Spectral Synthesis of Star-forming Galaxies in the Near-Infrared
  The near-infrared spectral region is becoming a very useful wavelength range
to detect and quantify the stellar population of galaxies. Models are
developing to predict the contribution of TP-AGB stars, that should dominate
the NIR spectra of populations 0.3 to 2 Gyr old. When present in a given
stellar population, these stars leave unique signatures that can be used to
detect them unambiguously. However, these models have to be tested in a
homogeneous database of star-forming galaxies, to check if the results are
consistent with what is found from different wavelength ranges. In this work we
performed stellar population synthesis on the nuclear and extended regions of
23 star-forming galaxies to understand how the star-formation tracers in the
near-infrared can be used in practice. The stellar population synthesis shows
that for the galaxies with strong emission in the NIR, there is an important
fraction of young/intermediate population contributing to the spectra, which is
probably the ionisation source in these galaxies. Galaxies that had no emission
lines measured in the NIR were found to have older average ages and less
contribution of young populations. Although the stellar population synthesis
method proved to be very effective to find the young ionising population in
these galaxies, no clear correlation between these results and the NIR spectral
indexes were found. Thus, we believe that, in practice, the use of these
indexes is still very limited due to observational limitations.
