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Why do Black Holes Trace Bulges (& Central Surface Densities), Instead of Galaxies as a Whole?

Hopkins, Philip F. and Wellons, Sarah and Anglés-Alcázar, Daniel and Faucher-Giguère, Claude-André and Grudić, Michael Y. (2021) Why do Black Holes Trace Bulges (& Central Surface Densities), Instead of Galaxies as a Whole? . (Unpublished)

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Previous studies of fueling black holes (BHs) in galactic nuclei have argued (on scales ~0.01-1000pc) accretion is dynamical with inflow rates Ṁ∼ηM_(gas)/t_(dyn) in terms of gas mass M_(gas), dynamical time t_(dyn), and some η. But these models generally neglected expulsion of gas by stellar feedback, or considered extremely high densities where expulsion is inefficient. Studies of star formation, however, have shown on sub-kpc scales the expulsion efficiency f_(wind)=M_(ejected)/M_(total) scales with the gravitational acceleration as (1−f_(wind))/f_(wind)∼a_(grav)/⟨p˙/m∗⟩∼Σ_(eff)/Σ_(crit) where a¯g_(rav)≡GM_(tot)(<r)/r² and ⟨p˙/m∗⟩ ~ 10⁻⁷ cm s⁻² is the momentum injection rate from young stars. Adopting this as the simplest correction for stellar feedback, η→η(1−f_(wind)), we show this provides a more accurate description of simulations with stellar feedback at low densities. This has immediate consequences, predicting e.g. the slope and normalization of the M−σ and M−M_(bulge) relation, LAGN−SFR relations, and explanations for outliers in compact Es. Most strikingly, because star formation simulations show expulsion is efficient (f_(wind)∼1) below total-mass surface density M_(tot)/πr²<Σ_(crit)∼3×10⁹M⊙ kpc⁻² (where Σ_(crit)=⟨p˙/m∗⟩/(πG)), BH mass is predicted to specifically trace host galaxy properties above a critical surface brightness Σ_(crit) (B-band μ^(crit)_B∼19magarcsec⁻²). This naturally explains why BH masses preferentially reflect bulge properties or central surface-densities (Σ_(1kpc)), not 'total' galaxy properties.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper ItemGIZMO code
Hopkins, Philip F.0000-0003-3729-1684
Wellons, Sarah0000-0002-3977-2724
Anglés-Alcázar, Daniel0000-0001-5769-4945
Faucher-Giguère, Claude-André0000-0002-4900-6628
Grudić, Michael Y.0000-0002-1655-5604
Additional Information:We thank Jessie Christiansen for a number of suggestions. Support for PFH was provided by NSF Research Grants 1911233 & 20009234, NSF CAREER grant 1455342, NASA grants 80NSSC18K0562, HST-AR-15800.001-A. SW is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST2001905. CAFG was supported by NSF through grants AST-1715216 and CAREER award AST-1652522; by NASA through grant 17-ATP17-0067; by STScI through grant HST-AR- 16124.001-A; and by the Research Corporation for Science Advancement through a Cottrell Scholar Award and a Scialog Award. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations FTA-Hopkins supported by the NSF and TACC, and NASA HEC SMD-16-7592. Data Availability Statement: The data supporting the plots within this article are available on reasonable request to the corresponding author. A public version of the GIZMO code is available at http://www.tapir.caltech. edu/~phopkins/Site/GIZMO.html.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:galaxies: formation—quasars: general—quasars: supermassive black holes—galaxies: active—galaxies: evolution—accretion, accretion disks
Record Number:CaltechAUTHORS:20210323-124505549
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108528
Deposited By: Tony Diaz
Deposited On:23 Mar 2021 20:55
Last Modified:23 Mar 2021 20:55

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