2010/05/17 by Shiv K. Sethi, Zoltán Haiman, Kanhaiya Lal Pandey +1
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/721/1/615
submitted to ApJ, 5 emulateapj pages and 5 figures
arxiv created 2010/05/17 · openalex publication_date 2010/08/31 · arxiv updated 2015/05/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
It has been proposed that primordial gas in early dark matter halos, with virial temperatures T vir ≳ 10 4 K, can avoid fragmentation and undergo rapid collapse, possibly resulting in a supermassive black hole. This requires the gas to avoid cooling and to remain at temperatures near T ∼ 10 4 K. We show that this condition can be satisfied in the presence of a sufficiently strong primordial magnetic field, which heats the collapsing gas via ambipolar diffusion. If the field has a strength above ∣ B ∣ ≳3.6 (comoving) nG, the collapsing gas is kept warm ( T ∼ 10 4 K) until it reaches the critical density n crit ≈ 10 3 cm -3 at which the rotovibrational states of H 2 approach local thermodynamic equilibrium. H 2 cooling then remains inefficient and the gas temperature stays near ∼10 4 K, even as it continues to collapse at higher densities. The critical magnetic field strength required to permanently suppress H 2 cooling is somewhat higher than the upper limit of ∼2 nG from the cosmic microwave background. However, it can be realized in the rare ≳(2–3)σ regions of the spatially fluctuating B field; these regions contain a sufficient number of halos to account for z ≈ 6 quasar black holes.