(Abridged) We present new deep VLT/FORS optical spectra with intermediate resolution and large wavelength coverage of the GPS radio source and ULIRG PKS1345+12 (4C12.50; z=0.122), taken with the aim of investigating the impact of the nuclear activity
on the circumnuclear ISM. PKS1345+12 is a powerful quasar and is also the best studied case of an emission line outflow in a ULIRG. Using the density sensitive transauroral emission lines [S II]4068,4076 and [O II]7318,7319,7330,7331, we pilot a new technique to accurately model the electron density for cases in which it is not possible to use the traditional diagnostic [S II]6716/6731, namely sources with highly broadened complex emission line profiles and/or high (Ne > 10^4 cm^-3) electron densities. We measure electron densities of Ne=2.94x10^3 cm^-3, Ne=1.47x10^4 cm^-3 and Ne=3.16x10^5 cm^-3 for the regions emitting the narrow, broad and very broad components respectively. We calculate a total mass outflow rate of 8 M_sun yr^-1. We estimate the total mass in the warm gas outflow is 8x10^5 M_sun. The total kinetic power in the warm outflow is 3.4x10^42 erg s^-1. We find that only a small fraction (0.13% of Lbol) of the available accretion power is driving the warm outflow, significantly less than currently required by the majority of quasar feedback models (~5-10% of Lbol), but similar to recent findings by Hopkins et al. (2010) for a two-stage feedback model. The models also predict that AGN outflows will eventually remove the gas from the bulge of the host galaxy. The visible warm outflow in PKS1345+12 is not currently capable of doing so. However, it is entirely possible that much of the outflow is either obscured by a dense and dusty natal cocoon and/or in cooler or hotter phases of the ISM. This result is important not just for studies of young (GPS/CSS) radio sources, but for AGN in general.
We report the analysis of near-infrared imaging, polarimetric and spectroscopic observations of the powerful radio galaxy 3C433, obtained with the HST and UKIRT telescopes. The high spatial resolution of HST allows us to study the near-nuclear region
s of the galaxy (<1 kpc). In line with previous observations, we find that 3C433 has an unresolved core source that is detected in all near-IR bands, but dominates over the host galaxy emission at 2.05 um. Our analysis reveals: (1) the presence of a dust lane aligned close to perpendicular (PA$=70pm5degr$) to the inner radio jet axis (PA$=-12pm2degr$); (2) a steep slope to the near-IR SED ($alpha=5.8pm0.1$; F$_{ u}propto u^{-alpha}$); (3) an apparent lack of broad permitted emission lines at near-IR wavelengths, in particular the absence of a broad Pa$alpha$ emission line; and (4) high intrinsic polarization for the unresolved core nuclear source ($8.6pm1$ per cent), with an E-vector perpendicular (PA=$83.0pm 2.3degr$) to the inner radio jet. Using five independent techniques we determine an extinction to the compact core source in the range 3<A_V<67 mag. An analysis of the long wavelength SED rules out a synchrotron origin for the high near-IR polarization of the compact core source. Therefore, scattering and dichroic extinction are plausible polarizing mechanisms, although in both of these cases the broad permitted lines from the AGN are required to have a width >10^4 km/s (FWHM) to escape detection in our near-IR spectrum. Dichroic extinction is the most likely polarization mechanism because it is consistent with the various available extinction estimates. In this case, a highly ordered, coherent toroidal magnetic field must be present in the obscuring structure close to the nucleus.
We present new observational results that conclude that the nearby radio galaxy B2 0722+30 is one of the very few known disc galaxies in the low-redshift Universe that host a classical double-lobed radio source. In this paper we use HI observations,
deep optical imaging, stellar population synthesis modelling and emission-line diagnostics to study the host galaxy, classify the Active Galactic Nucleus and investigate environmental properties under which a radio-loud AGN can occur in this system. Typical for spiral galaxies, B2 0722+30 has a regularly rotating gaseous disc throughout which star formation occurs. Dust heating by the ongoing star formation is likely responsible for the high infrared luminosity of the system. The optical emission-line properties of the central region identify a Low Ionization Nuclear Emission-line Region (LINER)-type nucleus with a relatively low [OIII] luminosity, in particular when compared with the total power of the Fanaroff & Riley type-I radio source that is present in this system. This classifies B2 0722+30 as a classical radio galaxy rather than a typical Seyfert galaxy. The environment of B2 0722+30 is extremely HI-rich, with several nearby interacting galaxies. We argue that a gas-rich interaction involving B2 0722+30 is a likely cause for the triggering of the radio-AGN and/or the fact that the radio source managed to escape the optical boundaries of the host galaxy.
We present the results of a multiwavelength study of the z = 0.31 radio source PKS2250-41. Integral field unit and long-slit spectroscopy obtained using VIMOS and FORS1 on the VLT, and archival HST optical imaging observations are used to study the m
orphology, kinematics and ionisation state of the extended emission line region (EELR) surrounding this source, and also a companion galaxy at a similar redshift. Near-infrared imaging observations obtained using the NTT are used to analyse the underlying galaxy morphologies. The EELR displays a complex variety of different gas kinematics and ionization states, consistent with a mixture of radio source shocks and AGN photoionization. The radio galaxy is likely to lie within a group environment, and is plausibly undergoing interactions with one or more other objects. The disk-like galaxy to the northeast of the radio source lies at a similar redshift to the radio galaxy itself, and has its major axis position angle aligned with the filamentary continuum and line emission extending outwards from the radio galaxy. This filamentary structure is most plausibly interpreted as a tidal structure associated with an interaction involving the radio source host galaxy and the aligned companion galaxy to the north-east; this encounter may have potentially triggered the current epoch of radio source activity. Overall, PKS2250-41 displays some of the best evidence that radio source activity can be triggered in this manner. [abridged]
We present intermediate resolution, wide wavelength coverage spectra for a complete sample of 14 compact radio sources taken with the aim of investigating the impact of the nuclear activity on the circumnuclear (ISM) in the early stages of radio sour
ce evolution. We observe spatially extended line emission (up to 20 kpc) in the majority of sources which is consistent with a quiescent halo. In the nuclear apertures we observe broad, highly complex emission line profiles. Multiple Gaussian modelling of the [O III]5007 line reveals 2-4 components which can have FWHM and blueshifts relative to the halo of up to 2000 km/s. We interpret these broad, blueshifted components as material in outflow and discuss the kinematical evidence for jet-driven outflows. Comparisons with samples in the literature show that compact radio sources harbour more extreme nuclear kinematics than their extended counterparts, a trend seen within our sample with larger velocities in the smaller sources. The observed velocities are also likely to be influenced by source orientation with respect to the observers line of sight. Nine sources have associated HI absorption. In common with the optical emission line gas, the HI profiles are often highly complex with the majority of the detected components significantly blueshifted, tracing outflows in the neutral gas. The sample has been tested for stratification in the ISM (FWHM/ionisation potential/critical density) as suggested by Holt et al. (2003) for PKS1345+12 but we find no significant trends within the sample using a Spearman Rank analysis. This study supports the idea that compact radio sources are young radio loud AGN observed during the early stages of their evolution and currently shedding their natal cocoons through extreme circumnuclear outflows.
