Participation in the Multi-tiered Extragalactic survey (HerMES)
(Stevens)
The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy program designed to map a set of nested fields totalling approximately 380 square degrees. Within this survey we are leading the effort to determine the far-infrared properties of type-2 QSOs (those with only narrow optical emission lines).
Early results suggest that they are more FIR luminous than ordinary type-1 QSOs, showing that the simple unified scheme linking type-1 and type-2 QSOs via orientation does not apply (Stevens et al. 2012, MNRAS, in prep.). Further work will study the FIR environments of matched samples of type-1 and type-2 QSOs.
Distribution of 250 micron flux densities for Type 1 (left) and Type 2 (right) QSOs in the HerMES FLS and Lockman fields. The samples are matched in redshift and 24 micron flux. The solid line shows the normalised distribution of flux densities in the entire FLS field. While both populations are detected, note that the Type 2s are on average more positive.