Type Ia supernova data used by
Davis, Mörtsell, Sollerman, et al. (2007)
Dark Cosmology Centre

The data can be downloaded
as an ascii file from here.

abell0168_small.gif The Abell 0168 Cluster, part of one of our ESSENCE fields.
Image credit: Peter Challis

These data are a combination of the ESSENCE, SNLS and nearby supernova data reported in Wood-Vasey et al. (2007) and the Higher-z data reported in Riess et al. (2007). These were combined for Davis et al. (2007) and the data are provided in an ascii file in three columns, redshift, distance modulus and uncertainty in the distance modulus.
Please cite Davis et al. (2007), Wood-Vasey et al. (2007) and Riess et al. (2007) if making use of these data. The details are given below.

Combining the supernova data from Wood-Vasey et al. (2007, astro-ph/0701041) and the new Gold dataset from Riess et al. (2007, astro-ph/0611572 ) in a fully consistent way would require that these are simultaneously fit in the same manner as the local sample using the same lightcurve fitter (such as MLCS2k2).

Tamara Davis, tamarad@physics.uq.edu.au
Edvard Mörtsell, edvard@astro.su.se

How the data were combined

In Davis et al. 2007, astro-ph/0701510 we combined the datasets in a more simplistic way:

We took the combined ESSENCE / SNLS / nearby dataset from Table 4 of Wood-Vasey et al. (2007), using only the supernova that passed the light-curve-fit quality criteria. We took the HST data from Table 6 of Riess et al. (2007), using only the supernovae classified as gold.

To put these datasets on the same Hubble diagram we used 36 local supernovae that are in common between these two datasets. When disgarding supernovae with z<0.0233 (due to larger uncertainties in the peculiar velocities) we found an offset of 0.037 +/- 0.021 magnitudes between the datasets, which we then corrected for by subtracting this constant from the HST dataset. The dispersion in this offset was also accounted for in the uncertainties (see below).

The HST dataset had had an additional 0.08 magnitudes added to the distance modulus errors to allow for the intrinsic dispersion of the supernova luminosities. The value used by WV07 was instead 0.10 mag. We have adjusted for this difference by putting the Gold supernovae on the same scale as the ESSENCE supernovae. Finally, we also added (in quadrature) the dispersion of 0.021 magnitudes introduced by the simple offset desribed above to the errors of the 30 supernovae in the HST data set.


Davis, Mörtsell, Sollerman and ESSENCE, 2007, astro-ph/0701510

Wood-Vasey et al., 2007, astro-ph/0701041

Riess et al., 2007, astro-ph/0611572

Astier et al., 2006, A&A 447, 31

Contacts: Tamara Davis and Edvard Mörtsell