Mechanism for low RB scattering exclusive to high-mass hosts

Determine why non-standard scattering models that predict low total-to-selective extinction coefficients RB would manifest solely in high-stellar-mass (M⋆ > 10^10 M⊙) Type Ia supernova host galaxies, and establish whether a physical mechanism justifies such selective manifestation.

Background

The paper examines extinction modeling for Type Ia supernovae used in the SH0ES Cepheid-based calibration, critiquing the Popovic et al. (2023) dust model (P23) that assigns different mean RB values to low- and high-stellar-mass host galaxies. The authors find that applying the P23 model to calibration galaxies leads to systematic discrepancies, particularly for red supernovae in high-mass hosts, and propose a Milky Way-like RB distribution to alleviate these issues.

In discussing assumptions and caveats, the authors note that some non-standard scattering models have been hypothesized to produce low RB, but they question why such effects would appear only in high-mass hosts. This highlights an unresolved physical explanation for any abrupt change in RB associated with host galaxy stellar mass, motivating further investigation into the underlying mechanism or its absence.