) star formation. The process of high-mass
star formation does not have a well developed theoretical basis, in
part, because many complete observational studies of such regions have
not been made. Toward this end, I, in collaboration with the University
of Rochester's Near Infrared Group, have obtained
infrared continuum and spectral line images of such regions with
near-infrared broadband filters and narrow band (1-2% spectral
resolution) circular variable filters. These observations are combined
with radio wavelength continuum and millimeter wavelength molecular
aperture synthesis observations, obtained at similar spatial resolution,
to map dust extinction and dense molecular gas structures.
Massive stars spend more than 10% of their lives embedded in molecular clouds and are generally enshrouded in gas and dust when they reach the main-sequence. To account for this, we have mapped dust extinction on small spatial scales and compared these maps with dense molecular gas structures. These comparisons yield mass and molecular abundance estimates (see Fig. 2). Massive toroidal clouds are found in each region I have studied and may be ubiquitous features. Such toroidal clouds may provide the collimation necessary to form jets from strong stellar winds. Bipolar ionized outflows or jets appear well correlated with evolutionary stage, with the youngest objects producing the strongest jets. The jets appear to entrain molecular material, thereby powering bipolar outflows which last greater than 1.5 x 105 yrs.
At the University of Massachusetts, I am a postdoctoral research associate with the Two Micron All Sky Survey (2MASS) project. We are completing assembly and testing of the first of two three-array cameras while construction of telescopes is underway at two sites: one at Mt. Hopkins, AZ, the second at Cerro Tololo, Chile. The cameras and telescopes will be used to map the entire sky simultaneously in three near-infrared wavelength bands at a spatial resolution of 2'', over the course of four years.
A Multiwavelength Study of the Process of High Mass Star Formation, Howard, E. M. 1996, PhD Thesis, University of Rochester.
Near-Infrared Imaging of the Herbig-Haro Object HH124, Piche, F., Howard, E. M. & Pipher, J. L. 1995, MNRAS 275, 711.
A Near Infrared Study of the Monoceros R2 Region of High Mass Star Formation, Howard, E. M., Pipher, J. L., & Forrest, W. J. 1994, ApJ, 425, 707.
Infrared Photometry and Polarimetry of Cygnus X-3, Jones, T. J., Geherz, R. D., Kobulnicky, H. A., Molnar, L. A., & Howard, E. M. 1994, AJ, 108, 605.
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| Mosaic of the K3-50 region at K (2.23 µm), displayed on a linear scale from -1 × 10-15 to 2 × 10-14 erg cm-2 sec-1, obtained with the University of Rochester Third Generation InSb Infrared Array Camera at Mt. Lemmon Observatory. Radio positions of De Pree et al. (1994) for HII regions A, B, C1, C2, and D are marked with crosses and labeled. | Dust extinction map of the HII region A in K3-50 from Howard et al. (1996), overlaid with contours of HCO+ emission to show the correlation of dust and dense molecular gas. |
Eric Howard's personal Web site.
ehwd@kutath.phast.umass.edu