The C-Band All-Sky Survey: total intensity point-source detection over the northern sky

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p>We present a point-source detection algorithm that employs the second-order Spherical Mexican Hat wavelet filter (SMHW2), and use it on C-Band All-Sky Survey (C-BASS) northern intensity data to produce a catalogue of point sources. This catalogue allows us to cross-check the C-BASS flux-density scale against existing source surveys, and provides the basis for a source mask that will be used in subsequent C-BASS and cosmic microwave background (CMB) analyses. The SMHW2 allows us to filter the entire sky at once, avoiding complications from edge effects arising when filtering small sky patches. The algorithm is validated against a set of Monte Carlo simulations, consisting of diffuse emission, instrumental noise, and various point-source populations. The simulated source populations are successfully recovered. The SMHW2 detection algorithm is used to produce a $4.76\, \mathrm{GHz}$ northern sky source catalogue in total intensity, containing 1784 sources and covering declinations δ ≥ −10°. The C-BASS catalogue is matched with the Green Bank 6 cm (GB6) and Parkes-MIT-NRAO (PMN) catalogues over their areas of common sky coverage. From this we estimate the 90 per cent completeness level to be approximately $610\, \mathrm{mJy}$, with a corresponding reliability of 98 per cent, when masking the brightest 30 per cent of the diffuse emission in the C-BASS northern sky map. We find the C-BASS and GB6 flux-density scales to be consistent with one another to within approximately 4 per cent.</jats:p>

The C-Band All-Sky Survey (C-BASS): template fitting of diffuse galactic microwave emission in the northern sky

“…To remo v e the sources, we use a combination of catalogues. We use the C-BASSderived point source catalogue described in Grumitt et al ( 2020 ) for all sources that are detected at 10 σ or better and do not lie within | b | < 1 • of the Galactic plane. For fainter sources, or sources with a poor detection using C-BASS itself, we use several C -band point source catalogues: the Green Bank 6 cm (GB6) surv e y (Gre gory et al 1996 ), the Parkes-MIT-NRAO (PMN) survey (Wright et al 1994 ) (for low declinations), and the RATAN-800 surv e y (Mingaliev et al 2007 ) for sources missed by the GB6 surv e y around the North Celestial Pole (NCP).…”

“…Fig. 1 shows bright sources ( > 10 Jy at 4.76 GHz; Grumitt et al 2020 ) masked by a 2 • diameter aperture. There are also some fainter point sources ( S ν < 10 Jy at 4.76 GHz) that leave residuals in the C-BASS map after subtraction; we mask these using a smaller 1 • diameter aperture.…”