Direct Cosmological Simulations of the Growth of Black Holes and Galaxies

The Astrophysical Journal (Impact Factor: 5.99). 05/2007; 676(1). DOI: 10.1086/524921
Source: arXiv


We investigate the coupled formation and evolution of galaxies and their embedded supermassive black holes using state-of-the-art hydrodynamic simulations of cosmological structure formation. For the first time, we self-consistently follow the dark matter dynamics, radiative gas cooling, and star formation, as well as BH growth and associated feed-back processes, starting directly from initial conditions appropriate for the ACDM cosmology. Our modeling of the black hole physics is based on an approach that we have developed in simulations of isolated galaxy mergers. Here we examine (1) the predicted global history of BH mass assembly, (2) the evolution of the local black hole-host mass correlations, and (3) the conditions that allow rapid growth of the first quasars, and the properties of their hosts and descendants today. We find a total BH mass density in good agreement with observational estimates. The BH accretion rate density peaks at lower redshift and evolves more strongly at high redshift than the star formation rate density, but the ratio of black hole to stellar mass density shows only a moderate evolution at low redshifts. We find strong correlations between BH masses and properties of the stellar systems, agreeing well with the measured local MBH- σ and ABH-M* relationships, but also suggesting (dependent on the mass range) a weak evolution with redshift in the normalization and the slope. Our simulations also produce massive black holes at high redshift, due to extended periods of exponential growth in regions that collapse early and exhibit strong gas inflows. These first supermassive BH systems, however, are not necessarily the most massive ones today, since they are often overtaken in growth by quasars that form later. © 2008. The American Astronomical Society. All rights reserved.

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    • "In particular, the advent of digital astronomical surveys, beginning with the Sloan Digital Sky Survey[1], has dramatically increased the size of astronomical data. Similarly, modern cosmological simulations, such as BHCosmo[3] and Coyote Universe[7], produce datasets with billions of objects, and multiple terabytes in size. "
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    ABSTRACT: DiscFinder is a scalable approach for identifying large-scale astronomical structures, such as galaxy clusters, in massive observation and simulation astrophysics datasets. It is designed to operate on datasets with tens of billions of astronomical objects, even in the case when the dataset is much larger than the aggregate memory of compute cluster used for the processing.
    Proceedings of the 19th ACM International Symposium on High Performance Distributed Computing, HPDC 2010, Chicago, Illinois, USA, June 21-25, 2010; 08/2010
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    • "However, to get the right [α/F e]-enhancement some extreme assumptions need to be made. Granato et al. (2004), for example, allowed for Super- Eddington accretion at high redshifts (this assumption has also been used in the recent numerical simulations by Di Matteo et al. 2008), thus boosting BH growth which more rapidly meet the condition for self-regulation and quench star formation earlier than less massive galaxies. Granato et al. (2006) successfully adopted the same prescriptions to reproduce the bulk of the 850µ counts (see also Fontanot et al. 2009) observed with the submillimeter array SCUBA, a difficult task for hierarchical galaxy formation models (e.g., Granato et al., 2000). "
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    ABSTRACT: Supermassive black holes (BHs) appear to be ubiquitous at the center of all galaxies which have been observed at high enough sensitivities and resolution with the Hubble Space Telescope. Their masses are found to be tightly linked with the masses and velocity dispersions of their host galaxies. On the other hand, BHs are widely held to constitute the central engines of quasars and active galactic nuclei (AGN) in general. It is however still unclear how BHs have grown, and whether they have co-evolved with their hosts. In this Review I discuss how, in ways independent of specific models, constraints on the growth history of BHs and their host galaxies have been set by matching the statistics of local BHs to the emissivity, number density, and clustering properties of AGNs at different cosmological epochs. I also present some new results obtained through a novel numerical code which evolves the BH mass function and clustering adopting broad distributions of Eddington ratios. I finally review BH evolution in a wider cosmological context, connecting BH growth to galaxy evolution.
    New Astronomy Reviews 07/2009; 53(4-6-53):57-77. DOI:10.1016/j.newar.2009.07.006 · 6.43 Impact Factor
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    ABSTRACT: The effects of general relativity (GR) in astrophysical systems are often difficult to calculate, but they can have important consequences for observables. This thesis considers the impact of previously-ignored GR effects in two different types of compact binary systems. The first is the coalescence of massive black holes in high-redshift galaxies. The gravitational waves (GWs) from these systems can be detected by the proposed low-frequency gravitational wave detector LISA and used to determine the various parameters which characterize the binary. Most studies of LISA's parameter estimation capability have ignored a significant piece of physics: the relativistic precession of the binary's angular momentum vectors. In the first two-thirds of this thesis, we show how including precession effects in the waveform model helps to break various degeneracies and improve the expected parameter errors. We give special attention to the localization parameters, sky position and distance. When distance is converted to an approximate redshift, these parameters define a "pixel" on the sky in which astronomers can search for an electromagnetic counterpart to the GW event. The final third of this thesis focuses on stellar -mass compact binaries in which at least one member is a neutron star. The measurement of tidal effects in these systems may shed some light on the poorly understood high-density equation of state. We first calculate the point at which a neutron star tidally disrupts in the field of a black hole. Previous calculations of this effect have used Newtonian self-gravity, which is inappropriate for a neutron star; we correct this by using relativistic perturbation theory.
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