The diverse cold molecular gas contents, morphologies, and kinematics of type-2 quasars as seen by ALMA

Abstract

We present CO(2−1) and adjacent continuum observations of seven nearby radio-quiet type-2 quasars (QSO2s) obtained with ALMA at ∼0.2″ resolution (370 pc at z ∼ 0.1). These QSO2s are luminous (L[OIII] > 108.5 L⊙ ∼ MB < −23), and their host galaxies massive (M* ∼ 1011 M⊙). The CO morphologies are diverse, including disks and interacting systems. Two of the QSO2s are red early-type galaxies with no CO(2–1) detected. In the interacting galaxies, the central kiloparsec contains 18–25% of the total cold molecular gas, whereas in the spirals it is only ∼5–12%. J1010+0612 and J1430+1339 show double-peaked CO flux maps along the major axis of the CO disks that do not have an optical counterpart at the same angular resolution. Based on our analysis of the ionized and molecular gas kinematics and millimeter continuum emission, these CO morphologies are most likely produced by active galactic nucleus (AGN) feedback in the form of outflows, jets, and/or shocks. The CO kinematics of the QSO2s with CO(2−1) detections are dominated by rotation but also reveal noncircular motions. According to our analysis, these noncircular motions correspond to molecular outflows that are mostly coplanar with the CO disks in four of the QSO2s, and either to a coplanar inflow or vertical outflow in the case of J1010+0612. These outflows represent 0.2–0.7% of the QSO2s’ total molecular gas mass and have maximum velocities of 200–350 km s−1, radii from 0.4 to 1.3 kpc, and outflow mass rates of 8–16 M⊙ yr−1. These outflow properties are intermediate between those of the mild molecular outflows measured for Seyfert galaxies and the fast and energetic outflows shown by ultra-luminous infrared galaxies. This suggests that it is not only AGN luminosity that drives massive molecular outflows. Other factors such as jet power, coupling between winds, jets, and/or ionized outflows and the CO disks, and amount or geometry of dense gas in the nuclear regions might also be relevant. Thus, although we do not find evidence for a significant impact of quasar feedback on the total molecular gas reservoirs and star formation rates, it appears to be modifying the distribution of cold molecular gas in the central kiloparsec of the galaxies.

Warm molecular and ionized gas kinematics in the type-2 quasar J0945+1737

“…They were measured from SED fitting, using different templates, including the AGN contribution, and the "Code Investigating GALaxy Emission" (CIGALE 2 . This stellar mass is much lower than that estimated from the K-band magnitude of the QSO2, of M ≈ 10 11.0 M (see Ramos Almeida et al 2022 for details on the stellar mass determination 3 ). Despite the large uncertainties (∼0.3 dex in the case of the SED fitting value and ∼0.2 dex in the case of the Kband value), this might be indicative of either an overestimation of the AGN component in the SED fit or a strong AGN contribution to the K-band flux.…”

“…Other factors that could contribute to launch warm molecular outflows might be the geometry of the ionized outflows and/or jets, and jet power (Ramos Almeida et al 2022). Molecular gas tends to be distributed in discs, with the warm molecular gas having larger velocity dispersion (Hönig 2019).…”

“…Other factors that could contribute to launch warm molecular outflows might be the geometry of the ionized outflows and (or) jets, and jet power (Ramos Almeida et al 2022). Molecular gas…”

“…This molecular gas is more likely to be entrained by the jets-ionized winds when the latter are coplanar with them, than when they subtend a larger angle (see Fig. 4 in Ramos Almeida et al 2022). Detailed studies of the multi-phase outflow geometries are needed to tackle this complex parameter space.…”

“…For example, ionized outflows reach higher velocities than the warm molecular outflowing gas. In addition, there are cases, like the Teacup (Ramos Almeida et al 2017), in which the warm molecular outflow is not detected, unlike its cold molecular counterpart (Ramos Almeida et al 2022). This likely happens because the bulk of the warm molecular gas is usually following circular rotation in the galaxy plane, whereas ionized gas is more easily disrupted, leaving the galaxy plane and showing non-circular motions (see e.g., Riffel et al 2021 and references therein).…”