[Sandage (1972)] found that the optical luminosity function of radio galaxy hosts was similar to that of first ranked cluster members, and he noted that their optical morphology was similar to bright E galaxies. Although it was therefore generally believed that the hosts of all radio galaxies were gE types, subsequent large surveys of radio galaxies showed a good deal of evidence for peculiar morphologies (e.g., [Heckman et al. 1986]). We find that the host galaxy of NVSS 2146+82 is likely typical, i.e. it is a gE galaxy, but with evidence of some peculiar morphological features.
The broadband colors of NVSS 2146+82 are typical of bright FR II host galaxies. The absolute magnitude we derive for the host is MV = -22.9 at z=0.145 if we adopt a K correction of 0.46 magnitudes in the V passband ([Kinney et al. 1996]). This magnitude is consistent with the host being a gE galaxy, and also is very similar to the mean V magnitude for 50 low redshift FR IIs of -22.6 ([Zirbel 1996]).
Similar to other FR II host galaxies, we find the optical morphology of the host elliptical of NVSS 2146+82 to be disturbed. In Figure 10, the four distinct objects besides the host galaxy and foreground star have been identified as having non-stellar morphologies with the Faint Object Classification and Analysis System (FOCAS, [Valdes 1982]). If these four galaxies share the same redshift as the gE host of NVSS 2146+82, they all lie 50-100 kpc away from its nucleus, a distance that implies that they may be dynamically interacting with it. Figure 10 also shows what appears to be a bridge of diffuse optical light that almost connects NVSS 2146+82 to the galaxy to the southwest. This bridge may indicate that this smaller galaxy has recently passed close enough to NVSS 2146+82 to interact with it gravitationally. There is also a fifth object 5'' to the southeast of the center of NVSS 2146+82, which could be in the process of merging with the gE galaxy. However, due to the faintness of this object and its proximity to the nucleus of 2146+82, we are unable to classify this object definitively as a galaxy with the FOCAS software. Although we cannot conclude based on this image that NVSS 2146+82 is undergoing a merger, its outer isophotes do show evidence that it has been disturbed.
Correlations between the radio power and optical emission line
luminosities in radio galaxies have been established in several studies
(e.g., [Rawlings & Saunders 1991]; [Zirbel & Baum 1995]; [Tadhunter et al. 1998]). These
radio/optical correlations are assumed to arise primarily due to the
fact that both the radio jet and the ionization source originate in the
central engine. The radio core power at 5 GHz (log P [W Hz-1] = 23.85) and the H
N2] luminosity (log L [W] = 35.2) for NVSS 2146+82 lie well within the dispersion in the
correlation in these quantities found for low redshift FR IIs
([Zirbel & Baum 1995]). This apparently indicates that the physical
conditions that cause this radio/optical correlation to arise may be
similar in this GRG and in "normal'' FR IIs.
The shape of the emission line profiles in NVSS 2146+82 are not unique; emission line profiles and narrow band imaging of Seyfert galaxies and radio galaxies have shown evidence for interaction between the radio synchrotron emitting plasma and the optically emitting ionized gas (see e.g., [Whittle 1989]). Although the majority of objects that show kinematic evidence for interactions between the radio jets and ionized gas clouds tend to have more compact radio structures, the double peaked line profiles seen in NVSS 2146+82 appear similar to those seen in radio galaxies with jet/cloud interactions. A recent model ([Taylor, Dyson, & Axon 1992]) for interactions between the nuclear radio emission and NLR gas in Seyferts produces [OIII] profiles for objects near the plane of the sky that are very similar to the double peaked profiles seen in NVSS 2146+82. The model of Taylor et al. (1992) produces double peaks in the line profiles of objects oriented close to the plane of the sky because the emission lines are postulated to arise from gas that is being accelerated as a bowshock expands into the ionized medium surrounding the nucleus. They model the bowshock as a series of annuli, and each annulus contributes most of its luminosity at the two extreme radial velocities found along the line of sight. Although the specifics of the model of Taylor et al. (1992), such as the discrete plasmon emission from the radio nucleus, may not necessarily apply in the case of NVSS 2146+82, it suggests that the narrow line profiles observed for this FR II (which is assumed to be very near the plane of the sky) can be produced plausibly in a model where the ionized gas is in a cylindrical geometry around the radio jet.
Double peaked broad lines have been observed in radio galaxies (e.g., Pictor A [[Halpern & Eracleous 1994]]), however the model that is typically invoked to explain the broad line profiles requires the radio galaxy to be oriented close to the line of sight. Since NVSS 2146+82 does not show a broad line component and is unlikely to be oriented close to the line of sight, the accretion disk model relied on to fit double peaked broad lines in AGN is probably unrelated to the emission line profiles observed in NVSS 2146+82.
Although a jet/cloud interaction appears to be the most reasonable explanation for the double peaked narrow emission lines observed in the spectrum of NVSS 2146+82, it is also plausible that a gravitational interaction between the FR II host galaxy and its nearest companions may be the source of the ~ 450 km/sec separation between the blue and red emission line peaks. Higher spatial resolution long slit spectroscopy is necessary to determine which cause is more likely.