From: Ariel Goobar (ariel@physto.se)
Date: Mon Oct 20 2003 - 02:35:26 PDT
Hi again,
I am a bit surprised that you get a bias with
opposite sign. Two questions come to mind:
1) Are you using exactly the same template
and K-correcions at the simulation and
fitting stages?
2) What bias do you get on the fitted day
of max?
Cheers,
Ariel
On Mon, 20 Oct 2003 VAFadeyev@lbl.gov wrote:
>
>
>
> Ariel,
>
> This is what I see for z=1.2:
>
> Input stretch is 1.0 . The average fitted
> value from 25 simulations is 1.16 . There are
> two large positive outliers. After clipping
> the average becomes 1.04 .
>
> This suggests that if there is some bias,
> it may not be in the same direction as yours
> (on the plots you sent the average stretch < 1
> for z=1.2).
>
> The existence of the outliers is a bit worrisome;
> also, there are cases with abonormally small
> fit errors.
>
> vitaliy
>
>
>
> ----- Original Message -----
> From: VAFadeyev@lbl.gov
> Date: Monday, October 20, 2003 1:12 am
> Subject: Re: Optimization of observations for the HST search
>
> >
> >
> > Hi Ariel,
> >
> > it is good that the results are consistent.
> >
> > Your observation of the biases is very interesting. Was it ever
> > checked before that the LC parameter
> > extraction is self-consistent and bias-free, say
> > for lower redshift cases?
> >
> > The only reason why I switched off the randomization
> > was to save time. Otherwise I'd have to rerun
> > the code multiple times for every observation
> > sequence, derive the corresponding distributions etc.
> >
> > Initially I did briefly checked that with randomization turned on
> > there were no big biases
> > for z=1.3. This is close to your case of z=1.4,
> > where you don't have substantial biases either.
> > So perhaps this was not a very strict check.
> > Am rerunning that example for z=1.2 now. Will
> > report the results shortly.
> >
> > Cheers,
> > vitaliy
> >
> >
>
>
>
-- ___________________________________________________________________ Ariel Goobar (www.physto.se/~ariel) Department of Physics, Stockholm University AlbaNova University Center, SE-106 91 Stockholm, SWEDEN tel: +46 8 55378659 fax: +46 8 55378601
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