Cosmological model dependence of the galaxy luminosity function: far-infrared results in the Lemaître-Tolman-Bondi model
Résumé
Aims. This is the first paper of a series aiming at investigating galaxy
formation and evolution in the giant-void class of the Lemaître-Tolman-Bondi (LTB) models
that best fits current cosmological observations. Here we investigate the luminosity
function (LF) methodology, and how its estimates would be affected by a change on the
cosmological model assumed in its computation. Are the current observational constraints
on the allowed cosmology enough to yield robust LF results?Methods. We used the far-infrared source catalogues built on the
observations performed with the Herschel/PACS instrument and selected as
part of the PACS evolutionary probe (PEP) survey. Schechter profiles were obtained in
redshift bins up to z ≈ 4, assuming comoving volumes in both the standard
model, that is, the Friedmann-Lemaître-Robertson-Walker metric with a perfect fluid
energy-momentum tensor, and non-homogeneous LTB dust models, parametrized to fit the
current combination of results stemming from the observations of supernovae Ia, the cosmic
microwave background, and baryonic acoustic oscillations.Results. We find that the luminosity functions computed assuming both
the standard model and LTB void models show in general good agreement. However, the
faint-end slope in the void models shows a significant departure from the standard model
up to redshift 0.4. We demonstrate that this result is not artificially caused by the used
LF estimator which turns out to be robust under the differences in matter-energy density
profiles of the models.Conclusions. The differences found in the LF slopes at the faint end are
due to variation in the luminosities of the sources that depend on the geometrical part of
the model. It follows that either the standard model is over-estimating the number density
of faint sources or the void models are under-estimating it.
Origine : Publication financée par une institution
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