Query : 2019A&A...627A.152S

2019A&A...627A.152S - Astronomy and Astrophysics, volume 627A, 152-152 (2019/7-2)

The inner two degrees of the Milky Way. Evidence of a chemical difference between the Galactic Center and the surrounding inner bulge stellar populations.


Abstract (from CDS):

Context. Although there have been numerous studies of chemical abundances in the Galactic bulge, the central two degrees have been relatively unexplored due to the heavy and variable interstellar extinction, extreme stellar crowding, and the presence of complex foreground disk stellar populations. Aims. In this paper we discuss the metallicity distribution function, vertical and radial gradients, and chemical abundances of α-elements in the inner two degrees of the Milky Way, as obtained by recent IR spectroscopic surveys. Methods. We used a compilation of recent measurements of metallicities and α-element abundances derived from medium-high resolution spectroscopy. We compare these metallicities with low-resolution studies. Results. Defining "metal-rich" as stars with [Fe/H]>0, and "metal-poor" as stars with [Fe/H]<0, we find compelling evidence for a higher fraction (∼80%) of metal-rich stars in the Galactic Center (GC) compared to the values (50-60%) measured in the low latitude fields within the innermost 600 pc. The high fraction of metal-rich stars in the GC region implies a very high mean metallicity of +0.2dex, while in the inner 600pc of the bulge the mean metallicity is rather homogenous around the solar value. A vertical metallicity gradient of -0.27dex/kpc in the inner 600pc is only measured if the GC is included, otherwise the distribution is about flat and consistent with no vertical gradient.Conclusions. In addition to its high stellar density, the Galactic center/nuclear star cluster is also extreme in hosting high stellar abundances, compared to the surrounding inner bulge stellar populations; this has implications for formation scenarios and strengthens the case for the nuclear star cluster being a distinct stellar system.

Abstract Copyright: © M. Schultheis et al. 2019

Journal keyword(s): Galaxy: bulge - Galaxy: center - Galaxy: stellar content - stars: fundamental parameters - stars: abundances - infrared: stars

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13902 0
2 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 4219 3
3 Cl Terzan 5 Cl* 17 48 05.00 -24 46 48.0           ~ 819 1
4 NAME Baade Window reg 18 03.5 -30 01           ~ 596 3
5 NAME Galactic Bulge reg ~ ~           ~ 4168 0

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