Unsolved Problems of the Milky Way : Proceedings of the 169th Symposium of the International Astronomical Union, Held in the Hague, the Netherlands, August 23-29, 1994

Although the Milky Way is the most studied and best understood galactic system, there are many fundamental questions about our Galaxy that remain unanswered. This book concentrates on those questions which have the widest applicability in all of astrophysics, and for which answers are most likely to be forthcoming in the next few years. Is the Milky Way a barred spiral, and if so, what are its properties? Is the disk of the Milky Way axisymmetric and what does the answer tell us about its dynamical history? Is there a black hole at the center of the Galaxy? How far does the Galaxy extend? How much dark matter is there in the Milky Way system? And more. Front Matter....Pages i-xx Front Matter....Pages xxi-xxi Should the Outer Milky Way be Axisymmetric?....Pages 1-10 The Shape of the Disk: Clues from the Kinematics of Disk Stars....Pages 11-21 The Shapes of Dark Halos....Pages 23-30 The Axisymmetric Stability of the Milky Way....Pages 31-37 Faint Surface Photometry of the Halo of M31....Pages 39-45 A Survey of Surveys....Pages 47-55 Ellipticity of Outer Regions of Galactic Disks....Pages 57-58 Near Infrared Star Counts as a Probe of Asymmetries in the Galaxy’s Disk....Pages 59-60 Front Matter....Pages N1-N1 Morphology of the Galactic Bulge from COBE DIRBE Observations....Pages 61-69 Is There a Bulge Distinct from the Bar?....Pages 71-77 Dynamics of the Bar at the Galactic Centre....Pages 79-91 Results from the Optical Gravitational Lensing Experiment (OGLE)....Pages 93-102 Evidence for the Galactic Bar from the Two Color Photometry of the Bulge Red Clump Stars....Pages 103-109 M Giant Kinematics in Off-axis Fields between 150 and 300 PC from the Galactic Center....Pages 111-117 Results of the SiO Maser Survey of the Galactic Bulge IRAS Sources....Pages 119-124 3D N-Body Simulations of the Milky Way....Pages 125-131 Comparison with External Galaxies Dynamics....Pages 133-143 Properties of the Galactic Bar from Hydrodynamical Simulations....Pages 145-146 Position-Velocity Diagrams as a Probe of the Bar in Edge-On Galaxies....Pages 147-148 Front Matter....Pages N3-N3 Is there a Compact Central Mass Concentration in Our Galaxy?....Pages 149-168 Front Matter....Pages N3-N3 What is SGR A*?....Pages 169-180 Is SGR A* Underfed, Underefficient, or Underdone ?....Pages 181-187 Recurrent Starbursts or Intermittent Starburst/AGN Phenomena at the Galactic Center ?....Pages 189-192 Diameter and Proper Motion of SGR A*....Pages 193-198 The Radio Spectrum of SGR A*....Pages 199-204 Evolution in the Nucleus....Pages 205-214 Dynamical Evolution of Galactic Center Star Cluster and Importance of Stellar Collisions....Pages 215-223 A Comparison of Near Infrared Spectra of the Galactic Center He I Emission Line Sources and Early Type Mass Losing Stars....Pages 225-230 Mid-Infrared (4.8 – 12.4 and 20.0 μ m) Imaging of the Galactic Center: Modeling the Dust Emission and Energetics of the Central Parsec....Pages 231-240 Mini-Spiral at the Galactic Center: A Link Between its Structure and the Value of a Central Point Mass....Pages 241-246 What are the Radio Filaments Near the Galactic Center?....Pages 247-261 The Nature of the Galactic Center Arc....Pages 263-269 The Nature of the Scattering and Faraday Screens Toward the Galactic Center....Pages 271-277 The Galactic Center Star Cluster: Normal Evolution !?....Pages 279-280 C 18 O and HNCO in the Galactic Centre....Pages 281-282 Two New Views of the Galactic Center....Pages 283-284 Possible Evidence for a Binary Massive Black Hole in the Galactic Nucleus....Pages 285-286 Front Matter....Pages N5-N5 The Hot Gas in the Galactic Bulge....Pages 287-295 Motions and Deformations of the Inner-Galaxy Neutral Gas Layer....Pages 297-310 A Survey of OH in the Galactic Centre Region....Pages 311-316 Front Matter....Pages N5-N5 Stellar Populations in the Galactic Bulge....Pages 317-327 Metallicity, Structure and Kinematics of the Milky Way’s Bulge....Pages 329-334 Galactic Bulges as an Evolutionary Phenomenon: Observational Evidence from the Statistics of “Box/Peanut” Bulges....Pages 335-339 Observational Properties of SiO Masers in the Galactic Bulge IRAS Sources....Pages 341-342 Report on a Survey of H 2 O Masers towards the Galactic Center....Pages 343-344 Dynamical Properties of Galactic OH/IR Stars....Pages 345-346 Semiregular Variables in the Galactic Bulge....Pages 347-348 Instabilities of Uniformly Rotating Disks....Pages 349-350 F(E,L Z ) for Kent’s Model of the Galactic Bulge....Pages 351-352 Front Matter....Pages N7-N7 The Age Structure of the Older Parts of the Galaxy....Pages 353-366 Is the Dynamical History at Odds with the Chemical History?....Pages 367-379 Globular Clusters and the Formation of the Galactic Halo....Pages 381-388 Chemical and Dynamical History of the Milky Way....Pages 389-394 The Metal Pre-Enrichment of the Galactic Disk: Solving the G-Dwarf Problem....Pages 395-401 Did the Bulge Form All at Once?....Pages 403-410 Late-Type Giants in the Bulge, at High Galactic Latitudes and in the Plane....Pages 411-417 Effects of Chaos in the Galactic Halo....Pages 419-421 The Velocity Dispersion in the Cold Collapse....Pages 423-424 The Chemodynamical Evolution of Spheroidal Systems and the Resultant Stellar Abundance Distribution Function....Pages 425-426 Metallicity Structures of the Milky Way....Pages 427-428 Front Matter....Pages N7-N7 The Formation of the Galactic Bulge....Pages 429-430 The Scatter of Metallicities of Stars in the Solar Neighbourhood....Pages 431-432 Different Laws of Increasing of Stellar Dispersion: Observational Flaws or Natural Property of Stellar Population?....Pages 433-434 UBVI CCD Photometry of an Old Open Cluster AM-2....Pages 435-436 Front Matter....Pages N9-N9 What do Gamma Rays Tell us about the ISM? New Insight from the Compton Observatory....Pages 437-446 HI in the Milky Way....Pages 447-468 How Important is Neutral Carbon to an Understanding of the Dense Interstellar Medium?....Pages 469-478 Why is the HI Scale Height Constant with Galactocentric Radius ?....Pages 479-487 The Z Velocity Dispersion of Outer H I Disks....Pages 489-495 Diffuse [C II] Emission in the Galaxy....Pages 497-498 Vertical Equilibrium of HI in the Galactic Disk....Pages 499-500 Physical Conditions of Molecular Gas in the Galaxy....Pages 501-503 Does a Rotation Velocity Jump Generate the Outer Spiral Structure?....Pages 505-506 Dynamics of Thick Spirals....Pages 507-508 Potential-Density Basis Sets for Three-Dimensional Disks....Pages 509-510 The Dynamics of Planetary Nebulae in the Galaxy: Evidence for a Third Integral....Pages 511-512 The Existence of Moving Groups and the Disk Heating Problem....Pages 513-514 The Influence of Velocity Dispersion on Dynamical Friction in Stellar Discs....Pages 515-516 On the Spiral-Induced Nonlinear Dissipative Process to the Evolution of the Galactic Disk....Pages 517-518 Stability of a Collisionless Stellar Disk....Pages 519-520 Front Matter....Pages N9-N9 Stability of a Collisional Galactic Disk....Pages 521-522 Galactic Orbits of Different Galactic Population Objects....Pages 523-524 Local Variations of the Velocity Ellipsoid....Pages 525-526 Escape Velocities from Unstable Triple Stars....Pages 527-528 Hierarchical and Non-Hierarchical Triples....Pages 529-530 Criteria of Dynamical Isolation of Binaries and Multiples....Pages 531-532 Front Matter....Pages N11-N11 The Unsolved Problem of Stellar Origins....Pages 533-549 What do we Really Know about Cloud Formation?....Pages 551-560 Far-Outer Galaxy Molecular Clouds....Pages 561-566 Far-Infrared Spectral Observations of the Galaxy by the Far-Infrared Absolute Spectrophotometer....Pages 567-573 The Search for Cold Molecular Gas in the Outer Galaxy....Pages 575-581 How does Star Formation Affect the Large Scale Structure of the ISM?....Pages 583-590 The Structure of the Neutral Interstellar Medium: A Theory of Interstellar Turbulence....Pages 591-596 Are there Giant Vortices Near Solar Circle?....Pages 597-603 Distance and Metallicity of HVCS....Pages 605-606 Molecular Mass Distribution in the Outer Galaxy....Pages 607-608 A Hydromagnetic Model for the Hierarchical Structure of Molecular Clouds....Pages 609-610 Galactic Fine Structure at 843 MHZ....Pages 611-612 Neutral Gas Contributions to [S II ] Galactic Background Emission....Pages 613-614 Study of the Magnetic Field of the Galaxy Using Correlation Functions of the Intensity of Synchrotron Background Radio Emission....Pages 615-616 Front Matter....Pages N11-N11 HI Bubbles Around NGC 6888....Pages 617-618 Search for HI Bubbles around WR Stars: WR 149....Pages 619-620 GS64-01-97: Expanding Supershell in the Milky Way....Pages 621-622 Multi-Wavelength Study of the Giant Bubble in Cepheus....Pages 623-624 Non-Thermal Particles Near OB Associations....Pages 625-626 G54.4-0.3 — Multi-Frequency Investigation of an SNR in Interaction with the ISM....Pages 627-628 HST Spectroscopy of the Orion Nebula....Pages 629-632 Front Matter....Pages N13-N13 How Ought One Parameterize the Milky Way?....Pages 633-643 Does Our Galaxy Have a Massive Dark Corona ?....Pages 645-650 Mass Near the Sun....Pages 651-659 Outer Disc Rotation from Cepheid Variables....Pages 661-667 Where Does the Galaxy End?....Pages 669-680 How do the Stellar Disc and Thick Disc Stop ?....Pages 681-687 Proper Motion Study of the Galactic Rotation Curve....Pages 689-695 The Mass Distribution of the Milky Way Deduced from Globular Cluster Dynamics....Pages 697-702 The Rotation Curve from A-F Supergiants....Pages 703-706 The Structural Parameters of the Milky Way....Pages 707-708 A System of Galactic Constants Based on Stellar Dynamics....Pages 709-711 Estimation of Galactic Model Parameters by Interval Method....Pages 713-714 Back Matter....Pages 715-725