HerMES: SPIRE emission from radio-selected active galactic nuclei
Aussel, H.; Elbaz, D.; Pérez-Fournon, I.; Valtchanov, I.; Ivison, R. J.; Omont, A.; Clements, D. L.; Lagache, G.; Buat, V.; Dwek, E.; Wang, L.; Hatziminaoglou, E.; Franceschini, A.; Bock, J.; Cooray, A.; Solares, E. A. González; Ibar, E.; Marchetti, L.; Oliver, S. J.; Page, M. J.; Roseboom, I. G.; Symeonidis, M.; Vaccari, M.; Conley, A.; Cava, A.; Eales, S.; Panuzzo, P.; Boselli, A.; Amblard, A.; Arumugam, V.; Blain, A.; Castro-Rodríguez, N.; Chanial, P.; Conversi, L.; Dowell, C. D.; Glenn, J.; Griffin, M.; Isaak, K.; Levenson, L.; Lu, N.; Madden, S.; Maffei, B.; Mainetti, G.; Nguyen, H. T.; O'Halloran, B.; Papageorgiou, A.; Pearson, C. P.; Pohlen, M.; Rawlings, J. I.; Rizzo, D.; Rowan-Robinson, M.; Schulz, B.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Stevens, J. A.; Trichas, M.; Tugwell, K. E.; Vigroux, L.; Wright, G.; Xu, C. K.; Zemcov, M.; Scott, Douglas
United Kingdom, United States, France, Spain, Italy, Germany, Canada
Abstract
We examine the rest-frame far-infrared emission from powerful radio sources with 1.4-GHz luminosity densities of 25 ≤ log(L1.4/W Hz-1) ≤ 26.5 in the extragalactic Spitzer First Look Survey field. We combine Herschel/SPIRE flux densities with Spitzer/Infrared Array Camera and Multiband Imaging Photometer for Spitzer infrared data to obtain total (?m) infrared luminosities for these radio sources. We separate our sources into a moderate, 0.4 < z < 0.9, and a high, 1.2 < z < 3.0, redshift sub-sample and we use Spitzer observations of a z < 0.1 3CRR sample as a local comparison. By comparison to numbers from the Square Kilometre Array (SKA) Simulated Skies, we find that our moderate-redshift sample is complete and our high-redshift sample is 14 per cent complete. We constrain the ranges of mean star formation rates (SFRs) to be 3.4-4.2, 18-41 and 80-581 M⊙ yr-1 for the local, moderate- and high-redshift samples, respectively. Hence, we observe an increase in the mean SFR with increasing redshift which we can parametrize as ∼(1 + z)Q, where Q = 4.2 ± 0.8. However, we observe no trends of mean SFR with radio luminosity within the moderate- or high-redshift bins. We estimate that radio-loud active galactic nuclei (AGN) in the high-redshift sample contribute 0.1-0.5 per cent to the total SFR density at that epoch. Hence, if all luminous starbursts host radio-loud AGN we infer a radio-loud phase duty cycle of 0.001-0.005.
For reference, 2 per cent of the radio sources with unknown redshifts have significant detections in the SPIRE wavebands.