Issue |
A&A
Volume 399, Number 3, March I 2003
|
|
---|---|---|
Page(s) | 931 - 956 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20021604 | |
Published online | 14 February 2003 |
Age and metallicity distribution of the Galactic bulge from extensive optical and near-IR stellar photometry*
1
European Southern Observatory, Karl Schwarzschild Strasse 2, 85748, Garching bei München, Germany e-mail: arenzini@eso.org; mrejkuba@eso.org
2
Università di Padova, Dipart. di Astronomia, Vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: ortolani@pd.astro.it
3
INAF, Osservatorio Astronomico di Padova, Padova, Italy e-mail: greggio@pd.astro.it
4
European Southern Observatory, Alonso de Cordova 3107, Santiago 19, Chile e-mail: isaviane@eso.org
5
INAF, Osservatorio Astronomico Collurania, 64100, Teramo, Italy e-mail: cassisi@te.astro.it
6
Universidade de São Paulo, CP 3386, São Paulo 01060-970, Brazil e-mail: barbuy@astro.iag.usp.br
7
Department of Physics and Astronomy, Division of Astronomy and Astrophysics, University of California, Los Angeles, CA 90095-1562 e-mail: rmr@astro.ucla.edu
8
Universidade Federal do Rio Grande do Sul, Dept. de Astronomia, CP 15051, Porto Alegre 91501-970, Brazil e-mail: bica@if.ufrgs.br
Corresponding author: M. Zoccali, mzoccali@eso.org
Received:
25
June
2002
Accepted:
22
October
2002
We present a new determination of the metallicity distribution, age,
and luminosity function of the Galactic bulge stellar population. By
combining near-IR data from the 2MASS survey, from the SOFI imager at
ESO NTT and the NICMOS camera on board HST we were able to construct
color-magnitude diagrams (CMD) and luminosity functions (LF) with
large statistics and small photometric errors from the Asymptotic
Giant Branch (AGB) and Red Giant Branch (RGB) tip down to ~. This is the most extended and complete LF so far obtained
for the galactic bulge. Similar near-IR data for a disk control field
were used to decontaminate the bulge CMDs from foreground disk stars,
and hence to set a stronger constraint on the bulge age, which we found
to be as large as that of Galactic globular clusters, or
10 Gyr. No trace is found for any younger stellar population. Synthetic
CMDs have been constructed to simulate the effect of photometric
errors, blending, differential reddening, metallicity dispersion and
depth effect in the comparison with the observational data. By
combining the near-IR data with optical ones, from the Wide Field
Imager at the ESO/MPG 2.2 m telescope, a disk-decontaminated
(MK,V–K) CMD has been constructed and used to derive the bulge
metallicity distribution, by comparison with empirical RGB
templates. The bulge metallicity is found to peak at near solar value,
with a sharp cutoff just above solar, and a tail towards lower
metallicity that does not appreciably extend below [M/H]
.
Key words: Galaxy: bulge / stars: Hertzsprung-Russell (H-R) and C-M diagrams / stars: luminosity function, mass function
Based on observations collected at the European Southern Observatory, La Silla, Chile, obtained from the ESO/ST-ECF Science Archive Facility, and on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, operated by AURA Inc. under contract to NASA.
© ESO, 2003
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