We present measurements of black hole masses and Eddington ratios (
- Award ID(s):
- 1813609
- NSF-PAR ID:
- 10303703
- Date Published:
- Journal Name:
- The Astronomy and Astrophysics Review
- Volume:
- 28
- Issue:
- 1
- ISSN:
- 0935-4956
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract λ Edd) for a sample of 38 bright (M 1450< −24.4 mag) quasars at 5.8 ≲z ≲ 7.5, derived from Very Large Telescope/X–shooter near–IR spectroscopy of their broad Civ and Mgii emission lines. The black hole masses (on average,M BH∼ 4.6 × 109M ⊙) and accretion rates (0.1 ≲λ Edd≲ 1.0) are broadly consistent with that of similarly luminous 0.3 ≲z ≲ 2.3 quasars, but there is evidence for a mild increase in the Eddington ratio abovez ≳ 6. Combined with deep Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [CII ] 158μ m line from the host galaxies and VLT/MUSE investigations of the extended Lyα halos, this study provides fundamental clues to models of the formation and growth of the first massive galaxies and black holes. Compared to local scaling relations,z ≳ 5.7 black holes appear to be over-massive relative to their hosts, with accretion properties that do not change with host galaxy morphologies. Assuming that the kinematics of theT ∼ 104K gas, traced by the extended Lyα halos, are dominated by the gravitational potential of the dark matter halo, we observe a similar relation between black hole mass and circular velocity as reported forz ∼ 0 galaxies. These results paint a picture where the first supermassive black holes reside in massive halos atz ≳ 6 and lead the first stages of galaxy formation by rapidly growing in mass with a duty cycle of order unity. The duty cycle needs to drastically drop toward lower redshifts, while the host galaxies continue forming stars at a rate of hundreds of solar masses per year, sustained by the large reservoirs of cool gas surrounding them. -
null (Ed.)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 histories. ▪ Stellar-mass BHs were likely left behind by the first generation of stars at redshifts as high as ∼30, but their initial growth typically was stunted due to the shallow potential wells of their host galaxies. ▪ Conditions in some larger, metal-poor galaxies soon became conducive to the rapid formation and growth of massive seed holes, via gas accretion and by mergers in dense stellar clusters. ▪ BH masses depend on the environment (such as the number and properties of nearby radiation sources and the local baryonic streaming velocity) and on the metal enrichment and assembly history of the host galaxy. ▪ Distinguishing between assembly mechanisms will be difficult, but a combination of observations by the Laser Interferometer Space Antenna (probing massive BH growth via mergers) and by deep multiwavelength electromagnetic observations (probing growth via gas accretion) is particularly promising.more » « less
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