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The LAB HI survey (Leiden/Argentine/Bonn atomic hydrogen survey) is the most detailed all-sky data available on the atomic hydrogen gas in our Milky Way galaxy. Atomic hydrogen can be detected at the famous 21 cm radio wavelength.
This 3-dimensional velocity map slices the data close to the galactic plane (|b|
These spiral arms can be partially traced directly in the velocity data shown on this poster, especially in the outer galaxy. Negative velocity (approaching the Sun) appears as gas on the inside of the map, and positive velocity on the outside.
This image is dissected to show the warmer hydrogen gas that lies within the colder clouds. The colour shifts from magenta (1°K) to blue to green to red to light red (130 °K).
The poster also contains a circle giving longitude coordinates and a small reference schematic of the Milky Way showing the eight main components of the standard disk model (the four arms, the bar, the far and near 3kpc arms and the Orion spur). The reference image is aligned to allow direct comparison with the velocity map at the same longitudes.