The Assembly of the First Massive Black Holes

The existence of ∼10 9 M ⊙ supermassive black holes (SMBHs) within the first billion years of the Universe has stimulated numerous ideas for the prompt formation and rapid growth of black holes (BHs) in the early Universe. Here, we review ways in which the seeds of massive BHs may have first assembled, how they may have subsequently grown as massive as ∼10 9 M ⊙ , and how multimessenger observations could distinguish between different SMBH assembly scenarios. We conclude the following: ▪ The ultrarare ∼10 9 M ⊙ SMBHs represent only the tip of the iceberg. Early BHs likely fill a continuum from the stellar-mass (∼10M ⊙ ) to the supermassive (∼10 9 ) regimes, reflecting a range of initial masses and growth…

• NS
  National Science Foundation

  Awards: 1715661, 11991052, NNX15AB19G
• NA
  National Aeronautics and Space Administration

  Awards: NNX15AB19G, 2016YFA0400702, NNX17AL82G
• NN
  National Natural Science Foundation of China

  Awards: 11950410493, 11991052, 11721303, 2016YFA0400702
• MO
  Ministry of Urban Development