iraf.net

Hello!

I'm using ELLIPSE package to create radial profiles of different galaxies from HST ACS images.
I'm slightly confused by the units for "mag0" and "refer" in the task MAGPAR.

The magpar help page notes that the magnitude it will use for ELLIPSE's isophotal values will be :
m = mag0 - 2.5 * log10 ((intens - zerolevel) / refer)

The "intens" value, I believe, is in units of ADU (however please correct me if I'm wrong).
In order to get a correct magnitude for each isophote, should I input the exposure time into "refer", and the zero-point Vega magnitude for my filter in "mag0"?

The example on the magpar help page seems to use surface brightness (mag0 = mag/arc^2) to get to a magnitude value.
However, my mag0 value is in units of magnitude, so I want to make sure I am converting my values correctly.

Thanks!

****I believe intens is in units of ADU/pix^2****

Similar questions have been asked here and in the old mail logs before, but since this is an STSDAS task the question was always forwarded to STScI and I can't find a log of the answer. You can contact them at help@stsci.edu