The Hubble Constant from Supernovae

Type Ia Supernova Cosmology

“…This has been the classic distance ladder approach (see Jacobi et al 1992 for a comprehensive description of early methods). The HST key program (Freedman et al 2001) and the SN Ia programs by Sandage, Tammann and Saha, and SH 0 ES (see Saha and Macri 2016, for a complete bibliography of these efforts) have reduced the distance ladder to three steps: a local (geometric) anchor to calibrate the Cepheid period-luminosity (Leavitt) relation, calibrate SNe Ia with Cepheid distances and then use the Hubble diagram to step into the Hubble flow. Most prominent anchors are geometric distances to Milky Way Cepheids, eclipsing binaries in the Large Magellanic Clouds and the water megamasers in NGC 4258 (Humphreys et al 2013).…”

“…Measuring exact distances to SNe Ia has the problem that the volume reachable by reliable distance indicators is rather limited and the low rate of SNe Ia leads to very small samples. The Hubble Space Telescope (HST ) was critical for this method (see Saha and Macri 2016, for a review of these programs) and has by now yielded a sample of 19 SNe Ia with Cepheid distances (Riess et al 2016). The Cepheids were measured in the near-infrared (1.6µm) to reduce uncertainties in phase calibrations and absorption.…”