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Register a new userThe Extended Line Region of 3C 299
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We present results of HST observations of the radio galaxy 3C 299. The broad-band F702W (R) and F555W (V) images (WFPC2/PC) show an elliptical galaxy, with a comet-like structure extending to the NE in the radio jet direction. The [OIII]$lambda$5007 emission line map, shows a bi-conical structure centered on the nucleus, that overlaps the structure found in the broad-band filters. The radio core coincides with the center of the bi-conical structure and the radio axes are aligned with the direction of the cones. These data show clear evidence of a strong interaction between the radio jet and the NE morphology of the galaxy. We show evidence that this NE region is an ENLR; the line-ratio diagnostics show that models involving gas shocked by the radio-jet plus ionization from a precursor HII region, produced itself by the ionizing photons of the postshocked gas on the preshocked gas provide a good match to the observations. We investigate the spatial behavior of the ionizing parameter $U$, by determining the [OIII]/[OII] line ratio which is sensitive to the change of the ionization parameter, and trace its behavior over the ENLR along the radio jet direction. We find that [OIII]/[OII] does not follow a simple dilution model, but rather that it is approximately constant over a large range of distance from the nucleus thus requiring a local source of ionization which seems to be compatible with the shock models driven by the radio jet.
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We present Gemini Multiobject Spectrograph integral field spectroscopy of the extended emission-line region associated with quasar 3C 249.1. The kinematics of the ionized gas measured from the [O III] $lambda$5007 line is rather complex and cannot be explained globally by a simple dynamical model, but some clouds can be modeled individually as having locally linear velocity gradients. The temperatures of the ionized gas appear uniform (varying from ~12000 to 15000 K), while the densities vary from a few tens to a few hundreds cm^{-3}. The emission mechanism of all of the emission clouds, as indicated by the line-ratio diagnostics, is consistent both with shock + precursor and pure photoionization models. The total mass of the ionized gas is on the order of 10^9 M_Sun. We estimate the bulk kinetic energy and momentum of the extended emission-line region of 2.5*10^{57} ergs and 10^{50} dyne s, and a dynamical timescale of ~10 Myr. By comparing the injection rates of kinetic energy and momentum of different galactic wind models with the observation, we argue that the emission-line clouds are most likely a direct result from the feedback of the quasar. We also discuss the nature of the extended X-ray emission surrounding the quasar.
We present extensive ground-based spectroscopy and HST imaging of 3C79, an FR II radio galaxy associated with a luminous extended emission-line region (EELR). Surface brightness modeling of an emission-line-free HST R-band image reveals that the host galaxy is a massive elliptical with a compact companion 0.8 away and 4 magnitudes fainter. The host galaxy spectrum is best described by an intermediate-age (1.3 Gyr) stellar population (4% by mass), superimposed on a 10 Gyr old population and a power law (alpha_{lambda} = -1.8); the stellar populations are consistent with super-solar metallicities, with the best fit given by the 2.5 Z_sun models. We derive a dynamical mass of 4E11 M_sun within the effective radius from the velocity dispersion. The EELR spectra clearly indicate that the EELR is photoionized by the hidden central engine. Photoionization modeling shows evidence that the gas metallicity in both the EELR and the nuclear narrow-line region is mildly sub-solar (0.3 - 0.7 Z_sun) -- significantly lower than the super-solar metallicities deduced from typical active galactic nuclei in the SDSS. The more luminous filaments in the EELR exhibit a velocity field consistent with a common disk rotation. Fainter clouds, however, show high approaching velocities that are uncoupled with this apparent disk rotation. The striking similarities between this EELR and the EELRs around steep-spectrum radio-loud quasars provide further evidence for the orientation-dependent unification schemes. The metal-poor gas is almost certainly not native to the massive host galaxy. We suggest that the close companion galaxy could be the tidally stripped bulge of a late-type galaxy that is merging with the host galaxy. The interstellar medium of such a galaxy is probably the source for the low-metallicity gas in 3C79.
We present new Gemini spectroscopical data of the Extended Emission-Line Region of 3C~305 radio galaxy in order to achieve the final answer of the long-standing question about the ionizing mechanism. The spectra show strong kinematic disturbances within the most intense line-emitting region. The relative intensities amongst the emission lines agree with the gas being shocked during the interaction of the powerful radio jets with the ambient medium. The emission from the recombination region acts as a very effective cooling mechanism, which is supported by the presence of a neutral outflow. However, the observed intensity is almost an order of magnitude lower than expected in a pure shock model. So auto-ionizing shock models, in low-density and low-abundance regime, are required in order to account for the observed emission within the region. This scenario also supports the hypothesis that the optical emitting gas and the X-ray plasma are in pressure balance.
We have explored the nature of the extended emission-line region around the z=0.37 quasar 4C 37.43, using extensive ground-based and HST imaging and spectroscopy. The velocity field of the ionized gas shows gradual gradients within components but large jumps between components, with no obvious global organization. The HST [O III] image shows radial linear features on the east side of the QSO that appear to mark the edges of an ionization cone. Concentrating on the bright emission peaks ~4arcsec$ east of the quasar, we find through modeling that we require at least two density regimes contributing significantly to the observed emission-line spectrum: one with a density of ~2 cm^-3, having essentially unity filling factor, and one with a density of ~500 cm^-3, having a very small (~10^-5) filling factor. Because the temperatures of these two components are similar, they cannot be in pressure equilibrium, and there is no obvious source of confinement for the dense regions. We estimate that the dense regions will dissipate on timescales <~10^4 years and therefore need to be continuously regenerated, most likely by shocks. Because we know that some QSOs, at least, begin their lives in conjunction with merger-driven massive starbursts in their host galaxies, an attractive interpretation is that the extended emission region comprises gas that has been expelled as a result of tidal forces during the merger and is now being shocked by the galactic superwind from the starburst. This picture is supported by the observed distribution of the ionized gas, the presence of velocities ranging up to ~700 km s^{-1}, and the existence of at least two QSOs having similarly luminous and complex extended emission regions that are known to have ultra-luminous IR galaxy hosts with current or recent starbursts.
We present deep long slit spectra of Mkn79 in position angles PA=12$^{o}$ and PA=50$^{o}$ obtained with the WHT. These data prove the existence of an extended narrow line region in PA=12$^{o}$, which coincides with the triplet radio structure (Ulvestad & Wilson 1984) and the observed outflow of material from the nucleus at PA=10$^{o}$ (Whittle et al. 1988). The ratios of the high to low ionization lines indicate a higher level of gas excitation in PA=12$^{o}$ compared to PA=50$^{o}$. The [NII]$lambda$6583/H$alpha$ and [SII]$lambda$6717,31/H$alpha$ versus [OIII]$lambda$5007/H$beta$ line ratios are consistent with excitation by an AGN continuum rather than a HII region.
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