Direct Collapse Pre-supermassive Black Hole Objects as Ly<i>α</i> Emitters

Abstract The Direct Collapse scenario to form the supermassive black hole (SMBH) seeds offers the most promising way to explain the origin of quasars at z &gt; 7. Assuming atomic primordial gas, can Ly α photons escape from the central regions of the collapse and serve as a diagnostic for the detection of these pre-SMBH objects? Models of spherical collapse have found these photons to be trapped and destroyed. We use Ly α radiation transfer within the inflow-outflow geometry, based on earlier zoom-in cosmological modeling involving radiation transfer and magnetic forces. Adopting geometry that includes ongoing disk and spherical accretion, and formation of a biconical outflow funnel, we obtain the formation of a dense radiatively driven expanding shell. The Ly α transfer is performed using a Monte Carlo algorithm, accounting for the destruction of Ly α photons and the emergence of two-photon emission. We find that a substantial fraction of Ly α photons can escape through the funnel and calculate the line profiles, their line peak velocity shift, asymmetry, and cuspiness, by varying basic model parameters. The escaping Ly α emission is anisotropic and sensitive to the overall inflow-outflow geometry. The escaping fraction of Ly α radiation exceeds 95% from a z = 10 pre-SMBH object in principle detectable by the JWST NIRSpec in the multiobject spectroscopy mode, during ∼10 4 s for a 10 σ signal-to-noise ratio. Moreover, comparisons with line shapes from high- z galaxies and quasars allow us to separate them from pre-SMBH objects based on the line shape: the pre-SMBH lines show a profound asymmetry and extended red tail.