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

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.

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

This paper presents a comprehensive study on gamma-ray emitting narrow-line Seyfert 1 (NLSy1) galaxies, specifically focusing on their detection and properties, as revealed using data from the Sloan Digital Sky Survey (SDSS) and the Fermi-LAT. The research reports, for the first time, significant gamma-ray emission from four active galactic nuclei (AGN) recently classified as NLSy1 based on their optical spectra from SDSS. Additionally, it reclassifies three flat spectrum radio quasars (FSRQs) from the third Large Area Telescope AGN catalog (3LAC) as gamma-ray emitting NLSy1 (γ-NLSy1) galaxies.

The key findings of this research illustrate that γ-NLSy1 galaxies share spectral similarities with FSRQs but possess relatively low gamma-ray luminosities, in the range of (10^{46-47} \text{erg s}^{-1}). In the WISE color-color diagram, these γ-NLSy1 sources occupy regions typically dominated by FSRQs. Furthermore, the paper highlights that γ-NLSy1 galaxies have, on average, smaller black hole masses compared to FSRQs at similar redshifts, aligning with the idea that they could be low mass analogs of these quasars.

The analysis outlines a systematic methodology of identifying radio-loud NLSy1 galaxies in gamma-ray data by cross-matching with the NRAO VLA Sky Survey (NVSS) for radio detection and employing LAT data to confirm gamma-ray emission. This approach led to the identification of several new γ-NLSy1 sources, contributing significantly to the sample size previously limited in number.

The implications of the study are manifold. From a theoretical perspective, the similarities between γ-NLSy1 and FSRQs challenge traditional views on the environments and conditions under which relativistic jets can form. Typically, NLSy1s hosting these jets are thought to reside in spiral galaxies rather than the ellipticals commonly hosting FSRQs, presenting a paradox resolved through this evidence of γ-NLSy1s being lower black hole mass counterparts of FSRQs. Practically, the research enriches our understanding of AGN demographics, enabling refined models of jet formation and development across different galaxy morphologies and mass ranges.

Finally, the findings open avenues for further investigation into the unique astrochemical environments and the evolutionary pathways of these AGNs by suggesting a future focus on high-resolution imaging to ascertain host galaxy properties. The study heralds the possibility of discovering more such γ-NLSy1 sources as gamma-ray surveys become more comprehensive, thereby continuously expanding our perception of jet physics and AGN categorization.