Matrix Filters for the Detection of Extragalactic Point Sources in Cosmic Microwave Background Images

Abstract

Abstract-In this paper we introduce a new linear filtering technique, the so-called matrix filters, that maximizes the signalto-interference ratio of compact sources of unknown intensity embedded in a set of images by taking into account the crosscorrelations between the different channels. By construction, the new filtering technique outperforms (or at least equals) the standard matched filter applied on individual images. An immediate application is the detection of extragalactic point sources in Cosmic Microwave Background images obtained at different wavelengths. We test the new technique in two simulated cases: a simple two-channel case with ideal correlated color noise and more realistic simulations of the sky as it will be observed by the LFI instrument of the upcoming ESA's Planck mission. In both cases we observe an improvement with respect to the standard matched filter in terms of signal-to-noise interference, number of detections and number of false alarms.

Planck2013 results. XXVIII. ThePlanckCatalogue of Compact Sources

“…2.5). An additional algorithm, the matrix filter (Herranz & Sanz 2008;Herranz et al 2009), has been used to validate the catalogue; this is a multifrequency method that is also being used for the production of a multifrequency catalogue of non-thermal sources that will be published in a future paper. The two MHW2 pipelines have a number of features in common.…”

Extragalactic Compact Sources in the Planck Sky and Their Cosmological Implications

“…Nevertheless, the so called "spectral index", α, changes from source to source and this formula is not reliable when the range of frequencies is wide enough. In [36] a scheme for channel combination was proposed that makes the spectral behavior irrelevant. This method is called matrix multifilters (MTXFs) and relies on the application of a set (N × N matrix) of linear filters which combine the information of the N channels in such a way that: 1) an unbiased estimator of the source flux at each channel is obtained; and 2) the variance of the estimator is minimum.…”

Sparse point-source removal for full-sky CMB experiments: application to WMAP 9-year data

“…Multichannel techniques, which take into account either an estimate of the power spectrum of diffuse emissions (Herranz & Sanz 2008) or the alleged spectral signatures for the point sources (Lanz et al 2011;Vio et al 2013) have also been devised. Other multichannel techniques detect the point sources by cancelling the CMB contribution in the data by a weighted sum of the channels Ramos et al 2011;.…”