# Star formation and AGN activity in a sample of local Luminous Infrared Galaxies through multi-wavelength characterization

## TL;DR

This study characterizes star formation and AGN activity in 11 local LIRGs using high-resolution multi-wavelength imaging and spectral energy distribution modeling, revealing starburst dominance and detailed physical properties.

## Contribution

It provides the first high-resolution spatial analysis of both star formation and AGN activity in local LIRGs using combined radio and near-IR data, with comprehensive SED modeling.

## Key findings

- All sources are starburst-dominated except NGC6926 with ~64% AGN contribution.
- High star formation rates ranging from 40 to 167 solar masses per year.
- Median radio spectral index of approximately -0.8 indicating synchrotron emission.

## Abstract

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.