Innovations in the Analysis of Chandra-ACIS Observations

TL;DR

This paper presents new data analysis methods and publicly-available software for processing and analyzing Chandra ACIS X-ray observations, addressing challenges like source crowding and diffuse emission.

Contribution

It introduces innovative analysis techniques and software tools tailored for complex ACIS data, aiding both the authors' projects and the broader Chandra community.

Findings

Development of comprehensive analysis workflow for ACIS data

Implementation of new methods for source detection and diffuse emission analysis

Provision of publicly-available software package for the community

Abstract

As members of the instrument team for the Advanced CCD Imaging Spectrometer (ACIS) on NASA's Chandra X-ray Observatory and as Chandra General Observers, we have developed a wide variety of data analysis methods that we believe are useful to the Chandra community, and have constructed a significant body of publicly-available software (the ACIS Extract package) addressing important ACIS data and science analysis tasks. This paper seeks to describe these data analysis methods for two purposes: to document the data analysis work performed in our own science projects, and to help other ACIS observers judge whether these methods may be useful in their own projects (regardless of what tools and procedures they choose to implement those methods). The ACIS data analysis recommendations we offer here address much of the workflow in a typical ACIS project, including data preparation, point source detection via both wavelet decomposition and image reconstruction, masking point sources, identification of diffuse structures, event extraction for both point and diffuse sources, merging extractions from multiple observations, nonparametric broad-band photometry, analysis of low-count spectra, and automation of these tasks. Many of the innovations presented here arise from several, often interwoven, complications that are found in many Chandra projects: large numbers of point sources (hundreds to several thousand), faint point sources, misaligned multiple observations of an astronomical field, point source crowding, and scientifically relevant diffuse emission.