Specific IC 2118 information
Contents
The cloud
IC 2118, the Witch Head Nebula is a small cloud near the supergiant star Rigel in the constellation Orion. In the image at the right (taken by IRAS at 25 microns), IC 2118 is the structure at the bottom right corner. Rigel appears to be at least partially responsible for exciting and blowing off a significant portion of the nebula in this region. This cloud is about 210 parsecs away, similar in distance to the Orion Nebula Cluster (a.k.a. the ONC, or the sword of Orion). The ONC is a cluster of stars that are so bright that they too may be pushing around the gas and dust in the Witch Head Nebula.
What we are trying to do is characterize the process of pre-main sequence stellar evolution in this cluster. We want to be able to compare star formation in this cluster with others to see if there are similarities or differences.
Previous all-sky surveys, including both IRAS and 2MASS, have included this region, but not to the resolution or the wavelengths that Spitzer can provide, and there are few studies of this particular region in the literature.
Need to have more information here on a literature review
The observations
In our first observation of this region, we selected for observation by IRAC and MIPS a target area based on the IRAS survey and recent work conducted by Kun et al. (2004). Our Spitzer time was limited so we selected an area of the cloud that had a known IRAS source and 3 possible new classical T Tauri stars that were identified by Kun. The image below shows the region of IC 2118 (in IRAS 25 micron, with the proposed observations overlaid). In our second observation of this region, we were granted 11.5 hrs to go as far down the cloud as we could. We went about 2.5 degrees down the cloud with both IRAC and MIPS.
On the left, previous objects in this region are indicated. In the center, the first year's coverage using IRAC is indicated. On the right, you can see the second year's coverage using IRAC (cyan and magenta) and MIPS (pink, blue, and green).
A first look at the catalog with color-color plots
this discussion will center on using color-color plots with the catalog. Need to emphasize here (and earlier) that many of the tools and techniques developed for IC 2118 will work in any other star-forming region observed with Spitzer.
