A hard look at local, optically-selected, obscured Seyfert galaxies

TL;DR

This study analyzes the X-ray spectra of 19 obscured Seyfert galaxies using multiple telescopes, revealing high obscuration levels and correlations that support radiation pressure as a key factor in circumnuclear material distribution.

Contribution

First comprehensive X-ray spectral analysis of a local, optically-selected obscured Seyfert sample using multiple models and telescopes.

Findings

79-90% of sources are heavily obscured with N_H > 10^23 cm^-2

37-53% are Compton-thick with N_H > 10^24 cm^-2

Reprocessed emission fraction correlates with N_H and anti-correlates with luminosity

Abstract

We study the X-ray spectra of a sample of 19 obscured, optically-selected Seyfert galaxies (Sy 1.8, 1.9 and 2) in the local universe ($d \leq 175$~Mpc), drawn from the CfA Seyfert sample. Our analysis is driven by the high sensitivity of NuSTAR in the hard X-rays, coupled with soft X-ray spectra using XMM-Newton, Chandra, Suzaku, and Swift/XRT. We also analyze the optical spectra of these sources in order to obtain accurate mass estimates and Eddington fractions. We employ four different models to analyze the X-ray spectra of these sources, which all result in consistent results. We find that 79-90 % of the sources are heavily obscured with line-of-sight column density $N_{\rm H} > 10^{23}~\rm cm^{-2}$. We also find a Compton-thick ($N_{\rm H} > 10^{24}~\rm cm^{-2}$) fraction of $37-53$ %. These results are consistent with previous estimates based on multi-wavelength analyses. We find that the fraction of reprocessed to intrinsic emission is positively correlated with $N_{\rm H}$ and negatively correlated with the intrinsic, unabsorbed, X-ray luminosity (in agreement with the Iwasawa-Taniguchi effect). Our results support the hypothesis that radiation pressure regulates the distribution of the circumnuclear material.