Galactic synchrotron distribution derived from 152 H ii region absorption features in the full GLEAM survey. Issue 3 (29th June 2018)

• Record Type: Journal Article
• Authors: Su, H; Macquart, J P; Hurley-Walker, N; McClure-Griffiths, N M; Jackson, C A; Tingay, S J; Tian, W W; Gaensler, B M; McKinley, B; Kapińska, A D; Hindson, L; Hancock, P; Wayth, R B; Staveley-Smith, L; Morgan, J; Johnston-Hollitt, M; Lenc, E; Bell, M E; Callingham, J R; Dwarkanath, K S; For, B-Q; Offringa, A R; Procopio, P; Wu, C; Zheng, Q
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 479:Issue 3(2018)
• Page Start: 4041
• Page End: 4055
• Publication Date: 2018-06-29
• Subjects: cosmic rays -- H ii regions -- Galaxy: structure -- radio continuum: general; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty1732
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We derive the synchrotron distribution in the Milky Way disc from H ii region absorption observations over −40° < l < 40° at six frequencies of 76.2, 83.8, 91.5, 99.2, 106.9, and 114.6 MHz with the GaLactic and Extragalactic All-sky Murchison widefield array survey (GLEAM). We develop a new method of emissivity calculation by taking advantage of the Haslam et al. (1981 ) map and known spectral indices, which enable us to simultaneously derive the emissivity and the optical depth of H ii regions at each frequency. We show our derived synchrotron emissivities based on 152 absorption features of H ii regions using both the method previously adopted in the literature and our improved method. We derive the synchrotron emissivity from H ii regions to the Galactic edge along the line of sight and, for the first time, derive the emissivity from H ii regions to the Sun. These results provide direct information on the distribution of the Galactic magnetic field and cosmic ray electrons for future modelling.