Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA

H. Su; N. Hurley-Walker; C. A. Jackson; N. M. McClure-Griffiths; S. J. Tingay; L. Hindson; P. Hancock; R. B. Wayth; B. M. Gaensler; L. Staveley-Smith; J. Morgan; M. Johnston-Hollitt; E. Lenc; M. E. Bell; J. R. Callingham; K. S. Dwarkanath; B. Q. For; A. D. Kapińska; B. McKinley; A. R. Offringa; P. Procopio; C. Wu; Q. Zheng

doi:10.1093/mnras/stw2959

Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA

H. Su^*, N. Hurley-Walker, C. A. Jackson, N. M. McClure-Griffiths, S. J. Tingay, L. Hindson, P. Hancock, R. B. Wayth, B. M. Gaensler, L. Staveley-Smith, J. Morgan, M. Johnston-Hollitt, E. Lenc, M. E. Bell, J. R. Callingham, K. S. Dwarkanath, B. Q. For, A. D. Kapińska, B. McKinley, A. R. OffringaP. Procopio, C. Wu, Q. Zheng

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

11 Citations (Scopus)

Abstract

Synchrotron emission pervades the Galactic plane at low radio frequencies, originating from cosmic ray electrons interacting with the Galactic magnetic field. Using a low-frequency radio telescope, the Murchison Widefield Array (MWA), we measure the free-free absorption of this Galactic synchrotron emission by intervening HII regions along the line of sight. These absorption measurements allow us to calculate the Galactic cosmic ray electron emissivity behind and in front of 47 detected HII regions in the region 250° < l < 355°, |b| < 2°.We find that all average emissivities between the HII regions and the Galactic edge along the line of sight (εb) are in the range of 0.39 ~ 1.45 K pc^-1 with a mean of 0.77 K pc^-1 and a variance of 0.14 K pc^-1 at 88 MHz. Our best model, the two-circle model, divides the Galactic disc into three regions using two circles centring on the Galactic Centre. It shows a high emissivity region near the Galactic Centre, a low emissivity region near the Galactic edge, and a medium emissivity region between these two regions, contrary to the trend found by previous studies.

Original language	English
Pages (from-to)	3163-3174
Number of pages	12
Journal	Monthly Notices of the Royal Astronomical Society
Volume	465
Issue number	3
DOIs	https://doi.org/10.1093/mnras/stw2959
Publication status	Published - 1 Mar 2017

Access to Document

10.1093/mnras/stw2959

Cite this

Su, H., Hurley-Walker, N., Jackson, C. A., McClure-Griffiths, N. M., Tingay, S. J., Hindson, L., Hancock, P., Wayth, R. B., Gaensler, B. M., Staveley-Smith, L., Morgan, J., Johnston-Hollitt, M., Lenc, E., Bell, M. E., Callingham, J. R., Dwarkanath, K. S., For, B. Q., Kapińska, A. D., McKinley, B., ... Zheng, Q. (2017). Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA. Monthly Notices of the Royal Astronomical Society, 465(3), 3163-3174. https://doi.org/10.1093/mnras/stw2959

@article{f76257bd32cb49d38790df5f8b159428,

title = "Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA",

abstract = "Synchrotron emission pervades the Galactic plane at low radio frequencies, originating from cosmic ray electrons interacting with the Galactic magnetic field. Using a low-frequency radio telescope, the Murchison Widefield Array (MWA), we measure the free-free absorption of this Galactic synchrotron emission by intervening HII regions along the line of sight. These absorption measurements allow us to calculate the Galactic cosmic ray electron emissivity behind and in front of 47 detected HII regions in the region 250° < l < 355°, |b| < 2°.We find that all average emissivities between the HII regions and the Galactic edge along the line of sight (εb) are in the range of 0.39 ~ 1.45 K pc-1 with a mean of 0.77 K pc-1 and a variance of 0.14 K pc-1 at 88 MHz. Our best model, the two-circle model, divides the Galactic disc into three regions using two circles centring on the Galactic Centre. It shows a high emissivity region near the Galactic Centre, a low emissivity region near the Galactic edge, and a medium emissivity region between these two regions, contrary to the trend found by previous studies.",

keywords = "Cosmic rays, Galaxy: structure, HII regions, Radio continuum: general",

author = "H. Su and N. Hurley-Walker and Jackson, {C. A.} and McClure-Griffiths, {N. M.} and Tingay, {S. J.} and L. Hindson and P. Hancock and Wayth, {R. B.} and Gaensler, {B. M.} and L. Staveley-Smith and J. Morgan and M. Johnston-Hollitt and E. Lenc and Bell, {M. E.} and Callingham, {J. R.} and Dwarkanath, {K. S.} and For, {B. Q.} and Kapi{\'n}ska, {A. D.} and B. McKinley and Offringa, {A. R.} and P. Procopio and C. Wu and Q. Zheng",

note = "Publisher Copyright: {\textcopyright} 2016 The Authors.",

year = "2017",

month = mar,

day = "1",

doi = "10.1093/mnras/stw2959",

language = "English",

volume = "465",

pages = "3163--3174",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press ",

number = "3",

}

Su, H, Hurley-Walker, N, Jackson, CA, McClure-Griffiths, NM, Tingay, SJ, Hindson, L, Hancock, P, Wayth, RB, Gaensler, BM, Staveley-Smith, L, Morgan, J, Johnston-Hollitt, M, Lenc, E, Bell, ME, Callingham, JR, Dwarkanath, KS, For, BQ, Kapińska, AD, McKinley, B, Offringa, AR, Procopio, P, Wu, C & Zheng, Q 2017, 'Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA', Monthly Notices of the Royal Astronomical Society, vol. 465, no. 3, pp. 3163-3174. https://doi.org/10.1093/mnras/stw2959

TY - JOUR

T1 - Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA

AU - Su, H.

AU - Hurley-Walker, N.

AU - Jackson, C. A.

AU - McClure-Griffiths, N. M.

AU - Tingay, S. J.

AU - Hindson, L.

AU - Hancock, P.

AU - Wayth, R. B.

AU - Gaensler, B. M.

AU - Staveley-Smith, L.

AU - Morgan, J.

AU - Johnston-Hollitt, M.

AU - Lenc, E.

AU - Bell, M. E.

AU - Callingham, J. R.

AU - Dwarkanath, K. S.

AU - For, B. Q.

AU - Kapińska, A. D.

AU - McKinley, B.

AU - Offringa, A. R.

AU - Procopio, P.

AU - Wu, C.

AU - Zheng, Q.

PY - 2017/3/1

Y1 - 2017/3/1

N2 - Synchrotron emission pervades the Galactic plane at low radio frequencies, originating from cosmic ray electrons interacting with the Galactic magnetic field. Using a low-frequency radio telescope, the Murchison Widefield Array (MWA), we measure the free-free absorption of this Galactic synchrotron emission by intervening HII regions along the line of sight. These absorption measurements allow us to calculate the Galactic cosmic ray electron emissivity behind and in front of 47 detected HII regions in the region 250° < l < 355°, |b| < 2°.We find that all average emissivities between the HII regions and the Galactic edge along the line of sight (εb) are in the range of 0.39 ~ 1.45 K pc-1 with a mean of 0.77 K pc-1 and a variance of 0.14 K pc-1 at 88 MHz. Our best model, the two-circle model, divides the Galactic disc into three regions using two circles centring on the Galactic Centre. It shows a high emissivity region near the Galactic Centre, a low emissivity region near the Galactic edge, and a medium emissivity region between these two regions, contrary to the trend found by previous studies.

AB - Synchrotron emission pervades the Galactic plane at low radio frequencies, originating from cosmic ray electrons interacting with the Galactic magnetic field. Using a low-frequency radio telescope, the Murchison Widefield Array (MWA), we measure the free-free absorption of this Galactic synchrotron emission by intervening HII regions along the line of sight. These absorption measurements allow us to calculate the Galactic cosmic ray electron emissivity behind and in front of 47 detected HII regions in the region 250° < l < 355°, |b| < 2°.We find that all average emissivities between the HII regions and the Galactic edge along the line of sight (εb) are in the range of 0.39 ~ 1.45 K pc-1 with a mean of 0.77 K pc-1 and a variance of 0.14 K pc-1 at 88 MHz. Our best model, the two-circle model, divides the Galactic disc into three regions using two circles centring on the Galactic Centre. It shows a high emissivity region near the Galactic Centre, a low emissivity region near the Galactic edge, and a medium emissivity region between these two regions, contrary to the trend found by previous studies.

KW - Cosmic rays

KW - Galaxy: structure

KW - HII regions

KW - Radio continuum: general

UR - http://www.scopus.com/inward/record.url?scp=85014661666&partnerID=8YFLogxK

U2 - 10.1093/mnras/stw2959

DO - 10.1093/mnras/stw2959

M3 - Article

SN - 0035-8711

VL - 465

SP - 3163

EP - 3174

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 3

ER -

Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA

Abstract

Access to Document

Other files and links

Fingerprint

Cite this