William H. McCutcheon

Protostellar candidates in a sample of bright far-infrared IRAS sources

CO and radio continuum emission has been observed in the direction of 39 bright 100-micron sources from the IRAS point source catalog in an attempt to better understand the early stages of star formation. All 39 sources are found to be associated with molecular clouds and are generally characterized by high temperatures (15-40 K) and wide wings in the profiles (up to 34 km/s). Twenty-six of the 39 sources show wide (C-12)O lines, which are interpreted as a result of gas outflow associated with star formation processes. Of the 24 sources for which distances and 6-cm flux densities can be assigned, 11 are premain sequence objects, and 4 others are possibly in this category. Six of the eleven premain sequence sources have associated continuum emission. 30 refs.

THE STRUCTURE AND EVOLUTION OF THE LAGOON NEBULA. I. SUBMILLIMETER CONTINUUM AND CO LINE MAPPING

We present submillimeter- and millimeter-wave maps tracing the molecular gas and dust around the edge of the H ii region M8. The molecular material is clumped into cores on the scale of the beam (about 0.1 pc) whose temperatures can be estimated from CO observations. The masses of the clumps, estimated from their continuum fluxes, are consistent with a power-law mass function with index � 1:7 � 0:6, which agrees with determinations for other molecular clouds at similar resolutions, using molecular lines as tracers. The submillimeter clumps are sited at the interface between the H ii region and the background molecular cloud, where they are exposed to the ultraviolet flux of OB stars. The physical parameters of the clumps are compared to published models of molecular clouds undergoing photoevaporation, suggesting that the pressure of the ionized gas exceeds the internal pressure of the clumps and, therefore, that a shock front will be driven into the clumps. The clumps themselves currently appear to be gravitationally unbound, but the compression may be sufficient to induce collapse. Subject headings: H ii regions — ISM: individual (M8) — ISM: structure — stars: formation — submillimeter

The distribution and properties of cold dust in NGC 6334

NGC 6334 is a galactic star-forming region in Scorpius, heavily obscured by intervening dust. The region consists of several major sites of star formation known previously from far-infrared (IR) and radio-wavelength observations. We present images of NGC 6334 obtained at wavelengths of 850 and 450 μm with the Submillimeter Common-User Bolometric Array at the James Clerk Maxwell Telescope. These data highlight the distribution of dense cold dust, a particularly striking feature of which is a narrow ridge of emission passing between most of the star-forming centers. We use a clump-finding technique to quantify the distribution of dust emission throughout the region, and we obtain estimates of the sizes, masses, and temperatures of the clump ensemble under simple assumptions. Clump masses range from a minimum detectable of about 1 M ☉, up to almost 3000 M ☉. We find in particular that the ridge feature is characterized by a relatively narrow range of clump parameters as compared with the rest of NGC 6334, and we obtain a clump mass spectral index that lies between N(M) ∝ M –1.5 and M –1.0 for the high-mass clumps. The total mass of dust emitting at submillimeter wavelengths is about 16700 M ☉ for an assumed temperature of 25 K; a significant fraction of this mass is contained within the ridge feature. These data are compared with recently published observations of NGC 6334 obtained at 1.2 mm wavelength using a direct-detection scanning technique, and with images obtained by the GLIMPSE-II and Mid-course Space Experiment missions at wavelengths from 3.3 to 21 μm in the near IR (NIR). The most massive compact submillimeter-wavelength regions in the north are invisible at these shorter wavelengths, and the NIR and mid-IR emission generally have little correspondence with the cool dust distribution. In this paper we use these data sets and supplementary millimeter-wavelength spectral line observations to investigate the star-forming sites in NGC 6334 and to speculate on the significance of the ridge of material seen in the submillimeter images.

IRAS 23545 + 6508, a dissociating star - Prototype for a new observational class

The paper presents observations of a compact H I source coincident with a strong, far-infrared source, IRAS 23545 + 6508. It is believed that this object is representative of a new observational class which traces stars in the range of spectral types from B1 to B5 which are embedded in molecular clouds. Using methods based on birthrate statistics and other data, it is estimated that there are of order 1000 such sources within a radius of 2 kpc of the sun. 42 refs.