From: Greg Aldering (aldering@panisse.lbl.gov)
Date: Tue Apr 15 2003 - 09:08:07 PDT
>Should we use the heliocentric redshifts from the Hamuy paper (this is
>what we used in P99), or from NED?
>
>It won't make any difference to the cosmology (differences are tiny),
>but might affect the chisquare a bit.
>
>Does anybody have a strong opinion on this? I suspect the NED ones are
>probably "usually" better, but they are from a heterogenous set of
>references and as such I'm a little nervous just using them.
Just a word of caution here - NED is a huge database and it must be
difficult for them to get everything right on every entry. For
instance, I found that one batch of our SCP SNe discoveries was
attributed to the HZSST! The NED values can be checked against the
original source to root out errors. Redshifts coming from huge
galaxy redshift surveys might need to be viewed with caution since
again, they are going for statistics and can't carefully check each
redshift. Usually some level of confidence in the measurement is
provided (Tonry & Davis r-value, velocity uncertainty, etc.). Conversely,
Hamuy et al are not galaxy redshift experts and may have used
inferior measurement techniques in get the redshifts of their galaxies,
so their methodology ought to be examined too.
If we want to settle this, then such checking needs to be done. However,
I don't see the point in holding up the submission of the paper for just
this small problem. It is something we can work on while the referee is
taking his/her sweet time getting back to us.
- Greg
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