ZTF Early Observations of Type Ia Supernovae I: Properties of the 2018 Sample

Creators: Yao, Yuhan; Miller, Adam A.; Kulkarni, S. R.; Bulla, Mattia; Masci, Frank J.; Goldstein, Daniel A.; Goobar, Ariel; Nugent, Peter; Dugas, Alison; Blagorodnova, Nadia; Neill, James D.; Rigault, Michael; Sollerman, Jesper; Nordin, J.; Bellm, Eric C.; Cenko, S. Bradley; De, Kishalay; Dhawan, Suhail; Feindt, Ulrich; Fremling, C.; Gatkine, Pradip; Graham, Matthew J.; Graham, Melissa L.; Ho, Anna Y. Q.; Hung, T.; Kasliwal, Mansi M.; Kupfer, Thomas; Laher, Russ R.; Perley, Daniel A.; Rusholme, Ben; Shupe, David L.; Soumagnac, Maayane T.; Taggart, K.; Walters, Richard; Yan, Lin

Abstract

Early-time observations of Type Ia supernovae (SNe Ia) are essential to constrain the properties of their progenitors. In this paper, we present high-quality light curves of 127 SNe Ia discovered by the Zwicky Transient Facility (ZTF) in 2018. We describe our method to perform forced point-spread function photometry, which can be applied to other types of extragalactic transients. With a planned cadence of six observations per night (three g + three r), all of the 127 SNe Ia are detected in both g and r bands more than 10 days (in the rest frame) prior to the epoch of g-band maximum light. The redshifts of these objects range from z = 0.0181 to 0.165; the median redshift is 0.074. Among the 127 SNe, 50 are detected at least 14 days prior to maximum light (in the rest frame), with a subset of nine objects being detected more than 17 days before g-band peak. This is the largest sample of young SNe Ia collected to date; it can be used to study the shape and color evolution of the rising light curves in unprecedented detail. We discuss six peculiar events in this sample: one 02cx-like event ZTF18abclfee (SN 2018crl), one Ia-CSM SN ZTF18aaykjei (SN 2018cxk), and four objects with possible super-Chandrasekhar mass progenitors: ZTF18abhpgje (SN 2018eul), ZTF18abdpvnd (SN 2018dvf), ZTF18aawpcel (SN 2018cir), and ZTF18abddmrf (SN 2018dsx).

Additional Information

© 2019 The American Astronomical Society. Received 2019 July 22; revised 2019 September 27; accepted 2019 October 5; published 2019 December 3. Yuhan Yao thanks Yuping Huang for useful discussions on implementing forced photometry, and the Heising–Simons Foundation for financial support. We gratefully thank Yashvi Sharma, Zhuyun Zhuang, Dino Bektešević Charlotte Ward, Scott Adams, and Igor Andreoni for help with observations. The authors acknowledge Michael Fausnaugh and Seméli Papadogiannakis for sharing data from the TESS and PTF/iPTF samples, respectively, and an anonymous referee for useful comments that improved the paper. This work was supported by the GROWTH project funded by the National Science Foundation under PIRE grant No. 1545949. The data presented here were obtained [in part] with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. M.B. acknowledges support from the Swedish Research Council (Vetenskapsrådet), the Swedish National Space Board and the research environment grant "Gravitational Radiation and Electromagnetic Astrophysical Transients (GREAT)." A.A.M. is funded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). M.R. has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 759194—USNAC). A.Y.Q.H. is supported by a National Science Foundation Graduate Research Fellowship under grant No. DGE1144469. M.L.G. acknowledges support from the DIRAC Institute in the Department of Astronomy at the University of Washington. The DIRAC Institute is supported through generous gifts from the Charles and Lisa Simonyi Fund for Arts and Sciences, and the Washington Research Foundation. These results made use of the Discovery Channel Telescope at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. The upgrade of the DeVeny optical spectrograph has been funded by a generous grant from John and Ginger Giovale and by a grant from the Mt. Cuba Astronomical Foundation. MMT Observatory access was supported by Northwestern University and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). This work is based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. Note added in proof. Following the acceptance of this paper, Fremling et al. 2019 demonstrated that the redshift of SNe Ia could be measured with SNID with a typical uncertainty of ~0.004. We have therefore updated the redshifts presented in Table 3, to reflect the Fremling et al. 2019 study, as we initially reported redshifts to two decimal places in cases where the redshift was determined via SNID, and now we report those redshifts to three decimal places. We have not, however, adopted these changes in the following analysis as the redshift differences result in negligible changes to the final results.

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