Title: Spitzer Observations of IC 2118 Authors: S. Guieu (SSC), L. M. Rebull (SSC), J. R. Stauffer (SSC), F. J. Vrba (USNO), A. Noriega-Crespo (SSC), T. Spuck (OCHS), T. Roelofsen Moody (NJAC), B. Sepulveda (LHS), C. Weehler (LBHS), A. Maranto (McDonogh), D. M. Cole (SSC), N. Flagey (SSC), R. Laher (SSC), B. Penprase (Pomona), S. Ramirez (IPAC), S. Stolovy (SSC)
IC 2118, also known as the Witch Head Nebula, is a wispy, roughly cometary, ~5 degree long reflection nebula, and is thought to be a site of triggered star formation. In order to search for new young stellar objects (YSOs), we have observed this region in 7 mid- and far-infrared bands using the Spitzer Space Telescope and in 4 bands in the optical using the U. S. Naval Observatory 40-inch telescope. We find infrared excesses in 4 of the 6 previously-known T Tauri stars in our combined infrared maps, and we find 6 entirely new candidate YSOs, one of which may be an edge-on disk. Most of the YSOs seen in the infrared are Class II objects, and they are all in the "head" of the nebula, within the most massive molecular cloud of the region.
This reflection nebula is associated with the bright star Rigel in the constellation Orion. The Witch Head Nebula, also known as IC 2118, glows primarily by light reflected from bright star Rigel, located just off the upper right edge of the full image. Fine dust in the nebula reflects the light. The blue colour is caused not only by Rigel's blue colour but because the dust grains reflect blue light more efficiently than red.
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