Issue |
A&A
Volume 447, Number 1, February III 2006
|
|
---|---|---|
Page(s) | 185 - 198 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20053376 | |
Published online | 27 January 2006 |
Stellar populations in the CFHTLS
I. New constraints on the IMF at low mass
1
CNRS UMR6091, Observatoire de Besançon, BP 1615, 25010 Besançon Cedex, France e-mail: mathias@obs-besancon.fr
2
CNRS UMR 7095, Institut d'Astrophysique de Paris, 98bis Bld. Arago, 75014 Paris, France
3
Observatoire de Paris, LERMA, 61 avenue de l'Observatoire, 75014 Paris, France
4
Laboratoire d'Astrophysique de Marseille, OAMP, Université de Provence, UMR 6110, Traverse du Siphon-Les trois Lucs, 1302 Marseille, France
Received:
6
May
2005
Accepted:
12
September
2005
We present a stellar populations analysis of the first release of the
CFHTLS (Canada-France-Hawai Telescope Legacy Survey) data. A
detailed comparison between the Besançon model of the Galaxy and
the first data release of the CFHTLS-Deep survey is performed by
implementing the MEGACAM photometric system in this model using
stellar atmosphere model libraries. The reliability of the
theoretical libraries to reproduce the observed colours in the
MEGACAM system is investigated. The locations of various stellar
species like subdwarfs, white dwarfs, late-type and brown dwarfs,
binary systems are identified. The contamination of the stellar
sample by quasars and compact galaxies is quantified using
spectroscopic data from the VIMOS-VLT Deep Survey (VVDS) as a
function of i' magnitude and colour. A comparison between
simulated counts using the standard IMF at low masses show that the
number of very low mass dwarfs may have been underestimated in
previous studies. These observations favour a power law IMF following
with
for
or
for
for single stars. The
resulting LF is in agreement with the local LF as measured from the 5
or 25 pc samples. It is in strong disagreement with the Zheng et al.
(2001) LF measured from deep HST data. We show that this discrepancy
can be understood as an indication of a different IMF at low masses
at early epochs of the Galaxy compared to the local thin disc IMF.
Key words: Galaxy: stellar content / stars: luminosity function, mass function / stars: white dwarfs / binaries: general / stars: atmospheres / stars: low mass, brown dwarfs
© ESO, 2006
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