Star formation in the Large Magellanic Cloud

The Magellanic Clouds (Fig. 17.8) are the closest galaxies in which we can study star formation. At the 50 kpc distance of the LMC, a 1 parsec extent, subtends an angle of 4 arc sec. So the 20 arc sec resolution of typical millimeter telescopes corresponds to a size of 5 pc. This is adequate for studying giant molecular clouds with extents of tens of parsecs (though ultimately arrays like ALMA, shown in Fig. 4.32, will be needed to study small clouds and cloud cores). The Swedish-ESO-Submillimetre Telescope (SEST, Fig. 4.28b), placed in Chile, has been particularly well suited to study the Magellanic Clouds.

As Fig. 17.10 shows, the LMC is the site of many HII regions. As we discussed in Chapter 15, this implies the existence of recent massive (O and B) star formation. Fig. 17.10(a) shows an optical image of the brightest HII region in the LMC. Because of its appearance, it is called the Tarantula Nebula. The exciting star is 30 Dorado, and this is some-

Fig 17.10.

HII regions in the LMC. (a) Optical image of the Tarantula Nebula, 30 Dorado. (b) Image of the LMC, taken with an Ha filter, shows the locations of the HII regions.The two rectangular boxes show the regions of detailed study in Fig. 17.11. [(a) STScI/NASA; (b) Monica Rubio, University of Chile]

Fig 17.10.

HII regions in the LMC. (a) Optical image of the Tarantula Nebula, 30 Dorado. (b) Image of the LMC, taken with an Ha filter, shows the locations of the HII regions.The two rectangular boxes show the regions of detailed study in Fig. 17.11. [(a) STScI/NASA; (b) Monica Rubio, University of Chile]

times referred to as the 30 Dor complex. An Ha image of the whole LMC is shown in Fig. 17.10(b), showing HII regions all over the LMC. We will look in a little detail at the large dark cloud (visible in Fig. 17.8b) that runs south from 30 Dor, and an isolated HII region in the northeast corner of the image, known as N11. Both of these regions are indicated by the rectangular boxes on Fig. 17.10(b) Maps of the CO emission from these regions of detailed study are shown in Fig. 17.11, both by

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