Gas Content Regulates the Lifecycle of Star Formation and Black Hole Accretion in Galaxies

Abstract

Active galactic nucleus (AGN) feedback is expected to impact the amount of cold gas in galaxies by driving strong galactic winds, by preventing external gas inflows, or by changing the thermodynamical state of the gas. We use molecular gas mass estimates based on dust absorption (Hα/Hβ) to study gas content of large samples of type 2 AGN host galaxies in comparison with inactive galaxies. Using sparse principal component and clustering analysis, we analyze a suite of stellar and structural parameters of ∼ 27, 100 face-on, central galaxies at redshift z = 0.02 − 0.15 and with stellar mass M ≈ 10 10 − 2 × 10 11 M . We identify four galaxy groups of similar mass and morphology (mass surface density, velocity dispersion, concentration, and Sérsic index) that can be evolutionarily linked through a lifecycle wherein gas content mediates their star formation rate (SFR) and level of AGN activity. Galaxies first consume their gas mostly through bursty star formation, then enter into a transition phase of intermediate gas richness in which star formation and AGNs coexist, before settling into retirement as gas-poor, quiescent systems with residual levels of AGN activity (LINERs). Strongly accreting black holes (Seyferts) live in gas-rich, star-forming hosts, but neither their gas reservoir nor their ability to form stars seem to be impacted instantaneously (timescales 0.5 Gyr) by AGN feedback. Our results are inconsistent with AGN feedback models that predict that central, bulge-dominated, Seyfert-like AGNs in massive galaxies have significantly lower molecular gas fractions compared to inactive galaxies of similar mass, morphology, and SFR.

Compact Molecular Gas Distribution in Quasar Host Galaxies

“…Notwithstanding these compelling arguments, serious doubts remain as to whether AGN feedback effectively removes sufficient cold gas from the host galaxy to curtail its ongoing star formation activity. The interstellar medium content of the host galaxies of nearby AGNs shows no evidence of depletion relative to star-forming galaxies of similar stellar mass, based on gas masses de-rived from direct observations of neutral atomic hydrogen (Ho et al 2008;Fabello et al 2011;Geréb et al 2015;Zhu & Wu 2015;Ellison et al 2019) and CO (Maiolino et al 1997;Evans et al 2001;Scoville et al 2003;Evans et al 2006;Bertram et al 2007;Shangguan et al 2020a;Jarvis et al 2020), as well as inferred indirectly from dust emission (Shangguan et al 2018; or dust extinction (Zhuang & Ho 2020;Yesuf & Ho 2020). Far from being quenched, stars seem to form with even greater efficiency in the host galaxies of luminous AGNs (Shangguan et al 2020b;Zhuang & Ho 2020).…”

Can supernova shells feed supermassive black holes in galactic nuclei?

“…The mechanisms leading to the formation and growth of SMBHs in the centers of their host galaxies is an open unsolved problem in astrophysics. The mass of the SMBH is correlated with the mass of the bulge (Kormendy & Ho 2013) and some extraordinary starburst activities of active galactic nuclei (AGN) may be connected to accreting SMBHs (Yesuf & Ho 2020). However, this starburst activity usually occurs in regions enshrouded by dust, hiding completely their emission in optical wave bands.…”