On the brightness distribution of all-sky and partial radio-continuum surveys
Abstract
The foreground radiation emitted by the Galactic plane and bulge in regions of low Galactic Latitude is responsible for the high-end excess (asymmetry) in the histogram of the brightness distribution of radio-continuum surveys. Bennett et al. (2003) used this property of the all-sky survey of the WMAP satellite mission at the K-band, to construct foreground masks with different levels of severity to improve the reliability of the analysis of the Cosmic Microwave Background Radiation. The K-band is the most heavily contaminated of the 5 observing frequencies of WMAP by foreground emission which, at the K-band frequency of 23 GHz, is dominated by synchrotron radiation. Following their approach, we noticed that, since the histogram of the brightness distribution in the all-sky survey of Haslam et al. (1982) at 408 MHz shows a very similar asymmetric profile, this property should be found in all surveys with significant levels of Galactic contamination. In particular, we used the Rhodes/HartRAO survey of Jonas et al. (1998) at 2326 MHz and of the GEM project at 2300 MHz (Tello et al. 2012) over an equivalent band of declination (-48.5 deg < DEC2000 < 6.3 deg) as a test case. Only the asymmetry of the brightness distribution in the GEM survey was consistent with the WMAP and Haslam profiles, even after reducing their sky coverage to the same declination band of the partial surveys. Given the importance of the spatial variability and frequency dependance of the synchrotron spectral index between 408 MHz and 23 GHz to derive foreground templates, the use of the GEM survey at 2.3 GHz offers a consistent perspective.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39.2093V