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Title: Primordial Origins of Supermassive Black Holes

Abstract

Supermassive black holes (SMBHs) are orphans—since no known progenitors exist, their origins are mysterious. They are so massive that even if the first stars collapsed into black holes, they would struggle to even come close to supermassive sizes. I investigate whether primordial black holes (PBHs), formed by overdensities in the Big Bang, could be the progenitors of SMBH. I use the cosmology code Enzo to simulate the growth of single solar mass PBHs over the course of ~325 Myr to see if the PBHs can reach supermassive sizes. Additionally, I compare Bondi accretion to viscous accretion. I use two methods to test whether PBHs could grow fast enough to become SMBHs. First: comparison to the growth of their surrounding halos -- if a PBH is roughly 10 3 M⊙ by the time its halo is 10 8 M⊙, PBH–SMBH evolution is possible. Second: comparison to observed early SMBHs. If our PBHs reach similar sizes by similar times, PBH–SMBH evolution could be a viable pathway for those early observed SMBHs. Aside from the main results, I discovered that Bondi accretion and viscous accretion result in drastically different accretion rates. While black holes growing with Bondi accretion grew on order 10 -4,more » black holes with viscous accretion grew on order 10 +4. This is likely due to the dependence of Bondi accretion on simulation resolution. Given sufficiently dense seeding points, I found that the growth of PBHs does match the growth needed to reach supermassive sizes. The PBHs reached 10 3 M⊙ by the time their halos were 10 8 M⊙, so they do have the potential to reach the sizes of many observed SMBHs. Their extrapolated growth barely fell short of observed early SMBHs, but if 10 - 100 M PBHs were seeded, their growth trajectory would be on track to reach the sizes of early SMBHs.« less

Authors:
 [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brigham Young Univ., Provo, UT (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1460661
Report Number(s):
LA-UR-18-26505
DOE Contract Number:  
AC52-06NA25396
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Cosmology, Computational Physics, Primordial Black Hole, Enzo

Citation Formats

Black, William Kevin. Primordial Origins of Supermassive Black Holes. United States: N. p., 2018. Web. doi:10.2172/1460661.
Black, William Kevin. Primordial Origins of Supermassive Black Holes. United States. doi:10.2172/1460661.
Black, William Kevin. Fri . "Primordial Origins of Supermassive Black Holes". United States. doi:10.2172/1460661. https://www.osti.gov/servlets/purl/1460661.
@article{osti_1460661,
title = {Primordial Origins of Supermassive Black Holes},
author = {Black, William Kevin},
abstractNote = {Supermassive black holes (SMBHs) are orphans—since no known progenitors exist, their origins are mysterious. They are so massive that even if the first stars collapsed into black holes, they would struggle to even come close to supermassive sizes. I investigate whether primordial black holes (PBHs), formed by overdensities in the Big Bang, could be the progenitors of SMBH. I use the cosmology code Enzo to simulate the growth of single solar mass PBHs over the course of ~325 Myr to see if the PBHs can reach supermassive sizes. Additionally, I compare Bondi accretion to viscous accretion. I use two methods to test whether PBHs could grow fast enough to become SMBHs. First: comparison to the growth of their surrounding halos -- if a PBH is roughly 103 M⊙ by the time its halo is 108 M⊙, PBH–SMBH evolution is possible. Second: comparison to observed early SMBHs. If our PBHs reach similar sizes by similar times, PBH–SMBH evolution could be a viable pathway for those early observed SMBHs. Aside from the main results, I discovered that Bondi accretion and viscous accretion result in drastically different accretion rates. While black holes growing with Bondi accretion grew on order 10-4, black holes with viscous accretion grew on order 10+4. This is likely due to the dependence of Bondi accretion on simulation resolution. Given sufficiently dense seeding points, I found that the growth of PBHs does match the growth needed to reach supermassive sizes. The PBHs reached 103 M⊙ by the time their halos were 108 M⊙, so they do have the potential to reach the sizes of many observed SMBHs. Their extrapolated growth barely fell short of observed early SMBHs, but if 10 - 100 M PBHs were seeded, their growth trajectory would be on track to reach the sizes of early SMBHs.},
doi = {10.2172/1460661},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {7}
}

Thesis/Dissertation:
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