A Statistical Standard Siren Measurement of the Hubble Constant from the LIGO/Virgo Gravitational Wave Compact Object Merger GW190814 and Dark Energy Survey Galaxies

Abstract

We present a measurement of the Hubble constant H-0 using the gravitational wave (GW) event GW190814, which resulted from the coalescence of a 23M(circle dot) black hole with a 2.6M(circle dot) compact object, as a standard siren. No compelling electromagnetic counterpart has been identified for this event; thus our analysis accounts for thousands of potential host galaxies within a statistical framework. The redshift information is obtained from the photometric redshift (photo-z) catalog from the Dark Energy Survey. The luminosity distance is provided by the LIGO/Virgo gravitational wave sky map. Since this GW event has the second-smallest localization volume after GW170817, GW190814 is likely to provide the best constraint on cosmology from a single standard siren without identifying an electromagnetic counterpart. Our analysis uses photo-z probability distribution functions and corrects for photoz biases. We also reanalyze the binary black hole GW170814 within this updated framework. We explore how our findings impact the H-0 constraints from GW170817, the only GW merger associated with a unique host galaxy. From a combination of GW190814, GW170814, and GW170817, our analysis yields H-0 = 72.0(-8.2)(+12) km s(-1) Mpc(-1) (68% highest-density interval, HDI) for a prior in H-0 uniform between [20and140] km s(-1)Mpc(-1). The addition of GW190814 and GW170814 to GW170817 improves the 68% HDI from GW170817 alone by similar to 18%, showing how well-localized mergers without counterparts can provide a significant contribution to standard siren measurements, provided that a complete galaxy catalog is available at the location of the event.