The dusty environment of the young galactic cluster NGC 2264.

Abstract

This is a study of the young galactic cluster NGC 2264. In it 12-100 $\mu$m IRAS data are used to analyze emission from the cluster dust. This dust is warmed by the young point sources in the cluster. Images of the region were obtained in the V, R, and I bands, and the point source data extracted are combined with a pre-existing J-H-K database to produce a six-band photometric survey of the cluster. This 4900-entry catalogue and methods to eliminate spurious detections and non-cluster stars from it are discussed. The cluster is estimated to consist of 350-650 members. A device to produce polarimetric images was designed, built, and used to obtain data to explore star formation environments. The nature of one such region in NGC 2264 is discussed, and the sources responsible for illuminating this reflection nebula are identified. It is concluded that multiple scattering and a disk geometry can explain the features observed. Spectra of 361 stars in the cluster region were obtained and by extending the MK system to the red part of the spectrum their spectral types are determined. Many T Tauri stars are identified and aspects of their emission lines are analyzed. It is shown that the spectral lines of many cluster stars of types later than G9 are in emission while those of earlier-type stars show incipient emission diluted by stellar flux. An evolutionary sequence of stars based upon photometry and spectroscopy is proposed. Stars from this spectral survey are dereddened and the extinctions obtained are interpreted. Spectral energy distributions are produced for the dereddened stars, revealing infrared excesses in many. These excesses are modelled by disk-star systems, and it is shown that inner holes are required in the disks to explain the observed levels of short wavelength emission.