ZTF SN Ia DR2: Overview

¹ Université Claude Bernard Lyon 1, CNRS, IP2I Lyon/IN2P3, IMR 5822, F-69622 Villeurbanne, France
² Department of Physics, Lancaster University, Lancs LA1 4YB, UK
³ The Oskar Klein Centre, Department of Physics, AlbaNova, SE-106 91 Stockholm, Sweden
⁴ School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland
⁵ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
⁶ Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁷ The Oskar Klein Centre, Department of Astronomy, AlbaNova, SE-106 91 Stockholm, Sweden
⁸ Sorbonne Université, CNRS/IN2P3, LPNHE, F-75005 Paris, France
⁹ Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, 15738 Zeuthen, Germany
¹⁰ Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS 50B-4206, Berkeley, CA 94720, USA
¹¹ Department of Astronomy, University of California, Berkeley, 501 Campbell Hall, Berkeley, CA 94720, USA
¹² Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA
¹³ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
¹⁴ Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771, USA
¹⁵ National Research Council of Canada, Herzberg Astronomy & Astrophysics Research Centre, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
¹⁶ Université Clermont Auvergne, CNRS/IN2P3, LPCA, F-63000 Clermont-Ferrand, France
¹⁷ Aix Marseille Université, CNRS/IN2P3, CPPM, Marseille, France
¹⁸ DIRAC Institute, Department of Astronomy, University of Washington, 3910 15th Avenue NE, Seattle, WA 98195, USA
¹⁹ Department of Physics, Duke University, Durham, NC 27708, USA
²⁰ IPAC, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
²¹ Division of Physics, Mathematics & Astronomy, 249-17, Caltech., Pasadena, CA 91108, USA
²² Institute of Space Sciences (ICE-CSIC), Campus UAB, Carrer de Can Magrans, s/n, E-08193 Barcelona, Spain
²³ Institut d’Estudis Espacials de Catalunya (IEEC), 08860 Castelldefels (Barcelona), Spain
²⁴ Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
²⁵ Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 1800 Sherman Ave, Evanston, IL 60201, USA
²⁶ Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125, USA
²⁷ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
²⁸ Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, ES-38711 Breña Baja, Spain
²⁹ Department of Astronomy, University of Washington, 3910 15th Avenue NE, Seattle, WA 98195, USA

^⋆ Corresponding authors; m.rigault@ip2i.in2p3.fr, mat.smith@lancaster.ac.uk

Received: 15 April 2024
Accepted: 24 September 2024

Abstract

We present the first homogeneous release of several thousand spectroscopically classified type Ia supernovae (SNe Ia) with spectroscopic redshifts. This release, named “DR2”, contains 3628 nearby (z < 0.3) SNe Ia discovered, followed, and classified by the Zwicky Transient Facility survey between March 2018 and December 2020. Of these, 3000 have good-to-excellent sampling and 2667 pass standard cosmology light curve quality cuts. This release is thus the largest SN Ia release to date, increasing by an order of magnitude the number of well-characterized low-redshift objects. With DR2, we also provide a volume-limited (z < 0.06) sample of nearly a thousand SNe Ia. With such a large, homogeneous, and well-controlled dataset, we are studying key current questions on SN cosmology, such as the linearity SNe Ia standardization, the SN and host dependencies, the diversity of the SN Ia population, and the accuracy of current light curve modeling. These, and more, are studied in detail in a series of articles associated with this release. Alongside the SN Ia parameters, we publish our forced-photometry gri-band light curves, 5138 spectra, local and global host properties, observing logs, and a Python tool to facilitate the use and access of these data. The photometric accuracy of DR2 is not yet suited for cosmological parameter inference, which will follow as the “DR2.5” release. We nonetheless demonstrate that our Hubble diagram of several thousands of SNe Ia has a typical 0.15 mag scatter.