On the mass radiated by coalescing black-hole binaries

The Astrophysical Journal (Impact Factor: 6.28). 06/2012; 758(1). DOI: 10.1088/0004-637X/758/1/63
Source: arXiv

ABSTRACT We derive an analytic phenomenological expression that predicts the final
mass of the black-hole remnant resulting from the merger of a generic binary
system of black holes on quasi-circular orbits. Besides recovering the correct
test-particle limit for extreme mass-ratio binaries, our formula reproduces
well the results of all the numerical-relativity simulations published so far,
both when applied at separations of a few gravitational radii, and when applied
at separations of tens of thousands of gravitational radii. These validations
make our formula a useful tool in a variety of contexts ranging from
gravitational-wave physics to cosmology. As representative examples, we first
illustrate how it can be used to decrease the phase error of the
effective-one-body waveforms during the ringdown phase. Second, we show that,
when combined with the recently computed self-force correction to the binding
energy of nonspinning black-hole binaries, it provides an estimate of the
energy emitted during the merger and ringdown. Finally, we use it to calculate
the energy radiated in gravitational waves by massive black-hole binaries as a
function of redshift, using different models for the seeds of the black-hole

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the consequences of superkicks on the population of supermassive black holes (SMBHs) in the Universe residing in brightest cluster galaxies (BCGs). BCGs are the most massive galaxies in the Universe, sitting at the center of galaxy clusters. There is strong observational evidence that they grew prominently at late times (up to a factor 2-4 in mass from z=1), mainly through mergers with satellite galaxies from the cluster, and they host the most massive SMBHs ever observed, with masses up to ten billion solar masses. Those SMBHs are also expected to grow hierarchically, together with their host galaxies, experiencing a series of mergers with other SMBHs brought in by merging satellites. Because of the asymmetric gravitational wave emission, some net linear momentum is emitted during the last stages of the binary inspiral and the remnant SMBH experiences a kick in the opposite direction. Kicks may be as large as ~5000 Km/s ("superkicks"), pushing the SMBHs out in the cluster outskirts for a time comparable to galaxy-evolution timescales. Therefore, measurements of the SMBH occupation fraction can be used to observationally test the existence of superkicks in nature. Because of their violent merger history, BCGs are the ideal objects to explore this possibility. Series of (super)kicks are expected to take place, increasing the total ejection probability. Moreover, BCGs host the SMBHs with the largest sphere of influence on the surrounding stars, which makes them the easiest targets for SMBH mass measurements. We predict, under a number of plausible assumptions, that superkicks can efficiently eject SMBHs from BCGs, bringing their occupation fraction down to a likely range 0.9<f<0.99 in the local Universe. A single observational confirmation of a missing nuclear SMBH would provide strong evidence for the occurrence of superkicks in the strong-gravity regime of BH mergers.
    Monthly Notices of the Royal Astronomical Society 05/2014; 446(1). DOI:10.1093/mnras/stu2049 · 5.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the results of a semianalytical model that evolves the masses and spins of massive black holes together with the properties of their host galaxies across the cosmic history. As a consistency check, our model broadly reproduces a number of observations, e.g., the cosmic star formation history; the black hole mass, luminosity, and galaxy mass functions at low redshift; the black hole-bulge mass relation; and the morphological distribution at low redshift. For the first time in a semianalytical investigation, we relax the simplifying assumptions of perfect coherency or perfect isotropy of the gas fueling the black holes. The dynamics of gas is instead linked to the morphological properties of the host galaxies, resulting in different spin distributions for black holes hosted in different galaxy types. We compare our results with the observed sample of spin measurements obtained through broad K? iron line fitting. The observational data disfavor both accretion along a fixed direction and isotropic fueling. Conversely, when the properties of the accretion flow are anchored to the kinematics of the host galaxy, we obtain a good match between theoretical expectations and observations. A mixture of coherent accretion and phases of activity in which the gas dynamics is similar to that of the stars in bulges (i.e., with a significant velocity dispersion superimposed to a net rotation) best describes the data, adding further evidence in support of the coevolution of massive black holes and their hosts.
    The Astrophysical Journal 09/2014; 794(2):104. DOI:10.1088/0004-637X/794/2/104 · 6.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Throughout the Universe many powerful events are driven by strong gravitational effects that require general relativity to fully describe them. These include compact binary mergers, black hole accretion and stellar collapse, where velocities can approach the speed of light, and extreme gravitational fields --$\Phi_{\rm Newt}/c^2 \simeq 1$-- mediate the interactions. Many of these processes trigger emission across a broad range of the electromagnetic spectrum. Compact binaries further source strong gravitational wave emission that could directly be detected in the near future. This feat will open up a gravitational wave window into our Universe and revolutionize its understanding. Describing these phenomena requires general relativity, and --where dynamical effects strongly modify gravitational fields-- the full Einstein equations coupled to matter sources. Numerical relativity is a field within general relativity concerned with studying such scenarios that cannot be accurately modeled via perturbative or analytical calculations. In this review, we examine results obtained within this discipline, with a focus on its impact in astrophysics.
    Annual Review of Astronomy and Astrophysics 05/2014; 52(1). DOI:10.1146/annurev-astro-081913-040031 · 24.04 Impact Factor


Available from