simulate[/qualifiers]
Simulate an image or photon event file. Up to 1000 point sources with random, or specified, position inside the image can be simulated above a background that can be flat or include spatial non-uniformities. Source intensities can follow up to two power-law logN-logS distributions, one for AGN and one for stars.
Additional source positions and intensities can be specified in a file called catalog file. This ascii file must contain the right ascension, the declination (in degrees, 1950.0) and the flux (in erg/cm2/s) of each source written in free format. All parameters for this command are included in a file called
xanadu/image/ximage/files/"satellite-name"_"detector-name".pf
Most of the parameters included in the parameter file can also be changed using the corresponding qualifiers. The PSF of each source can be changed and vignetting effects included. The energy spectrum and light curve of each source and background are also simulated if a .fits file is requested. Up to ten different spectral shapes can be used for a simulation. The details of each spectral shape are included in files that can be generated with XSPEC. The number of files and their names must be specified in the parameter file. If more than one spectral shape is requested, each simulated source is associated to one of the requested spectral shapes in a random way.
This specifies particle background in units of cts/s/arcmin**2
This specifies cosmic background in units of cts/s/arcmin**2
The name of file containing a list of sources to be simulated in addition to those from the logn-logs distributions. The catalog file must include three columns: ra, dec, and flux. The right ascension and declination must be in degrees and for the equinox epoch 1950.0. Each line corresponds to a source. The center of the simulated image will coincide with the position of the first source in the catalog file.
This qualifier is disabled.
The size in pixel of image to be simulated. Only square images are supported.
This specifies the satellite required. If it is not given ximage will prompt for it, and give a list of the currently supported missions.
This specifies the detector to be simulated. Detector names depend on the satellite requested. For a list of allowed detectors use command show detectors.
Flux in erg/cm2/s corresponding to the instrument sensitivity limit. If this qualifier is specified the exposure time necessary to achieve the requested sensitivity is automatically calculated unless the /exposure_time qualifier is used, in which case the /flux_limit qualifier is ignored. Note that, in order to simulate the cosmic X-ray background just below the sensitivity limit, several sources with flux below the flux limit are also generated.
The size of image pixels in units of arcseconds (must be an integer)
The rebinning factor between source simulation grid and field grid.
forces XIMAGE to generate a single source positioned at image centre with intensity of about 2000 counts. This image can be used to estimate the size of simulated PSF using command PSF.
Simulate a mini raster scan with 9 point sources located at regular positions within the image.
The ascii file containing the point spread function to be used for the simulation. The maximum psf size is 64x64 pixels. The ascii file should include n records (where n is n=psf_size*psf_size/10+1) and should be structured so that its first record contains only one real number equal to the psf size (e.g. 32) the following records contain 10 values, written in free format, specifying the psf brightness psf(i,j) scaled so that the total psf intensity is 1000. If the psf size is not a exact multiple of 10 one additional record, for each psf row, containing the remaining values must be added after the last full record of each row. For example if the psf size is 32 the ascii file should be made of 1+32*(3+1)=129 records. The first record includes the number 32.0, the following three records include 10 values each (psf(1,1-10), psf(1,11-20), and psf(1,21-30)), the fifth record include two values, psf(1,31),psf(1,32). The sixth to eighth record contain psf(2,1-10),psf(2,11-20), and psf(2,21-30), the ninth record psf(2,31),psf(2,32), and so on.
Make a file containing simulated event data in FITS format.
The name of the output fits events file to be generated.
The exposure time in seconds. The corresponding flux limit of the exposure is automatiacally calculated on the basis of the background, of the search box, and of the statistical significance (snr) requested. If the exposure time is not specified or is set to 0, the exposure time necessray to achieve the requested sensitivity is automatically calculated.
List the available satellite and detector.
The most of the parameters necessary for the simulation are stored into a parameter file called (VMS):
xanadu:[image.ximage.files]"satellite-name"_"detector-name".pf
or (unix)
xanadu/image/ximage/files/"satellite-name"_"detector-name".pf
(e.g. xmm_ccd.pf). The following is a description of all the parameters included:
parameter 1 : `output_data_file`
file where the positions and intensities of all
simulated sources are written.
parameter 2 : `flag_seed`
flag for radom number generator seed
flag_seed < 0 seed entered interactively at run time
flag_seed = 0 seed is radomly chosen
flag_seed > 0 seed is set equal to flag_seed, must be
a large odd number
parameter 3 : `flag_fits`
flag for the generation of a fits event file
flag = 1 -> file is generated; 0-> not generated
parameter 4 : `output_fits_file`
name of the fits output file
parameter 5 : `flag_positions`
flag_positions = 1 random positions in FOV
flag_positions = 2 positions distrib like M31
flag_positions = 0 position are read from from (catalog) file
parameter 6 : `catalog`
name of the file including positions and fluxes
of the sources to be simulated.
parameter 7 : `logns_1_slope`
(integral) slope of first LogN-LogS (LogN-LogS for AGN)
parameter 8 : `logns_1_norm`
normalization of first LogN-LogS (units of sources/sq deg)
parameter 9 : `logns_2_slope`
(integral) slope of second LogN-LogS (LogN-LogS for stars)
parameter 10 : `logns_2_norm`
normalization of second LogN-LogS (units of sources/sq deg)
parameter 11 : `flux_limit`
sensitivity limit of simulated field in ergs/cm2/s
parameter 12 : `snr`
signal-to-noise ratio corresponding to flux limit
parameter 13 : `search_cell`
search cell size in pixels
parameter 14 : `particle background`
particle background in cts/s/arcmin**2
parameter 15 : `cosmic background`
cosmic background in cts/s/arcmin**2
parameter 16 : `file_psf`
file including point-spread-function
parameter 17 : `zoom_s_f`
zoom factor between source and field
this allows the user to change the size of the psf
(by factors of two) without changing file_psf.
parameter 18 : `counts_flux`
conversion factor between 1.0 ct/s and erg/cm2/s
parameter 19 : `pixel_size`
pixels size in arcseconds (must be an integer)
parameter 20 : `size_of_image`
image size in pixels (max=512)
parameter 21 : `vign_1_2_3`
Coeff. for parabolic approximation for vignetting effect
three parameters corresponding to the coefficients of the
parabola that approximate vignetting effect as a function of
off-axis angle only.
parameter 22 : ignore_me
ignore this parameter
parameter 23 : ignore_me
ignore this parameter
parameter 24 : `no_of_spectra`
no of template spectrum files to be used for spectral
simulations
parameter 25 : `spectrum_1`
name of filele including template spectrum 1
parameter 26 : `spectrum_i`
name of filele including template spectrum i
parameter 27 : spectrum_n
name of filele including template spectrum n, n=no_of_spectra
Examples:
sim/sat=xmm/det=ccd/size=200/flux=5.e-15
Simulate a 200 x 200 pixels XMM CCD image with limiting sensitivity of
5.e-15 erg/cm2/s. Since the specified satellite is XMM the parameters which
were not given through qualifiers are read from the parameter-file.
sim/sat=sax/size=300/det=legspc/fits/out=sax.fits
Simulate a 300x300 pixel SAX Low-Energy GSPC image. A .fits file containing
spectral and timing information for every simulated photon is created. This
file can be used to extract (see command `extract`) simulated spectra and
light curves.
sim/sat=rosat/det=pspc/fits/out=rosat/cat=deep_survey
/exposure_time=100000
Simulate a ROSAT PSPC 100000 seconds exposure including all sources
contained in the file `deep_survey` (which could contain for example the
sources of the Eintein IPC deep survey). Since a `.fits` file will be
produced apectra and light curve for each source will be simulated as
specified in the parameter file.