Detectability of gravitational waves from binary black holes: Impact of precession and higher modes

Gravitational wave templates used in current searches for binary black holes omit the effects of precession of the orbital plane and higher-order modes. While this omission seems not to impact the detection of sources having mass ratios and spins similar to those of GW150914, even for total masses $M>200\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$, we show that it can cause large fractional losses of sensitive volume for binaries with mass ratio $q\ensuremath{\ge}4$ and $M>100\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$, measured in the detector frame. For the highest precessing cases, this is true even when the source is face-on to the detector. Quantitatively, we show that the aforementioned omission can lead to fractional losses of sensitive volume of $\ensuremath{\sim}15%$, reaching $>25%$ for the worst cases studied. Loss estimates are obtained by evaluating the effectualness of the SEOBNRv2-ROM double spin model, currently used in binary black hole searches, towards gravitational wave signals from precessing binaries computed by means of numerical relativity. We conclude that, for sources with $q\ensuremath{\ge}4$, a reliable search for binary black holes heavier than $M>100\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ needs to consider the effects of higher-order modes and precession. The latter seems especially necessary when Advanced LIGO reaches its design sensitivity.