The radio properties of optically obscured Spitzer sources

摘要: This paper analyses the radio properties of a subsample optically obscured (R ≥ 25.5) galaxies observed at 24 μm by Spitzer Space Telescope within First Look Survey. Ninety-six F 0.35 mJy objects out 510 are found to have counterpart 1.4 GHz, 610 MHz or both frequencies, respectively, down ∼40 and ∼200 μJy. IRAC photometry sets majority them in redshift interval z ≃ [1-3] allows for broad distinction between active galactic nucleus (AGN) dominated (∼47 per cent radio-identified sample) systems powered intense star formation (∼13 cent), remaining being impossible classify. The percentage identifications is strong function 24-μm flux: almost all sources brighter than ∼ 2 endowed with flux GHz 610MHz, while this fraction drastically decreases lowering level. number counts frequencies suggest that physical process(es) responsible activity these common origin regardless whether source shows mid-infrared emission compatible an AGN star-forming galaxy. We also find candidate follow (although large scatter) relationship 1.4-GHz fluxes reported Appleton et al. which identifies undergoing activity. However, more scattered relation 610-MHz fluxes. On other hand, inferred spectral indices α indicate our sample (∼60 estimated α) may belong population ultrasteep spectrum sources, typically 'frustrated' radio-loud AGN. interpret findings as indication concurrent activity, whereby thermal origin, mainly stems from nuclear source.