瞬变测量的速率估计I：评估iPTF的瞬变可探测性和体积灵敏度
Towards Rate Estimation for Transient Surveys I: Assessing Transient Detectability and Volume Sensitivity for iPTF
摘要：
在过去的几十年里，在时域天文学的各种途径中出现了瞬态检测设备，为我们提供了丰富的瞬态数据集。这些瞬变的速率在恒星形成、祖先模型、演化通道和宇宙学测量中具有重要意义。任何速率计算的关键组成部分是作为许多内在和外在参数的函数的勘测对特定瞬态类型的可探测性和时空体积灵敏度。对多维参数空间进行完全采样具有挑战性。相反，我们提出了一个计划，使用监督机器学习来评估瞬态的可检测性。该数据产品是一个分类器，它确定从与时域勘测望远镜相关联的图像减法流水线产生的源的检测可能性，同时考虑到瞬态的固有特性和观测条件。我们应用我们的方法评估了Palomar瞬变工厂（iPTF）中Ia型超新星（SNe~Ia）的时空体积敏感性，得到了$\langle VT\rangle_{\mathrm{Ia}}=2.93\pm 0.21\times 10^{-2}\mathrm{Gpc^{3}yr}$ .根据文献中的速率估计值，该体积灵敏度给出了iPTF可检测到的$680-1160$ SNe~Ia计数，这与存档数据一致。为了使这一方法具有更广泛的应用性，我们对长持续时间的IIp型超新星（SNe~IIp）进行了初步计算，发现了$\langle VT\rangle_{\mathrm{IIp}}=7.80\pm0.76\times10^{-4}\mathrm{Gpc^{3}yr}$。该分类器可用于计算快速的空间-时间体积灵敏度计算的任何通用的瞬态类型使用其光变曲线属性。因此，它可以被用来作为一种工具，以方便计算瞬态率在一系列的时域调查，给出合适的训练集。
英文摘要：
The last couple of decades have seen an emergence of transient detection facilities in various avenues of time domain astronomy which has provided us with a rich dataset of transients. The rates of these transients have implications in star formation, progenitor models, evolution channels and cosmology measurements. The crucial component of any rate calculation is the detectability and space-time volume sensitivity of a survey to a particular transient type as a function of many intrinsic and extrinsic parameters. Fully sampling that multi-dimensional parameter space is challenging. Instead, we present a scheme to assess the detectability of transients using supervised machine learning. The data product is a classifier that determines the detection likelihood of sources resulting from an image subtraction pipeline associated with time domain survey telescopes, taking into consideration the intrinsic properties of the transients and the observing conditions. We apply our method to assess the space-time volume sensitivity of type Ia supernovae (SNe~Ia) in the intermediate Palomar Transient Factory (iPTF) and obtain the result,$\langle VT\rangle_{\mathrm{Ia}}=2.93\pm 0.21\times 10^{-2}\mathrm{Gpc^{3}yr}$. With rate estimates in the literature, this volume sensitivity gives a count of $680-1160$ SNe~Ia detectable by iPTF which is consistent with the archival data. With a view toward wider applicability of this technique we do a preliminary computation for long-duration type IIp supernovae (SNe~IIp) and find $\langle VT\rangle_{\mathrm{IIp}}=7.80\pm0.76\times10^{-4}\mathrm{Gpc^{3}yr}$. This classifier can be used for computationally fast space-time volume sensitivity calculation of any generic transient type using their lightcurve properties. Hence, it can be used as a tool to facilitate calculation of transient rates in a range of time-domain surveys, given suitable training sets.
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