Supernovae seen through gravitational telescopes Tanja Petrushevska Academic dissertation for the Degree of Doctor of Philosophy in Physics at Stockholm University to be publicly defended on Monday 29 May 2017 at 10.15 in sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21. Abstract Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of objects behind them. The effect enables observations of very distant supernovae, that otherwise would be too faint to be detected by existing telescopes, and allows studies of the frequency and properties of these rare phenomena when the universe was young. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their well known brightness can be used to determine the magnification, which can be used to understand the lensing systems. In this thesis, galaxy clusters are used as gravitational telescopes to search for lensed supernovae at high redshift. Ground- based, near-infrared and optical search campaigns are described of the massive clusters Abell 1689 and 370, which are among the most powerful gravitational telescopes known. The search resulted in the discovery of five photometrically classified, core-collapse supernovae at redshifts of 0.671<z<1.703 with significant magnification from the cluster. Owing to the power of the lensing cluster, the volumetric core-collapse supernova rates for 0.4 ≤ z < 2.9 were calculated, and found to be in good agreement with previous estimates and predictions from cosmic star formation history. During the survey, two Type Ia supernovae in A1689 cluster members were also discovered, which allowed the Type Ia explosion rate in galaxy clusters to be estimated. Furthermore, the expectations of finding lensed supernovae at high redshift in simulated search campaigns that can be conducted with upcoming ground- and space-based telescopes, are discussed. Magnification from a galaxy lens also allows for detailed studies of the supernova properties at high redshift that otherwise would not be possible. Spectroscopic observations of lensed high-redshift supernovae Type Ia are of special interest since they can be used to test for evolution of the standard candle nature of these objects. If systematic redshift- dependent properties are found, their utility for future surveys could be challenged. In the thesis it is shown that the strongly lensed and very distant supernova Type Ia PS1-10afx at z=1.4, does not deviate from the well-studied nearby and intermediate populations of normal supernovae Type Ia. In a different study, the discovery of the first resolved multiply-imaged gravitationally lensed supernova Type Ia is also reported. Keywords: supernovae, strong gravitational lensing, star formation history, supernova rates. Stockholm 2017 http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141633 ISBN 978-91-7649-797-5 ISBN 978-91-7649-798-2 Department of Physics Stockholm University, 106 91 Stockholm SUPERNOVAE SEEN THROUGH GRAVITATIONAL TELESCOPES Tanja Petrushevska Supernovae seen through gravitational telescopes Tanja Petrushevska ©Tanja Petrushevska, Stockholm University 2017 ISBN print 978-91-7649-797-5 ISBN PDF 978-91-7649-798-2 Printed in Sweden by US-AB, Stockholm 2017 Distributor: Department of Physics, Stockhom University Cover image: Artist's interpretation of a supernova discovery with a gravitational telescope. Courtesy of Maedeh Mohammadpour Mir. Abstract Gravitational lenses such as galaxies and galaxy clusters, can magnify the flux of background galaxies. These galaxies at high redshift can host supernovae (SNe) which, thanks to the magnification boost due to lensing, can be observed, otherwise too faint to be detected by current telescopes. Under the right circumstances, the background galaxies may also have multiple images due to the strong lensing. Of particular interest is to detect lensed supernovae of type Ia (SNe Ia), because of their standard brightness. They could help improve lensing models and, if multiple images are observed, the Hubble constant can be measured independently. In this thesis, we use galaxy clusters as gravitational telescopes to search for lensed SNe at high redshift. We performed ground-based, near-infrared and optical search campaigns towards the massive clusters Abell 1689 and 370, which are among the most powerful gravitational telescopes known. Our search resulted in the discovery of five photometrically classified, core- collapse SNe at redshifts of 0.671 < z < 1.703 with significant magnification from the cluster. Owing to the power of the lensing cluster, we calculated the volumetric core-collapse SN rates for 0.4 z < 2.9,andfindgoodagreement with previous estimates and predictions from cosmic star formation history. During our survey, we also discovered two SNe Ia in A1689 cluster members, which allowed us to determine the cluster Ia rate. Furthermore, we discuss the expectations of finding lensed SNe at high redshift in simulated search campaigns that can be conducted with upcoming ground- and space-based telescopes. Magnification from a galaxy lens also allows for detailed studies of the SN properties at high redshift that otherwise would not be possible. Spec- troscopic observations of lensed high-redshift SNe Ia are of particular interest since they can be used to test for evolution of the standard candle nature of these objects. However, if systematic redshift-dependent properties are found, their utility for future surveys could be challenged. We investigate whether the properties of the strongly lensed and very distant SN Ia PS1- 10afx at z = 1.4,deviatesfromthewell-studiednearbyandintermediate populations of normal SNe Ia. In other study, we report the discovery of the first resolved multiply-imaged gravitationally lensed SN Ia. List of Accompanying Papers The following papers, referred to in the text by their Roman numerals, are included in this thesis. PAPER I: High-redshift supernova rates measured with the gravi- tational telescope A1689 T. Petrushevska, R. Amanullah, A. Goobar, S. Fabbro, J. Jo- hansson, T. Kjellsson, C. Lidman, K. Paech, J. Richard, H. Dahle, H. Dahle, R. Ferretti, J. P. Kneib, M. Limousin, J. Nordin and V. Stanishev , A&A, Vol. 594,A54(2016). DOI: 10.1051/0004-6361/201628925 PAPER II: iPTF16geu: A multiply-imaged gravitationally lensed Type Ia supernova A. Goobar, R. Amanullah, S. R. Kulkarni, P. E. Nugent, J. Johansson, C. Steidel, D. Law, E. Mörtsell, R. Quimby, N. Blagorodnova, A. Brandeker, Y. Cao, A. Cooray, R. Ferretti, C. Fremling, L. Hangard, M. Kasliwal, T. Kupfer, R. Lunnan, F. Masci, A. A.Miller, H. Nayyeri, J. D. Neill, E. O. Ofek, S. Papadogiannakis, T. Petrushevska, V. Ravi, J. Sollerman, M. Sullivan, F. Taddia, R. Walters, D. Wilson, L. Yan and O. Yaron, Science, Vol. 356,6335,291-295(2017). DOI: 10.1126/science.aal2729 PAPER III: Testing for redshift evolution of Type Ia supernovae us- ing the strongly lensed PS1-10afx at z = 1.4 T. Petrushevska, R. Amanullah, M. Bulla, M. Kromer, R. Fer- retti, A. Goobar and S. Papadogiannakis, submitted in A&A, (2017). PAPER IV: Searching for supernovae in the multiply-imaged galax- ies behind the gravitational telescope A370 T. Petrushevska, D. J. Lagattuta, R. Amanullah, A. Goobar, L. Hangard, S. Fabbro, C. Lidman, K. Paech, J. Richard, and J. P. Kneib to be submitted in A&A. Reprints were made with permission from the publishers. Other publications The following papers, referred to in the text by their letters, are not included in this thesis. PAPER A: Search for Lensed Supernovae by Massive Galaxy Clus- ters with the 2.5m Nordic Optical Telescope T. Petrushevska. Publications of the Astronomical Observatory of Belgrade, 92, 85-86,(2013). PAPER B: The Rise of SN 2014J in the Nearby Galaxy M82 A. Goobar, 33 additional authors including T. Petrushevska. ApJL, 784, 12,(2014). DOI: 10.1088/2041-8205/784/1/L12 PAPER C: The Peculiar Extinction Law of SN 2014J Measured with the Hubble Space Telescope R. Amanullah, 12 additional authors including T. Petrushevska. ApJL, 788, 21,(2014). DOI: 10.1088/2041-8205/788/2/L21 PAPER D: Diversity in extinction laws of Type Ia supernovae mea- sured between 0.2 and 2 µm R. Amanullah, 36 additional authors including T. Petrushevska. MNRAS, 453, 3,(2015). DOI: 10.1093/mnras/stv1505 PAPER E: Supernova spectra below strong circum-stellar interaction G. Leloudas, 11 additional authors including T. Petrushevska. A&A, 574, A61,(2015). DOI: 10.1051/0004-6361/201322035 PAPER F: Time-varying sodium absorption in the Type Ia supernova 2013gh R. Ferretti, 20 additional authors including T. Petrushevska. A&A, 592, A40,(2016). DOI: 10.1051/0004-6361/201628351 PAPER G: Color Me Intrigued: The Discovery of iPTF16fnm, a Su- pernova 2002cx-Like Object A. A. Miller, 15 additional authors including T. Petrushevska. submitted to ApJ,(2017). Author’s contribution The main focus of this thesis is the study of supernova properties through gravitational telescopes, and the thesis is accompanied by four papers which are relevant to the main theme. I led the projects presented in Papers I, III and IV, and done most of the work, including the preparation of the text and figures in the papers. In Paper II, I had more modest contribution. I contributed to the proposals that were written to obtain ground- and space- based observations and I investigated the spectroscopic properties of the supernova, the host and lensing galaxy. Not all the work during my PhD is enclosed in these four papers. Some of the contribution to the analysis done for the papers which are not attached in the thesis, is discussed in this thesis (Papers B, D).