(a) Compare the HI distributions in spiral and early-type (elliptical or S0) galaxies found at the NRAO Image Gallery. (Look at the HI distributions, not the images that show the HI kinematics, i.e., if it says 'Rotating Disk', skip for now.) Write a sentence or two contrasting the HI distributions in spiral and early-type galaxies.
(b) Look at this comparison of the relative size of the stellar and HI disks. Be sure to click on the link to NGC 5055. Approximately much larger are the HI disks than the optical disks in these galaxies?
(c) Look at this optical/HI comparison. The HI is traced by the contours, the optical is the background photograph. Describe what you see. This structure is often seen in the HI distributions of spiral galaxies. Some galaxies show similar structures even at optical wavelengths.
(d) Look at the comparison of optical and HI in the M81 group. The pictures are on the same scale. Describe what you see. What does the HI map reveal about this group?
(e) Check out a few of the images in the HI Rouges Gallery. Why are they called 'Rouges'? Compare the structures you see to the stellar structures. Why do you think that these peculiar features are more visible in the HI than the stars? (Refer also to the images in parts (b) and (c).)
(a) This image shows an overlay of optical, HI, and molecular gas (see caption). Write a sentence describing the distrubituion of molecular gas with respect to stars and HI.
(b) Here are some examples of molecular gas distributions in centers of galaxies. Describe the types of structures you see.
Last updated February 7, 2008
