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Session 105 - Galaxies: Counts & Kinematics.
Display session, Saturday, January 10
Exhibit Hall,

[105.01] An X-ray and Optical Investigation of the Environments of Nearby Radio Galaxies

N. Miller (NMSU), F. Owen (NRAO), J. Burns (U. Missouri), M. Ledlow (U. New Mexico), W. Voges (MPE)

Investigations of the cluster environment of radio sources have not shown a correlation between radio power and degree of clustering. However, it has been demonstrated that extended x-ray luminosity and galaxy clustering do exhibit a positive correlation. This study investigates a complete sample of 25 nearby (z \leq 0.06) radio galaxies which are not cataloged members of Abell clusters. The environment of these radio galaxies is studied in both the x-ray and the optical by means of the ROSAT All-Sky Survey (RASS), ROSAT pointed observations, and the Digitized Sky Survey (DSS). X-ray luminosities and extents are determined from the RASS, and the DSS is used to quantify the degree of clustering via the spatial two-point correlation coefficient, B_gg. Of the 25 sources, 20 were \ge 3 \sigma detections in the x-ray and 11 possessed B_gg's significantly in excess of that expected for an average galaxy. Adding the criterion that x-ray emission be resolved, 10 of the radio galaxies do appear to reside in poor clusters with extended x-ray emission suggestive of the presence of an intracluster medium. Eight of these galaxies also possess high spatial correlation coefficients, strengthening the claim that they lie in poor cluster environments. The unresolved x-ray emission from the other galaxies is most likely associated with AGN phenomena. Furthermore, although the sample size is small, it appears that the environments of FR I and FR II sources differ. FR I's tend to be more frequently associated with extended x-ray emission (10 of 18), whereas FR II's are typically point sources or non-detections in the x-ray (none of the 7 sources exhibit extended x-ray emission).

Program listing for Saturday