- ID:
- ivo://CDS.VizieR/J/A+A/611/A76
- Title:
- DLAS dust-corrected metallicity
- Short Name:
- J/A+A/611/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interpreting abundances of damped Ly-{alpha} absorbers (DLAs) from absorption-line spectroscopy has typically been a challenge because of the presence of dust. Nevertheless, because DLAs trace distant gas-rich galaxies regardless of their luminosity, they provide an attractive way of measuring the evolution of the metallicity of the neutral gas with cosmic time. This has been done extensively so far, but typically not taking proper dust corrections into account. The aims of this paper are to: (i) provide a simplified way of calculating dust corrections, based on a single observed [X/Fe], (ii) assess the importance of dust corrections for DLA metallicities and their evolution, and (iii) investigate the cosmic evolution of iron for a large DLA sample. We have derived dust corrections based on the observed [Zn/Fe], [Si/Fe], or [S/Fe], and confirmed their robustness. We present dust-corrected metallicities in a scale of [Fe/H]tot for 236 DLAs over a broad range of z, and assess the extent of dust corrections for different metals at different metallicities. Dust corrections in DLAs are important even for Zn (typically of 0.1-0.2, and up to 0.5dex), which is often neglected. Finally, we study the evolution of the dust-corrected metallicity with z. The DLA metallicities decrease with redshift, by a factor of 50-100 from today to ~12.6 billion years ago (z=5). When including dust corrections, the average DLA metallicities are 0.4-0.5dex higher than without corrections. The upper envelope of the relation between metallicity and z reaches solar metallicity at z<~0.5, although some systems can have solar metallicity already out to z~3.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/482
- Title:
- DLA system from SDSS DR5
- Short Name:
- J/MNRAS/435/482
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the chemical abundance measurements of the first large, medium-resolution, uniformly selected damped Lyman {alpha} system (DLA) survey. The sample contains 99 DLAs towards 89 quasars selected from the SDSS DR5 DLA sample in a uniform way. We analyse the metallicities and kinematic diagnostics, including the velocity width of 90 percent of the optical depth, {Delta}V_90_, and the equivalent widths of the SiII {lambda}1526 (W}{lambda}1526), CIV {lambda}1548 and MgII {lambda}2796 transitions. To avoid strong line-saturation effects on the metallicities measured in medium-resolution spectra (FWHM~71km/s), we derived metallicities from metal transitions which absorbed at most 35 percent of the quasar continuum flux. We find the evolution in cosmic mean metallicity of the sample, <Z>=(-0.04+/-0.13)z-(1.06+/-0.36), consistent with no evolution over the redshift range z~[2.2, 4.4], but note that the majority of our sample falls at z~[2.2, 3.5]. The apparent lack of metallicity evolution with redshift is also seen in a lack of evolution in the median {Delta}V_90_ and W{lambda}1526 values. While this result may seem to conflict with other large surveys that have detected significant metallicity evolution, such as Rafelski et al. who found <Z>=(-0.22+/-0.03)z-(0.65+/-0.09) over z~[0, 5], several tests show that these surveys are not inconsistent with our new result. However, over the smaller redshift range covered by our uniformly selected sample, the true evolution of the cosmic mean metallicity in DLAs may be somewhat flatter than the Rafelski et al. (2012ApJ...755...89R, Cat. J/ApJ/755/89) estimate.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A127
- Title:
- 13 dsph and ultra-faint galaxies analysis
- Short Name:
- J/A+A/641/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large homogeneous set of stellar parameters and abundances across a broad range of metallicities, involving 13 classical dwarf spheroidal (dSph) and ultra-faint dSph (UFD) galaxies. In total, this study includes 380 stars in Fornax, Sagittarius, Sculptor, Sextans, Carina, Ursa Minor, Draco, Reticulum II, Bootes I, Ursa Major II, Leo I, Segue I, and Triangulum II. This sample represents the largest, homogeneous, high-resolution study of dSph galaxies to date. With our homogeneously derived catalog, we are able to search for similar and deviating trends across different galaxies. We investigate the mass dependence of the individual systems on the production of alpha-elements, but also try to shed light on the long-standing puzzle of the dominant production site of r-process elements. We used data from the Keck observatory archive and the ESO reduced archive to reanalyze stars from these 13 classical dSph and UFD galaxies. We automatized the step of obtaining stellar parameters, but ran a full spectrum synthesis (1D, local thermal equilibrium) to derive all abundances except for iron to which we applied nonlocal thermodynamic equilibrium corrections where possible. The homogenized set of abundances yielded the unique possibility of deriving a relation between the onset of type Ia supernovae and the stellar mass of the galaxy. Furthermore, we derived a formula to estimate the evolution of alpha-elements. This reveals a universal relation of these systems across a large range in mass. Finally, we show that between stellar masses of 2.1x10^7^M_{sun}_ and 2.9x10^5^M_{sun}_ , there is no dependence of the production of heavy r-process elements on the stellar mass of the galaxy. Placing all abundances consistently on the same scale is crucial to answering questions about the chemical history of galaxies. By homogeneously analyzing Ba and Eu in the 13 systems, we have traced the onset of the s-process and found it to increase with metallicity as a function of the galaxy's stellar mass. Moreover, the r-process material correlates with the alpha-elements indicating some coproduction of these, which in turn would point toward rare core-collapse supernovae rather than binary neutron star mergers as a host for the r-process at low [Fe/H] in the investigated dSph systems.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A71
- Title:
- dSph RGB abundance and velocities
- Short Name:
- J/A+A/606/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From ESO VLT/FLAMES/GIRAFFE spectra, abundance measurements of Zn have been made in ~100 individual red giant branch (RGB) stars in the Sculptor dwarf spheroidal galaxy. This is the largest sample of individual Zn abundance measurements within a stellar system beyond the Milky Way. In the observed metallicity range, -2.7<=[Fe/H]<=-0.9, the general trend of Zn abundances in Sculptor is similar to that of {alpha}-elements. That is, super-solar abundance ratios of [Zn/Fe] at low metallicities, which decrease with increasing [Fe/H], eventually reaching subsolar values. However, at the higher metallicities in Sculptor, [Fe/H]>~-1.8, we find a significant scatter, -0.8<~[Zn/Fe]<~+0.4, which is not seen in any {alpha}-element. Our results are consistent with previous observations of a limited number of stars in Sculptor and in other dwarf galaxies. These results suggest that zinc has a complex nucleosynthetic origin, behaving neither completely like an {alpha}- nor an iron-peak element.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A5
- Title:
- DustPedia metallicities and HI masses
- Short Name:
- J/A+A/623/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of evolution in the dust-to-metal ratio allow to constrain the dominant dust processing mechanisms. In this work, we present a study of the dust-to-metal and dust-to-gas ratios in a subsample of ~500 DustPedia galaxies. Using literature and MUSE emission line fluxes, we derive gas-phase metallicities (oxygen abundances) for over 10000 individual regions and determine characteristic metallicities for each galaxy. We study how the relative dust, gas and metal contents of galaxies evolve by using metallicity and gas fraction as proxies for evolutionary state. The global oxygen abundance and nitrogen-to-oxygen ratio are found to increase monotonically as galaxies evolve. Additionally, unevolved galaxies (gas fraction >60%, metallicity 12+log(O/H)<8.2) have dust-to-metal ratios that are about a factor of 2.1 lower (factor of 6 lower for galaxies with gas fraction >80%) than the typical dust-to-metal ratio (Md/MZ~0.214) for more evolved sources. However, for high gas fractions, the scatter is larger due to larger observational uncertainties as well as a potential dependence of the dust grain growth timescale and supernova dust yield on local conditions and star formation histories. We find chemical evolution models with a strong contribution from dust grain growth describe these observations reasonably well. The dust-to-metal ratio is also found to be lower for low stellar masses and high specific star formation rates (with the exception of some sources undergoing a starburst). Finally, the metallicity gradient correlates weakly with the HI-to-stellar mass ratio, the effective radius and the dust-to-stellar mass ratio, but not with stellar mass.
- ID:
- ivo://CDS.VizieR/J/AJ/141/43
- Title:
- Dust properties in LMC molecular clouds
- Short Name:
- J/AJ/141/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The objective of this paper is to construct a catalog providing the dust properties and the star formation efficiency (SFE) of the molecular clouds in the Large Magellanic Cloud (LMC). We use the infrared (IR) data obtained with the Spitzer Space Telescope as part of the "Surveying the Agents of a Galaxy's Evolution" Legacy survey as well as the IRAS data. We also work with extinction (Av) maps of the LMC. A total of 272 molecular clouds have been detected in the LMC in a previous molecular survey, accounting for 230 giant molecular clouds (GMCs) and 42 smaller clouds. We perform correlations between the IR emission/extinction and atomic and molecular gas tracers.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/10
- Title:
- Dwarfs or giants? Stellar metallicities & distances
- Short Name:
- J/ApJ/886/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new fully data-driven algorithm that uses photometric data from the Canada-France Imaging Survey (CFIS; u), Pan-STARRS 1 (PS1; griz), and Gaia (G) to discriminate between dwarf and giant stars and to estimate their distances and metallicities. The algorithm is trained and tested using the Sloan Digital Sky Survey (SDSS)/SEGUE spectroscopic data set and Gaia photometric/astrometric data set. At [Fe/H]<-1.2, the algorithm succeeds in identifying more than 70% of the giants in the training/test set, with a dwarf contamination fraction below 30% (with respect to the SDSS/SEGUE data set). The photometric metallicity estimates have uncertainties better than 0.2dex when compared with the spectroscopic measurements. The distances estimated by the algorithm are valid out to a distance of at least ~80kpc without requiring any prior on the stellar distribution and have fully independent uncertainties that take into account both random and systematic errors. These advances allow us to estimate these stellar parameters for approximately 12 million stars in the photometric data set. This will enable studies involving the chemical mapping of the distant outer disk and the stellar halo, including their kinematics using the Gaia proper motions. This type of algorithm can be applied in the southern hemisphere to the first release of LSST data, thus providing an almost complete view of the external components of our Galaxy out to at least ~80kpc. Critical to the success of these efforts will be ensuring well-defined spectroscopic training sets that sample a broad range of stellar parameters with minimal biases. A catalog containing the training/test set and all relevant parameters within the public footprint of CFIS is available online.
488. DZ stars in SDSS DR4
- ID:
- ivo://CDS.VizieR/J/ApJ/663/1291
- Title:
- DZ stars in SDSS DR4
- Short Name:
- J/ApJ/663/1291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of a large spectroscopic and photometric sample of DZ white dwarfs based on our latest model atmosphere calculations. We revise the atmospheric parameters of the trigonometric parallax sample of Bergeron, Leggett, & Ruiz (2001, Cat. <J/ApJS/133/413>, 12 stars) and analyze 147 new DZ white dwarfs discovered in the SDSS. The inclusion of metals and hydrogen in our model atmosphere calculations leads to different atmospheric parameters than those derived from pure helium models.
- ID:
- ivo://CDS.VizieR/J/ApJS/235/5
- Title:
- EA-type eclipsing binaries observed by LAMOST
- Short Name:
- J/ApJS/235/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- About 3196 EA-type binaries (EAs) were observed by LAMOST by 2017 June 16 and their spectral types were derived. Meanwhile, the stellar atmospheric parameters of 2020 EAs were determined. In this paper, those EAs are cataloged and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EW-type binaries (EWs), indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs (0.4<P<1 days) are the same as those of EAs with the same periods, while their values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may have formed through a combination of these mechanisms.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A105
- Title:
- EELGs out to z~1 in zCOSMOS
- Short Name:
- J/A+A/578/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present line measurements and physical properties of a sample of 165 extreme emission-line galaxies (EELGs) in the zCOSMOS 20k-Bright Survey (Lilly et al., 2009, Cat. J/ApJS/184/218). The zCOSMOS spectra consist of ~1h integrations in the medium resolution LRRED grism setting (R~600 with 2.5{AA}/pixel), covering a wavelength range 5550<{lambda}<9650{AA}. Measured emission-line fluxes are given in units of 10^-17^erg/s/cm^2^. Flux errors have been derived following Perez-Montero et al. (2013A&A...549A..25P) and Amorin et al. (2012ApJ...749..185A and 2012ApJ...754L..22A). No extinction correction has been applied to these fluxes. For each galaxy the reddening constant, c(H{beta}), is presented. These values and their corresponding uncertainties have been derived from the H{alpha}/H{beta} or H{gamma}/H{beta} ratios, whenever possible. A reddening constant derived from the SED best-fitting was adopted for (a) those galaxies where the computation of c(H{beta}) from emission lines is not possible because of the lack of lines, or (b) the corresponding line ratio produces a negative extinction correction (i.e., Ha/Hb<2.82 or Hg/Hb<0.47, assuming Case B recombination with T_e_=2*10^4K, n_e_=100cm^-3^). Stellar mass and 1{sigma} uncertainties have been obtained from SED fitting (Bolzonella et al., 2010A&A...524A..76B) after removal of the flux contribution from strong emission lines.
