X-shooter reveals powerful outflows in z~1.5 X-ray selected obscured quasi stellar objects

TL;DR

This study uses X-shooter observations to identify powerful outflows in z~1.5 X-ray obscured quasars, revealing broad [OIII] emission lines indicative of AGN-driven winds in transitioning galaxy systems.

Contribution

The paper demonstrates the effectiveness of X-shooter in accurately determining redshifts and detecting high-velocity outflows in obscured QSOs, highlighting their AGN-driven nature.

Findings

Detection of broad, shifted [OIII] components in 6 out of 8 sources.

Outflow velocities exceeding 1000 km/s, indicative of AGN activity.

Outflow energetics consistent with AGN-driven winds rather than stellar processes.

Abstract

We present X-shooter at the Vewry Large Telescope observations of a sample of 10 luminous, X-ray obscured QSOs at z$\sim1.5$ from the XMM-COSMOS survey, expected to be caught in the transitioning phase from starburst to active galactic nucleus (AGN)-dominated systems. The main selection criterion is X-ray detection at bright fluxes (L$>=10^{44}$ erg s$^{-1}$) coupled to red optical-to-NIR-to-MIR colors. Thanks to its large wavelength coverage, X-shooter allowed us to determine accurate redshifts from the presence of multiple emission lines for five out of six targets for which we had only a photometric redshift estimate, with an 80 percent success rate, significantly larger than what is observed in similar programs of spectroscopic follow-up of red QSOs. We report the detection of broad and shifted components in the [OIII]$\lambda\lambda$5007,4959 complexes for six out of eight sources with these lines observable in regions free from strong atmospheric absorptions. The full width half-maximum (FWHM) associated with the broad components are in the range FWHM$\sim900-1600$ km s$^{-1}$, larger than the average value observed in SDSS Type 2 AGN samples at similar observed [OIII] luminosity, but comparable to those observed for QSO/ultraluminous infrared galaxies systems for which the presence of kpc scale outflows have been revealed through integral field unit spectroscopy. Although the total outflow energetics (inferred under reasonable assumptions) may be consistent with winds accelerated by stellar processes, we favour an AGN origin for the outflows given the high outflow velocities oberved (v$>1000$ km s$^{-1}$) and the presence of strong winds also in objects undetected in the far infrared.