Dave Clements

Talk: Dave Clements, 3:00pm - 3:30pm
The deepest Herschel-SPIRE Field
We present the first results from the deepest far-IR observations ever made. These come from the Herschel-SPIRE dark field, a region observed multiple times over the entire course of the Herschel mission for calibration and instrument health purposes. Our final images combine 141 separate observations to produce images at 250, 350 and 500 microns at least twice as deep as any other Herschel-SPIRE image. The resulting image is strongly affected by confusion, so as well as normal and guided source detection techniques, which yield number counts consistent with previous observations, we also apply the P(D) technique to asses the number counts well below the confusion limit. This P(D) analysis reaches submJy sensitivities, and suggests an additional ‘bump’ in the number counts, not predicted by current models of the far-IR galaxy population and its evolution. Additional observations are available over parts of this field from SCUBA2, at 850 microns, and from HST which allow us to gain further insights into this population. One unusual aspect of this field is that there is an unusually large fraction of SPIRE dropouts (ie. SPIRE undetected) in the SCUBA2 data. We conduct a stacking analysis of these sources and conclude that they are candidate high redshift dusty star forming galaxies, though their average fluxes are too high to make them responsible for the number count bump.