From: Greg Aldering (aldering@panisse.lbl.gov)
Date: Sun Apr 04 2004 - 14:46:11 PDT
For point sources of the same size, taken on images with the same depth
and with little host galaxy light, one expects a direct correspondence
between magnitude and apsig.
I plotted Y=mag+2.5*log10(apsig) versus X=magnitude for the new
candidates and for those from Adam's search. For the new search you
can see very tight loci in this parameter, however, there are multiple
loci with a large spread between them. If each locus is interpreted as
being from an image (something that could be found by probing the
candidates database outside SNtrak), then this suggests a rather large
variation in either the typical PSF or typical noise amongst images.
(Of course this assumes the ACS zeropoints are correct within an
additive constant - this should be true since the zeropoints are all
the same.) In comparison, the candidates from the 2003 search have a
much smaller spread in this parameter (by about a factor of 2).
No "bottom line" yet - just probing to try to understand the dataset
better.
- Greg
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