The Zwicky Transient Facility Bright Transient Survey. II. A Public Statistical Sample for Exploring Supernova Demographics*

Abstract

We present a public catalog of transients from the Zwicky Transient Facility (ZTF) Bright Transient Survey, a magnitude-limited (m<19 mag in either the g or r filter) survey for extragalactic transients in the ZTF public stream. We introduce cuts on survey coverage, sky visibility around peak light, and other properties unconnected to the nature of the transient, and show that the resulting statistical sample is spectroscopically 97% complete at <18 mag, 93% complete at <18.5 mag, and 75% complete at <19 mag. We summarize the fundamental properties of this population, identifying distinct duration-luminosity correlations in a variety of supernova (SN) classes and associating the majority of fast optical transients with well-established spectroscopic SN types (primarily SN Ibn and II/IIb). We measure the Type Ia SN and core-collapse (CC) SN rates and luminosity functions, which show good consistency with recent work. About 7% of CCSNe explode in very low-luminosity galaxies (M i >−16 mag), 10% in red-sequence galaxies, and 1% in massive ellipticals. We find no significant difference in the luminosity or color distributions between the host galaxies of SNe Type II and SNe Type Ib/c, suggesting that line-driven wind stripping does not play a major role in the loss of the hydrogen envelope from their progenitors. Future large-scale classification efforts with ZTF and other wide-area surveys will provide highquality measurements of the rates, properties, and environments of all known types of optical transients and limits on the existence of theoretically predicted but as yet unobserved explosions.

The Palomar Transient Factory Core-collapse Supernova Host-galaxy Sample. I. Host-galaxy Distribution Functions and Environment Dependence of Core-collapse Supernovae

“…H-rich SLSNe (SLSN-II, SLSN-IIb, and SLSN-IIn) are still too scarce to constrain their host properties and quantify environment-dependent production efficiencies. The Zwicky Transient Facility (ZTF; Bellm et al 2019;Graham et al 2019) build larger and more homogeneous samples in a shorter period of time (Fremling et al 2020;Perley et al 2020). Like PTF, it uses the P48 telescope, but with a new camera having a 6× larger field of view.…”

Bright, Months-long Stellar Outbursts Announce the Explosion of Interaction-powered Supernovae

“…We only consider SNe at locations that are observable by ZTF, with declinations larger than −30°. Our sample includes all objects that are classified as SNe of Type IIn, Ibn, or Ia-CSM, or as SLSNe-II by members of the ZTF team or on TNS (see, e.g., Perley et al 2020 for details). In addition, we include objects that show flash-spectroscopy features in early-time spectra, which were identified by Bruch et al (2020).…”

Is supernova SN 2020faa an iPTF14hls look-alike?

“…1. SN 2020faa was classified as a Type II SN (Perley et al 2020) based on a spectrum obtained on 2020 April 6 with the Liverpool telescope (LT) equipped with the SPectrograph for the Rapid Acquisition of Transients (SPRAT) instrument. That spectrum revealed broad Hα and Hβ in emission, the blue edge being shifted by ∼9000 km s −1 with respect to the narrow emission line from the galaxy that provided the redshift z = 0.041 consistent with CLU as mentioned above.…”