The location of an active nucleus and the soft X-ray shadowing by a tidal tail in the ULIRG Mrk 273

TL;DR

This study uses Chandra X-ray data to locate the active nucleus in ULIRG Mrk 273, revealing a hard X-ray source in the southwest nucleus and soft X-ray shadowing by a tidal tail, indicating complex nuclear and large-scale structures.

Contribution

It identifies the precise location of the active nucleus and demonstrates soft X-ray shadowing by a tidal tail, providing new insights into the structure of Mrk 273.

Findings

Active nucleus located in southwest nucleus

Tidal tail causes soft X-ray shadowing

Estimated cold gas column density in tidal tail

Abstract

Analysis of data from the Chandra X-ray Observatory for the double nucleus ULIRG Mrk 273 reveals an absorbed hard X-ray source coincident with the southwest nucleus, implying that this unresolved near infrared source is where an active nucleus resides while the northern nuclear region contains a powerful starburst which dominates the far infrared luminosity. There is evidence of a slight image extension in the 6-7 keV band, where a Fe K line is present, towards the northern nucleus. A large-scale, diffuse emission nebula detected in soft X-rays contains a dark lane that spatially coincides with a high surface-brightness tidal tail extending ~50 arcsec (40 kpc) to the south. The soft X-ray source is likely located behind the tidal tail which absorbs X-ray photons along the line of sight. The estimated column density of cold gas in the tidal tail responsible for shadowing the soft X-rays is nH >= 6e+21 cm-2, consistent with the tidal tail having an edge-on orientation.