Triggering the Formation of Direct Collapse Black Holes by Their Congeners

Bin Yue, Andrea Ferrara, Fabio Pacucci, Kazuyuki Omukai

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Direct collapse black holes (DCBHs) are excellent candidates for seeds of supermassive black holes observed at z ≳; 6. The formation of a DCBH requires a strong external radiation field to suppress H2 formation and cooling in a collapsing gas cloud. Such a strong field is not easily achieved by first stars or normal star-forming galaxies. Here we investigate a scenario in which a previously formed DCBH can provide the necessary radiation field for the formation of additional ones. Using a one-zone model and simulated DCBH Spectral Energy Distributions (SEDs) filtered through absorbing gas initially having column density N H, we derive the critical field intensity, Jcrit LW, to suppress H2 formation and cooling. For the SED model with cm-2, 8.0 ×1024 cm-2, and 5.0 ×1024 cm-2, we obtain , 35, and 54, all much smaller than the critical field intensity for normal star-forming galaxies X-ray photons from previously formed DCBHs build up a high-z X-ray background (XRB) that may boost the Jcrit LW. However, we find that in the three SED models, only increases to ≈80, 170, and 390, even when reaches the maximum value allowed by the present-day XRB level (0.22, 0.034, 0.006 M o yr-1 Mpc-3), which is still much smaller than the galactic value. Although considering the XRB from first galaxies may further increase Jcrit LW, we conclude that our investigation supports a scenario in which DCBHs may be more abundant than predicted by models only including galaxies as external radiation sources.

Original languageEnglish
Article number111
JournalAstrophysical Journal
Volume838
Issue number2
DOIs
Publication statusPublished - 2017 Apr 1

Keywords

  • X-rays: diffuse background
  • dark ages, reionization, first stars
  • quasars: supermassive black holes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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