Comp, dev, exp, psf, ... rex?

I get the first four (composite, deVaucouleurs, exponential, PSF), but what’s a REX?

From the few examples I’ve come across, it seems to mean something like “no idea!”, or “bad data”.


It’s short for “round exponential” – an EXP profile, but forced to be circular rather than elliptical. It’s meant to capture “faint fuzzy – wider than a PSF but just a smudge that is too faint to say much more about”. The idea is that it has only one free parameter – radius – so is an Occam’s Razor good-enough explanation for weak evidence.


Makes a lot of sense, and is quite consistent with the few examples I have stumbled across.

Thanks! :slight_smile: