- ID:
- ivo://CDS.VizieR/J/ApJ/856/142
- Title:
- Abundances of metal-poor stars in Sculptor
- Short Name:
- J/ApJ/856/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of the chemical abundances of metal-poor stars in dwarf galaxies provides a venue to constrain paradigms of chemical enrichment and galaxy formation. Here we present metallicity and carbon abundance measurements of 100 stars in Sculptor from medium-resolution (R~2000) spectra taken with the Magellan/Michigan Fiber System mounted on the Magellan-Clay 6.5m telescope at Las Campanas Observatory. We identify 24 extremely metal-poor star candidates ([Fe/H]{<}-3.0) and 21 carbon-enhanced metal-poor (CEMP) star candidates. Eight carbon-enhanced stars are classified with at least 2{sigma} confidence, and five are confirmed as such with follow-up R~6000 observations using the Magellan Echellette Spectrograph on the Magellan-Baade 6.5m telescope. We measure a CEMP fraction of 36% for stars below [Fe/H]=-3.0, indicating that the prevalence of carbon-enhanced stars in Sculptor is similar to that of the halo (~43%) after excluding likely CEMP-s and CEMP-r/s stars from our sample. However, we do not detect that any CEMP stars are strongly enhanced in carbon ([C/Fe]>1.0). The existence of a large number of CEMP stars both in the halo and in Sculptor suggests that some halo CEMP stars may have originated from accreted early analogs of dwarf galaxies.
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- ID:
- ivo://CDS.VizieR/J/AJ/160/173
- Title:
- Abundances of metal-poor stars in the Inner Bulge
- Short Name:
- J/AJ/160/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The bulge is the oldest component of the Milky Way. Since numerous simulations of Milky Way formation have predicted that the oldest stars at a given metallicity are found on tightly bound orbits, the Galaxy's oldest stars are likely metal-poor stars in the inner bulge with small apocenters (i.e., Rapo <~4kpc). In the past, stars with these properties have been impossible to find due to extreme reddening and extinction along the line of sight to the inner bulge. We have used the mid-infrared metal-poor star selection of Schlaufman & Casey (2014) on Spitzer/Galactic Legacy Infrared Mid-Plane Survey Extraordinaire data to overcome these problems and target candidate inner bulge metal-poor giants for moderate-resolution spectroscopy with Anglo-Australian Telescope/AAOmega. We used those data to select three confirmed metal-poor giants ([Fe/H]=-3.15, -2.56, -2.03) for follow-up high-resolution Magellan/Magellan Inamori Kyocera Echelle spectroscopy. A comprehensive orbit analysis using Gaia DR2 astrometry and our measured radial velocities confirms that these stars are tightly bound inner bulge stars. We determine the elemental abundances of each star and find high titanium and iron-peak abundances relative to iron in our most metal-poor star. We propose that the distinct abundance signature we detect is a product of nucleosynthesis in the Chandrasekhar-mass thermonuclear supernova of a CO white dwarf accreting from a helium star with a delay time of about 10Myr. Even though chemical evolution is expected to occur quickly in the bulge, the intense star formation in the core of the nascent Milky Way was apparently able to produce at least one Chandrasekhar-mass thermonuclear supernova progenitor before chemical evolution advanced beyond [Fe/H]~-3.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A51
- Title:
- Abundances of 12 metal-rich barium stars
- Short Name:
- J/A+A/533/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determined the atmospheric parameters and abundance pattern for a sample of metal-rich barium stars. We used high resolution optical spectroscopy. Atmospheric parameters and abundances were determined using the local thermodynamic equilibrium atmosphere models of Kurucz and the spectral analysis code MOOG. We show that the stars have enhancement factors, [s/Fe], from 0.25 to 1.16. Their abundance pattern of Na, Al, {alpha}-elements and iron group elements as well as their kinematical properties are similar to the characteristics of the other metal rich and super metal-rich stars already analyzed. We conclude that metal rich barium stars do not belong to the bulge population. We also show that metal rich barium stars are useful targets to probe the s-process enrichment in high metallicity environments.
- ID:
- ivo://CDS.VizieR/J/A+A/512/A63
- Title:
- Abundances of M33 HII regions
- Short Name:
- J/A+A/512/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the spatial distribution of metals in M33 using a new sample and literature data of HII regions, constraining a model of galactic chemical evolution with HII region and planetary nebula (PN) abundances. We consider chemical abundances of a new sample of HII regions complemented with previous literature data-sets. Supported by a uniform sample of nebular spectroscopic observations, we conclude that: i) the metallicity distribution in M33 is very complex, showing a central depression in metallicity probably due to observational bias; ii) the metallicity gradient in the disk of M33 has a slope of -0.037+/-0.009dex/kpc in the whole radial range up to ~8kpc, and -0.044+/-0.009dex/kpc excluding the central kpc; iii) there is a small evolution of the slope with time from the epoch of PN progenitor formation to the present-time. Description: Emission line fluxes, observed and dereddened of 33 HII regions are presented. Physical and chemical properties, such as electron temperatures and density, ionic and total chemical abundances of He, O, N, Ne, Ar, S, are derived.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A147
- Title:
- Abundances of microlensed bulge dwarf stars. V.
- Short Name:
- J/A+A/549/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a detailed elemental abundance analysis of dwarf stars in the Galactic bulge, based on high-resolution spectra that were obtained while the stars were optically magnified during gravitational microlensing events. The analysis method is the same as for a large sample of F and G dwarf stars in the Solar neighbourhood, enabling a fully differential comparison between the Bulge and the local stellar populations in the Galactic disc.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A89
- Title:
- Abundances of microlensed Bulge dwarf stars. VI.
- Short Name:
- J/A+A/605/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a detailed elemental abundance analysis of dwarf stars in the Galactic bulge, based on high-resolution spectra that were obtained while the stars were optically magnified during gravitational microlensing events. The analysis method is the same as for a large sample of F and G dwarf stars in the Solar neighbourhood, enabling a fully differential comparison between the Bulge and the local stellar populations in the Galactic disc.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A134
- Title:
- Abundances of microlensed stars in the Bulge
- Short Name:
- J/A+A/533/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a detailed elemental abundance analysis of dwarf stars in the Galactic bulge, based on high-resolution spectra that were obtained while the stars were optically magnified during gravitational microlensing events. The analysis method is the same as for a large sample of F and G dwarf stars in the Solar neighbourhood, enabling a fully differential comparison between the Bulge and the local stellar populations in the Galactic disc.
- ID:
- ivo://CDS.VizieR/J/A+A/512/A41
- Title:
- Abundances of microlensed stars in the Bulge
- Short Name:
- J/A+A/512/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a detailed elemental abundance analysis of dwarf stars in the Galactic bulge, based on high-resolution spectra that were obtained while the stars were optically magnified during gravitational microlensing events. The analysis method is the same as for a large sample of F and G dwarf stars in the Solar neighbourhood, enabling a fully differential comparison between the Bulge and the local stellar populations in the Galactic disc.
- ID:
- ivo://CDS.VizieR/J/A+A/541/A15
- Title:
- Abundances of M22 subgiants
- Short Name:
- J/A+A/541/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an abundance analysis of 101 subgiant branch (SGB) stars in the globular cluster M22. Using low-resolution FLAMES/GIRAFFE spectra we have determined abundances of the neutron-capture strontium and barium and the light element carbon. With these data we explore relationships between the observed SGB photometric split in this cluster and two stellar groups characterized by different contents of iron, slow neutron-capture process (s-process) elements, and the {alpha} element calcium, which we previously discovered in M22's red-giant stars.
- ID:
- ivo://CDS.VizieR/J/AJ/147/131
- Title:
- Abundances of nearby late-type galaxies. I. Data
- Short Name:
- J/AJ/147/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the oxygen and nitrogen abundance distributions across the optical disks of 130 nearby late-type galaxies using around 3740 published spectra of HII regions. We use these data in order to provide homogeneous abundance determinations for all objects in the sample, including HII regions in which not all of the usual diagnostic lines were measured. Examining the relation between N and O abundances in these galaxies we find that the abundances in their centers and at their isophotal R_25_ disk radii follow the same relation. The variation in N/H at a given O/H is around 0.3dex. We suggest that the observed spread in N/H may be partly caused by the time delay between N and O enrichment and the different star formation histories in galaxies of different morphological types and dimensions. We study the correlations between the abundance properties (central O and N abundances, radial O and N gradients) of a galaxy and its morphological type and dimension.
