Article

Relativistic collapse and explosion of rotating supermassive stars with thermonuclear effects

The Astrophysical Journal (Impact Factor: 5.99). 08/2011; 749(1). DOI: 10.1088/0004-637X/749/1/37
Source: arXiv

ABSTRACT

We present results of general relativistic simulations of collapsing supermassive stars with and without rotation using the two-dimensional general relativistic numerical code Nada, which solves the Einstein equations written in the BSSN formalism and the general relativistic hydrodynamic equations with high-resolution shock-capturing schemes. These numerical simulations use an equation of state that includes the effects of gas pressure and, in a tabulated form, those associated with radiation and the electron-positron pairs. We also take into account the effect of thermonuclear energy released by hydrogen and helium burning. We find that objects with a mass of ≈5 × 105M
☉ and an initial metallicity greater than Z
CNO ≈ 0.007 do explode if non-rotating, while the threshold metallicity for an explosion is reduced to Z
CNO ≈ 0.001 for objects uniformly rotating. The critical initial metallicity for a thermonuclear explosion increases for stars with a mass ≈106M
☉. For those stars that do not explode, we follow the evolution beyond the phase of black hole (BH) formation. We compute the neutrino energy loss rates due to several processes that may be relevant during the gravitational collapse of these objects. The peak luminosities of neutrinos and antineutrinos of all flavors for models collapsing to a BH are L
ν ~ 1055 erg s–1. The total radiated energy in neutrinos varies between E
ν ~ 1056 erg for models collapsing to a BH and E
ν ~ 1045-1046 erg for models exploding.

Download full-text

Full-text

Available from: Pedro J. Montero, Mar 12, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: I review our current understanding of massive black hole (MBH) formation and evolution along the cosmic history. After a brief introductory overview of the relevance of MBHs in the hierarchical structure formation paradigm, I discuss the main viable channels for seed BH formation at high redshift and for their subsequent mass growth and spin evolution. The emerging hierarchical picture, where MBHs grow through merger triggered accretion episodes, acquiring their mass while shining as quasars, is overall robust, but too simplistic to explain the diversity observed in MBH phenomenology. I briefly discuss which future observations will help to shed light on the MBH cosmic history in the near future, paying particular attention to the upcoming gravitational wave window.
    Full-text · Article · Oct 2011 · Advances in Astronomy
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The collapse of baryons into extremely massive stars with masses 104M ☉ in a small fraction of protogalaxies at z 10 is a promising candidate for the origin of supermassive black holes (SMBHs), some of which grow to a billion solar masses by z ~ 7. We determine the maximum masses such stars can attain by accreting primordial gas. We find that at relatively low accretion rates the strong ionizing radiation of these stars limits their masses to M * ~ 103M ☉ (/10–3M ☉ yr–1)8/7, where is the rate at which the star gains mass. However, at the higher central infall rates usually found in numerical simulations of protogalactic collapse (0.1 M ☉ yr–1), the lifetime of the star instead limits its final mass to ~106M ☉. Furthermore, for the spherical accretion rates at which the star can grow, its ionizing radiation is confined deep within the protogalaxy, so the evolution of the star is decoupled from that of its host galaxy. Lyα emission from the surrounding H II region is trapped in these heavy accretion flows and likely reprocessed into strong Balmer series emission, which may be observable by the James Webb Space Telescope. This, strong He II λ1640, and continuum emission are likely to be the key observational signatures of the progenitors of SMBHs at high redshift.
    Full-text · Article · Dec 2011 · The Astrophysical Journal
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent observations of quasars powered by supermassive black holes (SMBHs) out to z 7 constrain both the initial seed masses and the growth of the most massive black holes (BHs) in the early universe. Here we elucidate the implications of the radiative feedback from early generations of stars and from BH accretion for popular models for the formation and growth of seed BHs. We show that by properly accounting for (1) the limited role of mergers in growing seed BHs as inferred from cosmological simulations of early star formation and radiative feedback, (2) the sub-Eddington accretion rates of BHs expected at the earliest times, and (3) the large radiative efficiencies of the most massive BHs inferred from observations of active galactic nuclei at high redshift ( 0.1), we are led to the conclusion that the initial BH seeds may have been as massive as 105M ☉. This presents a strong challenge to the Population III seed model, which calls for seed masses of ~100 M ☉ and, even with constant Eddington-limited accretion, requires 0.09 to explain the highest-z SMBHs in today's standard ΛCDM cosmological model. It is, however, consistent with the prediction of the direct collapse scenario of SMBH seed formation, in which a supermassive primordial star forms in a region of the universe with a high molecule-dissociating background radiation field, and collapses directly into a 104-106M ☉ seed BH. These results corroborate recent cosmological simulations and observational campaigns which suggest that these massive BHs were the seeds of a large fraction of the SMBHs residing in the centers of galaxies today.
    Full-text · Article · Nov 2012 · The Astrophysical Journal
Show more