The C-Band All-Sky Survey (C-BASS): constraining diffuse Galactic radio emission in the North Celestial Pole region. Issue 2 (22nd February 2019)

• Record Type: Journal Article
• Authors: Dickinson, C; Barr, A; Chiang, H C; Copley, C; Grumitt, R D P; Harper, S E; Heilgendorff, H M; Jew, L R P; Jonas, J L; Jones, Michael E; Leahy, J P; Leech, J; Leitch, E M; Muchovej, S J C; Pearson, T J; Peel, M W; Readhead, A C S; Sievers, J; Stevenson, M A; Taylor, Angela C
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 485:Issue 2(2019)
• Page Start: 2844
• Page End: 2860
• Publication Date: 2019-02-22
• Subjects: radiation mechanisms: non-thermal -- radiation mechanisms: thermal -- surveys -- diffuse radiation -- radio continuum: ISM; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz522
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The C-Band All-Sky Survey (C-BASS) is a high sensitivity all-sky radio survey at an angular resolution of 45 arcmin and a frequency of 4.7 GHz. We present a total intensity map of the North Celestial Pole (NCP) region of sky, above declination >+80°, which is limited by source confusion at a level of ≈0.6 mK rms. We apply the template-fitting (cross-correlation) technique to WMAP and Planck data, using the C-BASS map as the synchrotron template, to investigate the contribution of diffuse foreground emission at frequencies ∼20–40 GHz. We quantify the anomalous microwave emission (AME) that is correlated with far-infrared dust emission. The AME amplitude does not change significantly (${\lt }10\, {{\ \rm per\ cent}}$ ) when using the higher frequency C-BASS 4.7 GHz template instead of the traditional Haslam 408 MHz map as a tracer of synchrotron radiation. We measure template coefficients of 9.93 ± 0.35 and $9.52\pm 0.34\, $ K per unit τ353 when using the Haslam and C-BASS synchrotron templates, respectively. The AME contributes $55\pm 2\, \mu$ K rms at 22.8 GHz and accounts for ${\approx } 60{{\ \rm per\ cent}}$ of the total foreground emission. Our results show that a harder (flatter spectrum) component of synchrotron emission is not dominant at frequencies ≳5 GHz; the best-fitting synchrotron temperature spectral index is β = −2.91 ± 0.04 from 4.7 to 22.8 GHz and β = −2.85 ± 0.14 from 22.8 to 44.1 GHz. Free–free emission is weak, contributing ${\approx } 7\, \mu$ K rms (${\approx } 7{{\ \rm per\ cent}}$ ) at 22.8 GHz. The best explanation for the AME is still electric dipole emission from small spinning dust grains.