Ionized outflows in SDSS type 2 quasars at z~0.3-0.6

TL;DR

This study investigates ionized gas outflows in SDSS type 2 quasars at z~0.3-0.6, revealing prevalent outflows characterized by blue asymmetries and broad line components, indicating common outflow phenomena in these quasars.

Contribution

It provides the first detailed analysis of ionized gas kinematics in a sample of type 2 quasars at intermediate redshift, highlighting the ubiquity of outflows and their spectral signatures.

Findings

Blue asymmetries dominate in [OIII] lines, indicating outflows.

Highly perturbed gas shows broad lines and blueshifts, consistent with outflowing gas.

Ionized gas outflows are common in optically selected type 2 quasars at z~0.3-0.6.

Abstract

We have analyzed the spatially integrated kinematic properties of the ionized gas within the inner r<few kpc in 13 optically selected SDSS type 2 quasars at z~0.3-0.6, using the [OIII]4959,5007 lines. The line profiles show a significant asymmetry in 11 objects. There is a clear preference for blue asymmetries, which are found in 9/13 quasars at 10% intensity level. In coherence with studies on other types of active and non active galaxies, we propose that the asymmetries are produced by outflows where differential dust extinction is at work. This scenario is favoured by other results we find: in addition to quiescent ambient gas, whose kinematic properties are consistent with gravitational motions, we have discovered highly perturbed gas in all objects. This gas emits very broad lines (R=FWHM[OIII]/FWHM(stars)>~2). While the quiescent gas shows small or null velocity shifts relative to the systemic velocity, the highly perturbed gas trends to show larger shifts which, moreover, are blueshifts in general. Within a given object, the most perturbed gas trends to have the largest blueshift as well. All together support that the perturbed gas, which is responsible for the blue asymmetries of the line profiles, is outflowing. Although some bias affects the sample, we argue that ionized gas outflows are a common phenomenon in optically selected type 2 quasars at 0.3< z < 0.6.