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Point Spread Function

 

Presently an analytical representation of the point spread function is available for the experiment ROSAT PSPC and ROSAT HRI. For ROSAT WFC it is not included in this release of EXSAS.        

For ROSAT PSPC a Gaussian representation of the point spread function as a function of off-axis-angle and energy is available. This function is used in the EXSAS spatial analysis commands (including Source Detection commands).

There is also a more complicated presentation available (Gaussian + exponential + Lorentzian function). The surface brightness of the point spread function is normalized to 1,

displaymath17675

The on-axis point spread function PSF(E,r), with energy E (in keV) and distance from the center of the point spread function r (in arcsec) can be calculated from the relations given below.  

displaymath17677

with

BR1 = 39.95 / E
BR2 = 861.9 / E

F1 = A1 / (2. tex2html_wrap_inline17679 )
F2 = A2 / (2. tex2html_wrap_inline17681 )
F3 = A3 / ( tex2html_wrap_inline17683 ) -
log(BR1 tex2html_wrap_inline17685 BR1) + 2. / (ALPHA-2.)))

ARG1 = 0.5 tex2html_wrap_inline17687
ARG2 = r / RC

SIGMA = tex2html_wrap_inline17689
RC = tex2html_wrap_inline17691
ALPHA = 2.119 + 0.212 tex2html_wrap_inline17693 E

A1 = 1.0 - A2 - A3
A2 = tex2html_wrap_inline17695
A3 = 0.059 tex2html_wrap_inline17697

The ring integrated surface normalized on-axis point spread function for ROSAT PSPC is plotted for energies of 0.1, 0.3, 0.5, 0.8, 1.0, 1.2 and 1.5 keV in Figure 5.13. It is also available in form of a table file, EXSAS_CAL:psf.tbl and EXSAS_CAL:psf_pspc_00.tbl, in the energy range 0.1 to 1.7 keV.

For off-axis angles of 5 to 50 arcmin (in steps of 5 arcmin) the point spread function is available in table form as well (EXSAS_CAL:psf_pspc_05.tbl, ..., EXSAS_CAL:psf_pspc_50.tbl).

For ROSAT HRI the point spread function is available in table form (EXSAS_CAL:psf_hri_05.tbl, EXSAS_CAL:psf_hri_10.tbl, ..., EXSAS_CAL:psf_hri_20.tbl) for off-axis angles of 0 (on-axis), 5, ..., 20 arcmin.

   figure5542
Figure 5.13: On-axis ROSAT PSPC surface brightness of the point spread function for energies of 0.1, 0.3, 0.5, 0.8, 1.0, 1.2 and 1.5 keV and distances to the center of the point spread function up to about 3000 arcsec. The normalization is as given in section 5.4.1 including a multiplicative factor of 3600.


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If you have problems/suggestions please send mail to rosat_svc@mpe-garching.mpg.de