Department of Physics & Astronomy
University of New Mexico

Center for Astrophysics Research and Technologies Seminar Series

Post-Merger Galaxies and (Still) Enigmatic Supermassive Black Hole Binaries

Presented by Greg Walsh

Pulsar timing arrays have ushered in the era of low-frequency gravitational-wave astronomy with evidence for the stochastic gravitational wave background (GWB). Although the source of the GWB remains unknown, it has long been believed that the cosmological ensemble of inspiralling supermassive black hole binaries (SMBHBs) is the most likely progenitor. Although significant attention has been given to electromagnetic identification of these systems, almost none have been successful, with only one closely-separated SMBH pair discovered using VLBI techniques, to date. In this talk, I will begin by describing the multi-scale radio and multi-wavelength emission properties of a sample of 28 post-merger galaxies and contextualize these results within the framework of SMBHB evolution. Then, I present the initial results of a 1300-hour VLBA program targeting 6 of these post-merger galaxies to directly search for evidence of SMBHBs at the milliarcsecond scale and discuss how these results are evolving our understanding of SMBHB evolution.

2:00 pm, Thursday, February 1, 2024

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