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: http://www.naic.edu/~gibson/himp/poster/2003/
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2002, Bull. A.A.S., 34, 1187, #50.02 Presented on Tuesday, January 7, 2003
We construct a detailed longitude-velocity diagram through the actual midplane of the Galactic H I disk. The Galactic midplane definition is based on single-dish sky surveys, and the detailed l-v slice (Fig. 1) is extracted from the Canadian Galactic Plane Survey (CGPS; Taylor et al. 2003).
Figure 1. CGPS H I emission in the Galactic midplane surface (see text). The emission is divided broadly into local arm gas near 0 km/s, Perseus arm gas near -40 km/s, and outer Galaxy gas at more extreme velocities. The arcminute resolution of the CGPS reveals considerable fine-scale detail not visible in prior surveys. Superposed on the general arm structure are many small velocity corrugations tracing gas kinematics in the disk. Note: other slices offset from this one were not shown in the AAS poster for lack of space, but they are available here.
Figure 2. Variation of the H I midplane with longitude and velocity. The red curve shows the cosine fit at each velocity pair. Outer Galaxy gas with both positive and negative velocities is shown in each panel.
|v | = +/- 61 km/s: 846x319 GIF [93 kB] | PS [57 kB] | |
|v | = +/- 78 km/s: 846x319 GIF [82 kB] | PS [53 kB] | |
|v | = +/- 95 km/s: 846x319 GIF [59 kB] | PS [48 kB] | |
|v | = +/-110 km/s: 846x319 GIF [53 kB] | PS [43 kB] |
Figure 3. Midplane surface defined by cosine fits (e.g. Fig. 2), from which the CGPS slice was constructed (gray box; Fig. 1). The black curves indicate constant Galactocentric radii of R = 9, 10, ..., 25 kpc, assuming a flat rotation curve with R0 = 8.5 kpc and V0 = 220 km/s.