The star formation properties of the observed and simulated AGN Universe: BAT versus EAGLE

Abstract

In this paper we present data from 72 low redshift, hard X-ray selected AGN taken from the Swift-BAT 58 month catalogue. We utilise spectral energy distribution fitting to the optical to IR photometry in order to estimate host galaxy properties. We compare this observational sample to a volume and flux matched sample of AGN from the EAGLE hydrodynamical simulations in order to verify how accurately the simulations can reproduce observed AGN host galaxy properties. After correcting for the known +0.2 dex offset in the SFRs between EAGLE and previous observations, we find agreement in the SFR and X-ray luminosity distributions; however we find that the stellar masses in EAGLE are 0.2 − 0.4 dex greater than the observational sample, which consequently leads to lower sSFRs. We compare these results to our previous study at high redshift, finding agreement in both the observations and simulations, whereby the widths of sSFR distributions are similar (∼0.4 − 0.6 dex) and the median of the SFR distributions lie below the star forming main sequence by ∼0.3 − 0.5 dex across all samples. We also use EAGLE to select a sample of AGN host galaxies at high and low redshift and follow their characteristic evolution from z = 8 to z = 0. We find similar behaviour between these two samples, whereby star formation is quenched when the black hole goes through its phase of most rapid growth. Utilising EAGLE we find that 23% of AGN selected at z ∼ 0 are also AGN at high redshift, and that their host galaxies are among the most massive objects in the simulation. Overall we find EAGLE reproduces the observations well, with some minor inconsistencies (∼ 0.2 dex in stellar masses and ∼ 0.4 dex in sSFRs).

Cosmological simulations predict that AGN preferentially live in gas-rich, star-forming galaxies despite effective feedback

“…These results show that the observational result of finding luminous AGN located preferentially in star-forming or gas-rich galaxies is not in tension with negative AGN feedback, as implemented in these cosmological simulations (see also e.g. Thacker et al 2014;Scholtz et al 2018;Jackson et al 2020). This is likely not surprising when noting that AGN and host galaxy star formation both require a gas reservoir.…”

Enhanced Star Formation Efficiency in the Central Regions of Nearby Quasar Hosts

“…Whether AGN feedback mediates BH−galaxy coevolution is still uncertain. Reports of suppressed star formation activity in local low-luminosity (Ho et al 2003;Ellison et al 2016;Leslie et al 2016;Jackson et al 2020) and luminous (Scholtz et al 2018;Stemo et al 2020) AGNs have upheld the notion that AGN feedback quenches star formation, driving the evolution of galaxies from star-forming to passive systems. Conversely, local Seyferts often show ongoing or recent star formation (e.g., Davies et al 2007;Esquej et al 2014), and compelling evidence indicates that the more luminous AGNs are commonly hosted in galaxies with star formation rates (SFRs) similar to those reported in typical inactive spirals (Harrison et al 2012;Rosario et al 2012Rosario et al , 2013Husemann et al 2014;Zhang et al 2016;Stanley et al 2017;Bernhard et al 2019;Schulze et al 2019;Grimmett et al 2020;Koss et al 2021;Vietri et al 2022), or even comparable to those of starbursts (Young et al 2014;Bernhard et al 2016;Pitchford et al 2016;Shangguan et al 2020a;Kirkpatrick et al 2020;Xie et al 2021).…”

Ionized Outflows in Nearby Quasars Are Poorly Coupled to Their Host Galaxies

“…Despite the ubiquitous evidence of multi-phase gas outflows in AGN hosts, the role of AGN feedback in establishing the host galaxy properties and its ability to quench ongoing star formation activity are still intensively debated. Local lowluminosity AGNs exhibit global star formation rates (SFRs) lower than those measured from the inactive, star-forming galaxy population (Ellison et al 2016;Leslie et al 2016;Jackson et al 2020), and some systems are effectively passive (Ho et al 2003). On the other hand, the more luminous nearby AGN-host galaxies are similar to the inactive galaxy population in several key properties, such as SFR, atomic hydrogen gas content, molecular gas mass, and dust emission and/or dust attenuation (Maiolino et al 1997;Evans et al 2001;Scoville et al 2003;Evans et al 2006;Bertram et al 2007;Ho et al 2008;Fabello et al 2011;Harrison et al 2012;Geréb et al 2015;Zhu & Wu 2015;Husemann et al 2017;Bernhard et al 2019;Ellison et al 2019;Shangguan et al 2018;Shangguan & Ho 2019;Shangguan et al 2020a;Grimmett et al 2020;Jarvis et al 2020;Yesuf & Ho 2020;Zhuang et al 2021).…”