Striking a Chord with Spectral Sirens: multiple features in the compact binary population correlate with H0

Spectral siren measurements of the Hubble constant (H0) 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 H0, 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 H0 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 ∼ 9 M⊙ and ∼ 32M⊙ and a roll-off at masses above ∼ 46M⊙. For the first time using real data, we show that all of these features carry cosmological information and that the peak near ∼ 32M⊙ consistently correlates with H0 most strongly. Introducing model-independent summary statistics, we show that these statistics independently correlate with H0, exactly what is required to limit systematics within future spectral siren measurements from the (expected) astrophysical evolution of the mass distribution.