From: Serena Nobili (serena@physto.se)
Date: Fri Dec 19 2003 - 07:58:26 PST
Hi Alex (cc Rob)
thanks for your email. You were extremely fast in reading the paper! I
will answer to all of your comments during the weekend, but the one about
the Bessel filter definition is the one which worries me more, not because
of the size of the corrections, but for the amount of work I have to do
now to get it fixed.
*** Rob, how was this done in the HST paper?
On Thu, 18 Dec 2003, Alex Conley wrote:
>
>K-corrections:
>
>a) Do you have the right I band filter? First, you should give a source
> for standard Bessel I band. You probably have the transmission from
> Bessel PASP 102:1181 (1990). If that is the filter curve you are using,
> you need to be aware that the normalized passbands in Table 2 are NOT
> the dimensionless transmission R, but are actually lambda * R. That is,
> the filter is slightly bluer than you may think. This is not explained
> in the text of the paper.
>
Does this applies to all BVRI filters?
> This is something that has been done incorrectly in all previous
> published SCP work. The effect is not large -- if you would like
> to see the size of the difference, take a look at
> http://panisse.lbl.gov/~aconley/kdiff.eps
>
what is the color code in this plot? I could not figure it out. Anyway I
see that the effect is very small, which is expected since both observed
and restframe filters are in the "wrong" units, so the total effect is
probably averaged out. This gives me confidence in the fact that this is
probably not going to change the results of the paper.
> This was discovered due to a note in Jha's thesis. I ended up emailing
> Mike Bessel directly to confirm this. So you should look up Bessel
> (1990), compare it to your filter curve, and if it the one you are using
> you have a (minor) problem -- but one that isn't too hard to fix.
> Just divide your filter file by lambda, renormalize, and redo all your
> K-corrections.
>
I checked it in Jha's thesis ( I guess it is the note in page 156). This
is scaring more for the IR data, when correcting from J-band to I-band,
since I suspect the J-band is done in the "right" way.
But I need to check how big the effect will be.
Thanks for having pointed this out.
Cheers
Serena
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