ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

20.13. UNIT CONVERSION AND COLOUR CORRECTION 257
CIA> corr_dark, pds
CIA> print, pds.cube_unit
ADU/G/s
After CUBE reduction these units will propagate into the EXPOSUREs.
CIA> reduce, pds
CIA> print, pds.image_unit
ADU/G/s
Likewise for MOSAIC creation.
CIA> raster_scan, pds
CIA> print, pds.raster_unit
ADU/G/s
20.13.2 Conversion to milli-janskys
At any stage in the processing you can attempt to convert pixel values to milli-janskys (mJy)
with conv flux. For example, after raster MOSAIC creation you can convert .raster pixels into
mJy with:
CIA> conv_flux, pds, /raster
CIA> print, pds.raster_unit
mJy/pix
Likewise, .cube IMAGE pixels may be converted by setting the keyword /cube, and.image
EXPOSURE pixels by setting /image.
conv flux uses the low-level conversion routine adu to mjansky. This is a useful routine
for finding the sensitivity of a particular CAM filter. For example, to convert a signal of 1 ADU
observed with the LW2 filter to mJy:
CIA> print, adu_to_mjansky( 1, ’lw2’ )
0.429129
20.13.3 Color correction
The conversion to mJy as performed by conv flux (Section 20.13.2 is given for the reference
wavelength of each filter and assumes a source with spectral shape that follows a F (λ) ∼ λ −1
law. In reality your source may have a spectrum that deviates from this law. To correct this
effect CIA provides the routine corr colour. You can use this routine to calculate a correction
factor that may be applied manually to the results of your CAM photometry. There are three
ways to calculate this correction factor: