First-Year Spectroscopy for the SDSS-II Supernova Survey

TL;DR

This paper details the spectroscopic observations and classification of supernovae from the SDSS-II survey's first season, enhancing understanding of supernova populations and improving their use in cosmology.

Contribution

It introduces a rapid-response spectroscopic program for supernovae, providing detailed classifications, redshifts, and host galaxy contamination removal methods for the SDSS-II survey.

Findings

129 SNe Ia classified and confirmed

Host galaxy contamination effectively removed

Spectroscopic data supports supernova population analysis

Abstract

This paper presents spectroscopy of supernovae discovered in the first season of the Sloan Digital Sky Survey-II Supernova Survey. This program searches for and measures multi-band light curves of supernovae in the redshift range z = 0.05 - 0.4, complementing existing surveys at lower and higher redshifts. Our goal is to better characterize the supernova population, with a particular focus on SNe Ia, improving their utility as cosmological distance indicators and as probes of dark energy. Our supernova spectroscopy program features rapid-response observations using telescopes of a range of apertures, and provides confirmation of the supernova and host-galaxy types as well as precise redshifts. We describe here the target identification and prioritization, data reduction, redshift measurement, and classification of 129 SNe Ia, 16 spectroscopically probable SNe Ia, 7 SNe Ib/c, and 11 SNe II from the first season. We also describe our efforts to measure and remove the substantial host galaxy contamination existing in the majority of our SN spectra.