Detection of extragalactic sources in cosmic microwave background maps with multifrequency techniques

Résumé

The observation and analysis of the Cosmic Microwave Background Radiation is a crucial task to understand the early Universe. When observing this radiation, we can also see other components of both Galactic and extragalactic origin, and instrumental noise. Our knowledge of the extragalactic sources is quite poor in the frequency range between 20 and 1000 GHz. The goal of this thesis is to adapt the matched multifilter (Herranz et al., 2002, MNRAS, 336, 1057) to detect extragalactic sources, because by using several frequencies in a simultaneous way, it uses more information from the data than the single-frequency methods, increasing its performance. The multifilter is applied to realistic simulations of Planck (Lanz et al., 2010, MNRAS, 403, 2120), comparing the results with the obtained by applying the single-frequency matched filter. The multifilter detects more objects and less spurious artifacts. The application of the multifilter to real data of WMAP at 61 and 94 GHz (Lanz et al., 2013, MNRAS, 428, 3048) results in an improvement of the number of detections of ~5 times with respect to other previous works with single-frequency methods, observing a steepening in the spectral behaviour of the sources above ~70 GHz.