Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/sas/5.4.1/doc/inthist.ps.gz Дата изменения: Fri Jan 10 22:42:02 2003 Дата индексирования: Tue Oct 2 07:56:12 2012 Кодировка: Поисковые слова: воздушные массы

XMM-Newton Science Analysis System Page: 1
inthist
January 10, 2003
Abstract
Plot histograms of the intensity distributions of sets of EPIC images for user
selected pixels size.
1 Instruments/Modes
Instrument Mode
EPIC MOS Imaging
EPIC pn Imaging
2 Use
pipeline processing yes
interactive analysis no
3 Description
This task takes the EPIC images in the input list of images, divides them by the images in the input list
of `exposure maps', rebins the resulting images to a user-specied bin size and plots the corresponding
intensity (count-rate) histograms (number of image bins containing a countrate within a certain interval)
to a single PostScript le. The last bin includes all rebinned pixels brighter than the maximum value
shown in the x-axis and it is marked with an arrow.
The rationale for developping this task is to allow the user to estimate quickly the intensity background
in a number of bands, and to assess the signicance of the detection of faint sources. To achieve this, it
is necessary that the input images are in a useful set of energy bands (such as the default EPIC IMAG-
ING energy bands), and that the images listed in the parameter exposuresets are their corresponding
exposure maps.
Furthermore, if the user-selected bin size binsize is the size of the point spread function, the number of
pixels above a given countrate is roughly the number of sources with uxes above that countrate.
xmmsas 20030110 1802-5.4.1

XMM-Newton Science Analysis System Page: 2
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
sets yes list of
data-sets
M1 image1.fits
M1 image2.fits
M1 image3.fits
M1 image4.fits
M1 image5.fits
list of valid data sets
List of FITS les containing the input images in dierent bands
exposuresets yes list of
data-sets
M1 expmap1.fits
M1 expmap2.fits
M1 expmap3.fits
M1 expmap4.fits
M1 expmap5.fits
list of valid data sets
List of FITS les containing the exposure maps for the corresponding images listed in sets.
tmp atsets no list of
le-
names
flat 1.img
flat 2.img
flat 3.img
flat 4.img
flat 5.img
list of valid le names
List of FITS les that will contain the temporary atelded images (images divided by their corresponding
exposure maps). If this parameter is left blank, the temporary atelded images are called flat i.img,
where i goes from 1 to the number of images in parameter sets.
binsize yes real 0.01667 > 0:0
Size of the rebinned pixels in degrees for histogramming. It will be rounded to the nearest integer multiple
of the pixel size in the input image
outle yes le-
name
inthist.ps valid le name
Name of the output Post Script le containing plots of the histograms
5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
InvalidDataType (fatal)
Data type in input image is not permitted
IncNumImg (fatal)
The number of images in sets is not equal to the number of images in exposuresets
xmmsas 20030110 1802-5.4.1

XMM-Newton Science Analysis System Page: 3
IncNumFlat (fatal)
The number of images in sets is not equal to the number of temporary les in tmpflatsets
ErrFarith (fatal)
Problem raised while trying to divide a given image by a given exposure map using farith
ErrIntmakehist (fatal)
Problem raised while trying to create histograms using intmakehist module
badDevice (fatal)
Specied PGPLOT device cannot be opened
MissingFitsKeyw (fatal)
The WCS keyword CDELT1 is not included in the input image
AllocationError (fatal)
Failed allocation for internal array
BadParamValue (fatal)
The requested bin size is smaller than one of the input images pixel size, larger than one of
the input image's size or it results in a binned image with only one pixel
NotImage (warning)
One of the input images is not an EPIC image
corrective action:
NotExpMap (warning)
One of the input exposure maps is not an EPIC exposure map
corrective action:
EmptyHistogram (warning)
All intensities in one or more of the bands are equal
corrective action: Check input le names
6 Input Files
1. List of input Images. Each Image is a PPS product called \EPIC IMAGE".
2. List of Exposure maps for the corresponding images in sets. Each Exposure map is a PPS
product called \EPIC EXPOSURE MAP".
7 Output Files
1. Post Script le in which each physical page will be divided in 6 boxes. In each box a
histogram for each of the input images will be plotted. The last one will contain some useful
information such as the binned pixel size, exposure time, etc.
This le is a PPS product named \EPIC Postscript intensity histogram".
8 Algorithm
inthist is a perl script which does the following:
xmmsas 20030110 1802-5.4.1

XMM-Newton Science Analysis System Page: 4
1. Read input parameters and check for errors
2. Run the FTOOLS task farith to at eld the input images
3. Run the F90 module intmakehist:
module intmakehist
Read input flatfielded images and parameters
Open output Post Script file
Foreach (input image){
Rebin to specified binsize
Estimate histogram mean and variance using sigma clipping
Compute optimal histogram binsize and display range based on
mean and variance
Build and plot intensity histogram
}
Close Post Script file
end module intmakehist
9 Comments
 If the proper (recommended) binning size is used, it should be possible to measure source
counts with the positive tail of the histograms
 Rounds up rebinned pixel size to the nearest integer multiple of the elementary pixel size of
the input images
 Ignores pixels on the edges that do not t in an integer number of rebinned pixels
 Temporary les are created with the names specied in the parameter tmpflatsets and are
deleted when they are no longer needed, at the end of the task.
10 Future developments
In the future, and with low priority, the task might include the possibility to overlay histograms from
template (source-free) images for comparison. In this way it would be possible, for example, to check for
the presence of extended low surface brightness sources.
References
xmmsas 20030110 1802-5.4.1