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The C-Band All-Sky Survey (C-BASS): constraining diffuse Galactic radio emission in the North Celestial Pole region

Dickinson, C. and Barr, A. and Chiang, H. C. and Copley, C. and Grumitt, R. D. P. and Harper, S. E. and Heilgendorff, H. M. and Jew, L. R. P. and Jonas, J. L. and Jones, Michael E. and Leahy, J. P. and Leech, J. and Leitch, E. M. and Muchovej, S. J. C. and Pearson, T. J. and Peel, M. W. and Readhead, A. C. S. and Sievers, J. and Stevenson, M. A. and Taylor, Angela C. (2019) The C-Band All-Sky Survey (C-BASS): constraining diffuse Galactic radio emission in the North Celestial Pole region. Monthly Notices of the Royal Astronomical Society, 485 (2). pp. 2844-2860. ISSN 0035-8711.

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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 (⁠<10 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 ± 0.34 K per unit τ_(353) when using the Haslam and C-BASS synchrotron templates, respectively. The AME contributes 55 ± 2μK rms at 22.8 GHz and accounts for ≈60 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 ≈7μK rms (⁠≈7 per cent⁠) at 22.8 GHz. The best explanation for the AME is still electric dipole emission from small spinning dust grains.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Dickinson, C.0000-0002-0045-442X
Jones, Michael E.0000-0003-3564-6680
Pearson, T. J.0000-0001-5213-6231
Peel, M. W.0000-0003-3412-2586
Readhead, A. C. S.0000-0001-9152-961X
Sievers, J.0000-0001-6903-5074
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 February 17. Received 2019 February 15; in original form 2018 October 27. Published: 22 February 2019. The C-BASS project is a collaboration between Oxford and Manchester Universities in the UK, the California Institute of Technology in the U.S.A., Rhodes University, UKZN and the South African Radio Observatory in South Africa, and the King Abdulaziz City for Science and Technology (KACST) in Saudi Arabia. It has been supported by the National Science Foundation NSF awards AST-0607857, AST-1010024, AST-1212217, and AST-1616227, and NASA award NNX15AF06G, the University of Oxford, the Royal Society, the Science and Technology Facilities Council (STFC), and the other participating institutions. This research was also supported by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Technology. We would like to thank Russ Keeney for technical help at the Owens Valley Radio Observatory. CD acknowledges support from a European Research Council ERC Starting (Consolidator) Grant (no. 307209). CD also thanks the California Institute of Technology for their hospitality and hosting during several extended visits. MWP acknowledges funding from a FAPESP Young Investigator fellowship, grant 2015/19936-1. We make use of the HEALPIX package (Górski et al. 2005), IDL astronomy library and PYTHON astropy, matplotlib, numpy, healpy, and scipy packages. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The C-BASS collaboration would like to remember the late Prof. Rodney D. Davies and Prof. Richard J. Davis, who were both strong supporters of the C-BASS project (
Group:Astronomy Department
Funding AgencyGrant Number
University of OxfordUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
South African Radio Astronomy Observatory (SARAO)UNSPECIFIED
National Research Foundation (South Africa)UNSPECIFIED
European Research Council (ERC)307209
Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP)2015/19936-1
Subject Keywords:radiation mechanisms: non-thermal, radiation mechanisms: thermal, surveys, diffuse radiation, radio continuum: ISM
Issue or Number:2
Record Number:CaltechAUTHORS:20190801-103843596
Persistent URL:
Official Citation:C Dickinson, A Barr, H C Chiang, C Copley, R D P Grumitt, S E Harper, H M Heilgendorff, L R P Jew, J L Jonas, Michael E Jones, J P Leahy, J Leech, E M Leitch, S J C Muchovej, T J Pearson, M W Peel, A C S Readhead, J Sievers, M A Stevenson, Angela C Taylor, The C-Band All-Sky Survey (C-BASS): constraining diffuse Galactic radio emission in the North Celestial Pole region, Monthly Notices of the Royal Astronomical Society, Volume 485, Issue 2, May 2019, Pages 2844–2860,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97582
Deposited By: Tony Diaz
Deposited On:01 Aug 2019 17:57
Last Modified:09 Mar 2020 13:19

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