Understanding mechanical feedback from HERGs and LERGs

TL;DR

This study analyzes the properties and feedback mechanisms of about 1000 HERGs and LERGs, revealing that mechanical feedback is more prevalent and significant than previously estimated, impacting galaxy evolution models.

Contribution

It provides new observational evidence that mechanical feedback from radio galaxies is often underestimated in simulations, highlighting its importance in galaxy evolution.

Findings

84% of the sample release >10% of energy as mechanical feedback

HERGs have younger stellar populations and higher accretion rates than LERGs

Nearly 50% of HERGs release >10% of energy via radio jets

Abstract

The properties of $\sim 1000$ high-excitation and low-excitation radio galaxies (HERGs and LERGs) selected from the Heywood et al. (2016) $1 - 2$ GHz VLA survey of Stripe 82 are investigated. The HERGs in this sample are generally found in host galaxies with younger stellar populations than LERGs, consistent with other work. The HERGs tend to accrete at a faster rate than the LERGs, but there is more overlap in the accretion rates of the two classes than has been found previously. We find evidence that mechanical feedback may be significantly underestimated in hydrodynamical simulations of galaxy evolution; 84 % of this sample release more than 10 % of their energy in mechanical form. Mechanical feedback is significant for many of the HERGs in this sample as well as the LERGs; nearly 50 % of the HERGs release more than 10 % of their energy in their radio jets.