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Contact Patrick Broos if  you have problems or questions about this software.

ACIS Extract

Patrick Broos, Leisa Townsley, Konstantin Getman, Franz Bauer
Mar 2017


Innovations in the Analysis of Chandra-ACIS Observations, Broos et al. (2010)

Astrophysics Source Code Library


ACIS Extract (AE) is a software package that provides innovative and automated solutions to the varied challenges found in the analysis of X-ray data taken by the ACIS instrument on NASA's Chandra observatory.  AE is  written in the IDL language.

An extensive searchable user's guide is available.

What does AE do?   Well, suppose you have Level 2 event data from one or multiple ACIS observations, and you have a catalog of proposed point sources.  AE can perform virtually all the data processing and analysis tasks that lie between your Level 2 data and the LaTeX tables of source properties and spectral models that you desire for publication.

Point Source Catalog
Source detection is not part of AE.  However, source position estimates and source significance statistics produced by AE can be used to improve a proposed catalog of point sources.

Extraction Apertures
The source extraction apertures are contours of the local PSF.  Crowded fields are handled by shrinking the extractions regions so they do not overlap.

Background Estimation

Three strategies for extracting local background spectra are provided, including one designed for very crowded fields and fields with readout streaks.

Calibration Products
ARFs and RMFs are constructed for each source.  The ARFs are corrected to account for the energy-dependent fraction of events missed by the finite extraction apertures.

Timing Analysis
Source variability is quantified.  Three time series are produced for each source:
Source photometry is performed over any desired set of energy bands.

Spectral Modeling
Source spectra are grouped and spectral models are fit with XSPEC.

Collation of Results
Source properties, statistics, photometry, and spectral models are collated into a large FITS file for analysis, generation of LaTeX tables, etc.

Visual Review
Multiple Observations
The source catalog can be extracted from any number of observations (at different aim points or roll angles).  AE combines the extraction data products prior to position estimation, photometry, timing analysis, and spectral modeling.

Diffuse Sources
Given ds9 regions that define diffuse sources,  AE can extract and analyze them in much the same way as is done for point sources.

The implementation strategy for AE is to use CIAO tools for specific computations whenever possible, and ds9 for display of event data and extraction regions.

The authors happily acknowledge that AE is derived from the ideas, software, and testing efforts of David Alexander, George Chartas, Eric Feigelson,  Nicolas Grosso, Scott Koch, Bertil Olsson, Yohko Tsuboi, and the authors of various CIAO threads and manuals.   Support for this effort was provided by NASA contract NAS8-38252 to Gordon Garmire, the ACIS Principal Investigator

Other Notable Features

Installation Instructions

Third-party Packages

Please refer to the Installation Section of the AE user's guide for information on version requirements for each package, and for information on configuring your computing environment for AE.

Install TARA

The AE software uses a number of IDL routines from our TARA package.
Download the latest version of TARA (the tara*.tar.gz file with the highest version number), then unzip and untar the tarball.  For example:


    tar -xzvf ae2012nov1.tar.gz

Place the files extracted from the tarball in an appropriate place that is in your "IDL path".    

Install AE Programs & XSPEC Scripts

Download the latest version of AE (the ae*.tar.gz file with the highest version number), then unzip and untar the tarball.  For example:


    tar -xzvf ae2012nov1.tar.gz

Place the files extracted from the tarball in an appropriate place that is in your "IDL path".  The IDL manual describes how your IDL path can be configured.

Patrick Broos
Software Engineer, ACIS Team @PSU

Astronomy & Astrophysics
Pennsylvania State University
525 Davey Lab
University Park, PA 16802