Probing the stellar population of seyfert galaxies: a near infrared perspective

TL;DR

This study uses near-infrared spectra to analyze stellar populations, AGN, and dust in Seyfert galaxies, revealing differences between Sy1 and Sy2 types and indicating recent star formation activity.

Contribution

First application of the { extsc starlight} code with hot dust component in NIR spectra of Seyfert galaxies, highlighting differences in stellar and dust properties between Sy1 and Sy2.

Findings

Hot dust is prevalent in ~90% of Sy1 but only 25% of Sy2 galaxies.

A significant fraction of Sy1 galaxies show recent star formation indicators.

Intermediate-age stellar populations dominate the central regions of the sample.

Abstract

We employ IRTF SpeX NIR (0.8--2.4mu m) spectra to investigate the stellar population (SP), active galactic nuclei (AGN), featureless continuum (FC) and hot dust properties in 9 Sy1 and 15 Sy2 galaxies. Both the {\sc starlight} code and the hot dust as an additional base element were used for the first time in this spectral range. Our synthesis shows significant differences between Sy1 and Sy2 galaxies: the hot dust component is required to fit the K-band spectra of ~90% of the Sy1 galaxies, and only of ~25% of the Sy2; about 50% of the Sy2 galaxies require an FC component contribution >20%; this fraction increases to about 60% in the Sy1. In about 50% of the Sy2, the combined FC and young components contribute with more than 20%, while this occurs in 90% of the Sy1, suggesting recent star formation in the central region. The central few hundred parsecs of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1microns CN band can be used as a tracer of intermediate-age stellar populations.