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J.M. De Buizer, R.K. Pina (University of Florida Department of Astronomy)
Recent radio observations of methanol maser emission around young massive stars show many of these sources contain groups of unresolved maser spots aligned in linear structures. Moreover, the velocity gradient of these spots (as inferred by the frequency shift of the maser line) is indicative of orbital motion. It has thus been plausibly argued that these methanol maser spots occur in, and directly delineate, rotating circumstellar disks. This is an unanticipated result since the environments around these stars are considered to be antagonistic to the formation of disks. Using the University of Florida's mid-infrared camera/spectrometer OSCIR, we have made exploratory mid-IR observations of these highly embedded disk candidates. We find elongations in their thermal emission and/or double sources at position angles consistent with the disk orientation inferred from the alignment of the maser spots. We observed 18 of these methanol maser sites, and detected embedded sources in thirteen. Eight sites contain elongated sources, four of which are also double sources. Of the remaining five sites, one contains a double source, one contains multiple sources, and three contain marginal detections for which no morphology can be inferred. Derived luminosities from our observations are consistent with the embedded sources being O and B type stars. In addition to the disk recently imaged by TIMMI at ESO, the images presented here may be the first direct images of circumstellar disks around massive stars.
The author(s) of this abstract have provided an email address for comments about the abstract: debuizer@astro.ufl.edu, rpina@astro.ufl.edu