Formation of z ∼ 6 quasars from hierarchical galaxy mergers

Yuexing Cindy Li, Lars Hernquist, Brant Robertson, Thomas J. Cox, Philip F. Hopkins, Volker Springel, Liang Gao, Tiziana Di Matteo, Andrew R. Zentner, Adrian Jenkins, Naoki Yoshida

Research output: Contribution to journalArticle

216 Citations (Scopus)

Abstract

The discovery of luminous quasars at redshift z ∼ 6 indicates the presence of supermassive black holes (SMBHs) of mass ∼109 M when the universe was less than 1 billion years old. This finding presents several challenges for theoretical models because whether such massive objects can form so early in the ΛCDM cosmology, the leading theory for cosmic structure formation, is an open question. Furthermore, whether the formation process requires exotic physics such as super-Eddington accretion remains undecided. Here we present the first multiscale simulations that, together with a self-regulated model for the SMBH growth, produce a luminous quasar at z ∼ 6.5 in the ΛCDM paradigm. We follow the hierarchical assembly history of the most massive halo in a ∼3 Gpc3 volume and find that this halo of ∼8 × 1012 M forming at z ∼ 6.5 after several major mergers is able to reproduce a number of observed properties of SDSS J1148+5251, the most distant quasar detected at z = 6.42 (Fan et al. 2003). Moreover, the SMBHs grow through gas accretion below the Eddington limit in a self-regulated manner owing to feedback. We find that the progenitors experience vigorous star formation (up to 104 M yr-1) preceding the major quasar phase such that the stellar mass of the quasar host reaches 1012 M at z ∼ 6.5, consistent with observations of significant metal enrichment in SDSS J1148+5251. The merger remnant thus obeys a similar MBH-M bulge scaling relation observed locally as a consequence of coeval growth and evolution of the SMBH and its host galaxy. Our results provide a viable formation mechanism for z ∼ 6 quasars in the standard ΛCDM cosmology and demonstrate a common, merger-driven origin for the rarest quasars and the fundamental MBH-Mbulge correlation in a hierarchical universe.

Original languageEnglish (US)
Pages (from-to)187-208
Number of pages22
JournalAstrophysical Journal
Volume665
Issue number1 PART 1
DOIs
StatePublished - Aug 10 2007

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merger
quasars
cosmology
galaxies
accretion
formation mechanism
physics
halos
universe
metal
history
gas
simulation
stellar mass
star formation
assembly
histories
scaling
gases
metals

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Li, Y. C., Hernquist, L., Robertson, B., Cox, T. J., Hopkins, P. F., Springel, V., ... Yoshida, N. (2007). Formation of z ∼ 6 quasars from hierarchical galaxy mergers. Astrophysical Journal, 665(1 PART 1), 187-208. https://doi.org/10.1086/519297
Li, Yuexing Cindy ; Hernquist, Lars ; Robertson, Brant ; Cox, Thomas J. ; Hopkins, Philip F. ; Springel, Volker ; Gao, Liang ; Di Matteo, Tiziana ; Zentner, Andrew R. ; Jenkins, Adrian ; Yoshida, Naoki. / Formation of z ∼ 6 quasars from hierarchical galaxy mergers. In: Astrophysical Journal. 2007 ; Vol. 665, No. 1 PART 1. pp. 187-208.
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Li, YC, Hernquist, L, Robertson, B, Cox, TJ, Hopkins, PF, Springel, V, Gao, L, Di Matteo, T, Zentner, AR, Jenkins, A & Yoshida, N 2007, 'Formation of z ∼ 6 quasars from hierarchical galaxy mergers', Astrophysical Journal, vol. 665, no. 1 PART 1, pp. 187-208. https://doi.org/10.1086/519297

Formation of z ∼ 6 quasars from hierarchical galaxy mergers. / Li, Yuexing Cindy; Hernquist, Lars; Robertson, Brant; Cox, Thomas J.; Hopkins, Philip F.; Springel, Volker; Gao, Liang; Di Matteo, Tiziana; Zentner, Andrew R.; Jenkins, Adrian; Yoshida, Naoki.

In: Astrophysical Journal, Vol. 665, No. 1 PART 1, 10.08.2007, p. 187-208.

Research output: Contribution to journalArticle

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AU - Li, Yuexing Cindy

AU - Hernquist, Lars

AU - Robertson, Brant

AU - Cox, Thomas J.

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AU - Springel, Volker

AU - Gao, Liang

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AU - Jenkins, Adrian

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Li YC, Hernquist L, Robertson B, Cox TJ, Hopkins PF, Springel V et al. Formation of z ∼ 6 quasars from hierarchical galaxy mergers. Astrophysical Journal. 2007 Aug 10;665(1 PART 1):187-208. https://doi.org/10.1086/519297