J/A+A/534/A80 Metallicity of bulge clump giants in Baade's window (Hill+, 2011)
The metallicity distribution of bulge clump giants in Baade's window.
Hill V., Lecureur A., Gomez A., Zoccali M., Schultheis M., Babusiaux C.,
Royer F., Barbuy B., Arenou F., Minniti D., Ortolani S.
<Astron. Astrophys. 534, A80 (2011)>
=2011A&A...534A..80H 2011A&A...534A..80H
ADC_Keywords: Stars, giant ; Abundances, [Fe/H] ; Photometry, UBVRI ;
Photometry, infrared
Keywords: Galaxy: bulge - Galaxy: formation - Galaxy: abundances -
stars: abundances - stars: atmosphere
Abstract:
We seek to constrain the formation of the Galactic bulge by means of
analysing the detailed chemical composition of a large sample of red
clump stars in Baade's window. These stars were selected to minimise
the contamination by other Galactic components, so they are good
tracers of the bulge metallicity distribution in Baade's window, at
least for stars more metal-rich than ~-1.5. We used an automatic
procedure to measure [Fe/H] in a sample of 219 bulge red clump stars
from R=20000 resolution spectra obtained with FLAMES/GIRAFFE at the
VLT. The analysis was performed differentially with respect to the
metal-rich local reference star MuLeo. For a subsample of 162 stars,
we also derived [Mg/H] from spectral synthesis around the MgI triplet
at 6319Å.
The Fe and Mg metallicity distributions are both asymmetric with
median values of +0.16 and +0.21, respectively. They show only a small
proportion of stars at low metallicities, extending down to
[Fe/H]=-1.1 or [Mg/H]=-0.7 The iron distribution is clearly bimodal,
as revealed both by a deconvolution (from observational errors) and a
Gaussian decomposition. The decomposition of the observed Fe and Mg
metallicity distributions into Gaussian components yields two
populations of equal sizes (50% each): a metal-poor component centred
on [Fe/H]=-0.30 and [Mg/H]=-0.06 with a large dispersion and a narrow
metal-rich component centred on [Fe/H]=+0.32 and [Mg/H]=+0.35. The
metal-poor component shows high [Mg/Fe] ratios (around 0.3), while
stars in the metal-rich component are found to have near solar ratios.
Kinematical differences between the two components have also been
found: the metal-poor component shows kinematics compatible with an
old spheroid, while the metal-rich component is consistent with a
population supporting a bar. In view of their chemical and kinematical
properties, we suggest different formation scenarii for the two
populations: a rapid formation time scale as an old spheroid for the
metal-poor component (old bulge) and for the metal-rich component, a
formation on a longer time scale driven by the evolution of the bar
(pseudo-bulge).
Description:
Stellar parameters and [Fe/H] and [Mg/H] abundances (and associated
uncertainties) are given for a sample of 220 red clump stars selected
in Baade's Window towards the Galactic Bulge and observed at a
resolution of R=20,000 with the FLAMES/VLT multi-object spectrograph.
The cross-identified UBVI (OGLE) and JHK (2MASS) photometry used for
initial stellar parameter determination are also given.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 132 220 UBVI and JHK photometry for the selected
220 red clump stars in Baade's Window
table2.dat 54 220 Stellar parameters, [Fe/H] and [Mg/H]
of the 220 red clump stars in Baade's Window
table3.dat 73 220 Uncertainties on the stellar parameters and
associated uncertainties on [Fe/H] abundances
of the 220 red clump stars in Baade's Window
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AcA/49/319 : OGLE UBVI phot. in Baade's Window (Paczynski+, 1999)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Star Star name (BWc-NNN)
9- 16 A8 --- --- (BUL-SC45)
18- 23 I6 --- OGLE OGLE identifier, BUL-SC45 NNNNNN, from
Paczynski et al., 1999, Cat. J/AcA/49/319
25- 30 F6.3 mag Umag Johnson U magnitude
32- 36 F5.3 mag e_Umag rms uncertainty on Umag
38- 43 F6.3 mag Bmag Johnson B magnitude
45- 49 F5.3 mag e_Bmag rms uncertainty on Bmag
51- 56 F6.3 mag Vmag Johnson V magnitude
58- 62 F5.3 mag e_Vmag rms uncertainty on Vmag
64- 69 F6.3 mag Imag Johnson I magnitude
71- 75 F5.3 mag e_Imag rms uncertainty on Imag
77- 93 A17 --- 2MASS 2MASS identifier
95-100 F6.3 mag Jmag 2MASS J magnitude
102-106 F5.3 mag e_Jmag rms uncertainty on Jmag
108-113 F6.3 mag Hmag 2MASS H magnitude
115-119 F5.3 mag e_Hmag rms uncertainty on Hmag
121-126 F6.3 mag Kmag 2MASS K magnitude
128-132 F5.3 mag e_Kmag rms uncertainty on Kmag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Star Star name
9- 12 I4 K Teff Effective Temperature
14- 17 F4.2 [cm/s2] logg Surface gravity
19- 21 F3.1 km/s vt Microturbulence velocity
23- 27 F5.2 [Sun] [Fe/H] Fe/H abundance
29- 32 F4.2 [Sun] e_[Fe/H] Uncertainty on [Fe/H] (lower value)
34- 37 F4.2 [Sun] E_[Fe/H] Uncertainty on [Fe/H] (upper value)
40- 44 F5.2 [Sun] [Mg/H] ?=99.99 Mg/H abundance
46- 49 F4.2 [Sun] e_[Mg/H] ?=9.99 Uncertainty on [Mg/H] (lower value)
51- 54 F4.2 [Sun] E_[Mg/H] ?=9.99 Uncertainty on [Mg/H] (upper value)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Star Star name
9- 12 I4 K Teff Effective Temperature
14- 17 F4.2 [cm/s2] logg Surface gravity
19- 21 F3.1 km/s vt Microturbulence velocity
23- 27 F5.2 [Sun] [Fe/H] Metallicity ([Fe/H] abundance)
31- 34 F4.2 km/s e_vt Uncertainty on the microturbulence velocity
(lower value)
36- 39 F4.2 [Sun] E_[Fe/H]vt Uncertainty on Fe (upper value) arising
from the uncertainty on the microturbulence
velocity (lower value)
41- 43 I3 K E_Teff Uncertainty on the effective temperature
(upper value)
45- 48 F4.2 [Sun] E_[Fe/H]T Uncertainty on Fe (upper value) arising
from the uncertainty on the effective
temperature (upper value)
53- 56 F4.2 km/s E_vt Uncertainty on the microturbulence velocity
(upper value)
59- 62 F4.2 [Sun] e_[Fe/H]vt Uncertainty on Fe (lower value) arising
from the uncertainty on the microturbulence
velocity (upper value)
65- 67 I3 K e_Teff Uncertainty on the effective temperature
(lower value)(T)
70- 73 F4.2 [Sun] e_[Fe/H]T Uncertainty on Fe (lower value) arising
from the uncertainty on the effective
temperature (lower value)
--------------------------------------------------------------------------------
Acknowledgements:
Vanessa Hill, Vanessa.Hill(at)oca.eu
History:
* 05-Oct-2011: on-line version
* 28-Jan-2013: Signs of 2MASS name corrected
(End) Patricia Vannier [CDS] 26-Aug-2011