- ID:
- ivo://CDS.VizieR/J/AJ/148/67
- Title:
- Abundances of 156 bulge red giants
- Short Name:
- J/AJ/148/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities and chemical abundances of O, Na, Mg, Al, Si, Ca, Cr, Fe, Co, Ni, and Cu for a sample of 156 red giant branch stars in two Galactic bulge fields centered near (l,b)=(+5.25,-3.02) and (0,-12). The (+5.25,-3.02) field also includes observations of the bulge globular cluster NGC 6553. The results are based on high-resolution (R~20000), high signal-to-noise ration (S/N>~70) FLAMES-GIRAFFE spectra obtained through the European Southern Observatory archive. However, we only selected a subset of the original observations that included spectra with both high S/N and that did not show strong TiO absorption bands. This work extends previous analyses of this data set beyond Fe and the {alpha}-elements Mg, Si, Ca, and Ti. While we find reasonable agreement with past work, the data presented here indicate that the bulge may exhibit a different chemical composition than the local thick disk, especially at [Fe/H]>~-0.5. In particular, the bulge [{alpha}/Fe] ratios may remain enhanced to a slightly higher [Fe/H] than the thick disk, and the Fe-peak elements Co, Ni, and Cu appear enhanced compared to the disk. There is also some evidence that the [Na/Fe] (but not [Al/Fe]) trends between the bulge and local disk may be different at low and high metallicity. We also find that the velocity dispersion decreases as a function of increasing [Fe/H] for both fields, and do not detect any significant cold, high-velocity populations. A comparison with chemical enrichment models indicates that a significant fraction of hypernovae may be required to explain the bulge abundance trends, and that initial mass functions that are steep, top-heavy (and do not include strong outflow), or truncated to avoid including contributions from stars >40M_{sun}_ are ruled out, in particular because of disagreement with the Fe-peak abundance data. For most elements, the NGC 6553 stars exhibit abundance trends nearly identical to comparable metallicity bulge field stars. However, the star-to-star scatter and mean [Na/Fe] ratios appear higher in the cluster, perhaps indicating additional self-enrichment.
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- ID:
- ivo://CDS.VizieR/J/A+A/530/A54
- Title:
- Abundances of 650 bulge red giants
- Short Name:
- J/A+A/530/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the [alpha/Fe] abundance ratios for a large number of stars at several locations in the Milky Way bulge with the aim of constraining its formation scenario. We obtained FLAMES-GIRAFFE spectra (R=22500) at the ESO Very Large Telescope for 650 bulge red giant branch (RGB) stars and performed spectral synthesis to measure Mg, Ca, Ti, and Si abundances. This sample is composed of 474 giant stars observed in 3 fields along the minor axis of the Galactic bulge and at latitudes b=-4{deg}, b=-6{deg}, b=-12{deg}. Another 176 stars belong to a field containing the globular cluster NGC 6553, located at b=-3{deg} and 5{deg} away from the other three fields along the major axis.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A141
- Title:
- Abundances of disk and bulge giants
- Short Name:
- J/A+A/625/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation and evolution of the Galactic bulge and the Milky Way is still a debated subject. Observations of the X-shaped bulge, cylindrical stellar motions, and the presumed existence of a fraction of young stars in the bulge have suggested that it formed through secular evolution of the disk and not through gas dissipation and/or mergers, as thought previously. Our goal was to measure the abundances of six iron-peak elements (Sc, V, Cr, Mn, Co, and Ni) in the local thin and thick disks and in the bulge. These abundances can provide additional observational constraints for Galaxy formation and chemical evolution models, and help us to understand whether the bulge has emerged from the thick disk or not. We use high-resolution optical spectra of 291 K giants in the local disk mostly obtained by the FIES at NOT (signal-to-noise ratio (S/N) of 80-100) and 45K giants in the bulge obtained by the UVES/FLAMES at VLT (S/N of 10-80). The abundances are measured using Spectroscopy Made Easy (SME). Additionally, we apply non-local thermodynamic equilibrium (NLTE) corrections to the ratios [Mn/Fe] and [Co/Fe]. The thin and thick disks were separated according to their metallicity, [Ti/Fe], as well as proper motions and the radial velocities from Gaia DR2. The trend of [V/Fe] vs. [Fe/H] shows a separation between the disk components, being more enhanced in the thick disk. Similarly, the [Co/Fe] vs. [Fe/H] trend shows a hint of an enhancement in the local thick disk. The trends of V and Co in the bulge appear to be even more enhanced, although within the uncertainties. The decreasing value of [Sc/Fe] with increasing metallicity is observed in all the components, while our [Mn/Fe] value steadily increases with increasing metallicity in the local disk and the bulge instead. For Cr and Ni we find a flat trend following iron for the whole metallicity range in the disk and the bulge. The ratio of [Ni/Fe] appears slightly overabundant in the thick disk and the bulge compared to the thin disk, although the difference is minor. The somewhat enhanced ratios of [V/Fe] and [Co/Fe] observed in the bulge suggest that the local thick disk and the bulge might have experienced different chemical enrichment and evolutionary paths. However, we are unable to predict the exact evolutionary path of the bulge solely based on these observations. Galactic chemical evolution models could, on the other hand, allow us to predict them using these results.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A100
- Title:
- Abundances of disk giants: O, Mg, Ca and Ti
- Short Name:
- J/A+A/598/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic bulge is an intriguing and significant part of our Galaxy, but it is hard to observe because it is both distant and covered by dust in the disk. Therefore, there are not many high-resolution optical spectra of bulge stars with large wavelength coverage, whose determined abundances can be compared with nearby, similarly analyzed stellar samples. We aim to determine the diagnostically important alpha elements of a sample of bulge giants using high-resolution optical spectra with large wavelength coverage. The abundances found are compared to similarly derived abundances from similar spectra of similar stars in the local thin and thick disks. In this first paper we focus on the solar neighborhood reference sample. We used spectral synthesis to derive the stellar parameters as well as the elemental abundances of both the local and bulge samples of giants. We took special care to benchmark our method of determining stellar parameters against independent measurements of effective temperatures from angular diameter measurements and surface gravities from asteroseismology. In this first paper we present the method used to determine the stellar parameters and elemental abundances, evaluate them, and present the results for our local disk sample of 291 giants. When comparing our determined spectroscopic temperatures to those derived from angular diameter measurements, we reproduce these with a systematic difference of +10K and a standard deviation of 53K. The spectroscopic gravities reproduce those determined from asteroseismology with a systematic offset of +0.10dex and a standard deviation of 0.12dex. When it comes to the abundance trends, our sample of local disk giants closely follows trends found in other works analyzing solar neighborhood dwarfs, showing that the much brighter giant stars are as good abundance probes as the often used dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A28
- Title:
- Abundances of dwarfs and giants in 2 open clusters
- Short Name:
- J/A+A/515/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has been suggested that the classical chemical analysis may be affected by systematic errors that would introduce abundance differences between dwarfs and giants. For some elements, the abundance difference could be real. We address the issue by observing 2 solar-type dwarfs in NGC 5822 and 3 in IC 4756, and comparing their composition with that of 3 giants in either of the aforementioned clusters. We determine iron abundance and stellar parameters for dwarf stars. Then, abundances of calcium, sodium, nickel, titanium, aluminium, chromium, and silicon were determined for both giants and dwarfs. The standard equivalent width analysis was performed differentially with respect to the Sun. We find an iron abundance for dwarf stars equal to solar to within the margins of error for IC 4756, and slightly above for NGC 5822 ([Fe/H]=0.01 and 0.05dex respectively). We show that, for sodium, silicon, and titanium, abundances of giants are significantly higher than those of the dwarfs of the same cluster (about 0.15, 0.15, and 0.35dex). Other elements may also undergo some enhanced, but all within 0.1dex.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/99
- Title:
- Abundances of dwarfs & giants in NGC752 with HIRES
- Short Name:
- J/ApJ/878/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical composition of stars in open clusters provides the best information on the chemical evolution of stars via comparison of main-sequence stars with evolved giants. This is a case study of the abundances in the dwarfs and giants in the old open cluster NGC 752. It is also a pilot program for automated abundance determinations, including equivalent-width measurements, stellar parameter determinations, and abundance analysis. We have found abundances of 31 element-ion combinations in 23 dwarfs and six giants. The mean cluster abundance of Fe is solar with [Fe/H]=-0.01+/-0.06 with no significant difference between the dwarfs and giants. We find that the cluster abundances of other elements, including alpha-elements, to be at or slightly above solar levels. We find some evidence for CNO processing in the spectra of the giants. The enhancement of Na in giants indicates that the NeNa cycle has occurred. The abundances of Mg and Al are similar in the dwarfs and giants, indicating that the hotter MgAl cycle has not occurred. We find no evidence of s-process enhancements in the abundances of heavy elements in the giants.
- ID:
- ivo://CDS.VizieR/J/A+A/511/A56
- Title:
- Abundances of five open clusters
- Short Name:
- J/A+A/511/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present number of Galactic open clusters that have high resolution abundance determinations, not only of [Fe/H], but also of other key elements, is largely insufficient to enable a clear modeling of the Galactic disk chemical evolution. To increase the number of Galactic open clusters with high quality measurements, we obtained high resolution (R~30000), high quality (S/N~50-100 per pixel), echelle spectra with the fiber spectrograph FOCES, at Calar Alto, Spain, for three red clump stars in each of five Open Clusters. We used the classical equivalent width analysis method to obtain accurate abundances of sixteen elements: Al, Ba, Ca, Co, Cr, Fe, La, Mg, Na, Nd, Ni, Sc, Si, Ti, V, and Y. We also derived the oxygen abundance using spectral synthesis of the 6300{AA} forbidden line.
- ID:
- ivo://CDS.VizieR/J/AJ/139/2289
- Title:
- Abundances of five red giants in M5
- Short Name:
- J/AJ/139/2289
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present LTE chemical abundances for five red giants and one AGB star in the Galactic globular cluster (GC) M5 based on high-resolution spectroscopy using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan 6.5m Clay telescope. Our results are based on a line-by-line differential abundance analysis relative to the well-studied red giant Arcturus.
- ID:
- ivo://CDS.VizieR/J/A+A/465/799
- Title:
- Abundances of Galactic Bulge red giants
- Short Name:
- J/A+A/465/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper investigates the peculiar behaviour of the light elements (even, e.e. alpha-elements, and odd atomic numbers) in red giants of the galactic bulge, both in terms of the chemical evolution of the bulge, and in terms of possible deep-mixing mechanisms in these evolved stars. Abundances of the four light elements O, Na, Mg, and Al are measured in 13 core He-burning giant stars (red clump stars) and 40 red giant branch stars in four 25' fields spanning the bulge from -3 to -12{deg} galactic latitude. Special care was taken in the abundance analysis, performing a differential analysis with respect to the metal-rich solar-neighbourhood giant mu Leo, which best resembles our bulge sample stars. This approach minimises systematic effects that can arise in the analysis of cool metal-rich stars due to continuum definition issues and blending by molecular lines (CN) and, cancels out possible model atmosphere deficiencies.
- ID:
- ivo://CDS.VizieR/J/A+A/513/A35
- Title:
- Abundances of Galactic red giants
- Short Name:
- J/A+A/513/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation and evolution of the Galactic bulge and its relationship with the other Galactic populations is still poorly understood. To establish the chemical differences and similarities between the bulge and other stellar populations, we performed an elemental abundance analysis of alpha- (O, Mg, Si, Ca, and Ti) and Z-odd (Na and Al) elements of red giant stars in the bulge as well as of local thin disk, thick disk and halo giants. We use high-resolution optical spectra of 25 bulge giants in Baade's window and 55 comparison giants (4 halo, 29 thin disk and 22 thick disk giants) in the solar neighborhood. All stars have similar stellar parameters but cover a broad range in metallicity (-1.5<[Fe/H]<+0.5). A standard 1D local thermodynamic equilibrium analysis using both Kurucz and MARCS models yielded the abundances of O, Na, Mg, Al, Si, Ca, Ti and Fe. Our homogeneous and differential analysis of the Galactic stellar populations ensured that systematic errors were minimized.
