From: Vitaliy Fadeyev (VAFadeyev@lbl.gov)
Date: Sun Apr 04 2004 - 16:43:04 PDT
> Let me also remind people that Adam has an HST ISR which discusses the
> number of photoelectrons deposited by CRs. There is a minimum
> deposition, from which we once calculate that any CR will deposit
> enough e- such that it will be as bright or brighter than a SN Ia at
> z ~ 1.2 at maximum. This might prove useful in judging some tough cases.
Yes, most CRs are very bright. Redshift 1.2 SN at max correspoints to about 24 mag
according to Ariels note.
> Finally, in reading the WIKI notes, I'm baffled by the number of cases
> where a single CR has made it into the sum. It doesn't seem like this
> should never happen for the above minimum deposition and the depth of
> these images.
What frequently happens in the case of a single CR is that its weak "shadow",
i.e. diffused signal in the neighbouring CCD cells, is mixing up with low-level
2-3 sigma fluctuations, which happen "naturally". Another test is to compare the discovery
magnitude as reported by the search software with the aperture photometry
of the images not obviously affected by CRs. If the latter magnitude is larger
by a unit or more, then this is a false case.
vitaliy
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