The Massive and Distant Clusters of WISE Survey 2: Second Data Release

We present the second data release of the Massive and Distant Clusters of WISE Survey 2 (MaDCoWS2). We expand from the equatorial first data release to most of the Dark Energy Camera Legacy Survey area, covering a total area of 6498 deg2. The catalog consists of 133,036 S/N ≥ 5 galaxy cluster candidates at 0.1 ≤ z ≤ 2, including 6790 candidates at z > 1.5. We train a convolutional neural network (CNN) to identify spurious detections, and include CNN-based cluster probabilities in the final catalog. We also compare the MaDCoWS2 sample with literature catalogs in the same area. The larger sample provides robust results that are consistent with our first data release. At S/N ≥ 5, we rediscover 59−91% of clusters in existing catalogs that lie in the unmasked area of MC2. The median positional offsets are under 250 kpc, and the standard deviation of the redshifts is 0.031(1+z). We fit a redshift-dependent power law to the relation between MaDCoWS2 S/N and observables from existing catalogs. Over the redshift ranges where the surveys overlap with MaDCoWS2, the lowest scatter is found between S/N and observables from optical/infrared surveys. We also assess the per- formance of our method using a mock light cone measuring purity and completeness as a function of cluster mass. The purity is above 90%, and we estimate the 50% completeness threshold at a virial mass of log(M/M⊙)≈ 14.3. The completeness estimate is uncertain due to the small number of massive halos in the light cone, but consistent with the recovery fraction found by comparing to other cluster catalogs.

本研究发布了大质量遥远星系团WISE巡天2号（Massive and Distant Clusters of WISE Survey 2，缩写MaDCoWS2）的第二批数据发布成果。本次数据集从首批数据发布的赤道天区范围，拓展至暗能量相机遗产巡天（Dark Energy Camera Legacy Survey）的绝大部分天区，总覆盖面积为6498平方度（deg²）。该星表包含133036个信噪比（Signal-to-Noise Ratio，简称S/N）≥5的星系团候选体，红移（redshift，简称z）范围为0.1≤z≤2，其中红移z>1.5的候选体共计6790个。本研究训练了卷积神经网络（Convolutional Neural Network，简称CNN）以甄别虚假探测结果，并将基于CNN得到的星系团归属概率纳入最终星表。本研究还将MaDCoWS2样本与同一天区的已发表星表进行了比对。更大的样本量提供了可靠的分析结果，且与本研究首批数据发布的结论保持一致。在信噪比S/N≥5的条件下，我们可重新探测到MC2未掩蔽天区内已发表星表中59%~91%的星系团。位置偏移的中值小于250千秒差距（kiloparsec，简称kpc），红移的标准差为0.031(1+z)。我们针对MaDCoWS2的信噪比S/N与已发表星表中可观测物理量之间的关系，拟合了依赖于红移的幂律模型。在巡天与MaDCoWS2覆盖重叠的红移区间内，信噪比S/N与光学/红外巡天可观测物理量之间的散射程度最低。本研究还利用模拟光锥评估了本方法的性能，通过该模拟光锥可得到以星系团质量为变量的探测纯度与完备率。探测纯度高于90%，我们估算得到50%完备率对应的位力质量为log(M/M⊙)≈14.3，其中M⊙为太阳质量（Solar Mass）。由于模拟光锥中大质量暗物质晕的数量较少，完备率的估算存在一定不确定性，但该结果与通过比对其他星系团星表得到的恢复率一致。