- ID:
- ivo://CDS.VizieR/J/AJ/127/840
- Title:
- VRI photometry of Fornax red giants
- Short Name:
- J/AJ/127/840
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared spectra were obtained for 117 red giants in the Fornax dwarf spheroidal galaxy with the FORS1 spectrograph on the VLT, in order to study the metallicity distribution of the stars and to lift the age-metallicity degeneracy of the red giant branch (RGB) in the color-magnitude diagram (CMD). Metallicities are derived from the equivalent widths of the infrared calcium triplet lines at 8498, 8542, and 8662{AA} calibrated with data from globular clusters, the open cluster M67, and the LMC. For a substantial portion of the sample, the strength of the calcium triplet is unexpectedly high, clearly indicating that the main stellar population of Fornax is significantly more metal-rich than could be inferred from the position of its RGB in the CMD.
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- ID:
- ivo://CDS.VizieR/J/A+A/568/L8
- Title:
- VUDS extreme emission line 0.2<~z<~0.9 galaxies
- Short Name:
- J/A+A/568/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 31 low-luminosity (-14.5>~M_AB_(B)>~-18.8), extreme emission line galaxies (EELGs) at 0.2<~z<~0.9 identified by their unusually high rest-frame equivalent widths (100<=EW[OIII]<=1700{AA}) as part of the VIMOS Ultra Deep Survey (VUDS). VIMOS optical spectra of unprecedented sensitivity (I_AB_~25mag) along with multiwavelength photometry and HST imaging are used to investigate spectrophotometric properties of this unique sample and to explore, for the first time, the very low stellar mass end (M_*_<~10^8^M_{sun}_) of the luminosity-metallicity (LZR) and mass-metallicity (MZR) relations at z<1. Characterized by their extreme compactness (R_50_<1kpc), low stellar mass and enhanced specific star formation rates (sSFR=SFR/M_*_~10^-9^-10^-7^yr^-1^), the VUDS EELGs are blue dwarf galaxies likely experiencing the first stages of a vigorous galaxy-wide starburst. Using Te-sensitive direct and strong-line methods, we find that VUDS EELGs are low-metallicity (7.5<~12+log(O/H)<~8.3) galaxies with high ionization conditions (log(q_ion_)>~8cm/s), including at least three EELGs showing HeII{lambda}4686{AA} emission and four extremely metal-poor (<~10% solar) galaxies. The LZR and MZR followed by VUDS EELGs show relatively large scatter, being broadly consistent with the extrapolation toward low luminosity and mass from previous studies at similar redshift. However, we find evidence that galaxies with younger and more vigorous star formation --as characterized by their larger EWs, ionization and sSFR-- tend to be more metal poor at a given stellar mass.
- ID:
- ivo://CDS.VizieR/J/AJ/153/179
- Title:
- VVV Survey RR Lyr stars in Southern Galactic plane
- Short Name:
- J/AJ/153/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep near-IR images from the VISTA Variables in the Via Lactea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295{deg}<l<350{deg}, -2.24{deg}<b<-1.05{deg}). The sample's distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyrae population does not extend beyond l~340{deg}, and the sample's spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A42
- Title:
- weak G-band stars abundances
- Short Name:
- J/A+A/587/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Weak G-band (wGb) stars are a very peculiar class of red giants; they are almost devoided of carbon and often present mild lithium enrichment. Despite their very puzzling abundance patterns, very few detailed spectroscopic studies existed up to a few years ago, which prevented any clear understanding of the wGb phenomenon. We recently proposed the first consistent analysis of published data for a sample of 28 wGb stars and were able to identify them as descendants of early A-type to late B-type stars, although we were not able to conclude on their evolutionary status or the origin of their peculiar abundance pattern. Using new high-resolution spectra, we present the study of a new sample of wGb stars with the aim of homogeneously deriving their fundamental parameters and surface abundances for a selected set of chemical species that we use to improve our insight on this peculiar class of objects. We obtained high-resolution and high signal-to-noise spectra for 19 wGb stars in the southern and northern hemisphere that we used to perform consistent spectral synthesis to derive their fundamental parameters and metallicities, as well as the spectroscopic abundances for Li, C, ^12^C/^13^C, N, O, Na, Sr, and Ba. We also computed dedicated stellar evolution models that we used to determine the masses and to investigate the evolutionary status and chemical history of the stars in our sample. We confirm that the wGb stars are stars with initial masses in the range 3.2 to 4.2M_{sun}_. We suggest that a large fraction could be mildly evolved stars on the subgiant branch currently undergoing the first dredge-up, while a smaller number of stars are more probably in the core He burning phase at the clump. After analysing their abundance pattern, we confirm their strong nitrogen enrichment anti-correlated with large carbon depletion, characteristic of material fully processed through the CNO cycle to an extent not known in evolved intermediate-mass stars in the field and in open clusters. However, we demonstrate here that such a pattern is very unlikely owing to self-enrichment. In the light of the current observational constraints, no solid self-consistent pollution scenario can be presented either, leaving the wGb puzzle largely unsolved.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A145
- Title:
- What is the Milky Way outer halo made of?
- Short Name:
- J/A+A/608/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a framework where galaxies form hierarchically, extended stellar haloes are predicted to be an ubiquitous feature around Milky Way-like galaxies and to consist mainly of the shredded stellar component of smaller galactic systems. The type of accreted stellar systems are expected to vary according to the specific accretion and merging history of a given galaxy, and so is the fraction of stars formed in-situ versus accreted. Analysis of the chemical properties of Milky Way halo stars out to large Galactocentric radii can provide important insights into the properties of the environment in which the stars that contributed to the build-up of different regions of the Milky Way stellar halo formed. In this work we focus on the outer regions of the Milky Way stellar halo, by determining chemical abundances of halo stars with large present-day Galactocentric distances, >15 kpc. The data-set we acquired consists of high resolution HET/HRS, Magellan/MIKE and VLT/UVES spectra for 28 red giant branch stars covering a wide metallicity range, -3.1<[Fe/H]<-0.6. We show that the ratio of alpha-elements over Fe as a function of [Fe/H] for our sample of outer halo stars is not dissimilar from the pattern shown by MW halo stars from solar neighborhood samples. On the other hand, significant differences appear at [Fe/H]>-1.5 when considering chemical abundance ratios such as [Ba/Fe], [Na/Fe], [Ni/Fe], [Eu/Fe], [Ba/Y]. Qualitatively, this type of chemical abundance trends are observed in massive dwarf galaxies, such as Sagittarius and the Large Magellanic Cloud. This appears to suggest a larger contribution in the outer halo of stars formed in an environment with high initial star formation rate and already polluted by asymptotic giant branch stars with respect to inner halo samples.
- ID:
- ivo://CDS.VizieR/J/AJ/149/121
- Title:
- WOCS. LXV. Abundances in NGC 6819
- Short Name:
- J/AJ/149/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-dispersion spectra of 333 stars in the open cluster NGC 6819, obtained using the HYDRA spectrograph on the WIYN 3.5m telescope, have been analyzed to determine the abundances of iron and other metals from lines in the 400{AA} region surrounding the Li6708{AA} line. Our spectra, with signal-to-noise per pixel ranging from 60 to 300, span the luminosity range from the tip of the red giant branch to a point two magnitudes below the top of the cluster turnoff. We derive radial and rotational velocities for all stars, as well as [Fe/H] based on 17 iron lines, [Ca/H], [Si/H], and [Ni/H] in the 247 most probable, single members of the cluster. Input T_eff_ estimates for model atmosphere analysis are provided by (B-V) colors merged from several sources, with individual reddening corrections applied to each star relative to a cluster mean of E(B-V)=0.16. Extensive use is made of ROBOSPECT, an automatic equivalent width measurement program; its effectiveness on large spectroscopic samples is discussed. From the sample of likely single members, [Fe/H]=-0.03+/-0.06, where the error describes the median absolute deviation about the sample median value, leading to internal precision for the cluster below 0.01dex. The final uncertainty in the cluster abundance is therefore dominated by external systematics due to the temperature scale, surface gravity, and microturbulent velocity, leading to [Fe/H]=-0.02+/-0.02 for a sub-sample restricted to main sequence and turnoff stars. This result is consistent with our recent intermediate-band photometric determination of a slightly subsolar abundance for this cluster. [Ca/Fe], [Si/Fe], and [Ni/Fe] are determined to be solar within the uncertainties. NGC 6819 has an abundance distribution typical of solar metallicity thin disk stars in the solar neighborhood.
- ID:
- ivo://CDS.VizieR/J/AJ/159/220
- Title:
- WOCS LXXIX. M48. I. WIYN/Hydra spectra for M48 stars
- Short Name:
- J/AJ/159/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WIYN/Hydra spectra (R~13500, signal-to-noise=50-1000/pixel) of a 400{AA} region around Li 6708{AA} are used to determine radial and rotational velocities for 287 photometrically selected candidate members of the open cluster M48. The sample ranges from turnoff A stars to late-K dwarfs and eight giants. We combine our radial velocity (V_RAD_) measurements and power spectrum analysis with parallax and proper motion data from Gaia DR2 to evaluate membership and multiplicity. We classify 152 stars as single cluster members, 11 as binary members, 16 as members of uncertain multiplicity, 56 as single nonmembers, 28 as single "likely" nonmembers, two as single "likely" members, one as a binary "likely" member, five as binary nonmembers, 10 as "likely" members of uncertain multiplicity, three as nonmembers of uncertain multiplicity, and three as "likely" nonmembers of uncertain multiplicity. From a subsample of 95 single members, we derive V_RAD_=8.512{+/-}0.087km/s ({sigma}_{mu}_, and {sigma}=0.848km/s). Using 16 isolated Fe I lines for a subsample of 99 single members (that have {sigma}_Teff_<75K (from 10 colors from UBVRI), vsini<25km/s, and well-behaved Fe I lines), [Fe/H]M48=-0.063{+/-}0.007dex ({sigma}_{mu}_). [Fe/H] is independent of Teff over an unprecedentedly large range of 2500K. The minimum cluster binary fraction is 11%-21%. M48 exhibits a clear but modest broadening of the main-sequence turnoff, and there is no correlation between color and vsini.
- ID:
- ivo://CDS.VizieR/J/AJ/153/128
- Title:
- WOCS. LXXV. Hyades&Praesepe stellar lithium data
- Short Name:
- J/AJ/153/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WIYN/Hydra spectroscopy (at R~15000) of the moderately metal-rich Praesepe and Hyades open clusters was used to study their main-sequence (MS) iron ([Fe/H]) and lithium (A(Li)) abundances. Self-consistent [Fe/H] and Li analyses of these clusters of consistent age, which we re-evaluate, confirms that they have consistent [Fe/H] and provides a foundation to investigate the poorly understood G-dwarf and F-dwarf Li-depletions. Neither phenomenon agrees with standard stellar evolution theory, but possible explanations abound. We supplement our A(Li) with previously published results placed on a uniform abundance scale. This creates the largest self-consistently analyzed sample of A(Li) in both the Hyades (90) and Praesepe (110). For each star, high-precision UBVRI photometry was used to determine a 10-color-based T_eff_ and then to test for photometric peculiarities indicated by a large {sigma}_Teff_ (>75 K). The stars that have large {sigma}_Teff_ were predominantly found to be binaries or stars with peculiar (apparent) A(Li). When considering only proper-motion members that have low {sigma}_Teff_ and are also photometrically consistent with the cluster MS fiducial, each cluster has a more tightly defined Li morphology than previously observed and the two clusters' A(Li) are indistinguishable. This suggests that clusters of consistent age and metallicity may have consistent Li-depletion trends across a broad range of T_eff_; no additional major parameters are required, at least for these two clusters. We propose that the combined Hyades and Praesepe data offer more rigorous constraints than does either cluster alone, and we discuss newly revealed features of the combined Li-T_eff_ trend.
- ID:
- ivo://CDS.VizieR/J/AJ/155/138
- Title:
- WOCS.LXXVI.Velocity & abundances in NGC2506
- Short Name:
- J/AJ/155/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HYDRA spectra of 287 stars in the field of NGC 2506 from the turnoff through the giant branch are analyzed. With previous data, 22 are identified as probable binaries; 90 more are classified as potential non-members. Spectroscopic analyses of ~60 red giants and slowly rotating turnoff stars using line equivalent widths and a neural network approach lead to [Fe/H]=-0.27+/-0.07 (s.d.) and [Fe/H]=-0.27+/-0.06 (s.d.), respectively. Li abundances are derived for 145 probable single-star members, 44 being upper limits. Among turnoff stars outside the Li-dip, A(Li)=3.04+/-0.16 (s.d.), with no trend with color, luminosity, or rotation speed. Evolving from the turnoff across the subgiant branch, there is a well-delineated decline to A(Li)~1.25 at the giant branch base, coupled with the rotational spindown from between ~20 and 70 km/s to less than 20 km/s for stars entering the subgiant branch and beyond. A(Li) remains effectively constant from the giant branch base to the red giant clump level. A new member above the clump redefines the path of the first-ascent red giant branch; its Li is 0.6 dex below the first-ascent red giants. With one exception, all post-He-flash stars have upper limits to A(Li), at or below the level of the brightest first-ascent red giant. The patterns are in excellent qualitative agreement with the model predictions for low/intermediate-mass stars which undergo rotation-induced mixing at the turnoff and subgiant branch, first dredge-up, and thermohaline mixing beyond the red giant bump.
1430. xCOLD GASS catalog
- ID:
- ivo://CDS.VizieR/J/ApJS/233/22
- Title:
- xCOLD GASS catalog
- Short Name:
- J/ApJS/233/22
- Date:
- 02 Nov 2021 07:14:32
- Publisher:
- CDS
- Description:
- We introduce xCOLD GASS, a legacy survey providing a census of molecular gas in the local universe. Building on the original COLD GASS survey, we present here the full sample of 532 galaxies with CO (1-0) measurements from the IRAM 30m telescope. The sample is mass-selected in the redshift interval 0.01<z<0.05 from the Sloan Digital Sky Survey (SDSS) and therefore representative of the local galaxy population with M_*_>10^9^M_{sun}_. The CO (1-0) flux measurements are complemented by observations of the CO (2-1) line with both the IRAM 30 m and APEX telescopes, HI observations from Arecibo, and photometry from SDSS, WISE, and GALEX. Combining the IRAM and APEX data, we find that the ratio of CO (2-1) to CO (1-0) luminosity for integrated measurements is r_21_=0.79+/- 0.03, with no systematic variations across the sample. The CO (1-0) luminosity function is constructed and best fit with a Schechter function with parameters L_CO_^* ^=(7.77+/-2.11)x10^9^K.(km/s).pc^2^, {phi}^*^=(9.84+/-5.41)x10^-4^Mpc^-3^, and {alpha}=-1.19+/-0.05. With the sample now complete down to stellar masses of 10^9^M_{sun}_, we are able to extend our study of gas scaling relations and confirm that both molecular gas fractions (f_H2_) and depletion timescale (t_dep_(H2)) vary with specific star formation rate (or offset from the star formation main sequence) much more strongly than they depend on stellar mass. Comparing the xCOLD GASS results with outputs from hydrodynamic and semianalytic models, we highlight the constraining power of cold gas scaling relations on models of galaxy formation.