Issue |
A&A
Volume 499, Number 3, June I 2009
|
|
---|---|---|
Page(s) | 697 - 710 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/200811118 | |
Published online | 25 March 2009 |
Recovery of the star formation history of the LMC from the VISTA survey of the Magellanic system
1
Osservatorio Astronomico di Padova – INAF, Vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: leandro.kerber@oapd.inaf.it
2
Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil
3
Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
4
Center for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK
Received:
9
October
2008
Accepted:
12
January
2009
The VISTA near infrared survey of the Magellanic System (VMC) will
provide deep YJKs photometry reaching stars in the oldest
turn-off point throughout the Magellanic Clouds (MCs).
As part of the preparation for the survey, we aim to access the
accuracy in the star formation history (SFH) that can be expected from
VMC data, in particular for the Large Magellanic Cloud (LMC).
To this aim, we first simulate VMC images containing not only the LMC
stellar populations but also the foreground Milky Way (MW) stars and
background galaxies. The simulations cover the whole range of density
of LMC field stars. We then perform aperture photometry over these
simulated images, access the expected levels of photometric errors and
incompleteness, and apply the classical technique of
SFH-recovery based on the reconstruction of colour-magnitude diagrams
(CMD) via the minimisation of a chi-squared-like statistics. We verify
that the foreground MW stars are accurately recovered by the
minimisation algorithms, whereas the background galaxies can be
largely eliminated from the CMD analysis due to their particular
colours and morphologies.
We then evaluate the expected errors in the recovered star formation
rate as a function of stellar age, SFR, starting from models with
a known age–metallicity relation (AMR). It turns out that, for a
given sky area, the random errors for ages older than ~0.4 Gyr
seem to be independent of the crowding. This can be explained by a
counterbalancing effect between the loss of stars from a decrease in
the completeness and the gain of stars from an increase in the
stellar density. For a spatial resolution of ~0.1 deg2, the
random errors in SFR
will be below 20% for this wide range of
ages. On the other hand, due to the lower stellar statistics for
stars younger than ~0.4 Gyr, the outer LMC regions will require
larger areas to achieve the same level of accuracy in the SFR
. If
we consider the AMR as unknown, the SFH-recovery algorithm is able to
accurately recover the input AMR, at the price of an increase of
random errors in the SFR
by a factor of about 2.5. Experiments of
SFH-recovery performed for varying distance modulus and reddening
indicate that these parameters can be determined with (relative)
accuracies of
~ 0.02 mag and
~ 0.01 mag,
for each individual field over the LMC. The propagation of these
errors in the SFR
implies systematic errors below 30%.
This level of accuracy in the SFR
can reveal significant
imprints in the dynamical evolution of this unique and nearby stellar system,
as well as possible signatures of the past interaction between the MCs
and the MW.
Key words: galaxies: evolution / Magellanic Clouds / surveys / infrared: stars: Hertzsprung-Russell (HR) and C-M diagrams / methods: numerical
© ESO, 2009
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