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

M E Jarvis,G Calistro Rivera,C De Breuck,Z-Y Zhang,V Mainieri,D M Alexander,A P Thomson,C Circosta,T Costa,G B Lansbury,P Jethwa,C M Harrison,D Kakkad,P Kharb

doi:10.1093/mnras/staa2196

Abstract

ABSTRACT We use a sample of powerful $z\, \approx \, 0.1$ type 2 quasars (‘obscured’; log [LAGN/erg s$^{-1}]\, \gtrsim \, 45$), which host kpc-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 – sSFR – of 1.7 Gyr−1), with the seven CO-detected quasars also having large molecular gas reservoirs (average Mgas = 1.3 × 1010 M⊙), 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/M⋆ = 0.1–1.2) and depletion times (Mgas/SFR = 0.16–0.95 Gyr) are consistent with those expected for the overall galaxy population with matched stellar masses and sSFRs. 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.

Highlights

The energy from accreting supermassive black holes is widely accepted to be responsible for the global quenching of star formation in massive galaxies (AGN feedback; e.g. see reviews in Alexander & Hickox 2012; Fabian 2012; Harrison 2017)
The values derived from our Bayesian analysis are consistent within errors to those derived from fitting a Gaussian directly to the data in 100 km s−1 bins
In order to assess if our AGN have depleted their host galaxies’ gas reservoir or decreased their star formation efficiency, we compare our results to studies of general galaxy populations and other AGN samples

Summary

Introduction

The energy from accreting supermassive black holes (i.e. active galactic nuclei, AGN) is widely accepted to be responsible for the global quenching of star formation in massive galaxies (AGN feedback; e.g. see reviews in Alexander & Hickox 2012; Fabian 2012; Harrison 2017). The physical mechanisms by which this energy couples to the gas on galactic scales and its precise impact on the host galaxy remains unclear. AGN are thought to be able to remove gas from their host galaxies via outflows. These outflows can be powered by the interaction be-. Tween interstellar gas and small-scale accretion disc winds (FaucherGiguere & Quataert 2012; Zubovas & King 2012) or directly via radiation pressure on dust (Ishibashi & Fabian 2015; Thompson et al 2015; Bieri et al 2017; Costa et al 2018a,b), for AGN with high Eddington ratios (‘quasar’ or ‘radiative mode’). While typically thought to operate primarily by preventing hot halo gas from cooling, via the so-called ‘radio’ or ‘maintenance mode’ (e.g. Churazov et al 2005), collimated jets are likely to drive outflows of interstellar gas (Wagner, Bicknell & Umemura 2012; Mukherjee et al 2016), blurring the division between ‘quasar’ and ‘maintenance’ modes (see e.g. Jarvis et al 2019)

Results

Discussion

Conclusion