Astrophysicist

Category: massive black hole demographics

Li et al. (2020)

Correlations between Black Holes and Host Galaxies in the Illustris and IllustrisTNG Simulations

by
Li, Yuan; Habouzit, Melanie; Genel, Shy; Somerville, Rachel; Terrazas, Bryan A.; Bell, Eric F.; Pillepich, Annalisa; Nelson, Dylan; Weinberger, Rainer; Rodriguez-Gomez, Vicente; Ma, Chung-Pei; Pakmor, Rüdiger; Hernquist, Lars; Vogelsberger, Mark

abstract
We study black hole-host galaxy correlations, and the relation between the overmassiveness (the distance from the average MBH-σ relation) of supermassive black holes (SMBHs) and the star formation histories of their host galaxies in the Illustris and TNG100 simulations. We find that both simulations are able to produce black hole scaling relations in general agreement with observations at z = 0, but with noticeable discrepancies. Both simulations show an offset from the observations for the MBH-σ relation, and the relation between MBH and the Sérsic index. The relation between MBH and stellar mass M* is tighter than the observations, especially for TNG100. For massive galaxies in both simulations, the hosts of overmassive SMBHs (those above the mean MBH-σ relation) tend to have larger Sérsic indices and lower baryon conversion efficiency, suggesting a multidimensional link between SMBHs and the properties of their hosts. In Illustris, the hosts of overmassive SMBHs have formed earlier and have lower present-day star formation rates, in qualitative agreement with the observations for massive galaxies with σ > 100 km s-1. For low-mass galaxies, such a correlation still holds in Illustris but does not exist in the observed data. For TNG100, the correlation between SMBH overmassiveness and star formation history is much weaker. The hosts of overmassive SMBHs generally have consistently larger star formation rates throughout history. These galaxies have higher stellar mass as well, due to the strong MBH-M*correlation. Our findings show that simulated SMBH scaling relations and correlations are sensitive to features in the modeling of SMBHs.

published in
The Astrophysical Journal, Volume 895, Issue 2, id.102, June 2020

link to paper
[ADS][arXiv]

Terrazas et al. (2020)

The relationship between black hole mass and galaxy properties: examining the black hole feedback model in IllustrisTNG

by
Terrazas, Bryan A.; Bell, Eric F.; Pillepich, Annalisa; Nelson, Dylan; Somerville, Rachel S.; Genel, Shy; Weinberger, Rainer; Habouzit, Mélanie; Li, Yuan; Hernquist, Lars; Vogelsberger, Mark

abstract
Supermassive black hole feedback is thought to be responsible for the lack of star formation, or quiescence, in a significant fraction of galaxies. We explore how observable correlations between the specific star formation rate (sSFR), stellar mass (Mstar), and black hole mass (MBH) are sensitive to the physics of black hole feedback in a galaxy formation model. We use the IllustrisTNG simulation suite, specifically the TNG100 simulation and 10 model variations that alter the parameters of the black hole model. Focusing on central galaxies at z = 0 with Mstar > 1010 M, we find that the sSFR of galaxies in IllustrisTNG decreases once the energy from black hole kinetic winds at low accretion rates becomes larger than the gravitational binding energy of gas within the galaxy stellar radius. This occurs at a particular MBH threshold above which galaxies are found to sharply transition from being mostly star forming to mostly quiescent. As a result of this behaviour, the fraction of quiescent galaxies as a function of Mstar is sensitive to both the normalization of the MBH-Mstar relation and the MBH threshold for quiescence in IllustrisTNG. Finally, we compare these model results to observations of 91 central galaxies with dynamical MBH measurements with the caveat that this sample is not representative of the whole galaxy population. While IllustrisTNG reproduces the observed trend that quiescent galaxies host more massive black holes, the observations exhibit a broader scatter in MBH at a given Mstar and show a smoother decline in sSFR with MBH.

published in
Monthly Notices of the Royal Astronomical Society, Volume 493, Issue 2, p.1888-1906, April 2020

links to paper
[ADS][arXiv]

Habouzit et al. (2019)

Linking galaxy structural properties and star formation activity to black hole activity with IllustrisTNG

by
Habouzit, Mélanie; Genel, Shy; Somerville, Rachel S.; Kocevski, Dale; Hirschmann, Michaela; Dekel, Avishai; Choi, Ena; Nelson, Dylan; Pillepich, Annalisa; Torrey, Paul; Hernquist, Lars; Vogelsberger, Mark; Weinberger, Rainer; Springel, Volker

abstract
We study the connection between active galactic nuclei (AGN) and their host galaxies through cosmic time in the large-scale cosmological IllustrisTNG simulations. We first compare BH properties, i.e. the hard X-ray BH luminosity function, AGN galaxy occupation fraction, and distribution of Eddington ratios, to available observational constraints. The simulations produce a population of BHs in good agreement with observations, but we note an excess of faint AGN in hard X-ray (L_x̃ 10^{43-44} erg/s), and a lower number of bright AGN (L_x\gt 10^{44} erg/s), a conclusion that varies quantitatively but not qualitatively with BH luminosity estimation method. The lower Eddington ratios of the 109 M_{\odot } BHs compared to observations suggest that AGN feedback may be too efficient in this regime. We study galaxy star formation activity and structural properties, and design sample-dependent criteria to identify different galaxy types (star-forming/quiescent, extended/compact) that we apply both to the simulations and observations from the CANDELS fields. We analyse how the simulated and observed galaxies populate the specific star formation rate – stellar mass surface density diagram. A large fraction of the z = 0 M_{\star }≥slant 10^{11} M_{\odot } quiescent galaxies first experienced a compaction phase (i.e. reduction of galaxy size) while still forming stars, and then a quenching event. We measure the dependence of AGN fraction on galaxies’ locations in this diagram. After correcting the simulations with a redshift and AGN luminosity-dependent model for AGN obscuration, we find good qualitative and quantitative agreement with observations. The AGN fraction is the highest among compact star-forming galaxies (16-20{{ per cent}} at z ̃ 1.5-2), and the lowest among compact quiescent galaxies (6-10{{ per cent}} at z ̃ 1.5-2).

published in
Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 4, p.4413-4443, April 2019

links to paper
[ADS][arXiv]

Weinberger et al. (2018)

Supermassive black holes and their feedback effects in the IllustrisTNG simulation

by
Weinberger, Rainer; Springel, Volker; Pakmor, Rüdiger; Nelson, Dylan; Genel, Shy; Pillepich, Annalisa; Vogelsberger, Mark; Marinacci, Federico; Naiman, Jill; Torrey, Paul; Hernquist, Lars

abstract
We study the population of supermassive black holes (SMBHs) and their effects on massive central galaxies in the IllustrisTNG cosmological hydrodynamical simulations of galaxy formation. The employed model for SMBH growth and feedback assumes a two-mode scenario in which the feedback from active galactic nuclei occurs through a kinetic, comparatively efficient mode at low accretion rates relative to the Eddington limit, and in the form of a thermal, less efficient mode at high accretion rates. We show that the quenching of massive central galaxies happens coincidently with kinetic-mode feedback, consistent with the notion that active supermassive black holes cause the low specific star formation rates observed in massive galaxies. However, major galaxy mergers are not responsible for initiating most of the quenching events in our model. Up to black hole masses of about 10^{8.5} M_{☉}, the dominant growth channel for SMBHs is in the thermal mode. Higher mass black holes stay mainly in the kinetic mode and gas accretion is self-regulated via their feedback, which causes their Eddington ratios to drop, with SMBH mergers becoming the main channel for residual mass growth. As a consequence, the quasar luminosity function is dominated by rapidly accreting, moderately massive black holes in the thermal mode. We show that the associated growth history of SMBHs produces a low-redshift quasar luminosity function and a redshift zero black hole mass – stellar bulge mass relation is in good agreement with observations, whereas the simulation tends to overpredict the high-redshift quasar luminosity function.

published in
Monthly Notices of the Royal Astronomical Society, Volume 479, Issue 3, p.4056-4072, September 2018

links to paper
[ADS][arXiv]

Weinberger et al. (2017)

Simulating galaxy formation with black hole driven thermal and kinetic feedback

by
Weinberger, Rainer; Springel, Volker; Hernquist, Lars; Pillepich, Annalisa; Marinacci, Federico; Pakmor, Rüdiger; Nelson, Dylan; Genel, Shy; Vogelsberger, Mark; Naiman, Jill; Torrey, Paul

abstract
The inefficiency of star formation in massive elliptical galaxies is widely believed to be caused by the interactions of an active galactic nucleus (AGN) with the surrounding gas. Achieving a sufficiently rapid reddening of moderately massive galaxies without expelling too many baryons has however proven difficult for hydrodynamical simulations of galaxy formation, prompting us to explore a new model for the accretion and feedback effects of supermassive black holes. For high-accretion rates relative to the Eddington limit, we assume that a fraction of the accreted rest mass energy heats the surrounding gas thermally, similar to the ‘quasar mode’ in previous work. For low-accretion rates, we invoke a new, pure kinetic feedback model that imparts momentum to the surrounding gas in a stochastic manner. These two modes of feedback are motivated both by theoretical conjectures for the existence of different types of accretion flows as well as recent observational evidence for the importance of kinetic AGN winds in quenching galaxies. We find that a large fraction of the injected kinetic energy in this mode thermalizes via shocks in the surrounding gas, thereby providing a distributed heating channel. In cosmological simulations, the resulting model produces red, non-star-forming massive elliptical galaxies, and achieves realistic gas fractions, black hole growth histories and thermodynamic profiles in large haloes.

published in
Monthly Notices of the Royal Astronomical Society, Volume 465, Issue 3, p.3291-3308, March 2017

links to paper
[ADS][arXiv]

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