This model calculates the X-ray scattering cross section of a population of dust grains as a function of energy, given a specific dust grain position and an extraction region. As the grain position gets closer to the source of the X-rays for a constant extraction region, the cross section drops as more X-rays remain within the extraction circle. For constant dust grain position, the cross section decreases with increasing extraction region size because more photons remain within it.
A detailed description of the model can be found in Smith, Valencic & Corrales (2016).
The model parameters are as follows.
|par1 =||interstellar hydrogen column density ( cm).|
|par2 =||the relative position of the dust along the line of sight. This varies between 0 for dust at the observer and 1 for dust at the source.|
|par3 =||the radius of the circular extraction region (arcsec).|
|par4 =||the dust model used (see Smith et al. 2016). The model options are 1=MRN, 2=WD, and 3=ZDABAS.|
The third and fourth parameters must be frozen.