Determining star formation rates in AGN hosts from strong optical emission lines

TL;DR

This paper investigates how to accurately measure star formation rates in galaxies hosting active galactic nuclei by accounting for AGN-induced ionization, proposing new calibration methods using optical emission lines.

Contribution

It introduces calibration techniques using Hα and [O III] emission lines to estimate star formation rates in AGN hosts, considering AGN ionization effects.

Findings

Calibrations with Hα and [O III] lines yield consistent SFR estimates.

Method accounts for AGN contribution to gas ionization.

Sample of 293 AGN hosts from MaNGA used for validation.

Abstract

The influence of Active Galactic Nuclei (AGN) on star formation within their host galaxies remains a topic of intense debate. One of the primary challenges in quantifying the star formation rate (SFR) within AGN hosts arises from the prevalent assumption in most methodologies, which attribute gas excitation to young stars alone. However, this assumption does not consider the contribution of the AGN to the ionization of the gas in their environment. To address this issue, we evaluate the use of strong optical emission lines to obtain the SFR surface density ($\Sigma{{\rm SFR_{AGN}}}$) in regions predominantly ionized by an AGN, using a sample of 293 AGN hosts from the MaNGA survey, with SFR measurements available through stellar population fitting. We propose calibrations involving the H$\alpha$ and [O\,{\sc iii}]$\lambda$5007 emission lines, which can be used to determine $\Sigma{{\rm SFR_{AGN}}}$, resulting in values consistent with those estimated through stellar population fitting.