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SynopsisCalculate an elliptical source region Syntaxsrcextent srcfile outfile [psffile] [regfile] [shape] [srcsize] [imgsize] [binfactor] [mincounts] [minthresh] [clobber] [verbose] DescriptionCalculate the sizes and associated errors of a photon-count source image or list of source images using the Mexican Hat Optimization (MHO) algorithm (Houck 2007). The uncertainty is a 90% confidence estimate derived from Monte Carlo trials using MARX simulated data. The MHO algorithm looks for a source approximately centered in the image and estimates the parameters of an elliptical Gaussian which best fits the source image. The elliptical Gaussian parameters [center position (x,y), 1-sigma semi-axes (a,b) and position angle (theta)] are derived by maximizing the Mexican-Hat wavelet transform. The tool also computes sqrt((1/2)(a^2+b^2)) as an 'apparent size' estimate which is more robust than the individual semi-major and semi-minor axis values. The tool applies the algorithm to both PSF and source images, and then tests whether the two apparent sizes are consistent given the image statistics. It derives an estimate of 'intrinsic size' as the radius of a gaussian by which the PSF image would need to be convolved to match the source image. The tool fits the PSF first, if it is present, and uses the result as an initial guess to guide fitting on the source image. The tool may also be used with a single input image, but the user must supply an initial guessed image size in the srcsize parameter. For technical details on how the tool works, please see the documents http://cxc.harvard.edu/csc/memos/files/Houck_source_extent.pdf http://cxc.harvard.edu/csc/memos/files/Houck_intrinsic_size.pdf Example 1srcextent srcfile="acisf00635_000N001_r0001b_regevt3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" psffile="acisf00635_000N001_r0001b_psf3.fits" regfile="acisf00635_000N001_r0001_reg3.fits" Calculate the source, PSF, and intrinsic source size from a source event file, normalized PSF image, and a FITS region file. Example 2srcextent srcfile="acisf00635_000N001_r0001b_regevt3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" psffile="acisf00635_000N001_r0001b_psf3.fits" regfile="ellipse.reg" Calculate the source, PSF, and intrinsic source size from a source event file, normalized PSF image, and an ASCII region file. Example 3srcextent srcfile="acisf00635_000N001_r0001b_img3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" psffile="acisf00635_000N001_r0001b_psf3.fits" Calculate the source, PSF, and intrinsic source size from a source image and a normalized PSF image. Example 4srcextent srcfile="acisf00635_000N001_r0001b_regevt3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" psffile="acisf00635_000N001_r0001b_projrays3.fits" regfile="acisf00635_000N001_r0001_reg3.fits" Calculate the source, PSF, and intrinsic source size from a source event file and a PSF event file. Example 5srcextent srcfile="acisf00635_000N001_r0001b_img3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" psffile="acisf00635_000N001_r0001b_projrays3.fits" regfile="acisf00635_000N001_r0001_reg3.fits" Calculate the source, PSF, and intrinsic source size from a source image and a PSF event file. Example 6srcextent srcfile="acisf00635_000N001_r0001b_img3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" Calculate the source size from a source image. Example 7srcextent srcfile="acisf00635_000N001_r0001b_regevt3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" regfile="ellipse.reg" Calculate the source size from a source event file. Example 8srcextent srcfile="acisf00635_000N001_r0001b_psf3.fits" outfile="acisf00635_000N001_r0001b_out3.fits" Calculate the PSF size from a PSF image. Example 9srcextent srcfile="acisf00635_000N001_r0001b_regevt3.fits,acisf00635_000N001_r0002 b_regevt3.fits" outfile="acisf00635_000N001_r0001b_out3.fits,acisf00635_000N001_r0002b_o ut3.fits" psffile="acisf00635_000N001_r0001b_psf3.fits,acisf00635_000N001_r0002b_p sf3.fits" regfile="acisf00635_000N001_r0001_reg3.fits,acisf00635_000N001_r0002_reg 3.fits" Calculate the source, PSF, and intrinsic source size for each source with a stack of source event files, PSF images, and corresponding region files. Parameters
Detailed Parameter DescriptionsParameter=srcfile (file required filetype=input stacks=yes)Source file, FITS image or FITS event list Parameter=outfile (file required filetype=input stacks=yes)Output file, FITS table Parameter=psffile (file not required filetype=input stacks=yes)PSF file, FITS image or FITS event list The Chandra HRMA PSF can be simulated with ChaRT and the instrument effects, including detector pixelization, can be simulated with MARX. See the ChaRT website for more information. Parameter=regfile (file not required filetype=input stacks=yes)Region File, ellipse or circle region, in FITS or ASCII Required for event lists. ASCII-format region files may only contain CIRCLE and ELLIPSE shapes currently. Parameter=shape (string not required default=gaussian)Source shape [gaussian,disk] Parameter=srcsize (real not required default=0)Crude estimate of source size Parameter=imgsize (real not required default=0)Size of image Parameter=binfactor (integer not required default=0)Image binning factor Parameter=mincounts (integer not required default=15)Minimum counts inside calculated ellipse threshold Parameter=minthresh (integer not required default=6)Minimum counts for source file threshold Parameter=clobber (boolean not required default=no)Clobber output file (yes/no) Parameter=verbose (integer not required default=3)Verbosity setting BugsSee the bugs page for this tool on the CIAO website for an up-to-date listing of known bugs. |
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The Chandra X-Ray
Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA. Email: cxcweb@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2004. All rights reserved. |
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