in_image = "gx493y322" Name of input image
msk_image = "gx493y322_m" Name of mask image
(sym_image = "gx49y379_s") Name of symmetrized image
(dobkg = yes) Recompute background parameters (yes/no)?
(dosym = yes) Symmetrize input image (yes/no)?
(mode = "q")
GALPARAM computes basic image moments of an object. GALPARAM is a stand-alone version of the subroutine GINIT_PARAM in GIMFIT2D. It only requires an input image in_image and a segmentation image msk_image produced by SExtractor. If required (dobkg=yes), GALPARAM can provide new estimates of local background mean and sigma for comparison with those provided by SExtractor.
It is recommended to set dobkg to yes in GALPARAM and GIMFIT2D so that they will recompute background parameters to work around a bug in SEXtractor. SExtractor evaluates background parameters around a given object using an annulus going around its lowest isophote. However, if one or more nearby galaxies fall inside that annulus, the background sigma gets severely overestimated. This error occurs even though SEXtractor has correctly flagged those bad pixels as belonging to nearby objects. If dobkg=yes, GINIT_PARAM uses background pixels (zero pixels in SEXtractor segmentation image) which are at least 5 pixels away from a pixel belonging to any objects in the segmentation image. This is 5-pixel buffer zone is necessary to avoid biasing the background estimate with galaxy flux below the lowest isophotes. The required size of this buffer zone was calculated from simulations.
If dosym=yes, then GALPARAM will create a symmetrized version of the input image in_image.