8. 16 Micron Imaging of Five Clusters of Galaxies using IRS

In chapters §4 and §5, AORs were developed to obtain deep imaging of five galaxy clusters. In this chapter, we describe how to construct a complementary survey using the IRS Peak-Up Imaging (PUI) mode.

PUI allows the observer to obtain photometric-quality images in two filters, one centered at 16 microns, and the other centered at 22 microns. Both Red (22 micron) and Blue (16 micron) Peak-Up images are obtained simultaneously, but at slightly different fields of view.

The Peak-Up capability is primarily intended for target acquisition. This means that the imaging field of view is small and the detector is less sensitive to the faintest sources. Nonetheless, the PUI mode at 16 microns fills in a wavelength gap between the longest wavelength of IRAC (8 microns) and the shortest wavelength of MIPS (24 microns).

PUI mode observations are taken in a $\sim$50 arcsecond by 80 arcsecond field of view, with a pixel scale of 1.8 arcseconds per pixel. Images are diffraction-limited, implying a FWHM of 2 pixels at 16 microns. In the example we develop in this section, the Blue image is of primary scientific interest. The Red image overlaps with MIPS observations already planned above in Chapter 5.