Seminar by Mudit Garg, University of Zurich
Our current understanding is that an environment – mainly consisting of gas, stars, or a third massive black hole (MBH) – is required to bring MBH binaries (MBHBs) with total mass ∼ [10^4, 10^7] MSun to near-merger from parsec separation. The final inspiral is driven by radiated gravitational waves (GWs) in near milli-Hz frequencies, which the recently adopted space-based mission LISA will observe in the 2030s up to high redshifts. Despite GWs dominating the binary evolution in the LISA band, a suitable environment can still non-negligibly speed up or slow down the binary inspiral, or sustain residual initial orbital eccentricity. Using realistic data analysis techniques, I show how well LISA will measure gas-induced perturbation or initial eccentricity, together or separately. I also explore if a small eccentricity can mimic a weak gas effect and vice versa to motivate synergies between LISA and electromagnetic observations. Moreover, I show how ignoring moderate gas effects (Eddington ratio ~0.1) or eccentricity (~10^(-2.5)) biases binary parameters and violates general relativity. Lastly, I demonstrate how spin-eccentricity correlations in the LISA band can break certain degeneracies regarding formation channels. Therefore, my results have rich implications for astrophysics, data analysis, fundamental physics, and cosmology. LISA will launch in a decade, making these studies exciting and valuable in unlocking the mysteries of MBHB evolution.
Host: Zoltan Haiman