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Foreground Data

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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°.

A separate HEALPix map was also made with recalibration applied following Patra et al. (2015), based on their absolutely calibrated sky brightness measurements between 110 and 175 MHz with the SARAS spectrometer. The recalibration was done by applying a scaling factor of 1.04824 to the original HEALPix map and then subtracting an offset of 22.418 K. Patra et al. quote a zero level error of 8 K and a scale error of 0.8% for the recalibrated map.

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

SARAS Measurement of the Radio Background At Long Wavelengths", Patra, N. et al. 2015, ApJ, 810, 138, 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