Astronomical Software

Thus spake Bob Day
"Charles Francis" wrote in message
...
[ snip ]

The teleconnection prediction is simply the same as
Reiss eq 11 multiplied by an extra factor of sqrt(1+z).

I did the fits and have posted the Matlab program and a plot
of Reiss's fit (in red) and your fit (in blue) on my website at
http://bobday.vze.com. Scroll to the bottom of the page --
they're under the heading "CF Fits". I added your extra factor
of sqrt(1+z) to the factor of (1+z) that's before the integral in
Riess's equation 11, making it (1+z)^(3/2). Is that correct?
The optimum fit is pretty strange though. The values that
produced the optimum were Omega_m = 1.22, and
Ho = 63.9. (I let Ho be a variable since no one knows quite
what it is -- some researchers still believe it's in the '50s.)
Chi-square was 187.2168. The optimum for Riess's equation 11
was Omega_m = 0.31 and Ho = 64.3, with a Chi-square value
of 177.0730.

This is fascinating, because it puts us well above critical mass. I have
been studying the special case fits, Omega=1, Omega_Lambda=0, and they
match the standard Omega=0.26 curve up to z=.7. They also seem good with
the data up to z=1.3. The qualitative analysis indicates values above
Omega=1 will improve the fit for high z, but I am suspicious. This would
put us well into the negative lambda regime - possible but I hate
physical laws without physical causes.

I think Riess only has three data points above z=1.4 . Actually the
number of points above z=1 is probably not enough for statistical
significance, given that there is quite a scatter below z=1. There seems
to be some issue with SN1997ff anyway, because correction for
gravitational lensing may not be accurate (see abstract below - any
comment, Philip? this is your field isn't it). How does it affect the
fit if you take out the two or three highest redshifts, which may be
unbalancing the result?

The teleconnection Omega=1 relation looks too close to call to the
Astier fit, for z up to about 1. He has a large scatter of points,
reinforcing the idea that there are not enough points about z=1.4 to be
valid. It looks to me like the teleconnection probably gives the better
fit. Any chance of testing that data?



astro-ph/0105355, Gravitational Lensing of the Farthest Known Supernova
SN 1997ff, Mörtsell, E.; Gunnarsson, C.; Goobar, A. ApJ 561, Issue 1,
pp. 106-110.

Abstract
We investigate the effects of gravitational lensing due to intervening
galaxies on the recently discovered Type Ia supernova at z~1.7, SN
1997ff, in the Hubble Deep Field North. We find that it is possible to
obtain a wide range of magnifications by varying the mass and/or the
velocity dispersion normalization of the lensing galaxies. In order to
be able to use SN 1997ff to constrain the redshift-distance relation,
very detailed modeling of the galaxies to control the systematic effects
from lensing is necessary. Thus, we argue that, based on our current
limited knowledge of the lensing galaxies, it is difficult to use SN
1997ff to constrain the values of OM and O?, or even to place severe
limits on gray dust obscuration or luminosity evolution of Type Ia
supernovae.

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Regards

--
Charles Francis
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