A novel multi-frequency technique for the detection of point sources in Cosmic Microwave Background maps

TL;DR

This paper introduces a new multi-frequency linear filtering technique called 'matched matrix filters' for detecting extragalactic point sources in Cosmic Microwave Background maps, improving detection rates over standard methods.

Contribution

The paper presents a novel filtering method that leverages full spatial and cross-channel information without assuming source spectral behavior, enhancing detection performance.

Findings

Outperforms standard matched filters at 30, 44, and 70 GHz.

Nearly doubles the number of true detections at 95% reliability.

Achieves similar performance to standard filters at 100 GHz.

Abstract

In this work we address the problem of simultaneous multi-frequency detection of extragalactic point sources in maps of the Cosmic Microwave Background. We apply a new linear filtering technique, the so called `matched matrix filters', that incorporates full spatial information, including the cross-correlation among channels, without making any a priori assumption about the spectral behaviour of the sources. A substantial reduction of the background is achieved thanks to the optimal combination of filtered maps. We describe in detail the new technique and we apply it to the detection/estimation of radio sources in realistic all-sky Planck simulations at 30, 44, 70 and 100 GHz. Then we compare the results with the mono-frequential approach based on the standard matched filter, in terms of reliability, completeness and flux accuracy of the resulting point source catalogs. The new filters outperform the standard matched filters for all these indexes at 30, 44 and 70 GHz, whereas at 100 GHz both kind of filters have a similar performance. We find a noticeable increment of the number of true detections for a fixed reliability level. In particular, for a 95% reliability we practically double the number of detections at 30, 44 and 70 GHz.