Re: question for HST paper

From: Peter Nugent (nugent@panisse.lbl.gov)
Date: Thu May 01 2003 - 07:18:45 PDT

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    > We have to make sure we don't get into circular arguments while
    > eg first using colors to type it, and then use same colors to
    > limit reddening.

    Fortunately for us SNe Ia are much bluer than Ib/c's and their color
    evolution is different as well so reddening and typing isn't a
    circular task.

    Now as for Rob's statement about the categories these should fall in.

    The color of a Ib/c at this z should be R-I>=0.8 before peak and it gets
    redder continuously. A Ia should have a color around R-I>=0.3-0.4 with a
    little slop due to choice of uberspectrum and stretch (a bluer one like
    Rob used for all his analysis makes it around 0.3, what I and the Israelis
    used puts it around 0.4) and the color curves are very different. Your
    measurements of the color (including all possible arbitrary systematics,
    like using both uberspectra for the k-corrs) for these SNe are better than
    0.1 mag. Thus according to the paper I cited (and their nice interactive
    website) and what I checked out on my own, the colors and their evolution
    are consistent with them both being Ia's at => 3 sigma. As Rob pointed
    out, they fit his Ia color curves nicely.

    Thus they should definitely go into the 'good' Ia category, because I
    think this is at the same level as the id'ing of the spectra as 'good'.
    And remember, the spectra are not-inconsistent with Ia's, they are just
    not that good S/N-wise, so there is no negative from them, just no
    positive either.

    Now before Saul says, 'Why don't we do this for the other SNe from P99 we
    threw out?' the simple answer is we can't since we in general have just 1
    color at peak (not 4-5 spread out) and their error bars on that 1 color
    are horrendous.

    Thus add my paragraph in where you id them and we are good to go as-is.

    Cheers,

    Peter 

    -- 
Peter E. Nugent
Staff Computational Scientist - Scientific Computing Group - NERSC
Lawrence Berkeley National Laboratory
M.S. 50F-1650 - 1 Cyclotron Road - Berkeley, CA, 94720-8139
Phone:(510) 486-6942 - Fax:(510) 486-5812
E-mail: penugent@LBL.gov - Web: http://supernova.LBL.gov/~nugent

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