Info

V) ° O HIRES

GO oCO 1 1 1

05h41m 05h40m RA (J2000)

Fig 17.11.

CO images (contours) of star forming regions in the LMC, with observations done on the SEST, on La Silla, Chile.These are superimposed on FIR images from IRAS (the gray scale). (a) The 30 Dor Complex. Notice the complex of giant molecular clouds. More detailed maps show two dozen GMCs in this complex, with properties very much like Milky Way GMCs. FIR peaks all have associated strong CO emission, suggesting there are dense cores there.There are also CO peaks away from FIR emission. Perhaps these are clouds that are not as far along the star formation process. (b) The Nil region. In this more open ring, the individual clouds are more easily seen. HIRES refers to a type of image processing, which enhances the angular resolution [author].

05h41m 05h40m RA (J2000)

04h58m

RA (J2000)

04h56m

04h58m

RA (J2000)

04h56m

themselves, and superimposed in the FIR images. We first look at the 30 Dor complex (Fig. 17.11a). The CO emission shows a complex of molecular clouds that extend over part of an arc for about 600 pc. A more detailed picture shows that this is composed of some two dozen clouds, each with an extent of tens of parsecs, and each with a mass

(determined from the virial theorem) of a few times 105M0. These are very much like giant molecular clouds, and this whole long dark cloud is like a GMC complex in the Milky Way. The FIR image shows a number of embedded regions where dust is being heated by ongoing or recent star formation, just as for massive star forming regions in the Milky Way. It appears that the Tarantula Nebula is at the northern end of this complex, and is in a region where there are more young stars, but less molecular clouds. It has been suggested that this is a site of sequential star formation, also similar to situations found in the Milky Way.

The N11 region, Fig. 17.11(b), has a more open appearance, so it is easier to see the structure. Here we see a ring of clouds (with an extension to the northwest). These clouds also look like Milky Way GMCs, and they also have masses of a few times 105 M0. All of these clouds have internal velocity dispersions comparable to Milky Way GMCs. This grouping has a similar appearance to the Orion region (partly shown in Fig. 15.4). So, it appears that star forming regions in the LMC are very similar to those in the Milky Way, despite the many differences between the LMC and the Milky Way.

0 0

Post a comment