9. Large-Area Mapping in the Trapezium at 24 - 160 microns using MIPS

We're going to design an observation that will cover a relatively large area of sky. This example will illustrate how to do a large area imaging survey, coordinating observations between IRAC $(3.6 - 8.0 \; \mu {\rm m})$ and MIPS $(24 - 160 \; \mu {\rm m})$. The MIPS observations are described in this chapter, and the complementary IRAC program is developed in §10. For this project, we will use MIPS and IRAC to survey the Orion Nebula Cluster (ONC), which surrounds (and includes) the Trapezium. Our goal is to survey this region and obtain photometry for G stars therein. This region is well-studied at many wavelengths ranging from IRAS to Chandra, and is expected to produce a very high flux in the specific Spitzer bands, particularly at the longer wavelengths. In fact, it is likely to be rather blindingly bright, as many Galactic star-forming regions are. The GTOs, not surprisingly, have snapped up the ONC region with all the instruments already. However, because we would like to demonstrate certain specific features, and even though similar observations of the cluster are already in the ROC (and are likely to be saturated at least in part), we will plunge ahead in this example anyway; the authors of this cookbook, at least, found this exercise useful, specifically because we are coming from an optical background, and Spitzer infrared considerations (sensitivity and backgrounds in particular) can be significantly different from those of optical observations. In planning these observations, we will use Spot to grab images from IRAS and 2MASS to aid in estimating background and exposure times. We will take into account possible detector saturation and latency effects. This example can be applied to wide-field mapping of nearly any Galactic star-forming region and/or regions of high background.