The NANOGrav 11 yr Data Set: Limits on Supermassive Black Hole Binaries in Galaxies within 500 Mpc

Supermassive black hole binaries (SMBHBs) should form frequently in galactic nuclei as a result of galaxy mergers. At sub-parsec separations, become strong sources low-frequency gravitational waves (GWs), targeted by Pulsar Timing Arrays (PTAs). We used recent upper limits on continuous GWs from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 11yr dataset to place constraints putative SMBHBs nearby massive galaxies. compiled comprehensive catalog ~44,000 galaxies local universe (up redshift ~0.05) and populated them with hypothetical binaries, assuming that total mass binary is equal SMBH derived global scaling relations. Assuming circular equal-mass emitting at NANOGrav's most sensitive frequency 8nHz, we found 216 are within sensitivity volume. ranked potential based GW detectability calculating signal-to-noise ratio (S/N) such would induce NANOGrav array. placed chirp binaries. For 19 galaxies, only very unequal-mass allowed, secondary less than 10 percent primary, roughly comparable SMBHB Milky Way. Additionally, were able exclude delivered major mergers (mass least 1/4) several these also first limit density purely data.