Near-infrared morphologies of the host galaxies of narrow-line Seyfert 1 galaxies

TL;DR

This study uses near-infrared imaging to analyze the host galaxy morphologies of nine narrow-line Seyfert 1 galaxies, revealing diverse structures and interactions that influence their nuclear activity and evolution.

Contribution

It provides the first detailed morphological analysis of NLS1 host galaxies using NIR imaging, highlighting the prevalence of pseudo-bulges, bars, and interactions in these galaxies.

Findings

All modeled host galaxies are disk-like.

Most hosts have pseudo-bulges and bars.

A significant fraction show signs of interactions.

Abstract

We present $J$-band near-infrared (NIR) imaging of the host galaxies of nine narrow-line Seyfert 1 galaxies (NLS1). Based on high-frequency radio observations at 37~GHz, seven of them could host powerful, most likely relativistic jets. Host galaxy morphology studies of NLS1 galaxies are scarce, but exceedingly important for understanding the seemingly heterogeneous nature of the NLS1 population as well as their evolution and place in the active galactic nuclei (AGN) scheme. Increasing the sample size is essential for achieving statistically significant results. We determine the morphological types of the host galaxies by performing photometric decomposition of NIR images using a 2D image decomposition algorithm GALFIT. We were able to sufficiently model five of the nine host galaxies. Based on the fitting parameters, mainly the S\'{e}rsic index, all of them are disk-like galaxies. Sources with clearly distinguishable bulge components all have pseudo-bulges, and four out of five sources show a component resembling a bar. A surprisingly large fraction, three out of five, show signs of interaction or disturbed morphology. Our results suggest that spiral galaxies with pseudo-bulges are able to launch and maintain powerful jets. They also imply that interaction - mainly minor mergers - may have a role in initially triggering higher levels of nuclear activity in NLS1 galaxies. Furthermore, our results support the heterogeneous nature of the NLS1 class and indicate that this diversity is caused by different evolutionary stages, possibly due to mergers.