Gamma-ray Emitting Narrow Line Seyfert 1 Galaxies in The Sloan Digital Sky Survey

TL;DR

This study reports the first detection of gamma-ray emission from four narrow line Seyfert 1 galaxies, revealing their similarities to flat spectrum radio quasars but with lower black hole masses, expanding understanding of jet phenomena in different AGN environments.

Contribution

First identification of gamma-ray emission from four NLSy1 galaxies, linking their properties to FSRQs and suggesting they are low black hole mass counterparts.

Findings

Gamma-ray emission detected in four NLSy1 galaxies.

Gamma-ray properties similar to FSRQs but with lower luminosity.

NLSy1 galaxies have smaller black hole masses than FSRQs.

Abstract

The detection of significant $\gamma$-ray emission from radio-loud narrow line Seyfert 1 (NLSy1s) galaxies enables us to study jets in environments different than those in blazars. However, due to the small number of known $\gamma$-ray emitting NLSy1 ($\gamma$-NLSy1) galaxies, a comprehensive study could not be performed. Here we report the first detection of significant $\gamma$-ray emission from four active galactic nuclei (AGN), recently classified as NLSy1 from their Sloan Digital Sky Survey (SDSS) optical spectrum. Three flat spectrum radio quasars (FSRQs) present in the third Large Area Telescope AGN catalog (3LAC) are also found as $\gamma$-NLSy1 galaxies. Comparing the $\gamma$-ray properties of these objects with 3LAC blazars reveals their spectral shapes to be similar to FSRQs, however, with low $\gamma$-ray luminosity ($\lesssim10^{46-47}$ erg s$^{-1}$). In the Wide-field Infrared Survey Explorer color-color diagram, these objects occupy a region mainly populated by FSRQs. Using the H$_{\beta}$ emission line parameters, we find that on average $\gamma$-NLSy1 have smaller black hole masses than FSRQs at similar redshifts. In the low-resolution SDSS image of one of the $\gamma$-NLSy1 source, we find the evidence of an extended structure. We conclude by noting that overall many observational properties of $\gamma$-NLSy1 sources are similar to FSRQs and therefore, these objects could be their low black hole mass counterparts, as predicted in the literature.