Star-Formation in Low Radio Luminosity AGN from the Sloan Digital Sky Survey

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dc.creatorde Vries, W. H.
dc.creatorHodge, J. A.
dc.creatorBecker, R. H.
dc.creatorWhite, R. L.
dc.creatorHelfand, D. J.
dc.date2007-04-16
dc.date.accessioned2026-07-07T11:20:17Z
dc.date.available2026-07-07T11:20:17Z
dc.descriptionWe investigate faint radio emission from low- to high-luminosity Active Galactic Nuclei (AGN) selected from the Sloan Digital Sky Survey (SDSS). Their radio properties are inferred by co-adding large ensembles of radio image cut-outs from the FIRST survey, as almost all of the sources are individually undetected. We correlate the median radio flux densities against a range of other sample properties, including median values for redshift, [OIII] luminosity, emission line ratios, and the strength of the 4000A break. We detect a strong trend for sources that are actively undergoing star-formation to have excess radio emission beyond the ~10^28 ergs/s/Hz level found for sources without any discernible star-formation. Furthermore, this additional radio emission correlates well with the strength of the 4000A break in the optical spectrum, and may be used to assess the age of the star-forming component. We examine two subsamples, one containing the systems with emission line ratios most like star-forming systems, and one with the sources that have characteristic AGN ratios. This division also separates the mechanism responsible for the radio emission (star-formation vs. AGN). For both cases we find a strong, almost identical, correlation between [OIII] and radio luminosity, with the AGN sample extending toward lower, and the star-formation sample toward higher luminosities. A clearer separation between the two subsamples is seen as function of the central velocity dispersion of the host galaxy. For systems with similar redshifts and velocity dispersions, the star-formation subsample is brighter than the AGN in the radio by an order of magnitude. This underlines the notion that the radio emission in star-forming systems can dominate the emission associated with the AGN.
dc.descriptionAccepted for publication in Astronomical Journal; 15 pages, 8 color figures
dc.identifierhttps://arxiv.org/abs/0704.2074
dc.identifierhttp://arxiv.org/abs/0704.2074
dc.identifierAstron.J.134:457-465,2007
dc.identifierdoi:10.1086/518866
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/193915
dc.subjectAstrophysics
dc.titleStar-Formation in Low Radio Luminosity AGN from the Sloan Digital Sky Survey
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