Regions of Recent Star Formation

The symposium on "Neutral Clouds near HII Regions" was prompted by an obvious need to bring together workers specifically interested in the dynamical and photochemical effects in regions showing clear evidence of on-going star formation. This is currently an are a of considerable research activity with much new observational material over the wavelength range from X-ray to radio. Furthermore, the field isbeginning to mature. No longer is molecular spectroscopy concerned only with the search for new lines and with preliminary surveys. No longer are evolving HII regions modelled with the naive assumption of constant density. Similarly, ideas of successive star formation, "champagne" and "blister" models of HII regions, and refinements to abundance calculations are examples which show that theoretical initiative is keeping pace. We were both surprised and gratified by the number of contributed papers and the extent to which they addressed the subject matter. In the proceedings we have grouped these papers near the most appropriate of the four invited review papers. The subjects of these reviews are in the general areas of "Evolution of HII Regions", "Dynamical Interactions", "Chemistry in Active Regions" and "Infrared and Maser Sources". The symposium comprised 42 orally presented papers and 23 poster papers. AII but two are reproduced in this volume.

The Dynamical Evolution of HII Regions in Non-Uniform Environments (Review).- HII Regions in Collapsing Massive Molecular Clouds.- The Dynamical Evolution of an HII Region.- Radio Continuum Observations of W1.- Interaction of the HII Region S236 with the Surrounding Medium.- Optical and Millimeter Wavelength Study of the Complex Sh2-147/Sh2-153.- The HII Region W40 and its Molecular Cloud.- HII Bubbles and Shocks in Molecular Clouds.- A Multi-purpose Scanning Fabry-Perot Interferometer System.- Fine Structure Lines in HII Regions Interacting with Molecular Clouds.- Excited OH in Absorption Towards W3(OH).- Ultra-compact HII Regions Embedded in Infrared Sources.- Dynamical Effects of Stellar Winds and Shocked Gas on Interstellar Clouds (Review).- A Calculation of Molecule Abundances Behind Slow Shocks.- Gravitational Instabilities in Shock Compressed Gas Layers.- Magnetic Fields and the Evolution of Shocked Gas Clouds.- Radiation-Hydrodynamics of HII Regions and Molecular Clouds.- High Velocity Gas in Molecular Clouds.- High Velocity CO Emission Around T Tauri Stars.- Observations and Interpretation of the Line Profiles of Excited H2 in Orion.- High Velocity H2 Line Emission in the NGC 2071 Region.- Infrared Atomic Hydrogen Line Formation in Luminous Stars.- Atomic Hydrogen Zones Associated with HII Regions.- The NGC 7538 Region: The Distribution and Dynamics of Molecules Compared with those of HI and H+.- Atomic and Ionized Hydrogen in Cepheus 0B3.- Neutral Hydrogen Observations of the Puppis Window.- Neutral Hydrogen Towards Tycho’s Supernova Remnant.- The Velocities of the Neutral and Ionized Components of HII Regions.- A CO Survey of 372 Optical HII Regions.- HI and CO Observations of Distant HII Regions in the Galactic Anticenter.- Dynamics of CO Clouds Around HII Regions in the Outer Galaxy.- CO J=2-1 Observations of Southern Galactic Plane HII Regions.- Observations of CO J=3?2 Emission From Molecular Clouds.- Properties of Giant Molecular Clouds in the Galactic Molecular Ring.- Changes of the Star Formation Rate and the Initial Mass Function with Galactic Radius.- Infrared and Maser Sources in Regions of Star Formation (Review).- High Velocity CO Line Wings and the Dynamics of Star Forming Molecular Cloud Cores.- Kinematics of Molecular Gas in Orion from Observations of the 13 CO J=2?1 Line.- Molecular Hydrogen Emission From Broad Wing Cloud Cores.- Asymmetric Broad HCO+ Line Wings in Cores of Molecular Clouds.- Some of the Problems Raised by CO and HCO+ Observations in the Rho Ophiuchi Cloud.- CO J=3?2 and Far Infrared Continuum Observations of L1551, Orion KL and IRC + 10216.- CO in the Horsehead Nebula.- Small Scale Clumping in the Orion Molecular Cloud.- The ON-1 CO Cloud Complex — Onset of Star Formation.- CO Observations of the Molecular Cloud Encompassing Sharpless 222.- Formation of a BO.5 Star Due to the Interaction of a Shock Wave with a Molecular Cloud in IC1805.- Chemistry Relevant to Molecular Clouds near HII Regions (Review).- Selective Photodestruction of CO Isotopic Species.- X-Ray Ionization and the Chemistry of the Orion Molecular Cloud.- Methyl Cyanide as a Probe of the Temperature and Density in SgrB2; Quasi-Equilibrium in Molecular Rotational Levels.- High Spatial Resolution Observations of HCN in S 235B.- A Model for the Formaldehyde Maser Near NGC 7538 - IRS 1.- H2CO Near Compact HII Regions - New WSRT Results.- Is a BN-Type Object the Energy Input to the NH3 Cloud in NGC 2071?.- VLA Observations of OH Masers and Associated Ultracompact Continuum Sources.- Carbon Monoxide in the Magellanic Clouds.- Molecular Line Mapping of OMC-1.- An Upper Limit to the Atomic Carbon Abundance in the Orion Plateau.- Observations of Neutral Carbon in the NGC 1977 Bright Rim.- Observations of CO in TMC 1.- CO Emission Associated with Cold Neutral Hydrogen.- On the Correlation of CH Abundance and Extinction in Dark Nebulae.- Author Index.- Index of Astronomical Objects.