# Evidence for a Young Stellar Population in Nearby Type 1 Active Galaxies

## TL;DR

This study provides evidence that nearby type 1 AGN host galaxies contain younger stellar populations, with luminosity excess correlating with accretion rates, indicating a link between star formation and black hole growth.

## Contribution

It reveals a correlation between stellar population age and AGN activity, demonstrating that active galaxies have younger stars and lower mass-to-light ratios compared to inactive galaxies.

## Key findings

- Bulges of type 1 AGNs are more luminous than inactive galaxies with similar black hole mass.
- Luminosity excess correlates with AGN accretion rate.
- Younger stellar populations are likely present in active galaxy bulges.

## Abstract

To understand the physical origin of the close connection between supermassive black holes and their host galaxies, it is vital to investigate star formation properties in active galaxies. Using a large dataset of nearby type 1 active galactic nuclei (AGNs) with detailed structural decomposition based on high-resolution optical images obtained with the Hubble Space Telescope, we study the correlation between black hole mass and bulge luminosity and the (Kormendy) relation between bulge effective radius and surface brightness. In both relations, the bulges of type 1 AGNs tend to be more luminous than those of inactive galaxies with the same black hole mass or the same bulge size. This suggests that the central regions of AGN host galaxies have characteristically lower mass-to-light ratios than inactive galaxies, most likely due to the presence of a younger stellar population in active systems. In addition, the degree of luminosity excess appears to be proportional to the accretion rate of the AGN, revealing a physical connection between stellar growth and black hole growth. Adopting a simple toy model for the increase of stellar mass and black hole mass, we show that the fraction of young stellar population flattens out toward high accretion rates, possibly reflecting the influence of AGN-driven feedback.