The Standardizability of Type Ia Supernovae in the Near-Infrared: Evidence for a Peak Luminosity-Decline Rate Relation in the Near-Infrared

TL;DR

This study investigates the potential for standardizing Type Ia supernovae in the near-infrared by examining the correlation between peak luminosity and decline rate, finding evidence for a relation especially in J and H bands that could improve distance measurements.

Contribution

The paper provides the first evidence of a peak luminosity-decline rate relation in the near-infrared for Type Ia supernovae, suggesting improved standardization methods in these wavelengths.

Findings

Modest evidence for a luminosity-decline rate relation in Y band.

Stronger evidence for the relation in J and H bands.

Applying decline rate corrections reduces scatter in distance estimates.

Abstract

We analyze the standardizability of Type Ia supernovae (SNe Ia) in the near-infrared (NIR) by investigating the correlation between observed peak NIR absolute magnitude and post-maximum B-band decline rate. A sample of 27 low-redshift SNe Ia observed by the Carnegie Supernova Project between 2004 to 2007 is used. All 27 objects have pre-maximum coverage in optical bands, with a subset of 13 having pre-maximum NIR observations as well. We describe the methods used to derive absolute peak magnitudes and decline rates from both spline- and template-fitting procedures, and confirm prior findings that fitting templates to SNe Ia light curves in the NIR is problematic due to the diversity of post-maximum behaviour of objects that are characterized by similar decline rate values, especially at high decline rates. Nevertheless, we show that NIR light curves can be reasonably fit with a template, especially if the observations begin within 5 days after NIR maximum. For the subset of 13 objects in our dataset that excludes the highly reddened and fast declining SNe Ia, and includes only those objects for which NIR observations began prior to five days after maximum light, we find modest evidence for a peak luminosity-decline rate relation in Y, and stronger evidence in J and H. Using Rv values differing from the canonical value of 3.1 is shown to have little effect on the results. A Hubble diagram is presented for the NIR bands and the B band. The resulting scatter for the combined NIR bands is 0.13 mag, while the B band produces a scatter of 0.22 mag. The data suggest that applying a correction to SNe Ia peak luminosities for decline rate is likely to be beneficial in the J and H bands to make SNe Ia more precise distance indicators, but of only marginal importance in the Y band.