Professor Campbell observes mid- and far-infrared wavelength emission from the dust component of interstellar clouds in which high-mass, high-luminosity stars have been recently formed. Broad band, high spatial resolution far-infrared observations of clouds containing ultracompact HII (ionized hydrogen) regions and hot, high-mass stars were obtained on the NASA Kuiper Airborne Observatory (KAO,shown above), an 0.9-meter telescope on a C141 aircraft. Computer radiative transfer models were created of the clouds to match the data. Models which match the data are used to deduce the density structures of the warm neutral clouds surrounding the HII regions, and the luminosities of the central stars. (The stars themselves are hidden optically by the dust in the clouds.) The density structures of the clouds in turn give information about the star formation process, in addition to information about how such clouds evolve after their central cores form stars. A paper was published in The Astrophysical Journal in 1995 on such clouds in the complex radio source W3, and a paper is in press for the January 1, 2004 issue of The Astrophysical Journal on a cloud in the complex G34.3+0.2. A preprint is available in Research Files The new paper may be one of the last published on data obtained on the KAO which retired in 1995. Colby students were co-authors on both papers.
Professor Campbell is anticipating flying on the Strotospheric Observatory for Infrared Astronomy (SOFIA), the sucessor to the KAO. SOFIA is a modified Boeing 747 carrying a 2.5-meter telescope. He has arranged to fly with the team developing the High-resolution Airborne Wideband Camera (HAWC) at the University of Chicago on SOFIAs early flights, expected to be in October 2004. He expects to propose to observe G34.3+0.2, W3, and similar regions to improve on the observations by the KAO.
The G34.3+0.2 was observed in the mid-infrared in May 1995 at the NASA Infrared Telescope Facility (IRTF), a 3-meter telescope on Mauna Kea, Hawaii. The mid-infrared observations were sensitive to hotter dust nearer to the central stars than the cooler dust observed in the far-infrared. Interpretation of these observations focusesd on the dust inside or just outside the HII regions, and the discovery of hot spots representing highly obscured protostars. A paper on this work was published in The Astrophysical Journal in 2000. He is coauthor on a similar study of M17, published in The Astronomical Journal in 2002. Professor Campbell is a collaborator with Drs. Joseph Hora and Lynne Deutsch at the Smithsonian Astrophysical Observatory for mid-infrared observations of W3 on the IRTF completed in November, 2002. In addition to studying the hot dust near the high luminosity young stars in W3, they are investigating the nature of the photodissociation regions surrounding the HII regions, and the role of polycyclic aromatic hydocarbon particles in the vicinity of the high-mass stars.
In collaboration with Dr. T.K. Sridharan at SAO, Dr. Hora, Dr. Marc Kassis (Keck Observatory), and Dr. Deutsch, Professor Campbell began a mid-infrared survey of high-mass protostellar objects (HMPOs) on the IRTF in September 2003. The HMPOs were initially identified by Dr. Sridharan and others in a paper in The Astrophysical Journal in 2002.
At Colby's Collins Observatory in 2002, Professor Campbell began a new program to search for periodic variability of Herbig Ae/Be stars in visible and very short wavelength near-infrared light. These are intermediate-mass pre-main sequence stars. Tomas Vorobjov '06 and Kimberly Prescott '04 observed several of these stars in the winter of 2002-2003. Kimberly is analysing data on them for her senior project.
