The International Astronomical Union has encouraged the study of our galaxy through a series of symposia. This volume contains the proceedings of IAU Symposium No. 84 on the Large-Scale Characteristics of the Galaxy, held in College Park, Maryland, from June 12 to 17, 1978. Symposium No. 84 was jointly sponsored by IAU 2ommission 33, Structure and Dynamics of the Galactic System, and by Commission 34, Interstellar Matter and Planetary Nebulae. The Scientific Organizing Committee consisted of F. J. Kerr (chairman), B. J. Bok, W. B. Burton, J. Einasto, K. C. Freeman, P. O. Lindblad, D. Lynden-Bell, R. Sancisi, S. E. Strom, H. van Woerden, and R. Wielen. The topics and speakers were chosen in order to emphasize current observational material and theoretical results pertaining to various morphological aspects of our galaxy. In preparing the program particular care was taken to relate recent work on other galaxies to the situation in our own galaxy. The meetings were held in the Center for Adult Education on the campus of the University of Maryland. The Local Organizing Committee consisted of B. M .. Zuckerman (chairman), A. P. Henderson, P. D. Jackson, T. A. Matthews, B. F. Perry, V. C. Rubin, P. R. Schwartz, F. W. Stecker, J. D. Trasco, and G. Westerhout. Joan Ball ably assisted this committee. The National Science Foundation made a financial con tribution to the general support of the meeting. The National Radio Astronomy Observatory assisted with some of the participants' travel expenses.

Proceedings of IAU Symposium No. 84 held at College Park, Maryland, U.S.A., June 12-17, 1978

Inhalt
I. Perspective.- Large-scale structure of spiral galaxies: problems old and new.- Disk and spheroidal components of external galaxies: an overview.- II. The Disk Component.- to the session.- The galactic distribution of OH/IR stars.- Giant molecular clouds in the galaxy; distribution, mass, size and age.- An out-of-plane CO survey of the first galactic quadrant.- Radio observations of the galactic plane CH distribution.- HI in the galactic disk.- Optical HII regions.- Radio studies of the distribution of ionized gas.- Line and continuum surveys of the galactic plane with the 100-m telescope.- The distribution of formaldehyde in the galaxy.- Spectral-line sky surveys from the NASA-JPL SETI project.- Galactic dust and extinction.- The distribution of young stars, clusters and cepheids in the Milky Way and M33-a comparison.- Faint optical spiral tracers.- The galactic distribution of 60 young open clusters.- Galactic structure from infrared studies.- Galactic nonthermal radiation. Distribution of SNRs and pulsars.- Pulsars as a galactic population.- Gamma-ray observations and the large-scale structure of the galaxy.- III. Spiral Structure.- The density-wave theory confronted by observations.- A mechanism for the origin and development of spiral arms in a galaxy.- An ejection theory of spiral structure.- On the maintenance of spiral structure.- Unstable spiral modes in the Milky Way system.- Lifetime of density waves and classification of spirals.- On a mechanism that structures galaxies.- Compression of interstellar clouds in spiral density-wave shocks.- The galactic density-wave, molecular clouds and star formation.- Observations of CO in the Perseus arm.- Gaseous response to bar-like distortions.- The four-armed response near the Lindblad resonances in galaxies.- On the use of the WKBJ density-wave theory at the Inner Lindblad Resonance.- IV. Galactic Kinematics and Distances.- The galactic distance scale.- RR Lyrae variables in Baade's window.- Quantitative classification of the galaxy from new data on the photometric properties of its spheroidal and disk components.- Rotation curves of high-luminosity spiral galaxies and the rotation curve of our galaxy.- Recent evidence on the rotation curve of our galaxy for R > Ro.- The circular velocity at the sun.- The galactic circular velocity near the sun.- Stellar kinematics and interstellar turbulence.- Age variations of the mean angular momentum.- A theory of galactic evolution.- An outward motion of young stars with respect to old stars.- V. Physical Properties of the Interstellar Medium.- to the session.- Energy balance in the interstellar medium.- A statistical study of local interstellar matter based on the Nancay 21-cm absorption survey.- General physical characteristics of the interstellar molecular gas.- Statistical modeling of CO emission in the galaxy.- CO observations of spiral structure and the lifetime of giant molecular clouds.- Implications for star formation in spiral galaxies from observations of nearby molecular clouds complexes.- The coldest molecular gas in our galaxy.- Global physical characteristics of the HI gas.- Large supernova remnants as common features of the disk.- A new class of extraordinary HI shell.- Chemical evolution of the galactic interstellar medium: abundance gradients.- A new look at the galactic magnetic field.- Stability of an interstellar medium with curved magnetic field lines.- VI. The Galactic Nucleus.- to the session.- HI in the inner few kiloparsecs of the galaxy.- The HI structure of the nuclear disk.- Some results from an HI survey of the central region of the galaxy.- Molecules in the inner few kpc of the galaxy.- Carbon monoxide and the 3-kpc arm.- HII regions and star formation in the galactic center.- Infrared observations of the nuclear region.- A study of the galactic center region using Mira variables.- Observations of the near infrared surface brightness distribution of the galaxy.- On the mass density distribution of the inner galaxy.- Dynamical interpretations of the galactic center region.- The basic state of the velocity field in the gas close to the galactic center.- Is there a massive black hole at the galactic center?.- Galactic center pulsar as a test of black hole existence and properties.- VII. Comparisons of our Galaxy with Other Galaxies.- The galactic nucleus compared to those of other galaxies.- Molecular structures of other galaxies compared to that of the galaxy.- HI and continuum structure of external galaxies compared to the situation in the galaxy.- Radial distributions of some constituents in M31, the galaxy and M33.- VIII. The Spheroidal Component.- Theoretical overview: Interactions among the galaxy's components.- The mass and light distribution of the galaxy: a three-component model.- Galactic mass modeling.- Three-integral, collision-free statistical mechanics and stellar systems.- Is there a composition gradient in the halo?.- Gamma-ray evidence for a galactic halo.- SAS-2 gamma ray observations related to a galactic halo.- Cosmic-ray evidence for a halo.- IX. The Galactic Warp.- Observational description of the warp in our galaxy.- Warping and thickness of galactic gas layers.- The persistence of warps.- Theoretical considerations of the warp and thickening.- X. High-Velocity Clouds and the Magellanic Stream.- to the session.- High-velocity clouds: review of observational properties.- The anticenter high-velocity-cloud stream as a galactic phenomenon.- A sensitive high-velocity HI survey.- 21-cm observations of high-velocity clouds.- The Magellanic Stream: observational considerations.- The Magellanic Stream: theoretical considerations.- Intergalactic HI and tidal debris within groups of galaxies.- The Magellanic Stream as a probe of the galactic halo.- The galactic wake model of the Magellanic Stream.- Our galaxy as a member of the Local Group.- XI. Summaries.- Afterthoughts from a theoretical point of view.- The galaxy in perspective an observer's synopsis.- A non-establishment view of the Symposium.