Near-IR search for lensed supernovae behind galaxy clusters

Abstract

Aims. Powerful gravitational telescopes in the form of massive galaxy clusters can be used to enhance the light collecting power over a limited field of view by about an order of magnitude in flux. This effect is exploited here to increase the depth of a survey for lensed supernovae at near-IR wavelengths. Methods. We present a pilot supernova search programme conducted with the ISAAC camera at VLT. Lensed galaxies behind the massive clusters A1689, A1835, and AC114 were observed for a total of 20 h divided into 2, 3, and 4 epochs respectively, separated by approximately one month to a limiting magnitude J < ∼ 24 (Vega). Image subtractions including another 20 h worth of archival ISAAC/VLT data were used to search for transients with lightcurve properties consistent with redshifted supernovae, both in the new and reference data. Results. The feasibility of finding lensed supernovae in our survey was investigated using synthetic lightcurves of supernovae and several models of the volumetric type Ia and core-collapse supernova rates as a function of redshift. We also estimate the number of supernova discoveries expected from the inferred star-formation rate in the observed galaxies. The methods consistently predict a Poisson mean value for the expected number of supernovae in the survey of between N SN = 0.8 and 1.6 for all supernova types, evenly distributed between core collapse and type Ia supernovae. One transient object was found behind A1689, 0.5 from a galaxy with photometric redshift z gal = 0.6 ± 0.15. The lightcurve and colors of the transient are consistent with being a reddened type IIP supernova at z SN = 0.59. The lensing model predicts 1.4 mag of magnification at the location of the transient, without which this object would not have been detected in the near-IR ground-based search described in this paper (unlensed magnitude J ∼ 25). We perform a feasibility study of the potential for lensed supernovae discoveries with larger and deeper surveys and conclude that the use of gravitational telescopes is a very exciting path for new discoveries. For example, a monthly rolling supernova search of a single very massive cluster with the HAWK-I camera at VLT would yield > ∼ 10 lensed supernova lightcurves per year, where type Ia supernovae would constitute about half of the expected sample. Conclusions.

Sn Refsdal: Photometry and Time Delay Measurements of the First Einstein Cross Supernova

“…However, each RELICS cluster target is only monitored over a period of 1-2 months, so RELICS and any similar cluster surveys will still have only a small chance of discovering another multiply imaged SN in the near future. Such programs are much more likely to find lensed SNe with significant magnification but no multiple images (Sullivan et al 2000;Goobar et al 2009), which can still be useful as a means for discovering distant SNe (Gunnarsson & Goobar 2003;Amanullah et al 2011) or for testing cluster lens models (Riehm et al 2011;Nordin et al 2014;Patel et al 2014;Rodney et al 2015a). …”

Deja Vu All Over Again: The Reappearance of Supernova Refsdal

“…Refsdal (1964) examined the utility of time-delay measurements of a strongly lensed, multiply imaged, resolved supernova (SN), but such an object was not found in the following five decades. A handful of SNe in galaxy-cluster fields have been magnified (∼1.4-4×) by the cluster's potential (Goobar et al 2009;Nordin et al 2014;Patel et al 2014;Rodney et al 2015a), but none has been multiply imaged. A luminous H-poor SN at redshift z=1.38 (Chornock et al 2013) was shown to be a highly magnified ( 30´) SNIa (Quimby et al 2013(Quimby et al , 2014, but the only existing exposures, taken from the ground, could not resolve multiple images of the SN.…”

Revised Lens Model for the Multiply Imaged Lensed Supernova, “Sn Refsdal” in Macs J1149+2223

“…Although several lensed SN candidates have been reported (Goobar et al 2009;Patel et al 2014;Quimby et al 2014), the recent discovery of a lensed SN in the field of MACS J1149+2223 (Kelly et al 2014a(Kelly et al , 2014b) is the first reported case of multiply imaged one, whose instances are detected and resolved.…”