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Dr. Sean McWilliams

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Princeton University
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Gravitational waves and stalled satellites from massive galaxy mergers at z < 1
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Pulsar timing arrays (PTAs), which are currently operating around the
world and achieving remarkable sensitivities, will observe
supermassive black holes (SMBHs) at redshifts z < ~1. Until now, all
estimates of the anticipated signal strength of these sources have
relied primarily on simulations to predict the relevant merger
rates. I will present results from a completely new approach, which
combines observational data and a fully self-consistent numerical
evolution of the galaxy mass function. This method, which we will
argue is superior to past estimates in several key ways, predicts a
merger rate for massive galaxies that is ~10 times larger than that
implied by previous calculations. I will explain why previous methods
applied to this problem will systematically underestimate this merger
rate. Finally, I will show that the new rate implies a range of
possible signal strengths that is already in mild tension with PTA
observations, with our model predicting a detection at the 95%
confidence level as early as 2016. This would make PTAs the first
instruments to directly detect gravitational waves, and would provide
unprecedented information about the dynamics of merging galaxies, and
merging bulges and supermassive black holes within those galaxies.

Back to Spring 2013 Astrophysics Seminars
Received Jan 24, 2013