Charlotte Ward (University of Maryland)

Charlotte Ward Colloquium: Tracing the first massive black hole seeds and their merger-driven growth with ZTF

Marsfield Lecture Theatre

Abstract

Over the last 3 years, the Zwicky Transient Facility (ZTF) has demonstrated the capability of wide-field time-domain surveys to discover the important black hole populations which trace the formation of the first massive black hole seeds and their merger-driven growth. For instance, our search for off-nuclear active galactic nuclei (AGN) in ZTF revealed 9 supermassive black holes (SMBHs) which may have been ejected from their host galaxy by gravitational wave recoil from SMBH mergers with misaligned spins. Likewise, our search for variable intermediate mass black holes (IMBHs) in dwarf galaxies found 200 new IMBH candidates, most of which could not have been found via their spectroscopic signatures alone. Finally, our study of periodically variable AGN with double-peaked broad emission lines revealed how single AGN can mimic SMBH binaries and mergers. We found these rare black holes amongst large populations of AGN in part by using innovative forward modelling techniques to improve photometric sensitivity and measure the separations between variable objects and their host galaxies. Our work is an exciting precursor to the Legacy Survey of Space and Time which we expect to detect substantially larger populations of recoiling SMBH and IMBH candidates.