J/MNRAS/479/4041 HII regions at 76.2MHz synchrotron emissivities (Su+, 2018)
Galactic synchrotron distribution derived from 152 H II region absorption
features in the full GLEAM survey.
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.,
Kapinska 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.
<Mon. Not. R. Astron. Soc., 479, 4041-4055 (2018)>
=2018MNRAS.479.4041S 2018MNRAS.479.4041S (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Radio continuum
Keywords: cosmic rays - HII regions - Galaxy: structure -
radio continuum: general
Abstract:
We derive the synchrotron distribution in the Milky Way disc from HII
region absorption observations over -40°<l<40° at six
frequencies of 76.2, 83.8, 91.5, 99.2, 106.9, and 114.6MHz 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. (1981A&A...100..209H 1981A&A...100..209H) map and known
spectral indices, which enable us to simultaneously derive the
emissivity and the optical depth of HII regions at each frequency. We
show our derived synchrotron emissivities based on 152 absorption
features of HII regions using both the method previously adopted in
the literature and our improved method. We derive the synchrotron
emissivity from HII regions to the Galactic edge along the line of
sight and, for the first time, derive the emissivity from HII regions
to the Sun. These results provide direct information on the
distribution of the Galactic magnetic field and cosmic ray electrons
for future modelling.
Description:
We use data obtained by the MWA as part of the GaLactic and
Extragalactic All-sky MWA survey (GLEAM; Wayth et al.,
2015PASA...32...25W 2015PASA...32...25W). We calculate the synchrotron emissivities both
behind and in front of 152 HII regions at six frequencies of 76.2,
83.8, 91.5, 99.2, 106.9, and 114.6MHz. This new method enables us to
derive the HII region optical depth and estimate the amount of flux
density missing from our observations at each frequency. We find that
the emissivities increase towards the Galactic centre.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 179 152 The derived synchrotron emissivities and optical
depths of HII regions at 76.2MHz
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See also:
VIII/100 : GaLactic and Extragalactic All-sky MWA survey (Hurley-Walker+, 2016)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- HII HII Region name (GLLL.lll+BB.bbb)
17- 20 F4.1 kpc Dist Distance from HII region to the sun
22- 24 F3.1 kpc e_Dist Distance error
26- 30 F5.2 10+3K Te Electron temperature
32- 35 F4.2 10+3K e_Te Electron temperature error
37- 40 F4.1 10+3K Th Measured brightness temperature in the
direction of the absorbed region
42- 44 F3.1 10+3K e_Th Th error
46- 49 F4.1 10+3K Tm Measured brightness temperature from the Sun
to the Galactic edge in the absence of HII
region emission from the GLEAM map
51- 53 F3.1 10+3K e_Tm Tm error
55- 59 F5.1 10+3K Tt Total brightness temperature from the Sun to
the Galactic edge in the absence of HII
region absorption derived from the Haslam map
61- 64 F4.1 10+3K e_Tt Tt error
66- 69 F4.1 10+3K Tb Derived brightness temperature of the
synchrotron emission from HII regions to
the Galactic edge
71- 75 F5.1 10+3K E_Tb Tb error (upper value)
77- 81 F5.1 10+3K e_Tb Tb error (lower value)
83- 86 F4.1 10+3K Tf Derived brightness temperature of the
synchrotron emission from the HII region to
the Sun
88- 92 F5.1 10+3K E_Tf Tf error (upper value)
94- 98 F5.1 10+3K e_Tf Tf error (lower value)
100-103 F4.1 10+3K Xb Brightness temperature of the emission on the
missing short interferometric spacings
between the Galactic edge and the Sun (1)
105-109 F5.1 10+3K E_Xb Xb error (upper value)
111-115 F5.1 10+3K e_Xb Xb error (lower value)
117-120 F4.1 10+3K Xf Brightness temperature of the emission on the
missing short interferometric spacings
between an HII region and the Sun (1)
122-126 F5.1 10+3K E_Xf Xf error (upper value)
128-132 F5.1 10+3K e_Xf Xf error (lower value)
134 A1 --- l_tau Limit flag on tau
135-138 F4.1 --- tau Optical depth of the HII region
140-142 F3.1 K/pc emb Average emissivity between the HII region and
the Galactic edge
144-147 F4.1 K/pc E_emb emb error (upper value)
149-152 F4.1 K/pc e_emb emb error (lower value)
154-157 F4.1 K/pc emf Average emissivity between the HII region and
the Sun
159-163 F5.1 K/pc E_emf emf error (upper value)
165-169 F5.1 K/pc e_emf emf error (lower value)
171-174 F4.2 K/pc embsim Emissivity between the HII region and the
Galactic edge derived from the simplified
method
176-179 F4.2 K/pc e_embsim embsim error
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Note (1): The emissivities will be ∼15 per cent lower if you accept a
synchrotron spectral index of -2.6 instead of -2.7 we used.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 04-May-2022