J/A+A/642/A81 APOGEE cool stars (Schultheis+, 2020)
Cool stars in the Galactic center as seen by APOGEE.
M giants, AGB stars, and supergiant stars and candidates.
Schultheis M., Rojas-Arriagada A., Cunha K., Zoccali M., Chiappini C.,
Zasowski G., Queiroz A.B.A., Minniti D., Fritz T., Garcia-Hernandez D.A.,
Nitschelm C., Zamora O., Hasselquist S., Fernandez-Trincado J.G.,
Munoz R.R.
<Astron. Astrophys., 642, A81 (2020)>
=2020A&A...642A..81S 2020A&A...642A..81S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Abundances ; Effective temperatures
Keywords: Galaxy: bulge - Galaxy: stellar content -
stars: fundamental parameters - stars: abundances
Abstract:
The Galactic center region, including the nuclear disk, has until
recently been largely avoided in chemical census studies because of
extreme extinction and stellar crowding. Large, near-IR spectroscopic
surveys, such as the Apache Point Observatory Galactic Evolution
Experiment (APOGEE), allow the measurement of metallicities in the
inner region of our Galaxy. Making use of the latest APOGEE data
release (DR16), we are able for the first time to study cool
Asymptotic Giant branch (AGB) stars and supergiants in this region.
The stellar parameters of five known AGB stars and one supergiant star
(VR 5-7) show that their location is well above the tip of the red
giant branch. We studied metallicities of 157 M giants situated within
150 pc of the Galactic center from observations obtained by the APOGEE
survey with reliable stellar parameters from the APOGEE pipeline
making use of the cool star grid down to 3200K. Distances,
interstellar extinction values, and radial velocities were checked to
confirm that these stars are indeed situated in the Galactic center
region. We detect a clear bimodal structure in the metallicity
distribution function, with a dominant metal-rich peak of
[Fe/H]~+0.3dex and a metal-poor peak around {Fe/H]=-0.5dex, which is
0.2dex poorer than Baade's Window. The α-elements Mg, Si, Ca,
and O show a similar trend to the Galactic bulge. The metal-poor
component is enhanced in the α-elements, suggesting that this
population could be associated with the classical bulge and a fast
formation scenario. We find a clear signature of a rotating nuclear
stellar disk and a significant fraction of high-velocity stars with
vgal>300km/s; the metal-rich stars show a much higher rotation
velocity (∼200km/s) with respect to the metal-poor stars (∼140km/s).
The chemical abundances as well as the metallicity distribution
function suggest that the nuclear stellar disk and the nuclear star
cluster show distinct chemical signatures and might be formed
differently.
Description:
Using the latest DR16 APOGEE data release, we studied cool M giants in
the GALCEN sample going down to temperatures of 3200K. Among those,
stellar parameters of a bunch of known and candidate AGB/supergiant
stars are now available thanks to the cool grid of MARCS model
atmospheres and significant improvements in the analysis of cool stars
by the APOGEE/ASPCAP team. The known (6) and candidate (15)
AGB/supergiant stars are situated well above the tip of the RGB,
confirming their status as cool luminous stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 60 5 Known AGB and supergiants with stellar
parameters from APOGEE-DR16
table2.dat 35 14 Supergiant candidates
tablea1.dat 18 157 *APOGEE IDs used in this paper for the analysis
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Note on tablea1.dat: The preliminary reduction version r13 has been used
with the corresponding allStar-r13-l33-58672.fits file. This file will be
provided once the official data release DR17 becomes public.
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Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- APOGEE APOGEE ID (2MHHMMSSss+DDMMSSs)
20- 23 I4 K Teff Effective temperature
25- 29 F5.2 [cm/s2] logg Surface gravity
31- 35 F5.2 [-] [M/H] Metallicity
37- 44 A8 --- Name Name, only for table1
46 I1 --- r_Name ? Reference for name (1)
48- 60 A13 --- SName Simbad name, only for table1
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Note (1): References as follows:
2 = Schultheis et al. (2003, Cat. J/A+A/405/531), [SLO2003] ANN
3 = Matsunaga et al. (2009, Cat. J/MNRAS/399/1709), [MKN2009] NNNN
4 = Davies et al. (2009ApJ...694...46D 2009ApJ...694...46D) and Cunha et al. (2007ApJ...669.1011C 2007ApJ...669.1011C)
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- APOGEE APOGEE ID (2MHHMMSSss+DDMMSSs)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 14-Jan-2021