High-redshift supermassive black holes: accretion through cold flows

Abstract

We use zoom-in techniques to re-simulate three high-redshift (z ≥ 5.5) halos which host 10 9 solar mass blackholes from the ∼ Gpc volume, MassiveBlack cosmological hydrodynamic simulation. We examine a number of factors potentially affecting supermassive blackhole growth at high redshift in cosmological simulations. These include numerical resolution, feedback prescriptions and formulation of smoothed particle hydrodynamics. We find that varying the size of the region over which feedback energy is deposited directly, either for fixed number of neighbours or fixed volume makes very little difference to the accretion history of blackholes. Changing mass resolution by factors of up to 64 also does not change the blackhole growth history significantly. We find that switching from the density-entropy formulation to the pressure-entropy formulation of smoothed particle hydrodynamics slightly increases the accretion rate onto blackholes. In general numerical details appear to have small effects on the main fueling mechanism for blackholes at these high redshifts. We examine the fashion by which this occurs, finding that the insensitivity to simulation technique seems to be a hallmark of the cold flow feeding picture of these high-z supermassive blackholes. We show that the gas that participates in critical accretion phases, in these massive objects at z > 6 ∼ 7 is in all cases colder, denser, and forms more coherent streams than the average gas in the halo. This is also mostly the case when the blackhole accretion is feedback regulated (z < 6), however the distinction is less prominent. For our resimulated halos, cold flows appear to be a viable mechanism for forming the most massive blackholes in the early universe, occurring naturally in ΛCDM models of structure formation. Not requiring fine tuning of numerical parameters, they seem to be physically inevitable in these objects.

The origin of the most massive black holes at high-z: BlueTides and the next quasar frontier

“…This also allows us to make predictions for the most massive black holes to be discovered in the near future. Large volume simulations such as MassiveBlack (Di Matteo et al 2012) and associated high-resolutions zooms (Feng et al 2014) already showed that the existence of the z = 6 SDSS quasar population, is consistent with our standard structure formation models. Crucially, the BlueTidessimulation with its increased resolution, allows us to study reliably the formation of massive black holes at even earlier times.…”

“…Here we have focussed our analysis on the massive galaxies and black holes at z 8 (for earlier discussion of z = 6 SDSS quasars, see e.g. Di Matteo et al 2012;Feng et al 2014). In Feng et al (2015 we discussed how the most massive galaxies at these epochs are likely disk dominated.…”

“…Although the limited time evolution and somewhat limited numerical resolution of the large volumes of BlueTidesprecludes more detailed studies and investigations we plan to use these clues to re-simulate some of these systems at higher resolution (Feng et al 2014, as we did with MB simulation, see e.g.) with the goal of studying in more detail the dependence and constrain seed black hole scenarios.…”

Blossoms from black hole seeds: properties and early growth regulated by supernova feedback

“…We therefore do not expect to find 10 9 M BHs in our simulations. We can, however, discuss our results in light of previous/concurrent work, specifically two types of different approaches, (i) smaller volumes, normally a zoom on a single halo, at higher resolution (e.g., Alvarez, Wise & Abel 2009;Johnson et al 2011;Aykutalp et al 2014), and (ii) larger halos and volumes at lower resolution aimed at studying z ∼ 6 quasars (e.g., Dubois et al 2013;Costa et al 2014;Feng et al 2014;Di Matteo et al 2016). Our simulations bridge the gap between these two regimes.…”

Mapping the Lyα Emission around a z ∼ 6.6 QSO with MUSE: Extended Emission and a Companion at a Close Separation

“…To sustain such vigorous accretion and intense star formation, the first QSOs need the presence of copious amounts of gas in their surroundings (e.g., Di Matteo et al 2012; Dubois et al 2012). Possibly, this gas is aggregated in dense flows able to penetrate into the virial radius of the halo and to funnel gas onto the central SMBH (e.g., Di Matteo et al 2012;Feng et al 2014). If the gas in the host galaxy and in the circumgalactic medium of a QSO is illuminated by the SMBH ionizing radiation and/or the intense starburst, then it may be observable as an extended "fuzz" of fluorescent Lyα emission (Rees 1988;Haiman & Rees 2001;Alam & MiraldaEscudé 2002).…”