Striking a Chord with Spectral Sirens: multiple features in the compact binary population correlate with $H_0$

TL;DR

This study analyzes gravitational-wave data to identify features in the black hole mass distribution that correlate with the Hubble constant, revealing key features that carry cosmological information and their potential to improve spectral siren measurements.

Contribution

It demonstrates, using real data, that specific features in the source-frame mass distribution are robust and carry significant information about the Hubble constant, including the first such analysis with real observations.

Findings

Identified prominent features in the mass distribution near 9 and 32 solar masses.

Showed that the peak near 32 solar masses correlates most strongly with $H_0$.

Developed model-independent statistics that independently correlate with $H_0$.

Abstract

Spectral siren measurements of the Hubble constant ($H_0$) rely on correlations between observed detector-frame masses and luminosity distances. Features in the source-frame mass distribution can induce these correlations. It is crucial, then, to understand (i) which features in the source-frame mass distribution are robust against model (re)parametrization, (ii) which features carry the most information about $H_0$, and (iii) whether distinct features independently correlate with cosmological parameters. We study these questions using real gravitational-wave observations from the LIGO-Virgo-KAGRA Collaborations' third observing run. Although constraints on $H_0$ are weak, we find that current data reveals several prominent features in the mass distribution, including peaks in the binary black hole source-frame mass distribution near $\sim$ 9 $\rm{M}_{\odot}$ and $\sim$ 32$\rm{M}_{\odot}$ and a roll-off at masses above $\sim$ 46$\rm{M}_{\odot}$. For the first time using real data, we show that all of these features carry cosmological information and that the peak near $\sim$ 32$\rm{M}_{\odot}$ consistently correlates with $H_0$ most strongly. Introducing model-independent summary statistics, we show that these statistics independently correlate with $H_0$, exactly what is required to limit systematics within future spectral siren measurements from the (expected) astrophysical evolution of the mass distribution.