Unveiling the First Black Holes With JWST: Multi-wavelength Spectral Predictions

Growing supermassive black holes (similar to 10(9) M-circle dot) that power luminous z > 6 quasars from light seeds-the remnants of the first stars-within a Gyr of the Big Bang poses a timing challenge. The formation of massive black hole seeds via direct collapse with initial masses similar to 10(4)-10(5) M-circle dot alleviates this problem. Viable direct-collapse black hole formation sites, the satellite halos of star-forming galaxies, merge and acquire stars to produce a new, transient class of high-redshift objects, obese black hole galaxies (OBGs). The accretion luminosity outshines that of the stars in OBGs. We predict the multi-wavelength energy output of OBGs and growing Pop III remnants at z = 9 for standard and slim disk accretion, as well as high and low metallicities of the associated stellar population. We derive robust selection criteria for OBGs-a pre-selection to eliminate blue sources, followed by color-color cuts ([F-090W-F-220W]> 0; -0.3<[F-200W-F-444W]< 0.3) and the ratio of X-ray flux to rest-frame optical flux (F-X/F-444W >> 1). Our cuts sift out OBGs from other bright, high-and low-redshift contaminants in the infrared. OBGs with predicted M-AB < 25 are unambiguously detectable by the Mid-Infrared Instrument (MIRI), on the upcoming James Webb Space Telescope (JWST). For parameters explored here, growing Pop III remnants with predicted M-AB < 30 will likely be undetectable by JWST. We demonstrate that JWST has the power to discriminate between initial seeding mechanisms.