DEHVILS is the largest published NIR sample with consistent coverage of maximum light across three NIR bands (Y, J, H).

Type Ia supernova (SN Ia) distance measurements depend on the properties of their host galaxies, and recent work suggests that the diversity of reddening laws in SN host galaxies may be responsible. In UKIRT’s NIR bands, SN distances are less sensitive to dust and therefore this paper tests whether the mass step persists in these bands. It found: (i) further evidence for improved Hubble residuals in the NIR, (ii) the existence (or nonexistence) of the mass step in the NIR cannot be concluded upon at this time (even though others have claimed it can be), and (iii) Hubble residuals in the NIR and optical are well-correlated.

The figure above compares simulated mass steps with different dust assumptions to the data from DEHVILS (left) and previous work (right). The simulation values show the effect of achromatic SN scatter (blue) and scatter due to a spread in dust reddening models (orange), and are the same in both panels. The shaded regions show 1σ uncertainties from the data.