Star formation and AGN activity in a sample of local Luminous Infrared
  Galaxies through multi-wavelength characterization
  Nuclear starbursts and AGN activity are the main heating processes in
luminous infrared galaxies (LIRGs) and their relationship is fundamental to
understand galaxy evolution. In this paper, we study the star-formation and AGN
activity of a sample of 11 local LIRGs imaged with subarcsecond angular
resolution at radio (8.4GHz) and near-infrared ($2.2\mu$m) wavelengths. This
allows us to characterize the central kpc of these galaxies with a spatial
resolution of $\simeq100$pc. In general, we find a good spatial correlation
between the radio and the near-IR emission, although radio emission tends to be
more concentrated in the nuclear regions. Additionally, we use an MCMC code to
model their multi-wavelength spectral energy distribution (SED) using template
libraries of starburst, AGN and spheroidal/cirrus models, determining the
luminosity contribution of each component, and finding that all sources in our
sample are starburst-dominated, except for NGC6926 with an AGN contribution of
$\simeq64$\%. Our sources show high star formation rates ($40$ to
$167M_\odot\mathrm{yr}^{-1}$), supernova rates (0.4 to
$2.0\mathrm{SN}\mathrm{yr}^{-1}$), and similar starburst ages (13 to
$29\mathrm{Myr}$), except for the young starburst (9Myr) in NGC6926. A
comparison of our derived star-forming parameters with estimates obtained from
different IR and radio tracers shows an overall consistency among the different
star formation tracers. AGN tracers based on mid-IR, high-ionization line
ratios also show an overall agreement with our SED model fit estimates for the
AGN. Finally, we use our wide-band VLA observations to determine pixel-by-pixel
radio spectral indices for all galaxies in our sample, finding a typical median
value ($\alpha\simeq-0.8$) for synchrotron-powered LIRGs.
