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The environmental dependence of radio-loud AGN activity and star formation in the 2dFGRS
Astrophysics · Submitted 23 Feb 2004
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim The AGN fraction appears to depend more strongly on the large-scale environment (group, cluster, etc) in which a galaxy is located than on its more local environment, except at the lowest galaxy surface densities where practically no radio-loud AGN are found.
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The abstract, sentence by sentence
By combining the 2-degree Field Galaxy Redshift Survey with the NRAO VLA Sky Survey at 1.4 GHz, the environments of radio loud AGN in the nearby Universe are investigated using both local projected galaxy densities and a friends-of-friends group finding algorithm. Radio-loud AGN are preferentially located in galaxy groups and poor-to-moderate richness galaxy clusters. The AGN fraction appears to depend more strongly on the large-scale environment (group, cluster, etc) in which a galaxy is located than on its more local environment, except at the lowest galaxy surface densities where practically no radio-loud AGN are found. The ratio of absorption-line to emission-line AGN changes dramatically with environment, with essentially all radio-loud AGN in rich environments showing no emission lines. This result could be connected with the lack of cool gas in cluster galaxies, and may have important consequences for analyses of optically-selected AGN, which are invariably selected on emission line properties. The local galaxy surface density of the absorption-line AGN is strongly correlated with radio luminosity, implying that the radio luminosities may be significantly boosted in dense environments due to confinement by the hot intracluster gas. The environments of a radio-selected sample of star forming galaxies are also investigated to provide an independent test of optical studies. In line with those studies, the fraction of star forming galaxies is found to decrease strongly with increasing local galaxy surface density; this correlation extends across the whole range of galaxy surface densities, with no evidence for the density threshold found in some optical studies.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | By combining the 2-degree Field Galaxy Redshift Survey with the NRAO VLA Sky Survey at 1.4 GHz, the environments of radio loud AGN in the nearby Universe are investigated using both local projected galaxy densities and a friends-of-friends group finding algorithm. | method 0.96 | 0.93 | 0.03 | asserted 0.94 |
| s1 | Radio-loud AGN are preferentially located in galaxy groups and poor-to-moderate richness galaxy clusters. | result 1.00 | 0.90 | 0.39 | asserted 1.00 |
| s2 | The AGN fraction appears to depend more strongly on the large-scale environment (group, cluster, etc) in which a galaxy is located than on its more local environment, except at the lowest galaxy surface densities where practically no radio-loud AGN are found. | result 1.00 | 0.91 | 0.54 | asserted 0.56 |
| s3 | The ratio of absorption-line to emission-line AGN changes dramatically with environment, with essentially all radio-loud AGN in rich environments showing no emission lines. | result 1.00 | 0.90 | 0.17 | asserted 1.00 |
| s4 | This result could be connected with the lack of cool gas in cluster galaxies, and may have important consequences for analyses of optically-selected AGN, which are invariably selected on emission line properties. | interpretation 1.00 | 0.29 | 0.07 | hedged possibility 1.00 |
| s5 | The local galaxy surface density of the absorption-line AGN is strongly correlated with radio luminosity, implying that the radio luminosities may be significantly boosted in dense environments due to confinement by the hot intracluster gas. | interpretation 0.71 | 0.89 | 0.12 | hedged possibility 0.77 |
| s6 | The environments of a radio-selected sample of star forming galaxies are also investigated to provide an independent test of optical studies. | contribution 0.87 | 0.89 | 0.03 | asserted 0.82 |
| s7 | In line with those studies, the fraction of star forming galaxies is found to decrease strongly with increasing local galaxy surface density; this correlation extends across the whole range of galaxy surface densities, with no evidence for the density threshold found in some optical studies. | result 1.00 | 0.96 | 0.13 | asserted 1.00 |
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Original abstract
By combining the 2-degree Field Galaxy Redshift Survey with the NRAO VLA Sky Survey at 1.4 GHz, the environments of radio loud AGN in the nearby Universe are investigated using both local projected galaxy densities and a friends-of-friends group finding algorithm. Radio-loud AGN are preferentially located in galaxy groups and poor-to-moderate richness galaxy clusters. The AGN fraction appears to depend more strongly on the large-scale environment (group, cluster, etc) in which a galaxy is located than on its more local environment, except at the lowest galaxy surface densities where practically no radio-loud AGN are found. The ratio of absorption-line to emission-line AGN changes dramatically with environment, with essentially all radio-loud AGN in rich environments showing no emission lines. This result could be connected with the lack of cool gas in cluster galaxies, and may have important consequences for analyses of optically-selected AGN, which are invariably selected on emission line properties. The local galaxy surface density of the absorption-line AGN is strongly correlated with radio luminosity, implying that the radio luminosities may be significantly boosted in dense environments due to confinement by the hot intracluster gas. The environments of a radio-selected sample of star forming galaxies are also investigated to provide an independent test of optical studies. In line with those studies, the fraction of star forming galaxies is found to decrease strongly with increasing local galaxy surface density; this correlation extends across the whole range of galaxy surface densities, with no evidence for the density threshold found in some optical studies.
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3 arXiv papers cite this in 4 sentences
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This is motivated by the prevalence of X-ray cavities or bubbles, which are low-density, X-ray dim regions filled with radio-emitting plasma injected by the SMBH jets, in CC clusters [ref] , as well as in many galaxy groups [ref] , which themselves represent a significant fraction of local radio galaxy hosts [ref] .
Recent Progress in Modeling the Macro- and Micro-Physics of Radio Jet Feedback in Galaxy Clusters · Jet Feedback in Galaxy Clusters: Observations and Theoretical Motivation · 0.99
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