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Foreground Data

Foreground

Product Name
All-sky 150 MHz Map
Coord. System
Galactic
Projection Type
HEALPix, nested, res 8 (Nside=256)
Resolution
5.0 degrees

Description

Landecker and Wielebinski (1970) produced an all-sky map of 150 MHz emission by combining data from their 150 MHz survey between declinations -25° and +25° with scaled data from the 178 MHz survey of Turtle and Baldwin (1962) north of +25° and scaled data from the 85 MHz survey of Yates, Wielebinski, and Landecker (1967) south of -25°. Landecker and Wielebinski quote a probable zero level error of 40 K and a probable scale error of 5%, or 7% south of -25°.

LAMBDA obtained the all-sky brightness temperature data from the Max Planck Institute for Radioastronomy Survey Sampler site on a Galactic coordinate grid with 0.5° spacing in l and b. These data contained sentinel values of -3200 at the Galactic poles and at l=180°, b=89.5°. The sentinel values at b = +90° were replaced with the median measured value for b=89.5°, those at b = -90° were replaced with the median for b=-89.5°, and the one at l=180°, b=89.5° was replaced with a linear interpolation between neighboring measured values at the same latitude. The data were then interpolated to Galactic coordinate HEALPix projection using cubic convolution interpolation. HEALPix res 8 (Nside=256) pixelization was used. This gives a mean pixel spacing of 0.23°.

Patra et al. 2015, ApJ, 810, 138, ADS provided a recalibration of the 150 MHz map based on comparison with absolutely calibrated sky brightness measurements between 110 and 175 MHz made with the SARAS spectrometer, and Monsalve et al. 2021, ApJ, 908, 145, ADS provided a recalibration based on comparison with absolutely calibrated measurements from the Experiment to Detect the Global EoR Signature (EDGES). The correction factors that were obtained are
SARAS: scale 1.048 +- 0.008, offset -22.4 +- 8.0 K
EDGES: scale 1.112 +- 0.023, offset 0.7 +- 6.0 K
Monsalve et al. note that the differences may be because EDGES is a southern hemisphere instrument, SARAS is a northern hemisphere instrument, and the all-sky 150 MHz map was constructed from separate southern, northern, and intermediate declination surveys.

None of these correction factors have been applied to the map that is hosted here.

More details can be found in:

"The Galactic Metre Wave Radiation: A two-frequency survey between declinations +25° and -25° and the preparation of a map of the whole sky", Landecker, T. L. and Wielebinski, R. 1970, Aust. J. Phys. Suppl., 16, 1, ADS

Max Planck Institute for Radioastronomy Survey Sampler site

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A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
Web Curator: Mr. Michael R. Greason