Supernovae in Low-Redshift Galaxy Clusters: Observations by the Wise Observatory Optical Transient Search (WOOTS)

TL;DR

WOOTS is a survey that discovered and spectroscopically confirmed supernovae in low-redshift galaxy clusters, mainly Type Ia, providing insights into supernova rates and challenges in distinguishing them from active galactic nuclei.

Contribution

This paper presents the design, data analysis, and follow-up procedures of WOOTS, a novel survey targeting supernovae in galaxy clusters at redshift 0.06-0.2, with a complete sample and spectroscopic confirmation.

Findings

7 supernovae associated with clusters

80% of flux-limited survey SNe are Type Ia

Difficulty in distinguishing SNe from active galactic nuclei

Abstract

We describe the Wise Observatory Optical Transient Search (WOOTS), a survey for supernovae (SNe) and other variable and transient objects in the fields of redshift 0.06-0.2 Abell galaxy clusters. We present the survey design and data-analysis procedures, and our object detection and follow-up strategies. We have obtained follow-up spectroscopy for all viable SN candidates, and present the resulting SN sample here. Out of the 12 SNe we have discovered, seven are associated with our target clusters while five are foreground or background field events. All but one of the SNe (a foreground field event) are Type Ia SNe. Our non-cluster SN sample is uniquely complete, since all SN candidates have been either spectroscopically confirmed or ruled out. This allows us to estimate that flux-limited surveys similar to WOOTS would be dominated (~80%) by SNe Ia. Our spectroscopic follow-up observations also elucidate the difficulty in distinguishing active galactic nuclei from SNe. In separate papers we use the WOOTS sample to derive the SN rate in clusters for this redshift range, and to measure the fraction of intergalactic cluster SNe. We also briefly report here on some quasars and asteroids discovered by WOOTS.