Description

A response matrix file (RMF) encapsulates the mapping between the physical properties of incoming photons (such as their energy) and their detected properties (such as detector pulse heights or PHA) for a given detector. For X-ray spectral analysis, the RMF encodes the probability R(E,p) that a detected photon of energy E will be assigned to a given channel value (PHA or PI) of p. The standard Legacy format (see the GSFC HEASARC journal Legacy, issue no. 2) for the RMF uses a binary table in which each row contains R(E,p) for a single value of E as a function of p. Non-zero sequences of elements of R(E,p) are encoded using a set of variable length array columns. This format is compact but hard to manipulate and understand. The rmfimg program converts this format to a simple 2-dimensional image of R(E,p) versus E and p, allowing one to visualize the response of the instrument.

An ancillary response file (ARF) contains the effective area A(E) including the probability that a photon of energy E will be detected at all. The total `response' is A(E)R(E,p). The Legacy format for ARF is a binary table of A(E) versus E. To make it easy to visualize A(E) together with R(E,p), rmfimg optionally allows you to create a two-dimensional `ARF image' A(E,p), which just replicates A(E) for each value of p. (To simply see the 1-dimensional function, you can use prism directly on the ARF, or use dmlist to dump it to an ascii file and use ChIPS to view it). Optionally, the output RMF image will be multiplied by the ARF to give an image of the total response.