Extragalactic point source detection in WMAP 7-year data at 61 and 94
  GHz
  The detection of point sources in Cosmic Microwave Background maps is usually
based on a single-frequency approach, whereby maps at each frequency are
filtered separately and the spectral information on the sources is derived
combining the results at the different frequencies. On the contrary, in the
case of multi-frequency detection methods, source detection and spectral
information are tightly interconnected in order to increase the source
detection efficiency.
  In this work we apply the \emph{matched multifilter} method to the detection
of point sources in the WMAP 7yr data at 61 and 94 GHz. This linear filtering
technique takes into account the spatial and the cross-power spectrum
information at the same time using the spectral behaviour of the sources
without making any a priori assumption about it. We follow a two-step approach.
First, we do a blind detection of the sources over the whole sky. Second, we do
a refined local analysis at their positions to improve the signal-to-noise
ratio of the detections. At 94 GHz we detect 129 5{\sigma} objects at
|b|>5{\deg} (excluding the Large Magellanic Cloud region); 119 of them are
reliable extragalactic sources and 104 of these 119 lie outside the WMAP Point
Source Catalog mask. Nine of the total 129 detections are known Galactic
sources or lie in regions of intense Galactic emission and one additional
(weak) high-Galactic latitude source has no counterpart in low-frequency radio
catalogues. Our results constitute a substantial improvement over the
NEWPS-3year catalogue.
