Extended Coronal Emission Lines in Active Galactic Nuclei

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 [SiVI] 1.963 $\mu$m and [SiVII] 2.48 $\mu$m on scales of up to 20 pc. Coronal line emission, extended to distances of $\sim$100 pc, is detected in some of the lines analyzed, particularly in [FeX] 6374\AA, [FeXI] 7891\AA, and [SiVII] 2.48$\mu$m. 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 had failed at detecting 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 distances < 30 pc.Comment: 4 pages, 6 figures, to appear in proceedings of IAU Symposium No. 222, The Interplay Among Black Holes, Stars and ISM in Galacti Nucle

The central parsecs of active galactic nuclei: challenges to the torus

Type 2 AGN are by definition nuclei in which the broad-line region and continuum light are hidden at optical/UV wavelengths by dust. Via accurate registration of infrared (IR) Very Large Telescope adaptive optics images with optical \textit{Hubble Space Telescope} images we unambiguously identify the precise location of the nucleus of a sample of nearby, type 2 AGN. Dust extinction maps of the central few kpc of these galaxies are constructed from optical-IR colour images, which allow tracing the dust morphology at scales of few pc. In almost all cases, the IR nucleus is shifted by several tens of pc from the optical peak and its location is behind a dust filament, prompting to this being a major, if not the only, cause of the nucleus obscuration. These nuclear dust lanes have extinctions $A_V \geq 3-6$ mag, sufficient to at least hide the low-luminosity AGN class, and in some cases are observed to connect with kpc-scale dust structures, suggesting that these are the nuclear fueling channels. A precise location of the ionised gas H$\alpha$ and [\textsc{Si\,vii}] 2.48 $\mu$m coronal emission lines relative to those of the IR nucleus and dust is determined. The H$\alpha$ peak emission is often shifted from the nucleus location and its sometimes conical morphology appears not to be caused by a nuclear --torus-- collimation but to be strictly defined by the morphology of the nuclear dust lanes. Conversely, [\textsc{Si\,vii}] 2.48 $\mu$m emission, less subjected to dust extinction, reflects the truly, rather isotropic, distribution of the ionised gas. All together, the precise location of the dust, ionised gas and nucleus is found compelling enough to cast doubts on the universality of the pc-scale torus and supports its vanishing in low-luminosity AGN. Finally, we provide the most accurate position of the NGC 1068 nucleus, located at the South vertex of cloud B.Comment: 23 pages, 10 figures, accepted for publication in MNRA

Near-infrared spectroscopy of nearby Seyfert galaxies - II. Molecular content and coronal emission

We present sub-arcsec near-infrared 1.5 - 2.5 micron moderate resolution long-slit spectra of eight nearby Seyfert galaxies (z<0.01), both parallel to the ionization cone and perpendicular to it. These spectra complement similar data on six Seyferts, presented in Reunanen, Kotilainen & Prieto (2002). Large concentrations of molecular gas (H2) are present in the nucleus regardless of the Seyfert type. The spatial extent of the H2 emission is larger perpendicular to the cone than parallel to it in 6/8 (75 %) galaxies, in agreement with the unified models of Active Galactic Nuclei. Broad BrGamma was detected in nearly half of the optically classified Seyfert 2 galaxies, including two objects with no evidence for hidden polarized Broad Line Region. Nuclear [FeII] emission is generally blueshifted which together with high BrGamma/[FeII] ratios suggests shocks as the dominant excitation mechanism in Seyfert galaxies. Bright coronal emission lines [SiVI] and [SiVII] are common in Seyferts, as they are detected in ~60 % of the galaxies. In three galaxies the coronal lines are extended only in the direction parallel to the cone. This could be explained by shock excitation due to the jet or superwind interacting with the interstellar medium.Comment: 19 pages, accepted for publication in MNRA

Optical Surface Photometry of a Sample of Disk Galaxies. II Structural Components

This work presents the structural decomposition of a sample of 11 disk galaxies, which span a range of different morphological types. The U, B, V, R, and I photometric information given in Paper I (color and color-index images and luminosity, ellipticity, and position-angle profiles) has been used to decide what types of components form the galaxies before carrying out the decomposition. We find and model such components as bulges, disks, bars, lenses and rings.Comment: 14 figures. Accepted for publication in A&

Chemical Abundances from the Continuum

The calculation of solar absolute fluxes in the near-UV is revisited, discussing in some detail recent updates in theoretical calculations of bound-free opacity from metals. Modest changes in the abundances of elements such as Mg and the iron-peak elements have a significant impact on the atmospheric structure, and therefore self-consistent calculations are necessary. With small adjustments to the solar photospheric composition, we are able to reproduce fairly well the observed solar fluxes between 200 and 270 nm, and between 300 and 420 nm, but find too much absorption in the 270-290 nm window. A comparison between our reference 1D model and a 3D time-dependent hydrodynamical simulation indicates that the continuum flux is only weakly sensitive to 3D effects, with corrections reaching <10% in the near-UV, and <2% in the optical.Comment: 10 pages, 5 figures, to appear in the proceedings of the conference A Stellar Journey, a symposium in celebration of Bengt Gustafsson's 65th birthday, June 23-27, 2008, Uppsal

Time-resolved infrared emission from radiation-driven central obscuring structures in Active Galactic Nuclei

The central engines of Seyfert galaxies are thought to be enshrouded by geometrically thick gas and dust structures. In this article, we derive observable properties for a self-consistent model of such toroidal gas and dust distributions, where the geometrical thickness is achieved and maintained with the help of X-ray heating and radiation pressure due to the central engine. Spectral energy distributions (SEDs) and images are obtained with the help of dust continuum radiative transfer calculations with RADMC-3D. For the first time, we are able to present time-resolved SEDs and images for a physical model of the central obscurer. Temporal changes are mostly visible at shorter wavelengths, close to the combined peak of the dust opacity as well as the central source spectrum and are caused by variations in the column densities of the generated outflow. Due to the three-component morphology of the hydrodynamical models -- a thin disc with high density filaments, a surrounding fluffy component (the obscurer) and a low density outflow along the rotation axis -- we find dramatic differences depending on wavelength: whereas the mid-infrared images are dominated by the elongated appearance of the outflow cone, the long wavelength emission is mainly given by the cold and dense disc component. Overall, we find good agreement with observed characteristics, especially for those models, which show clear outflow cones in combination with a geometrically thick distribution of gas and dust, as well as a geometrically thin, but high column density disc in the equatorial plane.Comment: 16 pages, 12 figures, accepted for publication in MNRA