Dartmouth Events

Abstract: The first black hole seeds formed when the age of the Universe was less than 500 Myr and played an important role in the growth of early (z=7) supermassive black holes (SMBHs). In this talk, I provide some insights on two questions.

 

First, how do we identify the first black holes in deep, multi-wavelength surveys? The observational signatures of black hole seeds remain largely unexplored, and as a result we are yet to detect these sources. I present detailed predictions for the spectra of different categories of black hole seeds, and a photometric method to identify them in surveys. The method selects two z > 6 objects in the CANDELS/GOODS-S survey. I will also present new HST data on the variability of CR7, a fascinating galaxy at z = 6.6 that has been proposed as host of either a black hole seed or a Pop III star formation region. I will explore the role that new facilities (e.g., JWST, ATHENA, Lynx) will play in the detection of the first black holes in the Universe.

 

Second, how do explain the presence of the first SMBHs by redshift 7? I present a probabilistic model for black hole growth, with important implications for the conditions that facilitate efficient growth at high-z. By bringing in a precise definition of "growth probability", the model demonstrates quantitatively the generally-accepted concept that the z=7 SMBHs are the "luckiest" members of ht eensemble of high-z black holes. We employ this formalism to predict the shape of the low-mass end of the M-sigma relation. Furthermore, we predict a deficit of black holes shining at bolometric luminosities around 10^42 erg/s. Joined with a detection bias, this could partly explain the scarce number of intermediate-mass black holes detected.