Christopher N. Beaumont

MOLECULAR RINGS AROUND INTERSTELLAR BUBBLES AND THE THICKNESS OF STAR-FORMING CLOUDS

The winds and radiation from massive stars clear out large cavities in the interstellar medium. These bubbles, as they have been called, impact their surrounding molecular clouds and may influence the formation of stars therein. Here we present James Clerk Maxwell Telescope observations of the J = 3-2 line of CO in 43 bubbles identified with Spitzer Space Telescope observations. These spectroscopic data reveal the three-dimensional structure of the bubbles. In particular, we show that the cold gas lies in a ring, not a sphere, around the bubbles indicating that the parent molecular clouds are flattened with a typical thickness of a few parsecs. We also mapped seven bubbles in the J = 4-3 line of HCO+ and find that the column densities inferred from the CO and HCO+ line intensities are below that necessary for collect and collapse models of induced star formation. We hypothesize that the flattened molecular clouds are not greatly compressed by expanding shock fronts, which may hinder the formation of new stars.

A BUBBLING NEARBY MOLECULAR CLOUD: COMPLETE SHELLS IN PERSEUS

We present a study of the shells (and bubbles) in the Perseus molecular cloud using the COMPLETE survey large-scale 12CO(1-0) and 13CO(1-0) maps. The 12 shells reported here are spread throughout most of the Perseus cloud and have circular or arc-like morphologies with a range in radius of about 0.1-3 pc. Most of them have not been detected before most likely because maps of the region lacked the coverage and resolution needed to distinguish them. The majority of the shells are coincident with infrared nebulosity of similar shape and have a candidate powering source near the center. We suggest that they are formed by the interaction of spherical or very wide angle winds powered by young stars inside or near the Perseus molecular cloud--a cloud that is commonly considered to be forming mostly low-mass stars. Two of the 12 shells are powered by high-mass stars close to the cloud, while the others appear to be powered by low- or intermediate-mass stars in the cloud. We argue that winds with a mass loss rate of about 10-8 to 10-6 M # yr-1 are required to produce the observed shells. Our estimates indicate that the energy input rate from these stellar winds is similar to the turbulence dissipation rate. We conclude that in Perseus the total energy input from both collimated protostellar outflows and powerful spherical winds from young stars is sufficient to maintain the turbulence in the molecular cloud. Large-scale molecular line and IR continuum maps of a sample of clouds will help determine the frequency of this phenomenon in other star-forming regions.

A UNIFORM CATALOG of MOLECULAR CLOUDS in the MILKY WAY

The all-Galaxy CO survey of Dame, Hartmann, & Thaddeus (2001) is by far the most uniform, large-scale Galactic CO survey. Using a dendrogram-based decomposition of this survey, we present a catalog of 1064 massive molecular clouds throughout the Galactic plane. This catalog contains

A simple perspective on the mass-area relationship in molecular clouds

2.5 \times 10^8

CLASSIFYING STRUCTURES IN THE INTERSTELLAR MEDIUM WITH SUPPORT VECTOR MACHINES: THE G16.05-0.57 SUPERNOVA REMNANT

solar masses, or

DIVERSE PROTOSTELLAR EVOLUTIONARY STATES IN THE YOUNG CLUSTER AFGL961

25^{+10.7}_{-5.8} \%

Discerning the Form of the Dense Core Mass Function

of the Milky Ways estimated H

Building an Optimal Census of the Solar Neighborhood with Pan-STARRS Data

_2

The bones of the Milky Way

mass. We track clouds in some spiral arms through multiple quadrants. The power index of Larsons first law, the size-linewidth relation, is consistent with 0.5 in all regions - possibly due to an observational bias - but clouds in the inner Galaxy systematically have significantly (~ 30%) higher linewidths at a given size, indicating that their linewidths are set in part by Galactic environment. The mass functions of clouds in the inner Galaxy versus the outer Galaxy are both qualitatively and quantitatively distinct. The inner Galaxy mass spectrum is best described by a truncated power-law with a power index of

Quantifying Observational Projection Effects Using Molecular Cloud Simulations

\gamma=-1.6\pm0.1