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Session 39 - AGNs, QSOs, Active Galaxies.
Display session, Wednesday, June 11
South Main Hall,
We present UBVRI imaging, photometry, and optical spectroscopy of the FR II radio galaxy NVSS 2146+82. This galaxy, which was discovered by the NRAO VLA Sky Survey (NVSS), has an angular extent of 20' from lobe to lobe. Our spectroscopy indicates that the optical counterpart of the radio core is at a redshift of z=0.145, and therefore the linear size of the radio structure is approximately 4 Mpc (H_0=50). Typically, the linear sizes of FR IIs are hundreds of kpc to 1-2 Mpc. At 4 Mpc, NVSS 2146+82 is the second largest FR II known, compared to the 6 Mpc size of 3C 236. As a population, FR IIs are typically found in disturbed elliptical hosts which reside in poor to very poor cluster environments. Our observations of NVSS 2146+82, however, show no obvious evidence of disturbed morphology in the host, and it is in a relatively rich environment (approximately 15 companions to V=20 in a 0.5 Mpc radius). The group in which NVSS 2146+82 resides includes 4 companions within 40 kpc of the host galaxy, 2 of which appear to be closer than 20 kpc. The apparent richness of the Mpc environment surrounding NVSS 2146+82 has two major implications. It is believed that the amount of intracluster material entrained by the jet is one of the determinants of the radio morphology of the galaxy. Therefore, one expects the largest linear size FR IIs to reside in the poorest environments. Most (70%) low redshift FR IIs inhabit groups with \leq 10 members. The observation that the second largest FR II known lies in an overdense region may indicate that group richness is not the dominant determinant of radio morphology. In addition, the presence of several companions within tens of kpc of the AGN implies that there are significant dynamical interactions occuring. It is puzzling that NVSS 2146+82, with its highly linear morphology and large linear size, is found in a group that appears to be undergoing dynamical evolution.
