Witnessing the key early phase of quasar evolution: an obscured AGN pair in the interacting galaxy IRAS 20210+1121

TL;DR

This paper reports the discovery of an obscured AGN pair in the interacting galaxy system IRAS 20210+1121, providing insight into early quasar evolution during galaxy collisions.

Contribution

It presents the first detailed X-ray analysis of an obscured AGN pair in an interacting galaxy system, highlighting a key early phase in quasar activation.

Findings

Discovery of an obscured Seyfert-like nucleus in the northern galaxy.

Identification of a Type 2 quasar embedded in starburst emission in the southern galaxy.

Evidence of a Compton-Thick absorber indicating an early quasar evolutionary stage.

Abstract

We report the discovery of an active galactic nucleus (AGN) pair in the interacting galaxy system IRAS 20210+1121 at z = 0.056. An XMM-Newton observation reveals the presence of an obscured (Nh ~ 5 x 10^{23} cm^-2), Seyfert-like (L_{2-10 keV} = 4.7 x 10^{42} erg/s) nucleus in the northern galaxy, which lacks unambiguous optical AGN signatures. Our spectral analysis also provides strong evidence that the IR-luminous southern galaxy hosts a Type 2 quasar embedded in a bright starburst emission. In particular, the X-ray primary continuum from the nucleus appears totally depressed in the XMM-Newton band as expected in case of a Compton-Thick absorber, and only the emission produced by Compton scattering ('reflection') of the continuum from circumnuclear matter is seen. As such, IRAS 20210+1121 seems to provide an excellent opportunity to witness a key, early phase in the quasar evolution predicted by the theoretical models of quasar activation by galaxy collisions.