Identifying Elusive Electromagnetic Counterparts to Gravitational Wave
  Mergers: an end-to-end simulation
  Combined gravitational-wave (GW) and electromagnetic (EM) observations of
compact binary mergers should enable detailed studies of astrophysical
processes in the strong-field gravity regime. Networks of GW interferometers
have poor angular resolution on the sky and their EM signatures are predicted
to be faint. Therefore, a challenging goal will be to unambiguously pinpoint
the EM counterparts to GW mergers. We perform the first comprehensive
end-to-end simulation that focuses on: i) GW sky localization, distance
measures and volume errors with two compact binary populations and four
different GW networks, ii) subsequent detectability by a slew of
multiwavelength telescopes and, iii) final identification of the merger
counterpart amidst a sea of possible astrophysical false-positives. First, we
find that double neutron star (NS) binary mergers can be detected out to a
maximum distance of 400 Mpc (or 750 Mpc) by three (or five) detector GW
networks respectively. NS -- black-hole (BH) mergers can be detected a factor
of 1.5 further out. The sky localization uncertainties for NS-BH mergers are
50--170 sq. deg. (or 6--65 sq. deg.) for a three (or five detector) GW network
respectively. Second, we quantify relative fractions of optical counterparts
that are detectable by different size telescopes. Third, we present five case
studies to illustrate the diversity of challenges in secure identification of
the EM counterpart at low and high Galactic latitudes. For the first time, we
demonstrate how construction of low-latency GW volumes in conjunction with
local universe galaxy catalogs can help solve the problem of false positives.
