Extragalactic point source detection in Wilkinson Microwave Anisotropy Probe 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. In contrast, in the case of multifrequency detection methods, source detection and spectral information are tightly interconnected in order to increase the source detection efficiency. In this work we apply the matched multifilter method to the detection of point sources in the Wilkinson Microwave Anisotropy Probe (WMAP) 7-year 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. Secondly, 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 5s objects at |b| > 5° (excluding the Large Magellanic Cloud region); 119 of them are reliable extragalactic sources and 104 of these 119 lie outside the WMAP Point Source Catalogue 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 New Extragalactic WMAP Point Source (NEWPS) 3-year catalogue. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.The authors acknowledge partial financial support from the Spanish Ministerio de Economía y Competitividad projects AYA2010-21766-C03-01 and CSD2010-00064. LFL acknowledges the Spanish CSIC for a JAE-Predoc fellowship and the hospitality of the Scuola Internazionale Superiore di Studi Avanzati (SISSA) of Trieste during two research stays in 2010 and 2011. ML-C thanks the Spanish Ministerio de Economía y Competitividad for a Juan de la Cierva fellowship. JG-N, GdZ, and MM acknowledge financial support from ASI/INAF Agreement I/072/09/0 for the Planck LFI activity of Phase E2. DH wishes to acknowledge the Spanish Ministerio de Educación for a José Castillejo Fellowship (JC2010-0096) and the Astronomy Group at the Cavendish Laboratory for their hospitality during a research stay in 2011.Peer Reviewe