LIGO (0.02 %3C z %3C 0.03, 40 to 80 Mpc) survey collection

The search for electromagnetic counterparts for the in-spiral of binary black holes is impeded by poor initial source localizations and a lack of a compelling model for the counterpart; therefore, rapid electromagnetic follow-up is required to understand the astrophysical context of these sources.

Because astrophysical sources of gravitational radiation are likely to reside in galaxies, it would make sense to search rst in regions where the LIGO-Virgo probability is large and where the density of galaxies is large as well. Under the Bayesian prior assumption that the probability of a gravitational-wave event from a given region of space is proportional to the density of galaxies within the probed volume, one can calculate an improved localization of the position of the source simply by multiplying the LIGO-Virgo skymap by the density of galaxies in the range of redshifts.