16 μm Imaging around the Hubble Deep Field–North with theSpitzerIRS

We present a pilot study of 16 micron imaging within the GOODS northernfield. Observations were obtained using the PeakUp imaging capability of theSpitzer IRS. We survey 35 square arcminutes to an average 3 sigma depth of0.075 mJy and detect 149 sources. The survey partially overlaps the area imagedat 15 microns by ISO, and we demonstrate that our photometry and galaxy-numbercounts are consistent with their measurements. We infer the total infraredluminosity of 16 micron detections using a comparison to local templates andfind a wide range of L_IR} from ~10^9 to 10^{12} L_sun. Approximately one fifthof the detected sources have counterparts in the Chandra 2 Msec catalog, and weshow that the hard band (2-8 keV) detected sources are likely to have strongAGN contributions to the X-ray flux. The ultradeep sensitivity of Chandraimplies some X-ray detections may be purely starbursting objects. We examinethe 16 to 24 micron flux ratio and conclude that it shows evidence for thedetection of redshifted PAH emission at z~0.5 and z>0.8.