星系团背后透镜状超新星的近红外搜索- II。首次发现和未来展望
Near-IR Search for Lensed Supernovae Behind Galaxy Clusters - II. First Detection and Future Prospects
摘要：
以大质量星系团为形式的强大引力望远镜可以用来在有限的视场内增强光收集能力，大约是通量的一个数量级。这种效应在这里被利用来增加近红外波长的透镜超新星调查的深度。本文介绍了在VLT用ISAAC相机进行的SN搜索试验计划。大质量星系团A1689、A1835和AC 114后面的透镜星系被观测了总共20小时，分别分为2、3和4个历元，间隔大约一个月，极限星等J<24（织女星）。图像减法，包括另外20小时的档案ISAAC/VLT数据的价值被用来搜索与红移超新星的光变特性一致的瞬态，无论是在新的和参考数据。在我们的调查中发现透镜超新星的可行性进行了研究，使用合成的超新星的光变曲线和几个模型的体积Ia型和核心坍缩超新星率作为红移的函数。我们还根据观测星系中推断的恒星形成率估计了预计发现的超新星数量。这些方法一致地预测了调查中SNe的预期数量的泊松平均值在N_SN=0.8和1.6之间，对于所有超新星类型，均匀分布在核心塌陷和Ia型SN之间。在A1689后面发现了一个瞬变天体，距离一个光度红移z_gal=0.6 +- 0.15的星系0.5”。瞬态的光变曲线和颜色与在z_SN=0.59时变红的IIP SN型一致。透镜模型预测在瞬变的位置处的放大率为1.4个星等，如果没有这个星等，在本文描述的近红外地基搜索中就不会探测到这个物体（未透镜星等J~25）。（节略）
英文摘要：
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. A pilot SN search program conducted with the ISAAC camera at VLT is presented. Lensed galaxies behind the massive clusters A1689, A1835 and AC114 were observed for a total of 20 hours split into 2, 3 and 4 epochs respectively, separated by approximately one month to a limiting magnitude J<24 (Vega). Image subtractions including another 20 hours 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. 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 SNe in the survey between N_SN=0.8 and 1.6 for all supernova types, evenly distributed between core collapse and Type Ia SN. 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 SN at z_SN=0.59. The lensing model predicts 1.4 magnitudes 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). (abridged)
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