From: Andy Howell (DAHowell@lbl.gov)
Date: Wed Feb 26 2003 - 18:00:18 PST
Greg, I understand the gist of what you are saying, and it could be right,
even though it is a very slippery argument (now we're arguing that
selection
effects are good for you). Certainly our R-band high-z searches should
pick
out U-bright SNe. But I do have a couple of things to say about the
details
of what you said.
First, be careful about mixing presumed causes of UV brightness. Some
supernoave
with high stretch are bluer, but this may have nothing to do with
metallicity.
E.g. there is no evidence that SN 1991T is blue because of metallicity
effects.
SNe with more Ni will be hotter and bluer. Of course metallicity could
affect the U-V brightness too, but high stretch does not necessarily
equate to
a metallicity effect. (I know you were just paraphrasing Alex, not
necessarily
taking a stand on the cause of UV brighness, but the point is worth making)
Second, you said:
>You can see this in action by looking at our stretch distribution, for
>U-band-select SNe which all have high stretch. If you go to Jha's U-B
>vs stretch plot, you see these are the bluest SNe. And, you might
agree that
>if you place a prior on Jha's stretch and color appropriate for a
>high-redshift search simulation, the dispersion is probably smaller (for
>instance, you strongly deselect againt low stretch and/or red SNe.
I don't see this. Our U-affected SNe in this paper are:
name z stretch
97201 0.863 1.05 +/- 0.01
97226 0.778 1.06 +/- 0.04
9878 0.644 0.76 +/- 0.03
98104 0.638 1.05 +/- 0.05
This spans the range in Jha's plot from the lowest U-B=-0.85 at s=1.04
to the highest U-B= -0.1 at s=0.82.
Also, one of our assumptions is inconsistent with us having a bluer sample
than Jha. Rob assumed a *redder* typical U-B (-0.4) than Jha quotes
elsewhere
in his thesis (-0.5).
-Andy
This archive was generated by hypermail 2.1.4 : Wed Feb 26 2003 - 18:00:19 PST