Identification of the Infrared Non-thermal Emission in Blazars

Blazars constitute themost interesting and enigmatic class of extragalactic γ -ray sources dominated by non-thermal emission. In this Letter, we show how the Wide Infrared Survey Explorer (WISE) infrared data make it possible to identify a distinct region of the [3.4]–[4.6]–[12] μm color–color diagram where the sources dominated by the thermal radiation are separated from those dominated by non-thermal emission, in particular the blazar population. This infrared non-thermal region, which we indicate as the WISE blazar strip (WBS), will constitute a new powerful diagnostic tool when the full WISE survey data are released. TheWBS can be used to extract new blazar candidates, to identify those of uncertain type and also to search for the counterparts of unidentified γ -ray sources. We show one example of the value of the use of the WBS identifying the TeV source VER J0648+152, recently discovered by VERITAS.