A High Resolution View of the Warm Absorber in the Quasar MR2251-178

TL;DR

This study provides a detailed high-resolution X-ray spectral analysis of the warm absorber in quasar MR2251-178, revealing multiple ionization components, variable absorption features, broad emission lines, and a highly ionized outflow, enhancing understanding of quasar outflows.

Contribution

First high-resolution spectral analysis of MR2251-178's warm absorber revealing multiple components, variability, and outflow characteristics, with implications for quasar outflow models.

Findings

Detected at least 3 warm absorbing components with different ionization levels.

Observed variability in the lowest ionization absorber between observations.

Confirmed presence of a highly ionized outflow with velocity ~-15600 km/s.

Abstract

High resolution X-ray spectroscopy of the warm absorber in the nearby quasar, MR2251-178 (z = 0.06398) is presented. The observations were carried out in 2011 using the Chandra High Energy Transmission Grating and the XMM-Newton Reflection Grating Spectrometer, with net exposure times of approximately 400 ks each. A multitude of absorption lines from C to Fe are detected, revealing at least 3 warm absorbing components ranging in ionization parameter from log(\xi/erg cm s^-1) = 1-3 and with outflow velocities < 500 km/s. The lowest ionization absorber appears to vary between the Chandra and XMM-Newton observations, which implies a radial distance of between 9-17 pc from the black hole. Several broad soft X-ray emission lines are strongly detected, most notably from He-like Oxygen, with FWHM velocity widths of up to 10000 km/s, consistent with an origin from Broad Line Region (BLR) clouds. In addition to the warm absorber, gas partially covering the line of sight to the quasar appears to be present, of typical column density N_H = 10^23 cm^-2. We suggest that the partial covering absorber may arise from the same BLR clouds responsible for the broad soft X-ray emission lines. Finally the presence of a highly ionised outflow in the iron K band from both 2002 and 2011 Chandra HETG observations appears to be confirmed, which has an outflow velocity of -15600 \pm 2400 km/s. However a partial covering origin for the iron K absorption cannot be excluded, resulting from low ionization material with little or no outflow velocity.