Re: K-corrections: another voice in the debate

From: Serena Nobili (serena@physto.se)
Date: Wed Mar 10 2004 - 04:13:29 PST

  • Next message: Serena Nobili: "Re: K-corrections"

    Hi Alex,

    thanks for checking this out. The difference you found using my templates
    are due to restframe/observed frame,i.e. I am using restframe dates. This
    makes our results coincide perfectly, which I believe is already a good
    point.

    For the difference you found between the results obtained using Rob's
    templates and mine, they agree with what have been already pointed out by
    Chris for K_JI. These differences are in fact within the quoted uncertainty
    of 0.05. I believe also that Rob's work in the I-band is probably not as
    accurate as in B,V and R, nor as in the Nobili et al. 2003 paper, since it
    was not a relevant band for the Knop et al paper (Rob, do you agree with
    this?). I any case, the quoted uncertainty (0.05) takes care of these
    differences, giving us confidence in what we are doing.

    I attach a plot where the K-corrections you computed are plotted versus
    restframe days. As you see the black and the cyan lines coincide, since
    they have both been computed using my templates. The red line instead is
    computed using Rob's template.
    Cheers,

            Serena

    On Tue, 9 Mar 2004, Alex Conley wrote:

    >Hello Serena,
    >
    > I have run my K-corrections on the same dates as yours, and I have to
    >report that I also get a rather different result than you do. This is
    >displayed graphically for the z=0.05 case in the first attachment (I got
    >the line styles wrong in the legend-- sorry). Shown are your values, my
    >values, and the values I get with my code and filter curves using your
    >uberspectra. The values that I get with your uberspectra are very similar
    >to yours. The difference is probably due to one or both of the following:
    > (i) I assumed that the dates were observer frame, and you used rest
    > frame.
    > (ii) I am using versions of Bessell's filters with the linear function
    > removed and you are not.
    >In any case, they are close enough not to worry about.
    >
    >The comparison with my K-corrections is not so close. The differences
    >are pretty substantial, with my K-corrections generally being smaller.
    >You shouldn't pay attention to dates past about 30 days because the color
    >model has run out of steam.
    >
    >The other attachment has the actual numbers for the three cases that
    >you gave, as well as a side by side comparison for z=0.05.
    >
    >Alex
    >

    -- 
    

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