From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Sat May 17 2003 - 13:54:26 PDT
On Sat, May 17, 2003 at 01:35:40PM -0700, Greg Aldering wrote:
> I believe that correct way to isolate the E(B-V) uncertainties is to
> Monte Carlo only the E(B-V) errors and then look at the distribution of
> best-fit values of Om in a flat universe. This would be very time
> consuming if you let script M and alpha vary, since you have to
> marginalize over their probabilities. A fast, but less accuract way
> would be to let MINUIT or some other solver crank out the best-fit
> values based on the equations for Om, script M, and alpha (with Ol =
> 1-Om).
Are you talking about in the extinction-corrected fit? If so, that
ought to just give approximately a spread of OM which is the same as the
spread we get by using the current error bars in the chisquare fit.
(That is, if we treat the errors as Gaussian.) This is assuming you're
talkinging about Monte Carloing each SN's EBV based on its dEBV. Or,
probably more accuratley, it will give you a spread which is the
quadrature difference between the dOM size from the extinction-corrected
and not-extinction-corrected fits; very close, anyway. It's not clear
to me, though, how measuring the size of that spread tells us what the
extinction systematic ought to be for a non-extinction-corrected fit; it
only tells us how much of the statistical uncertainty in the extinction
corrected fit comes from color errors.
-Rob
-- --Prof. Robert Knop Department of Physics & Astronomy, Vanderbilt University robert.a.knop@vanderbilt.edu
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