Dust Obscured NuclearSupernovae Revealed by Spitzer

Supernova rates serve as an important probe of star formation models and initial mass functions. Optical ground-based surveys typically discover nearly 3-10 Xs fewer SNe than predicted due to high dust extinction in the nuclear regions of star forming galaxies. A successful SN survey in the local universe must be conducted at longer wavelengths and with a space-based telescope, which has a stable PSF to reduce the necessity for any subtraction algorithms and thus residuals. Here, we report on a 2-yr Spitzer/IRAC 3.6 μm survey for dust-extinguished SNe in the nuclear regions of forty luminous infrared galaxies (LIRGs) within 200 Mpc. The asymmetric Spitzer PSF results in worse than expected subtraction residuals when implementing standard template subtraction. Forward-modelling techniques improve our sensitivity by ∼1.5 mag. We report the detection of nine SNe, five of which were not discovered by optical surveys. After adjusting our predicted rates to account for the sensitivity of our survey, we find that the number of detections is consistent with the models. While this search is none the less hampered by a difficult-to-model PSF and the relatively poor resolution of Spitzer, it will benefit from future missions, such as Roman, with higher resolution and more symmetric PSFs.