Mappings and transformations between any
source of photons () with physical properties () and the
corresponding detected events () with properties () can be
represented using a response function, (), expressed as
The CXC maintains three responses, each of which has a minimum set of redistribution function(s), as described below:
MKRMF is designed to work with arbitrary redistribution functions, allow flexibility in defining matrix grids, and provide multi-dimensional matrix solutions to the equation above.
MKRMF utilizes redistribution functions which are stored externally using FITS Embedded Functions (FEFs), a new CXC standard for storing analytical or tabulated functions in a FITS format. In this manner, the same tool can be used to create multiple response matrices by supplying the appropriate FEF. The FEF file itself is generated using another CXC tool, dmwritefef, whose inputs are described below.
source = gauss1d[g1]+gauss1d[g2]
name min max units scale offset ENERGY 0 200 keV 3.6e-3 0.047 PHA 0 4096 ADU none none
With MKRMF, the user has three options for defining the matrix grids: command line, FITS binary table, or ASCII table. Each of these is implemented using the SAO parameter file interface.
axis1 = param1, param2, param3, param4, param5 param1: name of the axis param2: the low value of the grid array param3: the high value of the grid array param4: the number of bins in the grid param5: flag indicating whether linear or logarithmic grids are usedFor the archetypal case of a CCD response matrix, we might use:
% mkrmf axis1 = energy,0.1,10.0,1500,linear \ axis2 = pha,1,4096,4096,liwhich specifies that the energy axis is to consist of 1500 linearly spaced bins from 0.1 to 10.0 KeV. Similarly, the pha axis will contain 4096 linear bins from pha values 1 to 4096.
axis1 = param1, param2 param2: name of an external file where grids are tabulatedwhere
param1follows the same description above. For example,
% mkrmf axis1 = energy,example5_pspc.fitsindicates that the external file,
"example5_pspc.fits", tabulates matrix grids along the ``energy'' axis.
axis1 = param1, param2, param3, param4, param5 param3: the total column number (1 or 2) param4: number of the i_th column in the file param5: number of the j_th column in the file if param3=2For example,
% mkrmf axis1 = energy,example5_pspc.ascii, 2, 2, 3instructs the tool to read the lower boundary of the energy grid from the second column and the upper boundary from the third column.
The RMF file produced by MKRMF is currently encoded in one of two FITS formats: legacy and cxc. The 2-D legacy format retains the HEASARC OGIP 92-002 standard which is appropriate for CCD detector responses and compatible with tools such as XSPEC. This format is not however extensible to higher dimensional response matrices such as those needed to model the HETG and LETG gratings on-oard Chandra. Consequently, the CXC has defined a new FITS standard for storing compressed response matrices which is used by other tools in the data analysis system such as SHERPA (Doe et al. 1998). Using this format, RMFs of arbitrary dimensionality can be stored. In the case of standard 2-D RMFs, such as for X-ray CCDs, the user has the option of creating standard HEASARC format files which are backward compatible with XSPEC/FTOOLS or CXC format RMFs. The form and contents of the CXC RMF format is summarized in the table below.
|Low cell bound
|High cell bound
elements for row
|format of each column|
Doe, S., Ljungberg, M., Siemiginowska, A., & Joye, W. 1998, in ASP Conf. Ser., Vol. 145, Astronomical Data Analysis Software and Systems VII, ed. R. Albrecht, R. N. Hook, & H. A. Bushouse (San Francisco: ASP), 157
Wise, M. 1998, Response Matrix Tool: Design Specification and Data Product Interface Control Document, CXC