Effects of binary stellar populations on direct collapse black hole formation

TL;DR

This study investigates how binary stellar populations influence the formation of direct collapse black holes by affecting the Lyman--Werner radiation field, revealing significant differences from single stellar populations.

Contribution

It demonstrates that binary stellar populations can significantly alter the critical flux needed for DCBH formation due to their spectral energy distribution effects.

Findings

Binary populations with ages > 10 Myr produce more LW photons.

J$_{crit}$ can be up to 100 times higher for binary populations.

Binary SEDs produce fewer H$^-$ photodetaching photons.

Abstract

The critical Lyman--Werner flux required for direct collapse blackholes (DCBH) formation, or J$_{crit}$, depends on the shape of the irradiating spectral energy distribution (SED). The SEDs employed thus far have been representative of {{realistic}} single stellar populations. We study the effect of binary stellar populations on the formation of DCBH, as a result of their contribution to the Lyman--Werner radiation field. Although binary populations with ages $>$ 10 Myr yield a larger LW photon output, we find that the corresponding values of J$_{crit}$ can be up to 100 times higher than single stellar populations. We attribute this to the shape of the binary SEDs as they produce a sub--critical rate of H$^-$ photodetaching 0.76 eV photons as compared to single stellar populations, reaffirming the role that H$^-$ plays in DCBH formation. This further corroborates the idea that DCBH formation is better understood in terms of a critical region in the H$_2$--H$^-$ photo--destruction rate parameter space, rather than a single value of LW flux.