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Register a new userIntegral Field Spectroscopy of the Extended Emission-Line Region of 3C 249.1
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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.
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We present Gemini integral field spectroscopy and Keck II longslit spectroscopy of the extended emission-line region (EELR) around the quasar 4C 37.43. The velocity structure of the ionized gas is complex and cannot be explained globally by a simple dynamical model. The spectra from the clouds are inconsistent with shock or ``shock + precursor ionization models, but they are consistent with photoionization by the quasar nucleus. The best-fit photoionization model requires a low-metallicity (12+log(O/H) < 8.7) two-phase medium, consisting of a matter-bounded diffuse component with a unity filling-factor (N ~ 1 cc, T ~ 15000 K), in which are embedded small, dense clouds (N ~ 400 cc, T ~ 10^4 K). The high-density clouds are transient and can be re-generated through compressing the diffuse medium by low-speed shocks (V_S lesssim 100 kms). Our photoionization model gives a total mass for the ionized gas of about 3x10^{10} M_sun, and the total kinetic energy implied by this mass and the observed velocity field is ~2x10^{58} ergs. The fact that luminous EELRs are confined to steep-spectrum radio-loud quasars, yet show no morphological correspondence to the radio jets, suggests that the driving force producing the 4C 37.43 EELR was a roughly spherical blast wave initiated by the production of the jet. That such a mechanism seems capable of ejecting a mass comparable to that of the total interstellar medium of the Milky Way suggests that ``quasar-mode feedback may indeed be an efficient means of regulating star formation in the early universe.
Luminous extended emission-line regions (EELRs) on kpc scales surround a substantial fraction of steep-spectrum radio-loud QSOs. Although their existence has been known for over three decades, there are still major uncertainties on the physical processes responsible for their complex morphology and kinematics. We are obtaining deep integral field spectroscopy for a sample of EELRs around QSOs at z<0.5 with the Integral Field Unit (IFU) of the GMOS on the Gemini North telescope, aiming at extracting accurate kinematics of the EELRs, measuring important physical parameters (e.g., density, temperature, metallicity) and reliable intensity ratios of diagnostic emission lines from individual clouds that comprise an EELR. Here we present results from the observations of the EELR of quasar 4C 37.43. We show maps of gas kinematics measured from the [O III] 5007 line and line-ratio diagnostic diagrams comparing the data with predictions from ionization models. We find that the ionized gas shows rather complex global kinematics, while linear velocity gradients are often seen in individual clouds. Pure photoionization by the QSO continuum is the most likely ionization mechanism for most of the EELR clouds.
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.
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 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.
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