From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Thu Mar 20 2003 - 14:42:35 PST
On Thu, Mar 20, 2003 at 02:30:44PM -0800, Greg Aldering wrote:
> Regarding R_R, take a look at
> /home/astro34/aldering/njnunes/minuit/total_select_extinc.pro
> To the best of my recollection, this is the program that was used to
> assign R_R to each SN. It is based on calculations done by Peter -
> perhaps he can recall in more detail what procedure was used. I think we
> can guarentee that the light was treated as red light, not as blue light!
> This effect surfaced late in the analysis, but was discussed pretty
> thoroughly at the time. But, I agree that the effect seems awfully large
> in retrospect.
Not just awfully large-- implausibly large. Impossibly large, for the
reasons I stated in the last message.
That program you quote is just an interpolator. I would question how
it was made. I suspect, despite your guarantee, that it was not done
correctly, and that effectively the light was treated as blue (e.g. by
deredshifting the filter). That is the only possible explanation I can
think of for the completely unreasonable range of R_B's which are
quoted.
These are the R_B's I get when I integrate my umedian template spectrum,
redshifted, through the O'Donnell law and the R-band filter:
z AR/E(B-V)
--------------
0.00 : 2.74
0.05 : 2.72
0.10 : 2.72
0.15 : 2.71
0.20 : 2.70
0.25 : 2.71
0.30 : 2.70
0.35 : 2.70
0.40 : 2.70
0.45 : 2.70
0.50 : 2.68
0.55 : 2.66
0.60 : 2.65
0.65 : 2.63
0.70 : 2.61
0.75 : 2.59
0.80 : 2.57
That's more the sort of range of variation I'd expect. Also, it goes in
the direction I'd expect : as you get to higher and higher redshift,
eventually you are going to start shifting the "dead" left side of the
rest-U-band SN spectrum into the blue side of the observed R-band
filter, thereby weighting the redder side of the observed R-band filter
more. Thus, it seems reasonable to get a *lower* R_R for supernovae at
higher redshift, when you're talking about Milky Way extinction.
-Rob
-- --Prof. Robert Knop Department of Physics & Astronomy, Vanderbilt University robert.a.knop@vanderbilt.edu
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