Speaker
Description
Binary black holes (BHBs) embedded in dense gas hold the promise of "multi-messenger astrophysics": when they are detected both through gravitational waves (GWs) and electromagnetic (EM) observations, they will enable novel science. This is true both for massive BHBs, whose GWs will be detectable by the future LISA satellite and by on-going pulsar timing arrays (PTAs), as well as for stellar-mass BHBs detected through ground-based GW detectors. In both cases, identifying coalescing binaries through their EM signatures will help clarify their astrophysical origin and yield novel probes of cosmology, fundamental physics, and accretion physics. In this talk, I will describe how circumbinary gas may impact the orbital evoluton of binaries, while producing characteristic EM signatures for both massive and stellar-mass BHBs, based on hydrodynamical simulations and analytic models. In both cases, several binary candidates have been identified in optical surveys, and LSST should soon be able to uncover robust binaries based on their high-quality, multi-band light-curves.