From: Serena Nobili (serena@physto.se)
Date: Mon Feb 02 2004 - 04:58:35 PST
Dear Lifan,
I don't really understand from your e-mail, whether you get a dispersion
of 0.14 using my Imax or yours. I am doing some checks and I have a doubt
concerning the uncertainty of the redshift. Are you propagating that in
the uncertainty on the effective magnitude? I am trying to do so and I
get a dispersion of 0.14 magnitude, assuming the uncertainty on
velocity=300 km/s and data with z > 0.01. The way I get 0.14 mag is by
subtracting the average error square from the r.m.s. square, i.e.
sqrt(rms^2-<err>^2) = 0.14
If I select data with z > 0.015, then I get:
sqrt(rms^2-<err>^2) = 0.166
As the uncertainty is dominated by the one on the redshift, thus
the cut on the redshift range is quite relevant to the measured
dispersion. Is this what you are doing?
For what concerns the uncertainties in the fitted Imax, they were checked
with a Monte Carlo, and found always consistent with the simulation. As
you see the uncertainty on 1996C is slightly larger than the one on
1996bo, for instance, which has much smaller uncertainties in the data
points. You find the description of the simulation in the paper (section
2.3). Please let me know if you think that is not clear enough.
Cheers
Serena
On Sat, 31 Jan 2004, Lifan Wang wrote:
>Hi, Serena,
>
> I have looked at your Imax fits. I am getting a dispersion of 0.14
>if there is no color and dm15 cuts. I am still looking into this issue, but
>I am concerned with the Imax errors shown in your table. Many of them are
>really tiny even when the data are really bad, such as in the case of 96C.
> Gerson and are still working on the comparison. We will have a better
>feeling of what's going on next week.
>
> Cheers,
>
> Lifan
>
>
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