Abstract
We present calculations on the formation of massive black holes of
105 M⊙ at z > 6, which can be the seeds of
supermassive black holes at z ≳ 6. Under the assumption of compact
star cluster formation in merging galaxies, star clusters in haloes of
˜ 108-109 M⊙ can undergo
rapid core collapse, leading to the formation of very massive stars
(VMSs) of ˜ 1000 M⊙ that collapse directly into
black holes with similar masses. Star clusters in haloes of ≳
109 M⊙ experience Type II supernovae before
the formation of VMSs, due to long core-collapse time-scales. We also
model the subsequent growth of black holes via accretion of residual
stars in clusters. Two-body relaxation refills the loss cones of stellar
orbits efficiently at larger radii and resonant relaxation at small
radii is the main driver for accretion of stars on to black holes. As a
result, more than 90 percent of stars in the initial cluster are
swallowed by the central black holes before z = 6. Using dark matter
merger trees, we derive black hole mass functions at z = 6-20. The mass
function ranges from 103-105 M⊙ at
z ≲ 15. Major merging of galaxies of ≳ 4 ×
108 M⊙ at z ˜ 20 leads successfully to
the formation of ≳ 105 M⊙ black holes by
z ≳ 10, which could be the potential seeds of supermassive black
holes seen today.
Original language | English |
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Pages (from-to) | 2423-2432 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 457 |
Issue number | 3 |
DOIs | |
Publication status | Published - 10 Feb 2016 |
Keywords / Materials (for Non-textual outputs)
- stars: black holes
- galaxies: formation
- galaxies: high-redshift
- quasars: supermassive black holes
- galaxies: star clusters: general