Image Analysis with CASA - ESO

Extract a spectrum – Script mode
Use the following set of CASA commands to extract a spectrum and output in an ascii file:
CASA> imgname = 'your_image.image' # specify input image cube
cubestat=imstat(imagename=imgname)
import numpy # make sure vector and array arithmetic options are loaded
cubeheader = imhead(imagename=imgname, mode="list") # set header variables
nspec = cubestat['trc'][3] + 1 # get the number of frequency channels.
f0 = float(cubeheader['crval4']) # reference freq in Hz
df = float(cubeheader['cdelt4']) # channel width in Hz
i0 = cubeheader['crpix4'] # reference pixel
freqspec = ((numpy.arange(nspec) ­ i0)*df + f0)
valspec = imval(imagename=imgname,box='128,128') # e.g. extract spec @ pixel 128,128
outspec = 'spec.txt' # specify name of output spectrum file
spectrum = numpy.vstack((freqspec, valspec['data']))
numpy.savetxt(outspec, numpy.transpose(spectrum)) # save the spectrum in ascii file
You can simply copy/paste these lines in your script, and adapt the parts in red
Note the use of imhead, imval with Python dictionaries
23