The Carnegie Supernova Project: Absolute Calibration and the Hubble Constant

Abstract We present an analysis of the final data release of the Carnegie Supernova Project I , focusing on the absolute calibration of the luminosity–decline rate relation for Type Ia supernovae (SNe Ia) using new intrinsic color relations with respect to the color-stretch parameter, s BV , enabling improved dust extinction corrections. We investigate to what degree the so-called fast-declining SNe Ia can be used to determine accurate extragalactic distances. We estimate the intrinsic scatter in the luminosity–decline rate relation and find it ranges from ±0.13 mag to ±0.18 mag with no obvious dependence on wavelength. Using the Cepheid variable star data from the SH0ES project, the SN Ia distance scale is calibrated and the Hubble constant is estimated using our optical and near-infrared sample, and these results are compared to those determined exclusively from a near-infrared subsample. The systematic effect of the supernova’s host galaxy mass is investigated as a function of wavelength and is found to decrease toward redder wavelengths, suggesting this effect may be due to dust properties of the host. Using estimates of the dust extinction derived from optical and near-infrared wavelengths and applying these to the H band, we derive a Hubble constant , whereas using a simple B − V color correction applied to the B band yields . Photometry of two calibrating SNe Ia from the CSP-II sample, SN 2012ht and SN 2015F, is presented and used to improve the calibration of the SN Ia distance ladder.