2007A&A...474..731G

We describe data reduction and analysis of fluctuations in the cosmic far-IR background (CFIB) in observations with the Multiband Imaging Photometer for Spitzer (MIPS) instrument 160µm detectors. We analyzed observations of an 8.5 square degree region in the Lockman Hole, part of the largest low-cirrus mapping observation with this instrument. We measured the power spectrum of the CFIB in these observations by fitting a power law to the IR cirrus component, the dominant foreground contaminant, and subtracting this cirrus signal. The CFIB power spectrum in the range 0.2arcmin^–1<k<0.5arcmin^–1 is consistent with previous measurements of a relatively flat component. However, we find a large power excess at low k, which falls steeply to the flat component in the range 0.03arcmin^–1<k<0.1arcmin^–1. This low-k power spectrum excess is consistent with predictions of a source clustering ``signature''. This is the first report of such a detection in the far-IR.