Population synthesis modelling of luminous infrared galaxies at
  intermediate redshift
  Luminous InfraRed Galaxies (LIRGs) are particularly important for studying
the build-up of the stellar mass from z=1 to z=0. We perform a multiwavelength
study of an LIRGs sample in the Extended Chandra Deep Field South at z=0.7,
selected at 24 \mu\m by MIPS onboard Spitzer Space Telescope and detected in 17
filters. Data go from the near-ultraviolet to the mid-infrared. This
multiwavelengths dataset allows us to place strong constraints on the spectral
energy distributions (SEDs) of galaxies, and thus to efficiently derive
physical parameters such as the SFR, the total infrared luminosity, attenuation
parameters, and star formation history. An important part of this work is
elaboration of a mock catalogue that allows us to have a reliability criterion
for the derived parameters. We studied LIRGs by means of an SED-fitting code
CIGALE. At first, this code creates synthetic spectra from the Maraston stellar
population models. The stellar population spectra are attenuated by using a
synthetic Calzetti-based attenuation law before adding the dust emission as
given by the infrared SED library. The originality of CIGALE is that it allows
us to perform consistent fits of the dust-affected ultaviolet-to-infrared
wavelength range. This technique appears to be a very powerful tool in the case
where we can have access to a dataset that is well-sampled over a wide range of
wavelengths. We are able to derive a star formation history and to estimate the
fraction of infrared luminosity reprocessed by an active galactic nucleus. We
study the dust temperatures of our galaxies detected at 70 \mu\m and find them
colder than predicted by models. We also study the relation between the SFR and
the stellar mass and do not find a tight correlation between either of them,
but instead a flat distribution and a large scatter, which is interpreted in
terms of variations in star formation history.
