Star and dust formation activities in AzTEC-3: A starburst galaxy at z =
  5.3
  Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally
use the observed optical to submillimeter spectral energy distribution (SED)
and estimates of the dynamical mass as observational constraints to derive the
star formation rate (SFR), the stellar mass, and age of these objects. An
important observational constraint neglected in the analysis is the mass of
dust giving rise to the IR emission. In this paper we add this constraint to
the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a
bolometric luminosity for this object, we construct stellar and chemical
evolutionary scenarios, constrained to produce the inferred dust mass and
observed luminosity before the associated stellar mass exceeds the
observational limit. We find that the model with a Top Heavy IMF provided the
most plausible scenario consistent with the observational constraints. In this
scenario the dust formed over a period of ~200 Myr, with a SFR of ~500 Msun/yr.
These values for the age and SFR in AzTEC-3 are significantly higher and lower,
respectively, from those derived without the dust mass constraint. However,
this scenario is not unique, and others cannot be completely ruled out because
of the prevailing uncertainties in the age of the galaxy, its bolometric
luminosity, and its stellar and dust masses. A robust result of our models is
that all scenarios require most of the radiating dust mass to have been
accreted in molecular clouds. Our new procedure highlights the importance of a
multiwavelength approach, and of the use of dust evolution models in
constraining the age and the star formation activity and history in galaxies.
