QSOFEED: Investigating warm molecular, low- and high-ionization atomic gas in six type-2 quasars with GTC/EMIR

TL;DR

This study uses near-infrared spectroscopy to analyze ionized and molecular gas outflows in six nearby type-2 quasars, revealing detailed kinematics and mass estimates, and comparing different gas phases.

Contribution

First detailed near-infrared spectroscopic analysis of ionized and warm molecular gas outflows in six type-2 quasars, providing insights into their properties and differences.

Findings

Ionized outflows have FWHM of 1200-2500 km/s.

Mass outflow rates range from 0.03 to 6 solar masses per year.

Warm molecular gas masses are similar to other QSO2s, but no molecular outflows detected.

Abstract

We present long-slit near-infrared spectroscopic observations of six nearby (z$\sim$0.1) radio-quiet type-2 quasars (QSO2s) from the Quasar Feedback (QSOFEED) sample. They have bolometric luminosities of $10^{45-46}~erg~s^{-1}$ and stellar masses of $ 10^{10.6-11.3}~M_{\odot}$. The observations were obtained with the instrument Espectr\'ografo Multiobjeto Infra-Rojo (EMIR) on the 10.4 m Gran Telescopio Canarias. The nuclear K-band spectra (central $\sim$1-3 kpc of the QSO2s) reveal signatures of high-velocity outflows in either the Pa$\alpha$ or Br$\gamma$ lines, depending on the redshift, and in the [Si VI] lines. The broadest kinematic components have full width at half maximum (FWHM) of $\sim$1200-2500 km $s^{-1}$. From the near-infrared hydrogen recombination lines we derived ionized outflow masses of $M_{Hion} \sim0.08-20\times 10^{6}~M_{\odot}$, mass outflow rates of $\dot{M}_{Hion}\sim0.03-6~M_{\odot}~yr^{-1}$, and kinetic powers of $\dot{E}_{Hion}\sim 10^{37.8-40.8}~erg~s^{-1}$. These ionized gas outflow masses and mass outflow rates have median values that are 5.9 and 5.8 times larger, respectively, than those derived from the [Si VI] line. Our study provides evidence, at least for these six QSO2s, that the near-infrared recombination lines and [Si VI] are tracing the same outflow (i.e., they have similar kinematics and radii), but they carry different amounts of mass. We detected warm molecular lines in the six QSO2s, from which we measured total (nuclear) gas masses from 1.1 (0.7) to 32 (13) $\times~10^3~M_{\odot}$, similar to other QSO2s with warm $H_2$ measurements reported in the literature, but we did not find any molecular outflow associated with them. Comparing with other five QSO2s with $H_2$ measurements reported in the literature, we find that the four QSO2s with detected $H_2$ outflows have total (nuclear) $H_2$ masses 2.2 (2.7) times larger, on average.