Title:	Direction dependence in supernova data: constraining isotropy
Authors:	Gupta, Shashikant Saini, T.D.
Keywords:	supernovae: general cosmological parameters large-scale structure of Universe
Issue Date:	Oct-2010
Publisher:	Wiley Interscience for the RAS
Citation:	Monthly Notices of the Royal Astronomical Society, 2010, Vol.407, p651
Abstract:	We revise and extend the extreme value statistic, introduced in Gupta et al., to study direction dependence in the high-redshift supernova data, arising either from departures, from the cosmological principle or due to direction-dependent statistical systematics in the data. We introduce a likelihood function that analytically marginalizes over the Hubble constant and use it to extend our previous statistic. We also introduce a new statistic that is sensitive to direction dependence arising from living off-centre inside a large void as well as from previously mentioned reasons for anisotropy. We show that for large data sets, this statistic has a limiting form that can be computed analytically. We apply our statistics to the gold data sets from Riess et al., as in our previous work. Our revision and extension of the previous statistic show that the effect of marginalizing over the Hubble constant instead of using its best-fitting value on our results is only marginal. However, correction of errors in our previous work reduces the level of non-Gaussianity in the 2004 gold data that were found in our earlier work. The revised results for the 2007 gold data show that the data are consistent with isotropy and Gaussianity. Our second statistic confirms these results.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/3978
ISSN:	1365-2966 (Online) 0035-8711
Alternative Location:	http://adsabs.harvard.edu/abs/2010MNRAS.407..651G http://arxiv.org/abs/1005.2868 http://dx.doi.org/ 10.1111/j.1365-2966.2010.16945.x
Copyright:	2010 The authors & the Royal Astronomical Society
Appears in Collections:	Research Papers (A&A)

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