Location: ERC 532
Scientific Advisors: Wendy L. Freedman, Richard G. Kron
Affiliations: Kavli Institute for Cosmological Physics
Ph.D. Thesis Defense
Defense date: July 7, 2017
On the Population II Distance Scale: The Tip of the Red Giant Branch Distances to Local Galaxies"
Ph.D. Committee members: Richard Kron (PhD Advisor), Michael Gladders, Stephen Kent, Daniel Fabrycky
"Currently there is a tension in values of the Hubble constant as measured in the local universe compared with estimates from the cosmic microwave background. Dylan Hatt's thesis uses an alternative method to classical Cepheids for measuring the local distance scale, a technique that holds promise for resolving the current disagreement.."
- Wendy L. Freedman, Ph.D. advisor
"Dylan's thesis work explores a technique for measuring distances to galaxies that is independent of the Cepheid distance scale. The thesis work involved new measurements of many thousands of giant-branch stars in several Local Group galaxies. Ultimately the project will help refine the distance scale and the value of the Hubble constant."
- Richard G. Kron, Ph.D. advisor
Thesis Abstract: The difference between direct and indirect measures of H0, i.e. via SNe Ia distances anchored by Cepheids and via modeling of the Cosmic Microwave Background, stands at an average > 3σ. This tension has motivated a second look at the calibration of the extragalactic distance scale. Population II stars have gained favor as an independent calibrator for SNe Ia, bypassing the possible systematics associated with the traditional Cepheid-based distance scale. I will present high-fidelity distances to five local galaxies -- IC 1613, NGC 4424, NGC 4526, NGC 4536, and NGC 1365 -- using the Tip of the Red Giant Branch, which is a prominent observable that is defined by well-understood stellar astrophysics. I will further compare these results with existing Cepheid-based distances and demonstrate that there is good correspondence between distances derived from stars of Population I and II.
Past Department Committees:
Department News & Highlights