Supernova (SN) classification and redshift estimation using photometric data only have become very important for the Large Synoptic Survey Telescope (LSST), given the large number of SNe that LSST will observe and the impossibility of spectroscopically following up all the SNe. We investigate the performance of a SN classifier that uses SN colors to classify LSST SNe with the Random Forest classification algorithm. Our classifier results in an AUC of 0.98 which represents excellent classification. We are able to obtain a photometric SN sample containing 99% SNe Ia by choosing a probability threshold. We estimate the photometric redshifts (photo-z) of SNe in our sample by fitting the SN light curves using the SALT2 model with nested sampling. We obtain a mean bias (⟨zphot−zspec⟩) of 0.012 with σ(1+zspeczphot−zspec)=0.0294 without using a host-galaxy photo-z prior, and a mean bias (⟨zphot−zspec⟩) of 0.0017 with σ(1+zspeczphot−zspec)=0.0116 using a host-galaxy photo-z prior. Assuming a flat ΛCDM model with Ωm=0.3, we obtain Ωm of 0.305±0.008 (statistical errors only), using the simulated LSST sample of photometric SNe Ia (with intrinsic scatter σint=0.11) derived using our methodology without using host-galaxy photo-z prior. Our method will help boost the power of SNe from the LSST as cosmological probes.
@article{arxiv.1701.05689,
title = {Photometric classification and redshift estimation of LSST Supernovae},
author = {Mi Dai and Steve Kuhlmann and Yun Wang and Eve Kovacs},
journal= {arXiv preprint arXiv:1701.05689},
year = {2018}
}
Comments
12 pages, 8 figures, 5 tables, accepted for publication in MNRAS