Submillimeter signatures from growing supermassive black holes before reionization

Abstract

The presence of supermassive black holes (SMBHs) with masses up to $M_{\bullet }\sim 10^9{M}_{\odot }$ at redshifts $z\simeq 7.5$ suggests that their seeds may have started to grow long before the reionization in ambient medium with pristine chemical composition. During their latest 500Myr episode of growing from $z\ge 10$ to $z\sim 7$ the black holes shine as luminous as $10^{11}–10^{12}{L}_{\odot }$, with a cumulative spectrum consisting of the intrinsic continuum from hot accretion disk, nebular hydrogen and helium spectral lines and free-free continuum from gas of host halos. Here we address the question of whether such a plain spectrum would allow us to trace evolution of these growing SMBHs. In our calculations we assume that host galaxies have stellar populations with masses smaller than the mass of their central black holes -- the so-called obese black hole galaxies. Within this model we show that for a sufficiently high mass of gas in a host galaxy -- not smaller than the mass of a growing black hole, the cumulative spectrum in the far-infrared reveals a sharp transition from a quasi-blackbody Rayleigh-Jeans spectrum of the black hole $\propto {\lambda }^{-2}$ to a flat free-free nebular continuum ${\lambda }^{0.118}$ on longer wavelength limit. Once such a transition in the spectrum is resolved, the black hole mass can be inferred as a combination of the observed wavelength at the transition ${\lambda }_k$ and the corresponding spectral luminosity. Possible observability of this effect in spectra of growing high-$z$ SMBHs and determination of their mass with the upcoming JWST and the planned space project Spektr-M is briefly discussed.

9 pages, 5 figures, accepted in the ApJ

References in corpus (16)

• A luminous quasar at a redshift of z = 7.085
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
• Supermassive black hole formation during the assembly of pre-galactic discs
• The Sloan Lens ACS Survey. V. The Full ACS Strong-Lens Sample
• The evolution of massive black hole seeds
• Super-Critical Growth of Massive Black Holes from Stellar-Mass Seeds
• Formation of massive black holes in rapidly growing pre-galactic gas clouds
• Rapid growth of seed black holes in the early universe by supra-exponential accretion
• The aftermath of the first stars: massive black holes
• Feedback-regulated Super Massive Black Hole Seed Formation
• Discovery of eight z ~ 6 quasars from Pan-STARRS1
• Direct collapse black hole formation from synchronized pairs of atomic cooling halos
• Conditions for Optimal Growth of Black Hole Seeds
• A No-Go Theorem for Direct Collapse Black Holes Without a Strong Ultraviolet Background
• Galaxy evolution studies with the SPace IR telescope for Cosmology and Astrophysics (SPICA): the power of IR spectroscopy

Cited by in corpus (1)

• Interstellar Medium in Extremely High Star-Formation Regions: A Prospect of Observations on the Millimetron Space Observatory