21. iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernovaAriel Goobar, Rahman Amanullah, S.R. Kulkarni, Tanja Petrushevska, 2017, original scientific article Abstract: We report the discovery of a multiply-imaged gravitationally lensed Type Ia supernova, iPTF16geu, at redshift z = 0.409. This phenomenon could be iden- tified because the light from the stellar explosion was magnified more than fifty times by the curvature of space around matter in an intervening galaxy.
We used high spatial resolution observations to resolve four images of the lensed supernova, approximately 0.300 from the center of the foreground galaxy. The observations probe a physical scale of ⇠1 kiloparsec, smaller than what is typical in other studies of extragalactic gravitational lensing. The large mag- nification and symmetric image configuration implies close alignment between the line-of-sight to the supernova and the lens. The relative magnifications of the four images provide evidence for sub-structures in the lensing galaxy. Keywords: lensed supernova, strong lensing, galaxy lens, multiply-lensed supernova Published in RUNG: 23.01.2018; Views: 3914; Downloads: 0 This document has many files! More... |
22. High-redshift supernova rates measured with the gravitational telescope A 1689Tanja Petrushevska, R. Amanullah, Ariel Goobar, S. Fabbro, Joel Johansson, Tor Kjellsson, Chris Lidman, K. Paech, Johan Richard, H. Dahle, Raphael Ferretti, J.P. Kneib, M. Limousin, Jakob Nordin, V. Stanishev, 2016, original scientific article Abstract: Aims. We present a ground-based, near-infrared search for lensed supernovae behind the massive cluster Abell 1689 at z = 0.18, which is one of the most powerful gravitational telescopes that nature provides.
Methods. Our survey was based on multi-epoch J-band observations with the HAWK-I instrument on VLT, with supporting optical data from the Nordic Optical Telescope.
Results. Our search resulted in the discovery of five photometrically classified, core-collapse supernovae with high redshifts of 0.671 < z < 1.703 and magnifications in the range ∆m = −0.31 to −1.58 mag, as calculated from lensing models in the literature.
Owing to the power of the lensing cluster, the survey had the sensitivity to detect supernovae up to very high redshifts, z ∼ 3, albeit for a limited region of space. We present a study of the core-collapse supernova rates for 0.4 ≤ z < 2.9, and find good agreement with previous estimates and predictions from star formation history. During our survey, we also discovered two Type Ia supernovae in A 1689 cluster members, which allowed us to determine the cluster Ia rate to be 0.14+0.19 −0.09 ± 0.01 SNuB h 2 (SNuB ≡ 10−12 SNe L −1 ,B yr−1), where the error bars indicate 1σ confidence intervals, statistical and systematic, respectively. The cluster rate normalized by the stellar mass is 0.10+0.13 −0.06 ± 0.02 in SNuM h 2 (SNuM ≡ 10−12 SNe M−1 yr−1). Furthermore, we explore the optimal future survey for improving the core-collapse supernova rate measurements at z & 2 using gravitational telescopes, and for detections
with multiply lensed images, and we find that the planned WFIRST space mission has excellent prospects.
Conclusions. Massive clusters can be used as gravitational telescopes to significantly expand the survey range of supernova searches, with important implications for the study of the high-z transient Universe. Keywords: supernovae: general – gravitational lensing: strong – galaxies: star formation – galaxies: clusters: individual: A 1689 –
techniques: photometric Published in RUNG: 23.01.2018; Views: 4299; Downloads: 0 This document has many files! More... |