The Swift BAT-detected Seyfert 1 Galaxies: X-ray Broadband Properties and Warm Absorbers

TL;DR

This study analyzes the broad-band X-ray spectra of 48 Seyfert 1-1.5 galaxies detected by Swift BAT, revealing properties of warm absorbers, soft excess, and reflection features, and providing insights into their ionized outflows and luminosities.

Contribution

It offers a uniform analysis of the X-ray properties of a largely unbiased Seyfert galaxy sample, including detection of warm absorbers and a correction method for luminosity estimates.

Findings

Over half of the sample shows O VII and O VIII edges, indicating warm absorbers.

Sources with strong absorption often exhibit a soft excess and flat photon index.

Ionized column densities are clustered around 10^{21} cm^{-2}, with weaker detections likely indicating low-density outflows.

Abstract

We present results from an analysis of the broad-band, 0.3-195 keV, X-ray spectra of 48 Seyfert 1-1.5 sources detected in the very hard X-rays with the Swift Burst Alert Telescope (BAT). This sample is selected in an all-sky survey conducted in the 14-195 keV band. Therefore, our sources are largely unbiased towards both obscuration and host galaxy properties. Our detailed and uniform model fits to Suzaku/BAT and XMM-Newton/BAT spectra include the neutral absorption, direct power-law, reflected emission, soft excess, warm absorption, and narrow Fe K-alpha emission properties for the entire sample. We significantly detect O VII and O VIII edges in 52% of our sample. The strength of these detections are strongly correlated with the neutral column density measured in the spectrum. Among the strongest detections, X-ray grating and UV observations, where available, indicate outflowing material. The ionized column densities of sources with O VII and O VIII detections are clustered in a narrow range with N$_{\rm warm} \sim 10^{21}$\,cm$^{-2}$, while sources without strong detections have column densities of ionized gas an order of magnitude lower. Therefore, we note that sources without strong detections likely have warm ionized outflows present but at low column densities that are not easily probed with current X-ray observations. Sources with strong complex absorption have a strong soft excess, which may or may not be due to difficulties in modeling the complex spectra of these sources. Still, the detection of a flat Gamma ~ 1 and a strong soft excess may allow us to infer the presence of strong absorption in low signal-to-noise AGN spectra. Additionally, we include a useful correction from the Swift BAT luminosity to bolometric luminosity, based on a comparison of our spectral fitting results with published spectral energy distribution fits from 33 of our sources.