DIRECTIONAL VARIATIONS OF THE NON-GAUSSIANITY PARAMETER f{sub NL}
- Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway)
- Dipartimento di Matematica, Universita di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, I-00133 Rome (Italy)
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberfoce Road, Cambridge, CB3 0WA (United Kingdom)
- Dipartimento di Fisica, G. Galilei, Universita di Padova and INFN, Sezione di Padova, via Marzolo 8, I-35131 Padova (Italy)
We investigate local variations of the primordial non-Gaussianity parameter f{sub NL} in the WMAP data, looking for possible influence of foreground contamination in the full-sky estimate of f{sub NL}. We first improve the needlet bispectrum estimate in Rudjord et al. on the full sky to f{sub NL} = 73 +- 31 using the KQ75 mask on the co-added V + W channel. We find no particular values of f{sub NL} estimates close to the galactic plane and conclude that foregrounds are unlikely to affect the estimate of f{sub NL} in the V and W bands even for the smaller KQ85 mask. In the Q band, however, we find unexpectedly high values of f{sub NL} in local estimates close to the galactic mask, as well as significant discrepancies between Q-band estimates and V/W-band estimates. We therefore conclude that the Q band is too contaminated to be used for non-Gaussianity studies even with the larger KQ75 mask. We further note that the local f{sub NL} estimates on the V + W channel are positive on all equatorial bands from the north to the south pole. The probability for this to happen in a universe with f{sub NL} = 0 is less than 1%.
- OSTI ID:
- 21392417
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 708; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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