyze the O abundance gradient, obtaining a similar complex shape than previously reported in the literature. We calculate the Cl abundance gradient including a significantly larger number of objects than in previous works. Our results show a gradient for Cl/H of -0.034 dex kpc^-1 and a dispersion around the gradient of 0.14 dex. We obtain values for the Ne/H and S/H abundance gradients with slopes of -0.038 dex kpc^-1 and -0.046 dex kpc^-1, respectively, with dispersions around the gradient higher than 0.25 dex. We also report the values for the slopes of the Cl/O, Ne/O and S/O abundance ratio gradients, which show dispersions around the gradient up to 0.4 dex. Such high dispersion although may be interpreted as indications of chemical inhomogeneities in the Galactic ISM, it might be also an artifact produced by the selected ionization correction factor.
We analyze the physical conditions, chemical composition and other properties of the photoionized Herbig-Haro object HH~204 through Very Large Telescope (VLT) echelle spectroscopy and Hubble Space ...Telescope (\textit{HST}) imaging. We kinematically isolate the high-velocity emission of HH~204 from the emission of the background nebula and study the sub-arcsecond distribution of physical conditions and ionic abundances across the HH object. We find that low and intermediate-ionization emission arises exclusively from gas at photoionization equilibrium temperatures, whereas the weak high-ionization emission from HH~204 shows a significant contribution from higher temperature shock-excited gas. We derive separately the ionic abundances of HH~204, the emission of the Orion Nebula and the fainter Diffuse Blue Layer.In HH~204, the O\(^{+}\) abundance determined from Collisional Excited Lines (CELs) matches the one based on Recombination Lines (RLs), while the O\(^{2+}\) abundance is very low, so that the oxygen abundance discrepancy is zero. The ionic abundances of Ni and Fe in HH~204 have similar ionization and depletion patterns, with total abundances that are a factor of 3.5 higher than in the rest of the Orion Nebula due to dust destruction in the bowshock. We show that a failure to resolve the kinematic components in our spectra would lead to significant error in the determination of chemical abundances (for instance, 40\% underestimate of O), mainly due to incorrect estimation of the electron density.
