New: PWDetect Version 1.3

A new version of PWDetect for Chandra imaging data is available. This is called V.1.3, as intermediate versions from V.1.0 were not released publically. This version is available here, only for Linux machines. The earlier version, PWDetect V.1.0, is still available for Linux, SunOS, and OSF1 machines.

PWDetect V.1.3 requires the same input files as V.1.0. However, the input parameter file pwdetect.par has changed with respect to V.1.0, with a few more free parameters added for more flexibility. The usage of newly added parameters is explained below. The output files of PWDetect V.1.3 are essentially the same as V.1.0, plus a few more (see below), mostly useful in handling especially difficult situations.

New features of pwdetect V1.1 with respect to pwdetect V1.0:

• Upgraded PSF, differently for each Chandra instrument.
• Output counts and fluxes are PSF-corrected (differently for each instrument).
• Concentric, spurious sources are not detected anymore.

• Pwdetect_1.2 handles up to 7 million events (rather than 3 millions as before).
• The edge of the analyzed image can be moved outwards (with respect to its automatically determined value) by a user-selectable distance (parameter edgemargin). A negative value moves the margin inwards.
• Weak spurious detections found around a bright source are removed.

• Vignetting is now different between HRC and ACIS.
• It is possible to perform detection at one single scale, equal to the maximum scale (parameter onescale=yes/no).
• The minimum (relative) exposure for inclusion in background computation is user-selectable (parameter relthr=0:1). We recommend setting this parameter to 0.9 (as we made in the simulations of spurious detections for a given background).

In addition, PWDetect V.1.3 writes in the working directory a number of intermediate files (ascii lists of intermediate detections, and their ds9-style regions files), useful if your final source list is unsatisfactory, and you want to trace back if e.g. a "missed" source was present at an intermediate stage, but dropped thereafter. This might easily occur in a dense cluster, where you may want to reduce the maximum scale for detection, or use just one single scale (now possible with the new parameter onescale). A file "psf_corrections" is also provided, listing the PSF-related corrections applied to each detected source, depending on both off-axis and azimuth, needed since the PSF is non-gaussian.

In addition to edgemargin, onescale, and relthr, two more new parameters are found in the new pwdetect.par:

liveshow produces some real-time visual description of PWDetect activity, by displaying the analyzed image with ds9, and adding sources detected at each scale (using xpa). Its functioning might be depending on the local configuration, however, and setting it to 0 is the safest option.

eband is the nominal energy for PSF computation. However, only the 1.5 keV PSF is included at the moment, so this parameter has currently no effect.

Should you have problems or questions, you may contact Francesco Damiani, main author of the PWDetect code. Please note, however, that we are currently able to give only limited support.

Last modified on July 30, 2008.