Radio Mapping [chapter]

E. R. Deul, W. B. Burton
1988 Mapping the Sky  
The mapping discussed in this paper is based on observations obtained from the 21-cm emission line of neutral atomic hydrogen. We will give an overview of the existing large surveys and present a homogeneous datacube that contains the most important surveys. This datacube was created by regridding the original observations, for the surveys included, onto a common denominator grid. Presenting a three dimensional dataset of intensities in one single image is impossible, therefore we made a film
more » ... re we made a film that displays in a time sequence a set of cuts (position-velocity maps) through the datacube. The advantage of showing the third coordinate in time is that the eye can now catch continuities in this coordinate that were previously hidden in the data. I. INTRODUCTION The hyperfine transition of neutral atomic hydrogen produces a spectral line at 21 cm wavelength. Spectra of this line, usually expressed in brightness temperature, show the Doppler shift of this line in terms of radial velocity with respect to the local standard of rest. Mapping a region of the sky we obtain spectra at consecutive points, thus building up a three-dimensional image, with the two mapping coordinates and one velocity coordinate, of that region. During the past decades several surveys of the galactic neutral atomic hy-311 S. Débarbat et ai (eds.), Mapping the Sky, 311-321. ©1988 by the IAU. use, available at https://doi.
doi:10.1007/978-94-009-3063-6_45 fatcat:tceqwcqnjrfc5dxq52sb2q3mwi