J/A+A/686/A52 All-sky B-field map (Bracco+, 2024)
A new analytical model of the cosmic-ray energy flux for Galactic diffuse radio
emission.
Bracco A., Padovani M., Galli D.
<Astron. Astrophys. 686, A52 (2024)>
=2024A&A...686A..52B 2024A&A...686A..52B (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Magnetic fields ; Interstellar medium
Keywords: magnetic fields - radiation mechanisms non-thermal - cosmic rays -
ISM: general - ISM: magnetic fields
Abstract:
Low-frequency radio observations of diffuse synchrotron radiation
offer a unique vantage point from which to investigate the intricate
relationship between gas and magnetic fields in the formation of
structures within the Galaxy, spanning from the diffuse interstellar
medium (ISM) to star-forming regions.
Achieving this pivotal objective hinges on a comprehensive
understanding of cosmic-ray properties; these dictate the effective
energy distribution of relativistic electrons, which are primarily
responsible for the observable synchrotron radiation. Notably,
cosmic-ray electrons (CRe) with energies of between 100MeV and 10GeV
play a crucial role in determining the majority of the sky brightness
below the GHz range. However, their energy flux (je) remains elusive
because of solar modulation. We propose a way to derive observational
constraints on this energy gap of interstellar CRe through the
brightness temperature spectral index of low-frequency radio emission,
here denoted βobs. We introduce a new parametric analytical
model that fits available data for je in accordance with the
βobs values measured in the literature between 50MHz and 1GHz
for diffuse emission in the Milky Way.
Our model accounts for multiple observations considering
magnetic-field strengths consistent with existing measurements below
10uG. We present a first all-sky map of the average component of the
magnetic field perpendicular to the line of sight and validate our
methodology against state-of-the art numerical simulations of the
diffuse ISM. This research makes headway in modeling Galactic diffuse
emission with a practical, parametric form. It provides essential
insights that will help preparations for the imminent arrival of the
Square Kilometre Array.
Description:
fits map of the Galactic magnetic field in HealPIX format with NSIDE=64
showing the plane-of-the-sky component of the Galactic magnetic field
averaged along the line of sight in units of 1E-6 Gauss. The map is
derived using the radio spectral index from Guzman et al.,
2011A&A...525A.138G 2011A&A...525A.138G.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 93 1 Information on fits file
fits/* . 1 fits files
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See also:
J/A+A/525/A138 : All-sky Galactic radiation at 45MHz (Guzman+, 2011)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Nx Number of pixels along X-axis
6- 7 I2 --- Ny Number of pixels along Y-axis
9- 11 I3 Kibyte size Size of FITS file
13- 40 A28 --- FileName Name of FITS file, in subdirectory fits
42- 93 A52 --- Title Title of the FITS file
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Acknowledgements:
Andrea Bracco, andrea.bracco(at)inaf.it
(End) Patricia Vannier [CDS] 15-Mar-2024