Sometimes, you need to know the total power in a particular radius of a FITS image, and the growth of this total power along the radius you choose for checking whether the object is extended or not, or contains some ring or disk structures. Therefore, this script could be very helpful for those kinds of quick checks.
Under the help of Zhangzheng Wen, who gave the idea of calculating the distance from a certain pixel to the image centre, I wrote this IDL radial_power.pro: (Download HERE)
;+ ; NAME: ; RADIAL_POWER ; ; PURPOSE: ; Calculating the radial_power, returning radius and normalized ; integrated power within the radius. ; ; CALLING SEQUENCE: ; PRO radial_power, image, radius, integrated ; ; INPUTS: ; image: read image from a FITS file and put it into a variable. ; ; KEYWORD INPUTS: ; ... ; ; KEYWORDS SWITCHES: ; ... ; OUTPUTS: ; radius: the radius from center to each circle. ; integrated: the normalized integrated power within the radius. ; ; EXAMPLES: ; IDL> image =... ; ;input the image into the variable after read the image from FITS file or other file format. ; IDL> radial_power, image, radius, integrated ; ;this will return the radius, and integrated. ; ; SIDEEFFECT: ; ... ; ; RESTRICTIONS: ; This pro is only useful for one peak structure, namely if ; you want to study two objects with comparable peak flux, ; this pro is not available, but you can edit it to make it ; function well. ; NEED "wherenan.pro" ; ; MODIFICATION HISTORY: ; Write, Chentao YANG (email@example.com), 2013-02-04 ; ;- PRO radial_power, image, radius, integrated ; make NaN values = 0 IF (SIZE(WHERE(FINITE(image,/NAN)), /N_ELEMENTS) GT 1) THEN image[WHERE(FINITE(image,/NAN))]=0 ; get the index of the maximum point s = SIZE(image,/dimensions) m = (WHERE(image EQ MAX(image))) y_max = m/s x_max = m MOD s image_size = SIZE(image) image_xdist = FINDGEN(image_size)#TRANSPOSE(FINDGEN(image_size)*0+1) image_ydist = TRANSPOSE(FINDGEN(image_size)#TRANSPOSE(FINDGEN(image_size)*0+1)) image_xdist = (image_xdist-x_max)^2 image_ydist = (image_ydist-y_max)^2 image_dist = SQRT(image_xdist+image_ydist) radius = FINDGEN(SQRT(MIN([MAX(image_xdist), MAX(image_ydist)]))*0.7) integrated = radius FOR i=0, (SIZE(radius, /N_ELEMENTS)-1) DO BEGIN integrated[i] = TOTAL(image[WHERE(image_dist LE radius[i])]) ENDFOR integrated = integrated/MAX(integrated) END