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Paper: The GOODS-North Radio Galaxies: On the Origin of the Radio Emission
Volume: 381, The Second Annual Spitzer Science Center Conference: Infrared Diagnostics of Galaxy Evolution
Page: 376
Authors: Morrison, G.; Dickinson, M.; Owen, F.; Daddi, E.; Chary, R.; Bauer, F.; Mobasher, B.; MacDonald, E.; Koekemoer, A.; Pope, A.
Abstract: We report on a preliminary study concerning the origin of radio emission within radio galaxies at L(1.4GHz)>1E24 W/Hz in the GOODS-N field. In the local universe, Condon et al. (1989) and Yun et al. (2001) have shown that in galaxies with radio luminosities greater than 1 × 1023 W/Hz the majority of the radio emission originates from a ‘monster’ i.e., an AGN. Using the Chandra 2Msec X-ray image centered on the GOODS-N field and a reprocessed VLA HDF A-array data plus newly acquired VLA B-array data (σ=5.3μJy), we find that radio galaxies (with spectroscopic redshifts; all have z>1) with L(1.4GHz)>1E24 W/Hz typically have an X-ray detection rate of 72% (60% emit hard X-rays suggesting an AGN origin for the radio emission) in contrast to 25% for radio galaxies with L < 1×1023 W/Hz. The ACS images of these L[1.4GHz] ≥ 1 × 1024 W/Hz galaxies typically show compact rather than extended galaxy morphology which is generally found for the less luminous radio emitting galaxies but a few appear to be ongoing galaxy mergers. We also present SED fitting for these luminous radio galaxies including Spitzer IRAC & MIPS 24u photometry and 60% show distinct power-law SED indicative of an AGN. Initial results tell us that the X-ray emitting radio galaxy population are generally not submm sources but the few (∼10%) that are SCUBA sources appear to be the small AGN population found by Pope et al. and others.
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