A comparative study of the physical properties for a representative sample of Narrow and Broad-line Seyfert galaxies

TL;DR

This study compares the physical properties of Narrow and Broad-line Seyfert 1 galaxies, revealing differences in outflow signatures and challenging the idea that NLSy1 are just a subclass of BLSy1 galaxies, using SDSS, XMM-Newton, and ROSAT data.

Contribution

It provides a comprehensive comparative analysis of NLSy1 and BLSy1 galaxies using spectral data and PCA, highlighting differences in outflow features and physical parameter spaces.

Findings

NLSy1 galaxies show three times higher outflow signatures than BLSy1.

High iron content and Eddington ratios may drive outflow differences.

NLSy1 and BLSy1 occupy distinct parameter spaces, questioning their subclass relationship.

Abstract

We present a comparative study of the physical properties of a homogeneous sample of 144 Narrow line Seyfert 1 (NLSy1) and 117 Broad-line Seyfert 1 (BLSy1) galaxies. These two samples are in a similar luminosity and redshift range and have optical spectra available in the 16$^{th}$ data release of Sloan Digital Sky Survey (SDSS-DR16) and X-ray spectra in either XMM-NEWTON or ROSAT. Direct correlation analysis and a Principal Component Analysis (PCA) have been performed using ten observational and physical parameters obtained by fitting the optical spectra and the soft X-ray photon indices as another parameter. We confirm that the established correlations for the general quasar population hold for both types of galaxies in this sample despite significant differences in the physical properties. We characterize the sample also using the line shape parameters, namely the asymmetry and kurtosis indices. We find that the fraction of NLSy1 galaxies showing outflow signatures, characterized by blue asymmetries, is higher by a factor of about 3 compared to the corresponding fraction in BLSy1 galaxies. The presence of high iron content in the broad-line region of NLSy1 galaxies in conjunction with higher Eddington ratios can be the possible reason behind this phenomenon. We also explore the possibility of using asymmetry in the emission lines as a tracer of outflows in the inner regions of Active Galactic Nuclei. The PCA results point to the NLSy1 and BLSy1 galaxies occupying different parameter spaces, which challenges the notion that NLSy1 galaxies are a subclass of BLSy1 galaxies.