Imaging of High Redshift Submillimeter Galaxies at 16 and 22microns with   the Spitzer/IRS: Revealing a population at z>2.5
  We present broad band imaging observations obtained with the ``peak up'' imagers of the Spitzer Space Telescope Infrared Spectrograph (IRS) at wavelengths of 16micron and 22micron for a number of sources detected primarily at submillimeter wavelengths, which are believed to be at high, though undetermined, redshift. We targeted 11 sources originally detected by SCUBA and 5 submillimeter sources detected at 1.2mm by MAMBO. Two optically discovered quasars with z>6 were also observed to determine if there is detectable dust emission at such high redshifts. Seven of the submillimeter sources and both high-redshift quasars were detected, and upper limits of about ~50microJy apply to the remainder. Using their mid-/far-IR colors, we demonstrate that all of the submillimeter sources are at z>1.4. The mid-IR colors for two of our detections and three of our strong upper limits suggest that these galaxies must be at z>2.5. We also introduce a technique for estimating redshifts and source characteristics based only on the ratio of fluxes in the 16micron and 22micron images. 
V. Charmandaris (1), K. I. Uchida (1), D. Weedman (1), T. Herter (1),   J.R. Houck (1), H.I. Teplitz (3), L. Armus (2), B.R....