J/A+A/618/A147 Fraction of bulge metal poor & metal rich stars (Zoccali+, 2018)
Weighing the two stellar components of the Galactic bulge.
Zoccali M., Valenti E., Gonzalez O.A.
<Astron. Astrophys. 618, A147 (2018)>
=2018A&A...618A.147Z 2018A&A...618A.147Z (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stellar distribution
Keywords: Galaxy: bulge - Galaxy: formation - Galaxy: stellar content -
Galaxy: structure
Abstract:
Recent spectroscopic surveys of the Galactic bulge have unambiguously
shown that the bulge contains two main components, which are best
separated by their iron content, but also differ in spatial
distribution, kinematics, and abundance ratios. The so-called metal
poor component peaks at [Fe/H]~-0.4, while the metal rich
component peaks at [Fe/H]~+0.3. The total metallicity distribution
function is therefore bimodal with a dip at [Fe/H]∼0. The relative
fraction of the two components changes significantly across the bulge
area.
We provide, for the first time, the fractional contribution of the
metal poor and metal rich stars to the stellar mass budget of the
Galactic bulge and its variation across the bulge area.
This result follows from the combination of the stellar mass profile
obtained empirically, by our group, from VISTA Variables in the Via
Lactea data, with the relative fraction of metal poor and metal rich
stars, across the bulge area, derived from the GIRAFFE Inner Bulge
spectroscopic Survey.
We find that metal poor stars make up 48% of the total stellar mass of
the bulge, within the region |l|<10, |b|<9.5 and that the
remaining 52% are made up of metal rich stars. The latter dominate the
mass budget at intermediate latitudes |b|∼4, but become marginal
in the outer bulge (|b|>8). The metal poor component is more
axisymmetric than the metal rich component, and it is at least
comparable and possibly slightly dominant in the inner few degrees. As
a result, the metal poor component, which does not follow the main
bar, is not marginal in terms of the total mass budget as previously
thought, and this new observational evidence must be included in bulge
models. While the trend of the total radial velocity dispersion
follows the total stellar mass, when we examine the velocity
dispersion of each component individually, we find that metal poor
stars have higher velocity dispersion where they make up a smaller
fraction of the stellar mass, and vice versa. This is due to the
kinematical and spatial distribution of the two metallicity components
being significantly different, as already discussed in the literature.
Description:
Percent contribution of metal poor and metal rich stars to the bulge
stellar mass, in the region -10<l<10, -10<b<10, as a function of
Galactic position.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 26 361 Percent contribution of metal poor and
metal rich stars
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See also:
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Saito+, 2012)
II/348 : VISTA Variable in the Via Lactea Survey DR2 (Minniti+, 2017)
J/A+A/562/A66 : GIRAFFE Inner Bulge Survey (GIBS). I. (Zoccali+, 2014)
J/A+A/584/A46 : GIRAFFE Inner Bulge Survey (GIBS). II. (Gonzalez+, 2015)
Byte-by-byte Description of file (#): table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 deg GLON [] Galactic longitude
5- 8 I4 deg GLAT Galactic latitude
9- 17 F9.4 % MP Percent of metal poor stars (1)
18- 26 F9.4 % MR Percent of metal rich stars (1)
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Note (1): The sum of all the entries in MP is 48.39%. This is the percent
contribution of metal poor stars to the mass budget in the whole area analyzed
here. The sum of all the entries in MR is 51.61%.
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Acknowledgements:
Manuela Zoccali, mzoccali(at)astro.puc.cl
(End) Patricia Vannier [CDS] 25-Oct-2018