# Galaxy Evolution in the Radio Band: The Role of Starforming Galaxies and Active Galactic Nuclei

## TL;DR

This paper models the statistical properties of radio-emitting star-forming galaxies and AGNs, predicting their contributions to radio surveys and their black hole accretion behaviors, with implications for upcoming SKA observations.

## Contribution

It introduces a model-independent approach to analyze the radio emission and host galaxy properties of star-forming galaxies and AGNs, providing new predictions for future radio surveys.

## Key findings

- Star-forming galaxies and AGNs have distinct Eddington ratio distributions.
- Predicted contributions of galaxies and AGNs vary with radio luminosity and redshift.
- Models are consistent with current data but require validation with future SKA data.

## Abstract

We investigate the astrophysics of radio-emitting star-forming galaxies and ac- tive galactic nuclei (AGNs), and elucidate their statistical properties in the radio band including luminosity functions, redshift distributions, and number counts at sub-mJy flux levels, that will be crucially probed by next-generation radio continuum surveys. Specifically, we exploit the model-independent approach by Mancuso et al. (2016a,b) to compute the star formation rate functions, the AGN duty cycles and the conditional probability of a star-forming galaxy to host an AGN with given bolometric luminosity. Coupling these ingredients with the radio emission properties associated to star formation and nuclear activity, we compute relevant statistics at different radio frequencies, and disentangle the relative con- tribution of star-forming galaxies and AGNs in different radio luminosity, radio flux, and redshift ranges. Finally, we highlight that radio-emitting star-forming galaxies and AGNs are expected to host supermassive black holes accreting with different Eddington ratio distributions, and to occupy different loci in the galaxy main sequence diagrams. These specific predictions are consistent with current datasets, but need to be tested with larger statistics via future radio data with multi-band coverage on wide areas, as it will become routinely achievable with the advent of the SKA and its precursors.