| Description |
One of the most puzzling discoveries of the Australia Telescope Large Area Survey (ATLAS) is the population of infrared-faint radio sources. While relatively bright at 1.4 and 2.3 GHz (10-20 mJy) these sources are neither seen on optical (r=25mag) nor on near- and mid-infrared (3.6-70 micron) Spitzer maps. Existing multiwavelength data, e.g. from SWIRE, suggests that these sources are high-redshift (2<z<5) radio-loud AGN, suffering from heavy obscuration of their optical/NIR emission. Therefore, powerful FIR re-emission is expected, but the FIR-submm maps obtained with Herschel (in the HERMES key project) are too shallow (50 mJy at 160 micron, 30 mJy at 250 micron) to detect these sources. If they are obscured high-z analogues of local templates like 3C48 the predicted 100-500 micron flux density is about 20 mJy, well detectable with Herschel. Therefore, we propose deep PACS 100+160 micron and SPIRE 250+350+500 micron maps of six representative sources, in order to determine the nature of these infrared-faint radio sources. This will provide crucial new insights on those radio-loud high redshift AGN, which cover a lower flux/luminosity range and are therefore more characteristic than the few extremely luminous high-z radio galaxies studied so far. |
