Probing the Universe's expansion and gravitational wave sources with ground-based optical telescopes

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

A research team at Carnegie-Mellon University will carry out an observational campaign of astronomical transient events using primarily the Dark Energy Camera (DECam), with a focus on the gravitational wave (GW) sources that will be detected in the upcoming LIGO/Virgo/KAGRA GW detectors observing run (expected during 2023-2024). So far, only one electromagnetic (EM) counterpart to a GW binary neutron star merger has been confidently identified. The goal of the project is to discover new electromagnetic counterparts to mergers of binary neutron stars, while also searching for the first optical transient events associated with GW neutron star-black hole mergers and massive stellar binary black holes. The team will make use of a state-of-the-art difference imaging software pipeline, and machine learning methods to identify transients and model their light curves. Finally, this program will use the DECam observations, in combination with spectroscopic data from other ground-based facilities and GW data, to study the environment of GW sources to understand the origin of gravitational wave sources, and to produce new measurements of the Hubble constant H0, a measure of the expansion rate of the universe, through a procedure called the standard siren method. As part of this program, the team will provide tutorials based on the new DECam data at local public high schools through the Teachers Training program, and providing outreach to the broader community through public lectures and articles. DECam is one of the very few currently functioning instruments with the capabilities to enable EM counterpart discoveries in the upcoming GW observing run. This project, therefore, serves an important role within the multi-messenger astronomy community. EM counterpart discoveries enable a wide range of scientific analyses that are otherwise inconclusive or impossible with GW data alone. These include constraining (1) the equation of state of neutron stars, (2) modifications to General Relativity, and (3) the production of the heaviest elements in the Universe. This project focuses on addressing two pressing questions in astrophysics: the puzzling “Hubble constant tension”, a discrepancy between values of H0 measured through different probes, and the origin of merging binary systems, whether facilitated by dynamical interactions or by stellar evolution. This award advances the goals of the Windows on the Universe Big Idea. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.