Constraints on the non-linear coupling parameter fnl with the Archeops data

Aims: We present a Gaussianity analysis of the Archeops Cosmic Microwave Background (CMB) temperature anisotropy data maps at high resolution to constrain the non-linear coupling parameter f_nl characterising well motivated non-Gaussian CMB models. We used the data collected by the most sensitive Archeops bolometer at 143 GHz. The instrumental noise was carefully characterised for this bolometer, and for another Archeops bolometer at 143 GHz used for comparison. Angular scales from 27 arcmin to 1.8 degrees and a large fraction of the sky, 21%, covering both hemispheres (avoiding pixels with Galactic latitude |b| < 15 degrees) were considered. Methods: The three Minkowski functionals on the sphere evaluated at different thresholds were used to construct a χ2 statistics for both the Gaussian and the non-Gaussian CMB models. The Archeops maps were produced with the Mirage optimal map-making procedure from processed time ordered data. The analysis is based on simulations of signal (Gaussian and non-Gaussian f_nl CMB models) and noise which were processed in the time domain using the Archeops pipeline and projected on the sky using the Mirage optimal map-making procedure. Results: The Archeops data were found to be compatible with Gaussianity after removal of highly noisy pixels at high resolution. The non-linear coupling parameter was constrained to f_nl= 70-400+590 at 68% CL and f_nl=70-920+1075 at 95% CL, for realistic non-Gaussian CMB simulations.