Thursday, July 30, 2020

Supermassive Black Holes Form Early

It takes about 100 million years after the Big Bang (the Universe is now about 13.8 billion years old) for supermassive black holes to form.
The observation of quasars at very high redshift such as Poniuaena is a challenge for models of super-massive black hole (SMBH) formation. This work presents a study of SMBH formation via known physical processes in star-burst clusters formed at the onset of the formation of their hosting galaxy. 
While at the early stages hyper-massive star-burst clusters reach the luminosities of quasars, once their massive stars die, the ensuing gas accretion from the still forming host galaxy compresses its stellar black hole (BH) component to a compact state overcoming heating from the BH--BH binaries such that the cluster collapses, forming a massive SMBH-seed within about a hundred Myr. Within this scenario the SMBH--spheroid correlation emerges near-to-exactly. The highest-redshift quasars may thus be hyper-massive star-burst clusters or young ultra-compact dwarf galaxies (UCDs), being the precursors of the SMBHs that form therein within about 200 Myr of the first stars. 
For spheroid masses <10^9.6 Msun a SMBH cannot form and instead only the accumulated nuclear cluster remains. The number evolution of the quasar phases with redshift is calculated and the possible problem of missing quasars at very high redshift is raised. SMBH-bearing UCDs and the formation of spheroids are discussed critically in view of the high redshift observations. 
A possible tension is found between the high star-formation rates (SFRs) implied by downsizing and the observed SFRs, which may be alleviated within the IGIMF theory and if the downsizing times are somewhat longer.
Pavel Kroupa, Ladislav Subr, Tereza Jerabkova, Long Wang "Very high redshift quasars and the rapid emergence of super-massive black holes" arXiv (July 28, 2020) (MNRAS, in press).

Footnote: Demerits to Professor Kroupa (whose work overall is excellent) for the incredibly long run on sentence in the abstract (part  of which is highlighted above).

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