Chandra and XMM Observations of Type II Quasars from the SDSS

TL;DR

This study uses Chandra and XMM to observe type II quasars from SDSS, revealing high absorption levels and flat spectra, indicating obscured active galactic nuclei with potential Compton-thick characteristics.

Contribution

First X-ray spectral analysis of SDSS-selected type II quasars, demonstrating significant absorption and providing insights into their obscuration properties.

Findings

Most quasars show high intrinsic absorption (N_H > 10^22 cm^-2).

Several objects are likely Compton-thick with N_H > 10^24 cm^-2.

Spectral slopes tend to be flatter than typical AGN spectra.

Abstract

We are carrying out sensitive X-ray observations with Chandra and XMM of type II quasars selected from the Sloan Digital Sky Survey based on their optical emission line properties. We present observations of four objects at redshifts 0.4 < z < 0.8 and an analysis of the archival data for four additional objects in the same redshift range. Six of the eight were detected in X-rays; five of them have sufficient signal to derive spectral information. All of the detected sources have intrinsic luminosities L(2-10 keV) > 5 x 10^43 erg s^-1. The five with sufficient counts for spectral fitting show evidence for significant absorption (N_H >~ a few x 10^22 cm^-2). At least three of the objects likely have N_H > 10^23 cm^-2; some may be Compton-thick (N_H > 10^{24} cm^-2). In the five objects for which we could fit spectra, the slopes tend to be significantly flatter than is typically observed in AGN; it is possible that this is due either to reprocessing of the nuclear emission or to a line of sight that passes through patchy absorption.