Search for Calibrators for the Submillimeter Array: I. High-Mass Star Forming Regions

Abstract

We present initial results of an ongoing search for interferometric calibrators at submillimeter (sub-mm) wavelengths with the Submillimeter Array (SMA). Powerful radio galaxies are commonly used as calibrators at centimeter and millimeter wavelengths, but many are not strong enough to serve as calibrators at sub-mm wavelengths because of their rapidly declining flux densities toward shorter wavelengths. The inability to find a calibrator close to the target source may limit or even prevent us from imaging many interesting sources at sub-mm wavelengths. Here, we investigate whether high-mass protostellar objects and ultracompact HII regions can serve as useful calibrators for the SMA. The dust emission associated with these objects makes them among the brightest sub-mm sources in the sky. Our observations at 0.85 mm (345 GHz) with an angular resolution of ~3" reveal that although a large fraction of the dust emission originates from an extended ``halo'' component, a compact unresolved component often remains that when sufficiently strong may serve as a useful calibrator. These observations also provide a first glimpse at the small-scale distribution of dust around ultracompact HII regions and high-mass protostellar objects at sub-mm wavelengths. We discuss the origin of the core-halo structure seen in many sources, and conclude with suggestions for future searches for calibrators with the SMA.

3 figures, accepted for publication in ApJ Letters

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• The Submillimeter Array
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Cited by in corpus (9)

• The Submillimeter Array
• The Early Evolution of Massive Stars: Radio Recombination Line Spectra
• Testing the massive disk scenario for IRAS 18089-1732
• Rotational Structure and Outflow in the Infrared Dark Cloud 18223-3
• Observations and Modeling of the 2-25um Emission From High Mass Protostellar Object Candidates
• VLBI Observations of Water Masers in Onsala 1: Massive Binary Star Forming Site?
• 654 GHz Continuum and C18O (6-5) Observations of G240.31+0.07 with the Submillimeter Array
• Subarcsecond Imaging of the High-Mass Star Forming Region Onsala 1
• The infrared environments of masers associated with star formation