The HELLAS2XMM Survey. XII. The infrared/sub-millimeter view of an X-ray selected Type 2 quasar at z=2

TL;DR

This study provides a detailed multi-wavelength analysis of a high-redshift, X-ray luminous Type 2 quasar, revealing its complex structure, intense star formation, and obscured AGN activity, suggesting it is in a transitional evolutionary phase.

Contribution

First detailed multi-wavelength modeling of an X-ray selected Type 2 quasar at z~2, combining optical, IR, and sub-millimeter data to understand its structure and star formation.

Findings

Star formation rate of about 1500 solar masses per year.

Obscured quasar with a dusty torus and intense starburst activity.

Likely in a transitional phase before expelling obscuring gas.

Abstract

We present multi-wavelength observations (from optical to sub-millimeter, including Spitzer and SCUBA) of H2XMMJ 003357.2-120038 (also GD158_19), an X-ray selected, luminous narrow-line (Type 2) quasar at z=1.957 selected from the HELLAS2XMM survey. Its broad-band properties can be reasonably well modeled assuming three components: a stellar component to account for the optical and near-IR emission, an AGN component (i.e., dust heated by an accreting active nucleus), dominant in the mid-IR, with an optical depth at 9.7 micron along the line of sight (close to the equatorial plane of the obscuring matter) of tau(9.7)=1 and a full covering angle of the reprocessing matter (torus) of 140 degrees, and a far-IR starburst component (i.e., dust heated by star formation) to reproduce the wide bump observed longward of 70 micron. The derived star-formation rate is about 1500 solar masses per year. The overall modeling indicates that GD158_19 is a high-redshift X-ray luminous, obscured quasar with coeval powerful AGN activity and intense star formation. It is probably caught before the process of expelling the obscuring gas has started, thus quenching the star formation.