VLT and GTC observations of SDSS J0123+00: a type 2 quasar triggered in a galaxy encounter?

TL;DR

This study reports the discovery of an extensive ionized nebula around a type 2 quasar, likely triggered by a galaxy encounter, challenging previous assumptions about such nebulae's association with radio luminosity.

Contribution

It provides the first detailed imaging and spectroscopy of a giant ionized nebula around a low-radio-luminosity type 2 quasar, linking it to galactic interactions.

Findings

The nebula extends up to 180 kpc, one of the largest around active galaxies.

The quasar is in a gas-rich, interacting environment with a tidal bridge.

Ionized gas is detected at least 133 kpc from the nucleus.

Abstract

We present long-slit spectroscopy, continuum and [OIII]5007 imaging data obtained with the Very Large Telescope and the Gran Telescopio Canarias of the type 2 quasar SDSS J0123+00 at z=0.399. The quasar lies in a complex, gas-rich environment. It appears to be physically connected by a tidal bridge to another galaxy at a projected distance of ~100 kpc, which suggests this is an interacting system. Ionized gas is detected to a distance of at least ~133 kpc from the nucleus. The nebula has a total extension of ~180 kpc. This is one of the largest ionized nebulae ever detected associated with an active galaxy. Based on the environmental properties, we propose that the origin of the nebula is tidal debris from a galactic encounter, which could as well be the triggering mechanism of the nuclear activity. SDSS J0123+00 demonstrates that giant, luminous ionized nebulae can exist associated with type 2 quasars of low radio luminosities, contrary to expectations based on type 1 quasar studies.