Re: Bias of our low-extinction method

From: Greg Aldering (aldering@panisse.lbl.gov)
Date: Fri May 23 2003 - 10:00:03 PDT

  • Next message: Robert A. Knop Jr.: "Re: Bias of our low-extinction method"

    On Fri, 23 May 2003, Robert A. Knop Jr. wrote:

    > On Fri, May 23, 2003 at 09:33:17AM -0700, Greg Aldering wrote:
    > > Yes, I used everything in your "Gerson table" of May 18th (the last
    > > one you circulated). Note that I only use the error bars on the color
    > > and the magnitude as being representative for purposes of the Monte
    > > Carlo simulation. Do you see a problem with that approach?
    >
    > No -- except that I should note that the E(B-V) error bars are not the
    > same as the (R-I) error bars, and the 0.0425 intrinsic U-B dispersion is
    > not included in the E(B-V) error bars in the table. (It is included in
    > dcc, though.)
    >

    Yes, I treated E(B-V) and R-I errors separately.

    I didn't include the U-B intrinsic scatter. This would be tricky for my
    current simulation because the SNe which require U-B are all at high
    redshift where extincted SNe are supressed in our sample. As I don't
    simulate the SN redshift distribution, my simulation can't account for
    this correlation properly.

    Note that the lack of redshift simulation could have other effects in my
    simulation in the sense that our error bars may be systematically smaller
    at low redshift than at high redshift. If so, the noisier high-redshift
    error bars might be letting in extincted SNe which are in fact never
    allowed into our sample due to the flux limit.

    To investigate further, we would have to couple our selection criteria to
    a more complete extinction/flux-limit simulation, like those that Gene has
    done. This should be possible, but could take a little time.

    - Greg



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