Cosmological simulations of quasar fueling to sub-parsec scales using Lagrangian hyper-refinement

Abstract

We present cosmological hydrodynamic simulations of a quasar-mass halo (M halo ≈ 10 12.5 M at z = 2) that for the first time resolve gas transport down to the inner 0.1 pc surrounding the central massive black hole. We model a multi-phase interstellar medium including stellar feedback by supernovae, stellar winds, and radiation, and a hyper-Lagrangian refinement technique increasing the resolution dynamically approaching the black hole. We do not include black hole feedback. We show that the sub-pc inflow rate (1) can reach ∼6 M yr −1 roughly in steady state during the epoch of peak nuclear gas density (z ∼ 2), sufficient to power a luminous quasar, (2) is highly time variable in the pre-quasar phase, spanning 0.001-10 M yr −1 on Myr timescales, and (3) is limited to short (∼2 Myr) active phases (0.01-0.1 M yr −1 ) followed by longer periods of inactivity at lower nuclear gas density and late times (z ∼ 1), owing to the formation of a hot central cavity. Inflowing gas is primarily cool, rotational support dominates over turbulence and thermal pressure, and star formation can consume as much gas as provided by inflows across 1 pc-10 kpc. Gravitational torques from multi-scale stellar non-axisymmetries dominate angular momentum transport over gas self-torquing and pressure gradients, with accretion weakly dependent on black hole mass. Sub-pc inflow rates correlate with nuclear (but decouple from global) star formation and can exceed the Eddington rate by ×10. The black hole can move ∼10 pc from the galaxy center on ∼0.1 Myr. Accreting gas forms pc-scale, rotationally supported, obscuring structures often misaligned with the galaxy-scale disk. These simulations open a new avenue to investigate black hole-galaxy co-evolution.

Kinematics and Star Formation of High-Redshift Hot Dust-Obscured Quasars as Seen by ALMA

“…That is, with BH masses on the order of ∼ 10 9 M or slightly above (see Table 5), a large number of EL events with typical efficiencies of η = 0.1 jointly lasting for a period significantly longer than t Salp would lead to final BH masses in excess of those seen in SMBHs hosted by the brightest cluster galaxies (BCGs) today (M • 10 10 M ; McConnell & Ma 2013). Therefore, if the EL Hot DOG phase is to be recurrent, each episode would need to be shorter than a few Myr (t e t Salp N −1 e λ Edd −1 , where N e is the number of episodes), which would be in agreement with the observed AGN flick-ering time, of about 10 5 yr (Schawinski et al 2015), and with recent ultra-high resolution simulations of the BH accretion rate down to the central sub-pc scale in high-redshift quasars at the center of proto-clusters (Angles-Alcazar et al 2020).…”

“…That is, the identification of the merger nature of a system is usually done through the detection of companion galaxies (e.g., Díaz-Santos et al 2018;Miller et al 2018;Hodge et al 2019); the dynamical state of the host galaxy is probed by the kinematics of the gas (e.g., Carniani et al 2013;Kimball et al 2015;Tadaki et al 2018); and the presence of an accreting SMBH is revealed by the fact that an obscured AGN dominates the bolometric output of the source (Tsai et al 2015). Each of these signatures has a characteristic spatial scaled attached to it: neighbor galaxies in the vicinity of high-z quasars are identified at projected distances greater than at least a few kpc (Petitjean et al 1996;McGreer et al 2014;Trakhtenbrot et al 2017;Decarli et al 2018Decarli et al , 2019Nguyen et al 2020); the dynamical state of the host, which is driven by the interaction between the pre-existing bound gas and the in-fall of companions, is characterized by physical scales of ∼ 1-2 kpc that, when tied to the gas velocity dispersion observed in the host galaxies (FWHM 500 km s −1 ), provides a time-scale of a few Myr; and the funneling of gas into the SMBH happens efficiently only inside of its sphere of influence (within a few hundred pc, considering BH mass estimates of M • ∼ 10 9 M ; Wu et al 2018;Tsai et al 2018;Jun et al 2020b;Finnerty et al 2020), where it can be transported further in by rotationally supported structures (Angles-Alcazar et al 2020). The lack of synchronicity and delay among all these phases (including with respect to the star-formation process; Hopkins 2012) can potentially generate the diversity of dynamical states displayed by Hot DOGs despite all sharing a common origin.…”

“…A larger sample is also required to perform statistical studies regarding the presence of galaxy companions, the time lags between the different accretion phases, and in general to accurately characterize the most luminous, dust-obscured population of galaxies so far detected in the Universe. Deeper observations are also critical to be able to perform a detailed modeling of their kinematics (see Appendix A), and investigate whether simulations of massive galaxy formation (e.g., Dekel et al 2009;Faucher-Giguère & Quataert 2012;Gaspari et al 2013;Anglés-Alcázar et al 2017b;Lupi et al 2019;Angles-Alcazar et al 2020) are able to reproduce the different morphologies, velocity fields, and potential quasardriven outflows in the most rapidly evolving galaxies at the nodes of the cosmic web. These simulations are critical, as they can be used to infer and predict the duration and recurrence of Hot DOG phase(s), thus allowing to quantitatively translate snap-shots of space into actual, distinctive physical stages of galaxy evolution.…”

Dust-Enshrouded AGN can Dominate Host-Galaxy-Scale Cold-Dust Emission

“…the hydrodynamical simulation may cause the BH accretion rate to be underestimated (e.g., Hayward et al 2014;Angles-Alcazar et al 2020). The Eddington ratio (λ edd ≡ L AGN /L edd ) varies from zero to one in the fiducial runs and thus spans a range of λ edd = 0 − 10 in the AGN-10x runs.…”

Supermassive black holes in cosmological simulations II: the AGN population and predictions for upcoming X-ray missions

“…In particular, the region around the BHs is not sufficiently resolved (in space and time) to capture short timescale variability. Both the simulations that resolve the region near BHs at sub-pc scales (Novak, Ostriker & Ciotti 2011;Angles-Alcazar et al 2020) and the observations have shown that the accretion rate onto BHs can change by orders of magnitude over short timescales that are not resolved in large-scale cosmological simulations (e.g., DeGraf et al 2017;Gabor & Bournaud 2014, and references therein). In order to account for the impact of AGN variability on the AGN luminosity function, we modify the luminosity of each simulated AGN: we randomly draw a new AGN luminosity from a log-normal distribution centered on the initial AGN luminosity and with a width of 0.3 (Fig.…”