用多种距离度量组合检测天文数据中的未知异常,提升发现新天体类别的能力。
In Search of the Unknown Unknowns: A Multi-Metric Distance Ensemble for Out of Distribution Anomaly Detection in Astronomical Surveys
- 融合多种距离度量构建异常评分,避免依赖单一度量的局限
- 在模拟与真实天文数据中均优于现有方法,显著提升新类异常发现率
- 代码开源,适合天文数据挖掘与可解释性要求高的研究者使用
基于距离的方法通过计算特征间的距离值来识别异常,但其性能常依赖于用户选定的单一度量(如欧氏距离),在高维复杂天文特征空间中可能表现不佳。本文提出新型异常检测方法DiMMAD,采用多度量集成策略,在特征空间中等效于使用多种几何结构。通过构建多样化的距离度量集成,克服了度量选择难题,生成不依赖单一距离定义的异常分数。该方法在模拟数据(面向即将开展的薇拉·C·鲁宾天文台时空巡天)和真实数据(来自齐尼克瞬变设施)上验证,能有效检测分布外异常——即可能代表新天体类别的异常,且在最大化新类发现多样性方面超越其他先进方法。对于罕见的分布内异常,表现与现有方法相当,但具备更好可解释性。所有代码开源:DiMMAD 实现于 DistClassiPy (https://github.com/sidchaini/distclassipy/),论文复现代码见 https://github.com/sidchaini/dimmad/。
原文摘要 · Abstract (English)
Distance-based methods involve the computation of distance values between features and are a well-established paradigm in machine learning. In anomaly detection, anomalies are identified by their large distance from normal data points. However, the performance of these methods often hinges on a single, user-selected distance metric (e.g., Euclidean), which may not be optimal for the complex, high-dimensional feature spaces common in astronomy. Here, we introduce a novel anomaly detection method, Distance Multi-Metric Anomaly Detection (DiMMAD), which uses an ensemble of distance metrics to find novelties. Using multiple distance metrics is effectively equivalent to using different geometries in the feature space. By using a robust ensemble of diverse distance metrics, we overcome the metric-selection problem, creating an anomaly score that is not reliant on any single definition of distance. We demonstrate this multi-metric approach as a tool for simple, interpretable scientific discovery on astronomical time series -- (1) with simulated data for the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time, and (2) real data from the Zwicky Transient Facility. We find that DiMMAD excels at out-of-distribution anomaly detection -- anomalies in the data that might be new classes -- and beats other state-of-the-art methods in the goal of maximizing the diversity of new classes discovered. For rare in-distribution anomaly detection, DiMMAD performs similarly to other methods, but may allow for improved interpretability. All our code is open source: DiMMAD is implemented within DistClassiPy: https://github.com/sidchaini/distclassipy/, while all code to reproduce the results of this paper is available here: https://github.com/sidchaini/dimmad/.
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