Soft X-ray properties of Ultraluminous IRAS Galaxies

TL;DR

This study analyzes the soft X-ray properties of 323 ULIRGs using ROSAT data, revealing detection rates, flux measurements, and insights into starburst and AGN contributions through X-ray and infrared comparisons.

Contribution

It provides the first comprehensive correlation of a large ULIRG sample with ROSAT data, including detection analysis and flux estimation methods.

Findings

22 ULIRGs detected in ROSAT survey observations

6 ULIRGs additionally detected in pointed observations

X-ray to infrared flux ratios used to distinguish starburst and AGN activity

Abstract

A sample of 323 Ultraluminous IRAS galaxies (ULIRGs) has been correlated with the ROSAT All-Sky Survey and ROSAT public pointed observations. 22 objects are detected in ROSAT survey observations, and 6 ULIRGs are detected in addition in ROSAT public pointed observations. The detection is based on a visual inspection of the X-ray contour maps overlaid on optical images of ULIRGs taken from the Digitized Sky Survey. Simple power law fits were used to compute the absorption-corrected fluxes of the ROSAT detected ULIRGs. The ratio of the soft X-ray flux to the far-infrared luminosity is used to estimate the contribution from starburst and AGN emitting processes. These results are compared with the ISO SWS ULIRG diagnostic diagram.