Session B09: Cecilia Payne-Gaposchkin Doctoral Dissertation Award in Astrophysics

From black holes to the Big Bang: astrophysics and cosmology with gravitational waves and their electromagnetic counterparts

The growing catalog of gravitational-wave signals from compact object mergers has allowed us to study the properties of black holes and neutron stars more precisely than ever before. Population-level studies of compact-objects mergers can reveal how these systems form and evolve. Multi-messenger observations of these events can shed light on the properties of their electromagnetic counterparts, such as short gamma-ray bursts and kilonovae. Finally, observations of the stochastic gravitational-wave background can constrain early-universe physics inaccessible with other means.

In my thesis, I demonstrate how we can leverage observations of gravitational waves and their electromagnetic counterparts to learn about astrophysics and cosmology. The first part focuses on methods for facilitating the detection of electromagnetic counterparts and the simultaneous analysis of gravitational-wave and electromagnetic data for mergers including a neutron star. I then transition to a detailed study of black hole spin, characterizing the measurability of spin in individual systems with current gravitational-wave detectors and presenting novel population-level analyses including a simultaneous search for the primordial stochastic background and the binary black hole foreground. Such analyses will be critical to the interpretation of the compact-object binaries and stochastic backgrounds accessible with present and future detectors.   

Gravitational Wave Paleontology: a New Frontier to Probe the Lives of Massive Binary Stars across Cosmic History

The rapidly increasing population of double compact object mergers detected with gravitational waves provides an unprecedented probe of the physics of black holes and neutron stars, and of the evolution of the binary massive stars that formed them. This will open the new frontier of `gravitational-wave paleontology': studying massive stars and binary evolution from their 'remnant' compact object mergers, with the goal of answering some of the biggest open questions in astrophysics today: How do these gravitational-wave sources form? What can we learn from them about the formation, lives, and explosive deaths of massive stars across cosmic time? How do these sources help to enrich the universe with heavy metals? In this thesis/talk, I outline the key bottleneck in gravitational-wave paleontology: the gravitational-wave progenitor Uncertainty Challenge. I will present what it is, and how I aim to quantify and understand the key uncertainties in theoretical models of the formation of gravitational-wave sources focusing on the formation from isolated massive binary stars, with the key goal to use the rapidly growing population of gravitational-wave observations as a new probe of the formation, lives, and deaths of massive binary stars through cosmic history   

Combining Spectroscopic And Imaging Galaxy Surveys For Improved Measurements Of Large-Scale Structure

Large galaxy imaging surveys promise to deliver extraordinary datasets to answer open questions about the nature of dark matter and dark energy, but these surveys suffer from challenges arising from the difficulty in constraining galaxy redshift. My thesis work leverages spectroscopic observations of small, well selected subsets of galaxies observed in imaging surveys to improve the utility of photometric datasets for cosmological studies. First, I will describe the new methodology designed to optimize use of overlapping spectroscopic information for the Dark Energy Survey Year 3 galaxy lensing analysis and exhibit the resulting cosmology constraints. Second, I will present a novel algorithm for accurately propagating uncertainties of probability distributions and illustrate the value of this algorithm for redshift calibration. Finally, I will show results using spectroscopy of galaxy cluster members to measure the impact of projection effects on clusters and comment on how this relates to optical cluster cosmology results. This thesis presents promising paths forward to take full advantage of forthcoming surveys to constrain the cosmological model.