The Impact of metallicity evolution of the universe on the maximum mass of LIGO binary black holes

Abstract

We can be biased against observing massive black holes to merge in the local universe as the bounds on the maximum black hole mass ($M_{BH}^{\rm max}$) depends on the assumptions regarding the metallicity evolution of the star forming gas across the cosmic time. We investigate the bounds on the metallicity evolution, mass distribution and delay times of the binary black hole sources based on the ten observed events by LIGO. We parametrize $M_{BH}^{\rm max}$ to be a function of metallicity which itself is modeled to evolve with redshift in either a modest or rapid fashion. Rapid metallicity evolution models predict a stringent bound of $M_{BH}^{\rm max}=44^{+9}_{-5}M_{\odot}$, while the bound on $M_{BH}^{\rm max}$ in the models with modest metallicity evolution is $M_{BH}^{\rm max}=52^{+16}_{-9} M_{\odot}$. Therefore, inferring $M_{BH}^{\rm max}$ from GW data depends on the assumed metal enrichment history of the universe that is not severely constrained at the moment.