A statistical standard siren measurement of the Hubble constant from the
  LIGO/Virgo gravitational wave compact object merger GW190814 and Dark Energy
  Survey galaxies
  We present a measurement of the Hubble constant $H_0$ using the gravitational
wave (GW) event GW190814, which resulted from the coalescence of a 23 $M_\odot$
black hole with a 2.6 $M_\odot$ 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 photo-$z$
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 $H_0 =
72.0^{+ 12}_{- 8.2 }~{\rm km~s^{-1}~Mpc^{-1}}$ (68\% Highest Density Interval,
HDI) for a prior in $H_0$ uniform between $[20,140]~{\rm km~s^{-1}~Mpc^{-1}}$.
The addition of GW190814 and GW170814 to GW170817 improves the 68\% HDI from
GW170817 alone by $\sim 18\%$, 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.
