Left: Spitzer Space Telescope IRAC large area mid-infrared image centered on the candidate high-mass protostellar object (HMPO) IRAS 19410+2336 (courtesy of Joe Hora and Giovanni Fazio, SAO).
Right: Colby's Gemini North high resolution mid-infrared image of IRAS 19410 in grayscale (courtesy of Jim DeBuizer, NASA) superimposed on contours of millimeter emission from Plateau de Bure Interferometer (courtesy of Henrik Beuther, MPIA). The two bright peaks at center bottom are enigmatic. They could be two separate HMPOs formed in the same clump of gas and dust shown by the green contours. Or they could represent emission from the two parts of the outflow cavity surrounding a single HMPO.
Since 2002, I have observed mid-infrared wavelength emission from the hot and warm dust components of molecular cloud cores containing candidate high-mass protostellar objects (HMPOs). I observed them on the IRTF and Gemini N telescopes with colleagues at SAO, NASA, Texas, and Keck Observatory. We have images of 20 HMPOS and with low resolution spectra of ten of them. The most interesting HMPOs in this group have also been observed with the SubMillimeter Array or the Plateau de Bure Interferometer so that the mid-IR emission can be correlated with the density of the molecular cloud cores. The first publication of analysis of some of these data is "Mid-Infrared Photometry and Spectra of Three High-Mass Protostellar Candidates at IRAS 18151-1208 and IRAS 20343+4129," M. F. Campbell, T. K. Sridharan, H. Beuther, J. H. Lacy, J. L. Hora,Q. Zhu, M. Kassis, M. Saito, J. M. De Buizer, S. H. Fung, and L. C. Johnson, Astrophysical Journal, Vol 673: 954-967 (2008). All of my research involves students: S. H. Fung and L. C. Johnson are Colby alumni, now graduate students at Stanford and the University of Washington.
I am working at making the best possible computer models of the HMPOs using the Monte Carlo radiative transfer code of Whitney, et al., ApJ, Vol 591: 1049-1063 (2003). This modeling, conducted with Colby students, has shown that fitting the standard theoretical model of cloud core collapse to specific data can be very difficult. While models of IRAS 18151-1208 made since the 2008 paper by Kaylea Nelson '08 as part of her Senior Scholars Thesis have been quite promising, satisfactory models have not been found for IRAS 19410+2336, the enigmatic object shown in the figures. Evan Eshelman '07 and Amanda Towner '10 studied this object as their senior projects. Danielle Nielsen '09 and Jack Moriarty '10 have worked on reducing data and making preliminary models of a third promising HMPO, IRAS 23151+5912. Dustin Hickey '11 is beginning a Senior Scholars Project investigating the calculations of the optical properties of intersellar dust and the effects of specific dust properties on the models of the HMPOs. We anticipate focusing on IRAS 18151, 19410, and 23151, and on HMPOs for which data comes available from Herschel Space Telescope. I look forward to additional student involvement.
I am also studying clusters associated with HMPOs observed by Spitzer Space Telescope in a program led by Howard Smith and Giovanni Fazio at SAO. This on-going project began as Jack Moriarty's 2010 Senior Scholars Thesis. He performed a color-color analysis to identify low-mass protostars around twenty HMPOs. He also used a locally-installed version of the Robitaille et al. SED fitter (Robitaille, T. P., et al. 2007, ApJS, 169, 328), to identify protostars and determine their properties, but found many ambiguities. Nearest neighbor studies of the low mass protostars identified by the color-color analysis in the clusters showed the clusters to be very diverse in their properties. We will next address the question: "Are proto clusters simply diverse, both when they contain only low mass protostars and when they contain a HMPO, or have we missed a basic underlying structure underlying clusters containing HMPOs?"