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Session 70 - The Milky Way.
Display session, Wednesday, January 15
Metropolitan Ballroom,
Exactly 10 years ago, at the January 1987 AAS meeting in Pasadena, we presented the first complete map of the Milky Way in the J=1-0 line of CO, the most widely used tracer of interstellar molecular gas. Since well before publication of that map, done at an effective angular resolution of 0.5° (Dame et al. 1987, ApJ, 322, 706), our twin 1.2 m telescopes in Cambridge, MA and on Cerro Tololo, Chile have been steadily mapping the Galaxy at several times higher angular resolution, observing every beamwidth (8.7') or half beamwidth. The telescopes have now mapped in this way the entire Galactic plane over a 4°6° strip of latitude, as well as many local clouds at higher latitude. Roughly half of these data, 270,000 spectra in all, have already been published as separate surveys of particular clouds or regions, and since 1985 have formed the basis for 13 Ph. D. dissertations. The other half of the data have been obtained in just the past few years in new large-scale surveys of the first and second Galactic quadrants; only small portions of these data have so far been published (Dame amp; Thaddeus 1994, ApJ, 436, L173; Digel et al. 1996, ApJ, 458, 561).
We have combined all of these data into two panoramic maps of the Milky Way at 8.7' resolution: one a spatial map integrated over all velocities, the second a longitude- velocity map integrated over 4° of Galactic latitude. These maps reveal as never before the very complex large- scale structure of the local molecular material, as well as several spiral arm features extending a good fraction of the way around the Galaxy. As we did 10 years ago, we intend to make these maps available as a color poster, hopefully in time for distribution at the Toronto meeting.
