Re: Optimization of observations for the HST search

From: Ariel Goobar (ariel@physto.se)
Date: Mon Oct 20 2003 - 02:35:26 PDT

  • Next message: Robert A. Knop Jr.: "Re: Optimization of observations for the HST search"

    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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