Figure 1 shows a ground-based image of M 20 with the WFPC2 field of view indicated. Figure 2 shows the WFPC2 images. Figure 3 shows a color composite of the WFPC2 images. Ground based image of the Trifid Nebula taken with the Palomar 1.5-m telescope. The WFPC2 field of view is indicated.
H a is shown as green.
Figure 4 shows surface brightness profiles across the head of the prominent column seen in the WFPC2 images. This is an example of a photoevaporative flow that is ionized by the same radiation field responsible for driving the flow. Modeling of these flows removes many of the uncertainties in interpretation of emission from H II regions. Figure 4 Surface brightness profiles across the head of the prominent column in M 20. The first figure shows the position of the band along which the profile was taken.