High molecular gas content and star formation rates in local galaxies that host quasars, outflows and jets

TL;DR

This study investigates the molecular gas content and star formation in local quasars with outflows and jets, finding that these active galaxies maintain large gas reservoirs and high star formation rates despite energetic feedback mechanisms.

Contribution

It provides new observational evidence that quasars with outflows and jets do not significantly deplete their molecular gas reservoirs or suppress star formation.

Findings

Most quasars are in starburst galaxies with large molecular gas reservoirs.

Molecular gas fractions and depletion times are similar to non-active galaxies.

CO excitation is dominated by star formation, not AGN activity.

Abstract

We use a sample of powerful z~0.1 type 2 quasars ('obscured'; log[L(AGN)/erg/s]>~45), which host kiloparsec-scale ionized outflows and jets, to identify possible signatures of AGN feedback on the total molecular gas reservoirs of their host galaxies. Specifically, we present Atacama Pathfinder EXperiment (APEX) observations of the CO(2-1) transition for nine sources and the CO(6-5) for a subset of three. We find that the majority of our sample reside in starburst galaxies (average specific star formation rates of 1.7/Gyr), with the seven CO-detected quasars also having large molecular gas reservoirs (average Mgas = 1.3x10^10Msun), even though we had no pre-selection on the star formation or molecular gas properties. Despite the presence of quasars and outflows, we find that the molecular gas fractions (Mgas/Mstar = 0.1-1.2) and depletion times (Mgas/SFR = 0.16-0.95Gyr) are consistent with those expected for the overall galaxy population with matched stellar masses and specific star formation rates. Furthermore, for at least two of the three targets with the required measurements, the CO(6-5)/CO(2-1) emission-line ratios are consistent with star formation dominating the CO excitation over this range of transitions. The targets in our study represent a gas-rich phase of galaxy evolution with simultaneously high levels of star formation and nuclear activity; furthermore, the jets and outflows do not have an immediate appreciable impact on the global molecular gas reservoirs.