The results of C17O and C18O observations of low luminosity young stars are discussed and the derived properties of the circumstellar molecular envelopes described. Much of the circumstellar material is quiescent and cold. The youngest sources have envelopes which contain up to ∼ 0.3 M⊙ of material within 3000–4000 AU of the central star. From a survey of sources in Taurus, both the timescale and mechanism of clearing of the circumstellar region are investigated. Neither the observed outflows nor standard infall models alone are capable of clearing the circumstellar regions quickly enough. Maps of the circumstellar material around two very young sources suggest that the stars form from flattened configurations of material.

In order to study the kinematics of protostellar collapse we present high-spatial resolution millimeter interferometer data of the class 0 source L1448 N. The L1448 N cloud core has fragmented into two rapidly rotating subcores containing three protostars. One subcore is a protobinary system with 2000 AU separation. Strong evidence for infall is seen towards the N(B) component.

A review of the importance of water maser observations toward young stellar objects (YSOs) is presented. Also, we present recent, differing types of observations of water masers near YSOs. Single antenna observations, taken regularly, characterize the variability of the masers and allow estimates of time and spatial scales. High resolution (∼ 1 mas) multi-epoch observations allow proper motions to be studied. Detailed analysis of such proper motions will allow the placement of the masers in the circumstellar (a disk) or near-stellar environment at the base of the outflow. Radio interferometric techniques are the best method of making estimates of the kinematics of the gas in these regions.

Observations during the past several years strongly imply that virtually every star, independent of final mass, goes through a phase of rapid outflow simultaneously with rapid accretion during formation. The structure and properties of outflows and accretion disks associated with low-mass star formation has received intensive observational attention during the past several years (see the reviews and references in Lada 1985; Edwards, Ray, and Mundt 1993; Fukui et al. 1993; and this symposium). Young stellar objects (YSOs) with Lbol < 103 L⊘ will be referred to as “low-mass” stars in this review. The range of physical properties of CO outflows associated with YSOs of all masses are enormous, see Fukui et al. (1993). I will focus attention in this review on what we know about massive YSOs and their environments.

Structures like the clumps identified in the CO maps of the Rosette Molecular Cloud and the dense cores such as those in B5, a cluster of cores and young low-mass stars, are key to considerations of star formation. Whether star formation is a self-inducing process or one that causes itself to turn off depends greatly on whether the responses of the interclump and intercore media to young stars cause the collapse of clumps or cores to be faster than their ablation. We present a naive introduction to the lengthscales over which such responses are significant, mention ways in which the responses might induce collapse, review some of the little that is known of how flows of media around clumps and cores ablate them, and then return to the issue of the lengthscales over which such responses are significant by considering the global properties of mass-loaded flows in clumpy star forming regions.

We describe the effects of environment on low-mass star formation, from the perspective that most stars in the galaxy form in dense clusters and aggregates in GMCs, often in the presence of massive OB stars. First, we discuss the observational evidence for circumstellar disks around stars of the Trapezium Cluster, and how they are affected by their environment. Second, we examine the more distant M 16, where photo-evaporation by OB stars may disrupt the star formation process, and may inhibit the development of circumstellar disks.

Many low-mass stars in the Orion nebula are associated with very compact (≃ 1 arcsec) emission knots, known variously as proplyds, PIGs or LV knots. Some of these knots are teardrop-shaped, with “tails” pointing away from the massive star θ1 Ori C, which is the principal exciting star of the nebula. We discuss models of such knots, which invoke the interaction of the fast stellar wind from θ1 Ori C with a transonic photoevaporated flow from the surface of an accretion disk around a young low-mass star. We review previous analytic work and compare the results of the model with the observed brightnesses, morphologies and emission line profiles of the knots, as well as presenting new results from numerical hydrodynamical simulations.

The present paper reviews the talks and poster papers presented at the IAU 182 symposium. The papers are divided into different subjects, highlighting their contributions to the field of outflows from young stars. The observational contributions were notable because of the results recently obtained with new instruments (e. g., with radio interferometers and space based observatories). The theoretical contributions were noted by the increased understanding of the production of collimated winds from young stars, and by numerical and analytic work on the propagation of the outflows.