4:00–5:00 pm Zoom Room (online)
Elias Oakes, "The Distance to the Fornax dSph via the Tip of the Red Giant Branch and Horizontal Branch Stars"
Host: Rich Kron
The Hubble constant (H0) tension stands at a more than 4σ discrepancy between measurements from the local distance ladder and the cosmic microwave background, with no physical explanation in sight. This tension motivates the development of an independent path to H0, to cross-reference existing distance measurements and control for systematics. The Carnegie-Chicago Hubble Program (CCHP) is approaching this problem by using Population II stars to establish an accurate and precise cosmic distance scale that is independent of, but parallel to, the well-established and commonly known Population I path using Cepheid variables. In this work, we determine the distance to the Fornax dwarf spheroidal (dSph) galaxy using three independent Population II distance methods: the Tip of the Red Giant Branch (TRGB), RR Lyrae period-luminosity and period-Wesenheit relations, and the magnitude of the Zero-Age Horizontal Branch (ZAHB) envelope. Using wide-field, ground-based imaging data, obtained at the Magellan 6.5m telescope at Las Campanas, Chile, we measure a TRGBbased distance modulus of μTRGB = 20.84 ± 0.06 mag, RR Lyrae distance modulus of μRRL = 20.75 ± 0.1 mag using archival variable star surveys, and ZAHB distance modulus of μZAHB = 20.81 ± 0.02 mag. Averaging these measurements yields a combined distance modulus of μ = 20.80±0.04 mag, which is consistent with an extensive catalog of published distance measurements to Fornax.
Immediately following the presentation there will be a reception honoring the Class of 2020 Astrophysics Majors.