From: Ariel Goobar (ariel@physto.se)
Date: Wed Apr 30 2003 - 02:47:19 PDT
Sorry, if the font was a bit small in my previous
message... anyway, I could not find anything in Rob's
latest opus on "other" sources of systematic uncertainties that
have been proposed e.g. "grey" dust and axion-photon
oscillations. Below is a suggestion on how such
a section could look like.
-Ariel
\section{Miscellaneous sources of systematic uncertainties}
Other potential sources of systematic uncertainties have
been suggested. E.g. Aguirre (1999) argued that the presence of
``grey'' dust, i.e. a homogeneous intergalactic component with weak
differential extinction properties over the restframe optical
wavelength regime could not be ruled out by the P99 data.
Since then, the Hubble diagram of Type Ia
supernovae beyond z=1 (Riess et al 2001) was claimed to
rule out the ``grey'' dust scenario as a non-cosmological
alternative explanation to the dimming of high-z SNe. However,
Goobar, Bergstr\"om and M\"ortsell (2002) showed that
the possibility of evolving
dust density makes such an interpretation premature, especially
since the most distant supernova in the Riess et al. (2001) (and
Blakeslee et al, 2003) sample was significantly magnified. A
direct test for
extinction along a wide wavelength range, restframe B-I,
have been performed by Riess et al (2000) on a single supernova,
SN99Q, not showing any evidence for reddening. The
statistical significance of their analysis has
however been challenged by Nobili et al (2003). Although the
situation remains inconclusive, there is no direct evidence
that ``grey'' dust is a dominant source of uncertainties but
it remains an important issue to be addressed by future
data sets including NIR observations.
More recently, the possibility of axion-photon oscillations
making high-z SNe to appear dimmer
was suggested by Cs\'aki, Kaloper and Terning (2002). M\"ortsell,
Bergstr\"om and Goobar (2002) performed a a full
density matrix calculation to show that the attenuation
would be wavelength dependent and could thus be explored with
spectroscopic studies of high-z sources. M\"ortsell and Goobar (2003)
analyzed the 3814 QSO spectra from the Sloan Digital
Sky Survey Early Data Release (redshifts between z=0.15 and z=5.03)
and found no evidence of oscillations setting a very conservative
upper limit on the possible dimming of z$\sim$0.8 SNe to 0.2 magnitudes.
For the current data sample, the above mentioned sources of systematic
uncertainties appear to be subdominant in the total error budget.
\bibitem{Aguirre} Aguirre, A., 1999, ApJ, 525, 583
\bibitem{blakeslee} Blakeslee et al, 2003, ApJ in press, astro-ph/0302402
\bibitem{csaki} Csaki, C., Kaloper N., and Terning, J., 2002,
Phys. Rev. Lett., 88, 61302
\bibitem{greydust} Goobar, A., Bergstr\"om, L, and M\"ortsell, 2002,
A\&A, 384, 1.
\bibitem{axion1} M\"ortsell,E., Bergstr\"om, L., and Goobar, A., 2002,
Phys.Rev D, 66, 047702.
\bibitem{axion2} M\"ortsell,E. and Goobar, A., 2003,
Journal of Cosmology and Astroparticle Physics 04, 003
\bibitem{riessNIR} A.~Riess {\it et al.}, ApJ, 536, 62
-- ___________________________________________________________________ Ariel Goobar (www.physto.se/~ariel) Department of Physics, Stockholm University AlbaNova University Center, SE-106 91 Stockholm, SWEDEN tel: +46 8 55378659 fax: +46 8 55378601
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