Chandra Source Catalog Release 2 (CSC 2.1)
Introduction
The Chandra Source Catalog version 2.1 (CSC 2.1) was released on April 2nd 2024; the current minor release is version 2.1.1, updated on 2024 October 18 (for more information see the Catalog Version History). It includes measured properties for 407,806 unique compact and extended X-ray sources and more than 1.3 million individual detections observed with either ACIS or HRC-I observations released publicly prior to the end of 2021. The total sky coverage is ~730 square degrees. CSC 2.1 consists of two types of data products: database tables (e.g. positions, significance, fluxes, hardness ratios, and variability indices) and file-based data products (e.g. images, PHA spectra, light curves, and sensitivity maps). Figure 1 shows the location of the observations in CSC 2.1. The DOI for the catalog is: doi:10.25574/csc2
[Version: full-size]
Figure 1: Detections in CSC 2.1
Structure of CSC 2.1
CSC 2.1 is hierarchical. Source/detection properties are provided at three different levels: master level, stack level, and per-observation level. This hierarchy results from the fact that source detection is performed upon stacking individual Chandra observations to improve the signal to noise ratio. The detected source position and the associated source region are used to compute the photometric, spectral, and variability properties of the source, both in the stack detection and in the individual observations contributing to the stack. However, observations are stacked together only if they have pointings within 1 arcmin of each other. Consequently, a single source can be detected in more than one stack. The master level properties are the best possible estimate of source properties, given the information contained in all contributing stacks. A full description of the catalog organization can be found in the Catalog Organization page.