Image Credit: NASA
CIERA Research Assistant Professor Giacomo Fragione was selected as one of 6 recipients for a highly-competitive NASA grant to design and carry out a LISA Preparatory Science Program. LISA will be the first mission of its kind, producing a unique data set with the potential to provide insight into many areas of astrophysics, fundamental physics, and cosmology. Realizing LISA’s science potential will require advance work to better understand LISA’s science targets and the specific ways in which LISA data can be used to understand them. The grant NASA has awarded Dr. Fragione is part of the LISA Preparatory Science (LPS) Program, which was created to help provide support to the projects that will complete the advance work required.
Dr. Fragione’s work focuses on intermediate-mass black holes (IMBHs), which are among the most puzzling objects in modern astrophysics. They play a crucial role in cosmology and galaxy formation, but very little is known about their origin and evolution. Observational evidence for IMBHs is still lacking because standard detection techniques, which use stellar and gas dynamics or X-ray and radio emission, suffer from various limitations, which have led to a handful of (often controversial) IMBH candidates. Recently, LIGO/Virgo has confirmed the first IMBH ever, from the detection of GW190521, demonstrating that gravitational waves (GWs) are uniquely well suited to measuring the properties of IMBHs.
LISA offers a unique opportunity to discover IMBHs out to large redshifts, since the inspiral and merger of IMBH binaries is a loud source of low-frequency GWs. Moreover, the intermediate mass-ratio inspiral (IMRI) of a stellar compact remnant into an IMBH is a potential target for multi-band detection, since LISA measurements will alert astronomers of an incoming merger detectable within the next few years by LIGO/Virgo/Kagra, Einstein Telescope, and Cosmic Explorer. The next decade may bring hundreds of GW events, promising a spectacular range of new science that touches on nearly every astronomical subfield, from stellar evolution to cosmology.
With so little known about IMBHs from previous observations, our ability to prepare for this new science relies almost entirely on theoretical modeling and predictions. Dr. Fragione will use the grant to focus on understanding the formation and GW signatures of IMBHs in dense stellar environments, where they are most likely to be produced and to form GW-emitting binaries through dynamical interactions with other compact objects. The final goal of the project will be to provide LISA Data Challenges with an extensive catalog of IMBH sources. This catalog will be an important guide for LISA data analysis and instrumental design strategies, and it will play a key role in extracting as much IMBH science as possible from LISA observations.
Congratulations to Dr. Fragione on having his proposal selected for a LISA Preparatory Science Program, and for receiving the grant from NASA for further research on IMBH!