Issue |
A&A
Volume 694, February 2025
ZTF SN Ia DR2
|
|
---|---|---|
Article Number | A9 | |
Number of page(s) | 16 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202450386 | |
Published online | 14 February 2025 |
ZTF SN Ia DR2: The spectral diversity of Type Ia supernovae in a volume-limited sample
1
School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland
2
Oskar Klein Centre, Department of Astronomy, Stockholm University, SE-10691 Stockholm, Sweden
3
Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
4
Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, E-08193 Barcelona, Spain
5
Institut d’Estudis Espacials de Catalunya (IEEC), E-08034 Barcelona, Spain
6
Univ Lyon, Univ Claude Bernard Lyon 1, CNRS, IP2I Lyon/IN2P3, UMR 5822, F-69622 Villeurbanne, France
7
Department of Physics, Lancaster University, Lancs LA1 4YB, UK
8
Oskar Klein Centre, Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden
9
Université Clermont Auvergne, CNRS/IN2P3, LPCA, F-63000 Clermont-Ferrand, France
10
National Research Council of Canada, Herzberg Astronomy & Astrophysics Research Centre, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
11
Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
12
Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
13
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 1800 Sherman Ave, Evanston, IL 60201, USA
14
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50B-4206, Berkeley, CA 94720, USA
15
Department of Astronomy, University of California, Berkeley, 501 Campbell Hall, Berkeley, CA 94720, USA
16
Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, ES-38711 Breña Baja, Spain
17
Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125, USA
18
Cahill Center for Astrophysics, California Institute of Technology, MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USA
19
Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
20
IPAC, California Institute of Technology, 1200 E. California Boulevard, Pasadena CA 91125, USA
⋆ Corresponding author; burgazu@tcd.ie
Received:
15
April
2024
Accepted:
10
October
2024
More than 3000 spectroscopically confirmed Type Ia supernovae (SNe Ia) are presented in the second data release (DR2) of the Zwicky Transient Facility survey. In this paper we detail the spectral properties of 482 SNe Ia near maximum light, up to a redshift limit of z ≤ 0.06. We measured the velocities and pseudo-equivalent widths (pEW) of key spectral features (Si IIλ5972 and Si IIλ6355) and investigated the relation between the properties of the spectral features and the photometric properties from the SALT2 light-curve parameters as a function of spectroscopic sub-class. We discuss the non-negligible impact of host galaxy contamination on SN Ia spectral classifications, and we investigate the accuracy of spectral template matching of the DR2 sample. We define a new subclass of underluminous SNe Ia (04gs-like) that lie spectroscopically between normal SNe Ia and transitional 86G-like SNe Ia (stronger Si IIλ5972 than normal SNe Ia, but significantly weaker Ti II features than 86G-like SNe). We model these 04gs-like SN Ia spectra using the radiative-transfer spectral synthesis code TARDIS and show that cooler temperatures alone are unable to explain their spectra; some changes in elemental abundances are also required. However, the broad continuity in spectral properties seen from bright (91T-like) to faint normal SN Ia, including the transitional and 91bg-like SNe Ia, suggests that variations within a single explosion model may be able to explain their behaviour.
Key words: supernovae: general
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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