Investigating the mixing between two black hole populations in LIGO-Virgo-KAGRA GWTC-3

Abstract

We introduce a population model to analyze the mixing between hypothesised power-law and $\sim 35M_{\odot }$ Gaussian bump black hole populations in the latest gravitational wave catalog, GWTC-3, estimating their co-location and separation. We find a relatively low level of mixing, $3.1_{-3.1}^{+5.0}\%$, between the power-law and Gaussian populations, compared to the percentage of mergers containing two Gaussian bump black holes, $5.0_{-1.7}^{+3.2}\%$. Our analysis indicates that black holes within the Gaussian bump are generally separate from the power-law population, with only a minor fraction engaging in mixing and contributing to the $\mathcal{M}\sim 14M_{\odot }$ peak in the chirp mass. This leads us to identify a distinct population of Binary Gaussian Black Holes (BGBHs) that arise from mergers within the Gaussian bump. We suggest that current theories for the formation of the massive $35M_{\odot }$ Gaussian bump population may need to reevaluate the underlying mechanisms that drive the preference for BGBHs.

Comments: 19 pages, 11 figures. Submitted to PRD