More than half of all low-redshift AGN exhibit UV and X-ray absorption by highly ionized gas. The observed UV and X-ray absorption lines are almost aiways blue-shifted at velocities of hundreds of km s−1, indicating that the absorbing gas is outflowing from the active nucleus. In some cases the inferred mass flux rivals the Eddington limit of the central black hole, an indication that these outflows are intimately related to the mass accretion and energy generation mechanism in AGN. The ejected material can also have an affect on the interstellar medium of the host galaxy and the surrounding intergalactic medium. Over the past several years, coordinated UV and X-ray observations of several bright AGN at high spectral resolution using HST, FUSE, Chandra, and XMM-Newton have contributed greatly to our understanding of these outflows. I will give an overview of these recent observations, summarize our FUSE survey of low-redshift AGN, and interpret the results in the context of models of winds from accretion disks and thermally driven winds from the obscuring torus.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We use low resolution, near-IR spectra of eight of the most distant quasars known, with redshifts in the range 4.9<z<6.4, to investigate the gas and dust properties in their circumnuclear regions. Half of these quasars are characterized by deep, broad and blueshifted absorption features associated with both high and low ionization species, i.e. they belong to the class of Broad Absorption Line (BAL) quasars, which are associated with powerful outflows of dense gas. The large fraction of BAL quasars, the depth and ionization state of the absorption features suggest that these most distant quasars are surrounded by a much larger amount of dense gas than lower redshift (z<4) quasars. We discuss the possible interpretation of this result in terms of extremely high accretion rates and the association with the early formation of quasars.

The spectral shape of all these very distant quasars, and in particular of the BAL quasars, is bluer than for quasars at z<4, suggesting an evolution of the properties of the dust responsible for the quasar reddening. We show that the observed spectral shape can be explained by an extinction curve due to dust produced by SNe. This finding would address the problem of the dust production at z>6, when the age of the universe was lower than the evolutionary timescales of AGB stars.

Finally, these spectra allow to investigate the Fe/α-element abundance ratio, which is a tracer of the star formation history, through the relative strengths of the FeII UV bump and the MgII doublet. We find indications for a large abundance of Fe even in the most distant quasars at z∼6. This finding requires that a strong burst of star formation occurred in the hosts of these quasars already at z>9.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Despite many years of effort, observational studies have not found a strong correlation between the presence of any proposed fueling mechanism and low-luminosity AGN. After a discussion of the mass requirements for fueling, I summarize this observational work and provide a number of hypotheses for why the nature of AGN fueling has remained unresolved. In particular, I stress the potential importance of the increasing number of candidate fueling mechanisms with decreasing mass accretion rate, the relevant spatial scales for different fueling mechanisms, and the lifetime of an individual episode of nuclear accretion. The episodic AGN lifetime is a particularly relevant complication if it is comparable to or shorter than the time that the responsible fueling mechanisms are observationally detectable. I conclude with a number of relatively accessible areas for future investigation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Radio-loud AGNs can inhabit regions with a very rich ISM. The presence of this rich medium is likely related to the origin and evolution of the host galaxy and of the active nucleus. Recent observations show that a large fraction of radio galaxies contains a significant young stellar population. This supports the idea that mergers are responsible for both the starburst phase and the triggering of the nuclear activity. The gas that reaches the central regions can have quite disturbed kinematics, likely due to the effects of the AGN activity and in particular of the powerful radio jets. The recent detection of fast nuclear gas outflows, observed both in ionised and neutral gas, is giving new and important insights into the physical conditions of the gaseous medium around the nucleus and the interaction between the AGN and this medium. Finally, as another example of the interplay between the radio activity and the ISM, the possibility of star formation induced by the passage of the radio jet will be discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

I will discuss a few select aspects of the most common and best understood galactic-scale outflow – starburst-driven superwinds, focusing on winds from nuclear starburst galaxies. I will show that modern observations, in particular in the soft and hard X-ray bands, complement and reinforce the existing paradigm of superwinds as flows collectively driven by multiple SNe. The properties of the diffuse X-ray emission from dwarf starburst galaxies, LBOL∼L[sstarf ] starburst in spiral galaxies, and ULIRGS, are all consistent with superwind activity. Where appropriate, I contrast the physics of starburst-driven winds with poorly collimated winds from AGN, and discuss what we know of the role of LLAGN and Seyfert nuclei in starburst superwind galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from new high angular resolution observations of the neutral hydrogen absorption using global VLBI, MERLIN, and VLA observations of the peculiar radio galaxy 3C 293. These results reveal extensive HI absorption against the inner kiloparsec of the radio jet in this source over a wide range of angular scales. In additional to these sub-arcsecond resolution radio observations we also present infrared imaging of the jet.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We provide an overview of a high spatial resolution study of the molecular emission (H2 and CO) in the few central arcsec region around the AGN in NGC1068. A 0.5″ resolution H2 2.12 μm line map obtained with VLT/ISAAC is presented and reveals interesting characteristics: two unequally bright knots located at 1″ (70 pc) from the nucleus, along a direction perpendicular to the ionizing cone axis. We propose a model involving differential extinction, produced in the emitting molecular disc itself, to explain the intensity difference between the two knots. This effect can arise from a simple configuration, in which the orientation of the molecular disc is slightly tilted with respect to that of the central Compton thick absorber, which blocks the X-rays along our line of sight.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Seyfert narrow line regions (NLR) have emission line ratios which are remarkably uniform, displaying only ∼0.5 dex variation between different galaxies. Existing models have been unable to explain these observations without the introduction of ad hoc assumptions, geometrical restrictions or new parameters. Here we introduce a new model: dusty radiation pressure dominated photoionization, which provides a natural self-regulating characteristic, leading to an invariance of the spectrum over a very wide range (>100) of ionization parameter. The dusty model is able to reproduce both the range and the absolute value of the observational line ratios not only in the standard optical diagnostic diagrams but also in UV diagnostic plots, providing an explanation to the problem in NLR observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Sensitive Infrared Spectral Energy Distributions (SEDs) drawn from the ISO data archive and supplemented with SCUBA and MAMBO observations, provide evidence for the geometric unification of powerful 3CR radio galaxies as “edge-on” quasars. Furthermore, detailed SEDs of 64 Palomar-Green quasars show a diversity of shapes, consistent with the physical evolution of the heating sources and the dust distribution around them.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A detailed analysis of the spectrum of I Zw 1 shows that the Narrow Line Region, unlike that of most Seyfert 1 galaxies, is a very low excitation region dominated by both permitted and forbidden Fe II lines. The physical conditions in this region are discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the results of combined Chandra, HST/STIS, and FUSE observations of the intrinsic absorption in the Seyfert 1 galaxy NGC 4151. Our previous studies revealed an unusually large column of outflowing gas, very close to the nucleus, which responds rapidly to changes in the ionizing continuum due to its high density. With the latest observations, we have discovered evidence that the large absorbing column consists of individual high and low ionization components, and that the column density of the latter has decreased due to bulk motion across our line-of-sight. The Chandra spectra have revealed the signature of both very high ionization lines such as H-like and He-like Si, and inner-shell lines from low ionization species which may be associated with the UV absorbers. With the FUSE observations, we have detected lines from less abundant elements, which have permitted us to constrain the physical conditions and covering factors of the UV absorbers. These results indicate a complex and heterogeneous absorbing system, the extreme properties of which are likely the result of a relatively large viewing angle with respect to the accretion-disk axis.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Near-infrared spectroscopic observations in the range 0.8-2.4μm are used to study the kinematics and excitation mechanisms of Molecular Hydrogen and [FeII] lines in a sample of AGNs. The width of H2 lines is narrower than [FeII] lines, therefore they do not originate from the same parcel of gas. The molecular emission is found to be purely thermal but with heating processes which vary among the objects. A clear correlation between H2/Brγ and [FeII] 1.257μm/Paβ is found for our sample objects supplemented with data from the literature. The correlation of these line ratios is a useful diagnostic tool in the NIR to separate emitting line objects by their level of nuclear activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

VLT and NTT spectra are used to examine the nuclear and extended coronal line emission in a sample of well-known Seyfert 1 and 2 galaxies. The excellent spatial resolution obtained with VLT allowed us to map [Si VI] 1.963μm and [Si VII] 2.48μm on scales of up to 20 pc. Coronal line emission, extended to distances of ∼102 pc, is detected in some of the lines analyzed, particularly in [Fe X] 6374Å, [Fe XI] 7891Å, and [Si VII] 2.48μm. Most coronal lines are strongly asymmetric towards the blue and broader than low-ionization lines. This result is particularly important for Circinus, where previous observations have failed to detect larger widths for high-ionization lines. Photoionization models are used to investigate the physical conditions and continuum luminosities necessary to produced the observed coronal emission. We found that an ionization parameter U>0.10 is necessary to reproduce the observations, although the clouds should be located at a distance <30 pc from the central engine.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

For the past 10 years there has been an active debate over whether fast shocks play an important role in ionizing emission line regions in Seyfert galaxies. To investigate this claim, we have studied the Seyfert 2 galaxy Mkn 78, using HST UV/optical images and spectroscopy. Since Mkn 78 provides the archetypal jet-driven bipolar velocity field, if shocks are important anywhere they should be important in this object. Having mapped the emission line fluxes and velocity field, we first compare the ionization conditions to standard photoionization and shock models. We find coherent variations of ionization consistent with photoionization model sequences which combine optically thick and thin gas, but are inconsistent with either autoionizing shock models or photoionization models of just optically thick gas. Furthermore, we find absolutely no link between the ionization of the gas and its kinematic state, while we do find a simple decline of ionization degree with radius. We feel this object provides the strongest case to date against the importance of shock related ionization in Seyferts.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present our recent results from the observation of the O VI λ λ1032,1038 emission doublet in Seyfert galaxies of type 2 with the FUV spectrograph on the FUSE satellite. These observations are part of our investigation to contrast the properties of the OVI emission line and the absorbing outflows in a sample of rigorously matched Seyfert 1s and 2s, in the framework of the Unified Scheme. The OVI emission line is an excellent diagnostic of the outflowing hot gas at temperatures of ∼106K. In the Unified Scheme, Seyferts of type 2 are those whose central regions are obscured by the ubiquitous dusty torus. We interpret our results in this framework.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Low-luminosity nebular emission is found in the centers of a large fraction of galaxies, and in many cases the energy source powering these systems is ambiguous. This is particularly true for H II/LINER “transition” objects, although a reasonable explanation for these sources is that their emission is the composite result of a weak accretion-powered system surrounded by star-forming regions. This contribution describes results from a Hubble Space Telescope spectroscopic survey that probes the structure of nearby transition objects and other emission nuclei. The results provide only limited support for the composite picture for these sources; the emission nuclei do not show a strong tendency for the nebular classification to depend on aperture size. The strongest variations in forbidden line ratios appear to be mediated by a gradient of decreasing nebular density with increasing radius.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We make use of extensive HST optical and VLA radio observations of the Seyfert galaxy Markarian 78 to analyse the properties of the jet flow. Our starting assumption is that the jet's power can be inferred from the energy stored in the radio lobe, and the jet's momentum flux can be inferred from the momentum of the ionized gas. Using the properties of three regions, we derive a jet flow power of ∼1040.5 erg s−1 and momentum flux of ∼1033.5 dyne. Assuming the jet contains both thermal and relativistic material, we find that the thermal component dominates both the jet's luminosity and its momentum flux. We find the jet to be mildly transonic, with speed only a few times that of the [OIII] velocities. The jet is, however, quite dense, with sufficient ram pressure to accelerate the ionized gas to the observed velocities. Over the region lifetime, the jet can provide the thermal component of the lobes, and likely does this by entraining ISM material en route. These jet properties seem, at least to us, to be eminently plausible, suggesting an approach of this kind may be appropriate for other radio quiet objects.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present single-dish observations of a sample of 27 nearby (z<0.018) Seyfert galaxies obtained with the ATNF/Mopra radiotelescope. The total neutral gas content for the sample is derived. We find that Seyfert galaxies are gas-rich objects with a median HI mass to blue luminosity ratio $M_{HI}/L_B\sim 0.38$ M$_\odot$/$L_\odot$, which tends to increase with decreasing optical and far-infrared luminosities. We have also found a correlation among the neutral hydrogen content of Seyfert 2 galaxies and the IRAS luminosities, similar to those found for normal spiral and starburst galaxies. Our results suggest a scenario where the star formation of Seyfert galaxies is similar to that found in starbursts, and that they are dependent of the initial neutral mass content of progenitors of galaxy disks in the blue compact-HII galaxy-Seyfert sequence. Within this sequence, the far-infrared luminosity and the total hydrogen mass correlate as $L_{fir}/L_\odot\propto (M_{HI}/M_\odot)^{1.5\pm 0.4}$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High velocity shocks may provide an important source of ionizing radiation in the NLR of active galaxies. Here we present preliminary results of a new grid of MAPPINGS III shock models for shock velocities up to 1000 km s−1. This grid significantly extends the parameter space covered by the previous models, and will serve as an important component in building multi-process models of the NLR.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We compare recent HST observations of Seyfert and quasar NLRs and find that type–2 AGNs follow a relation consistent with that expected for a distribution of gas ionized by a central source $R_{\rm NLR,2} \propto L^{0.32 \pm 0.05}$, while type–1 objects are fit with a steeper slope of 0.55±0.05. The latter is comparable to the scaling found for the BLR size with continuum luminosity (slope: 0.5–0.7). Therefore, we investigate what we can learn about the BLR size if the NLR size is only determined by the AGN luminosity. We find that NLR and BLR size are related linearly following $R_{\rm BLR} \propto R_{\rm NLR,1}^{0.88 \pm 0.1}$. This relation can be used to estimate BH masses.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html