HEALPix, nested, res 10 (Nside=1024)
Original Data Source:
The CHIPASS 1.4 GHz continuum map covers the sky south of +25 degrees declination with a resolution of 14.4 arcmin and a sensitivity of ~40 mK. The map results from a reprocessing of archival data from the HI Parkes All-Sky Survey (HIPASS) and the HI Zone of Avoidance (HIZOA) survey by Calabretta, Staveley-Smith, and Barnes (2014). Publicly available survey data in plate carree projection and J2000 equatorial coordinates (the extended source map and the associated sensitivity map) were interpolated to a Galactic coordinate HEALPix projection using cubic convolution interpolation. HEALPix res 10 (Nside=1024) pixelization was adopted. This gives a mean pixel spacing of 3.4 arcminutes, comparable to the 4.0 arcminute pixel spacing of the ATNF CHIPASS plate carree product.
Pixels in the original CHIPASS map were blanked for regions that were not observed (the region north of the declination limit and a small region around the South Celestial Pole) and near the peaks of 16 strong compact sources where data were saturated. These sources include Sgr A, Tau A, Ori A, and Cen A; see Table 3 of Calabretta, Staveley-Smith, and Barnes (2014) for the full list. In the HEALPix maps, pixels that are close (within about 0.2 degrees) to an unobserved pixel in the original CHIPASS map were set to a sentinel value of -1.e+30 in the brightness temperature map and set to zero in the sensitivity map. Pixels that are close to a saturated pixel in the original map were set to -1.1e+30 in the brightness temperature map and set to zero in the sensitivity map.
The HEALPix maps of brightness temperature and sensitivity are provided as a binary table extension in the FITS file lambda_chipass_healpix_r10.fits. Pixel numbers are implicit, in ascending order. The HEALPix brightness temperature map is also provided as a primary image array in HPX projection (Calabretta and Roukema 2007) in the FITS file lambda_chipass_HPX_r10.fits.
More details can be found in:
"A New 1.4 GHz Radio Continuum Map of the Sky South of Declination +25 deg", Calabretta, M. R., Staveley-Smith, L., & Barnes, D. G. (2014) PASA 31, e007, doi:10.1017/pasa.2013.36, ADS