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We study the ionised and highly ionised gas phases in the Seyfert~2 galaxy IC~5063 by means of VLT/MUSE integral field spectroscopy. Our analysis allowed us to detect a high-ionisation gas outflow traced by the coronal lines [\ion{Fe}{vii}]~$\lambda$6087 and [\ion{Fe}{x}]~$\lambda$6375. Both emissions are found to be extended. The former up to 1.2~kpc and 700~pc NW and SE from the nucleus, respectively. The latter reaches 700~pc NW of the nucleus. This is the first time that [\ion{Fe}{x}] emission is observed at such distances from the central engine in an active galactic nucleus. The [\ion{Fe}{vii}]~$\lambda$6087 emission peaks at the nucleus, with two secondary peaks at the position of the NW and SE radio-lobes. The gas kinematics is complex, with the coronal emission displaying split line profiles along the radio jet and line widths of several hundreds km~s$^{-1}$. Velocity shifts of up to 600~km~s$^{-1}$ in excess of the systemic velocity of the galaxy are found very close to the radio lobes and along the jet propagation. The extended coronal gas is characterised by temperatures reaching 20000~K and electron densities $>10^2$~cm$^{-3}$, with the larger values associated to the regions of larger turbulence, likely due to the passage of the radio jet. This hypothesis is supported by photoionisation models that combine the effects of the central engine and shocks. Our work highlights the strong relationship between extended coronal emission and the radio jet, with the former suitably tracing the latter, which in the case of IC~5063, propagates very close to the galaxy disc., Comment: 18 pages and 14 figures, accepted for publication in MNRAS

We employ MUSE/VLT data to study the ionised and highly ionised gas phases of the feedback in Circinus, the closest Seyfert 2 galaxy to us. The analysis of the nebular emission allowed us to detect a remarkable high-ionisation gas outflow beyond the galaxy plane traced by the coronal lines [Fe VII] $\lambda$6089 and [Fe X] $\lambda$6374, extending up to 700 pc and 350 pc NW from the nucleus, respectively. This is the first time that the [Fe X] emission is observed at such distances from the central engine in an AGN. The gas kinematics reveals expanding gas shells with velocities of a few hundred km s$^{-1}$, spatially coincident with prominent hard X-ray emission detected by Chandra. Density and temperature sensitive line ratios show that the extended high-ionisation gas is characterized by a temperature reaching 25000 K and an electron density > 10$^2$ cm$^{-3}$. We found that local gas excitation by shocks produced by the passage of a radio jet leads to the spectacular high-ionisation emission in this object. This hypothesis is fully supported by photoionisation models that accounts for the combined effects of the central engine and shocks. They reproduce the observed emission line spectrum at different locations inside and outside of the NW ionisation cone. The energetic outflow produced by the radio jet is spatially located close to an extended molecular outflow recently reported using ALMA which suggests that they both represent different phases of the same feedback process acting on the AGN., Comment: 24 pages, 25 figures. Accepted for publication in MNRAS

We build detailed composite models of photoionization and shock ionization based on the SUMA code to reproduce emission lines emitted from the Narrow Line Regions (NLR) of Seyfert 2 nuclei. The aim of this work is to investigate diagram AGN positions according to shock parameters, shock effects on the gas temperature and ionization structures and derive a semi-empirical abundance calibration based on emission-line ratios little sensitive to the shock presence. The models were used to reproduce optical (3000 < A < 7000) emission line intensities of 244 local (z < 0.4) Seyfert 2s, whose observational data were selected from Sloan Digital Sky Survey DR7. Our models suggest that shocks in Seyfert 2 nuclei have velocities in the range of 50-300 km/s and imply a narrower metallicity range (0.6 < (Z/Z) < 1.6) than those derived using pure photoionization models. Our results indicate that shock velocity in AGNs can not be estimated using standard optical line ratio diagrams, based on integrated spectra. Our models predict a different temperature structure and O+/O and O2+/O fractional abundances throughout the NLR clouds than those derived from pure photoionization models, mainly in shock-dominated objects. This suggests that, in order to minimize the shock effects, the combination of emission-lines emitted by ions with similar intermediate ionization potential could be good metallicity indicators. Finally, we derive two calibrations between the N/O abundance ratio and the N2O2=log([N II]6584/[O II]3727) and N2=log([N II]6584/H{\alpha}) indexes which agree with that derived from pure photoionization models., Comment: 15 pages, 15 figures. Accepted for publication in MNRAS

We have modelled the line ratios and the continuum spectral energy distribution (SED) of the short gamma-ray burst GRB100628A host galaxy complex. The results suggest that an active galactic nucleus (AGN) and a star-burst (SB) coexist in Nicuesa Guelbenzu et al.'s 'galaxy C'. The AGN spectrum is explained by a relatively strong flux. Two of the observed regions (blobs) are located in the ISM, outside the AGN photoionization cones. The strongest Hb line flux calculated by a SB dominated model was found in the tidal tail of galaxy C, while the strongest Hb line flux calculated by an AGN dominated model was found in the galaxy C bulk. O/H element abundances are near solar everywhere, while N/H spans a factor of ~10. The radio data have different origins, thermal bremsstrahlung and reprocessed radiation by dust. The infrared-optical photometric data measured from Nicuesa Guelbenzu et al.'s 'galaxy D', located outside the X-ray telescope (XRT) error circle, are reproduced by a black-body flux at 3000 K. This flux may represent the radiation of the underlying old star population observed throughout the SED in the infrared. AGNs in other SGRB hosts are investigated., Comment: 14 pages, 5 figures. arXiv admin note: text overlap with arXiv:1907.06175

We studied the properties of the gas of the extended narrow line region (ENLR) of two Seyfert 2 galaxies: IC 5063 and NGC 7212. We analysed high resolution spectra to investigate how the main properties of this region depend on the gas velocity. We divided the emission lines in velocity bins and we calculated several line ratios. Diagnostic diagrams and SUMA composite models (photo-ionization + shocks), show that in both galaxies there might be evidence of shocks significantly contributing in the gas ionization at high |V|, even though photo-ionization from the active nucleus remains the main ionization mechanism. In IC 5063 the ionization parameter depends on V and its trend might be explained assuming an hollow bi-conical shape for the ENLR, with one of the edges aligned with the galaxy disk. On the other hand, NGC 7212 does not show any kind of dependence. The models show that solar O/H relative abundances reproduce the observed spectra in all the analysed regions. They also revealed an high fragmentation of the gas clouds, suggesting that the complex kinematics observed in these two objects might be caused by interaction between the ISM and high velocity components, such as jets., Comment: 29 pages, 32 figures, accepted for publication in MNRAS

The distribution of N/O abundance ratios calculated by the detailed modelling of different galaxy spectra at z<4 is investigated. Supernova (SN) and long gamma-ray-burst (LGRB) host galaxies cover different redshift domains. N/O in SN hosts increases due to secondary N production towards low z (0.01) accompanying the growing trend of active galaxies (AGN, LINER). N/O in LGRB hosts decreases rapidly between z>1 and z ~0.1 following the N/H trend and reach the characteristic N/O ratios calculated for the HII regions in local and nearby galaxies. The few short period GRB (SGRB) hosts included in the galaxy sample show N/H <0.04 solar and O/H solar. They seem to continue the low bound N/H trend of SN hosts at z<0.3. The distribution of N/O as function of metallicity for SN and LGRB hosts is compared with star chemical evolution models. The results show that several LGRB hosts can be explained by star multi-bursting models when 12+log(O/H) <8.5, while some objects follow the trend of continuous star formation models. N/O in SN hosts at log(O/H)+12 <8.5 are not well explained by stellar chemical evolution models calculated for starburst galaxies. At 12+log(O/H) >8.5 many different objects are nested close to O/H solar with N/O ranging between the maximum corresponding to starburst galaxies and AGN and the minimum corresponding to HII regions and SGRB., Comment: 17 pages, 7 figures, to be published in the MNRAS

We revisited the line spectra emitted from long GRB (LGRB) host galaxies at z<0.5 in order to calculate by the detailed modelling of the line ratios the physical conditions and relative abundances in LGRB hosts in this redshift range. We have found lower metallicities than in LGRB hosts at higher z. New results about metallicities and physical conditions in the different regions throughout the LGRB 980425 host at z=0.0085 are presented. In particular, we have found that the effective starburst temperature in the supernova (SN) region is the highest throughout the host galaxy. The low ionization parameter reveals that the radiation source is far or somehow prevented from reaching the emitting gas in the SN region. The models constrained by a few oxygen, nitrogen and sulphur line ratios to Hb in LGRB 980425 host satisfactorily reproduce the HeII/Hb and [ArIII]/Hb line ratios. The modelling of the observed [SIV]10.51\mu/[SIII]18.71\mum and [NeIII]10.6\mum/[NeII]12.81\mum line ratios from LGRB 031203 host galaxy at z=0.105 shows that the mid-IR lines are emitted from geometrically thin shock dominated filaments which are not reached by the photoionizing flux, while the optical lines are emitted from the radiation dominated outflowing clouds., Comment: 13 pages, 6 figures, accepted for publication in the MNRAS

We analyze by detailed modelling the spectra observed from the sample galaxies at z$\sim$0.8 presented by Ly et al (2015), constraining the models by the [OIII]5007+4959/[OIII]4363 line ratios. Composite models accounting for shock and photoionization by AGN or starburst are adopted. O/H are about solar for all the objects, except for a few AGN clouds with O/H= 0.3 -0.5 solar. Starburst models reproduce most of the data within the observational errors. About half of the object spectra are well fitted by an accreting AGN. Some galaxies show multiple radiation sources, such as starburst+AGN, or a double AGN., Comment: 9 pages, 6 figures, accepted for publication in MNRAS

We compare the physical parameters and the relative abundances calculated throughout supernova (SN) and gamma-ray burst (GRB) host galaxies by the detailed modelling of the spectra. The results show that : 1) shock velocities are lower in long period GRB (LGRB) than in SN host galaxies. 2) O/H relative abundance in SN hosts are scattered within a range 8.0 <12+log(O/H)<8.85 but they are close to solar in LGRB hosts. N/H are lower than solar for both SN and LGRB. 3) The starburst temperatures within a few SN hosts reach Ts >10^5 K. Ts in LGRB hosts are 3-8 10^4 K. 4) Ha increases with the ionization parameter U. We suggest that SN-host symbiosis is stronger in terms of host galaxy activity than GRB-host in the range of energies related to the near UV - optical - near IR spectra., Comment: 20 pages, 9 figures. Accepted for publication in the MNRAS

We present the results of a meeting on numerical simulations of ionized nebulae held at the University of Kentucky in conjunction with the celebration of the 70th birthdays of Profs. Donald Osterbrock and Michael Seaton., Comment: http://adsabs.harvard.edu/abs/1995aelm.conf...83F. The Analysis of Emission Lines, Proc. STScI Symposium May 16--18, 1994, Eds. R.E. Williams & M. Livio, Cambridge University Press, p. 83

We explore the origin of the observed Lya and other UV lines from galaxies at z<3.7 by detailed modelling of the spectra. The objects are chosen among those showing a) UV-optical-near-IR lines, b) only UV lines and c) those showing Lya in the UV and a few optical lines. We also present UV line predictions for a sample of galaxies in the 0.06861000 km/s) component of the emitting gas is accompanied by relatively low preshock densities (n0 ~100-400 cm^-3) leading in some cases to broad forbidden lines. Some spectra are best reproduced by shock dominated models in which the photoionizing source is hidden or absent. Within more than 50 galaxies modelled in this work, only a few spectra from galaxies at z~2.5 correspond to a starburst temperature Ts>10^5 K, similar to that found in galaxies showing some activity., Comment: 17 pages, 9 figures, submitted

We investigate 'activity' and 'quiescence' in galaxies at relatively high redshifts by modelling the line(and continuum) spectra of each object. The models account consistently for photoionization and shocks. We claim that the starburst effective temperature, the flux from an AGN, and the shock velocity are critical to activity. The results confirm that two sample galaxies show intense starburst activity with temperatures reaching Ts=2x10^5K and shock velocities Vs> 250 km/s, while for the remaining galaxies of our sample the models show quiescent star formation with Ts< 7x10^4K. A Seyfert 2 like AGN is proposed in one galaxy. The O/H relative abundances derived by the detailed modelling of the spectra are nearly solar for all the sample galaxies, in contrast to those obtained by direct methods., Comment: 5 pages, 3 figures, in press in A&A

We present the detailed modelling of line spectra emitted from galaxies at redshifts 0.2

We have collected an heterogeneous sample of galaxies at redshifts 0.0010.35. 6) Metallicity (in terms of O/H) correlates with Ha luminosity (La) and therefore with the star formation rate with different trends regarding SBs and AGNs for La > 10^{41} erg s^{-1}. A rough correlation is seen also for N/H. There seems to be no correlation for low luminosity galaxies., Comment: 13 pages, 3 figures, submitted to the MNRAS

We revisit the spectra observed by Ramos Almeida et al. (2013) from an homogeneous sample of galaxies at 0.27

The line and continuum spectra of the merger galaxy Arp 220 are analysed with the aim of investigating the ionizing and heating sources. We refer to radio, optical, infrared and X-ray spectra. The results show that in agreement with other merger galaxies, the optical lines are emitted from gas photoionised by the AGN and heated by the shocks in the extended NLR. The infrared lines are better explained by the emission from gas close to the starburst. The starburst dominates the infrared emission. [OI] and [CI] lines in the far-infrared are formed in the internal region of extended clouds and are therefore absorbed, while [CII] lines are emitted from the external edges of outflowing clouds. The O/H relative abundances are about solar and N/H are higher than solar by a factor of 1.5, throughout the starburst region, while in the AGN extended NLR the O/H ratio is half solar. A relatively high dust-to-gas ratio is indicated by modelling the dust reprocessed radiation peak consistently with bremsstrahlung emitted from the clouds. The observed radio emission is thermal bremsstrahlung, while synchrotron radiation created by the Fermi mechanism at the shock front is absorbed., Comment: 15 pages, 8 figures, accepted for publication in the MNRAS

We have calculated the physical conditions throughout the NLR of the merger Seyfert galaxy NGC 6240 by modelling the observed optical and infrared line ratios. We have found that the optical spectra are emitted by clouds photoionised by the power-law radiation flux from the AGN (or AGNs), and heated mainly by the shock accompanying the propagation of the clouds outwards. The infrared line ratios are emitted from clouds ejected from a starburst which photoionises the gas by the black-body radiation flux corresponding to a stellar colour temperature of about 50,000 K. Both the flux from the AGN and the ionization parameters are low. The most characteristic physical parameters are the relatively high shock velocities (>400 km/s) and low preshock densities (about 40-60 cm-3) of the gas. The C/H, N/H, O/H relative abundances are higher than solar by a factor lower or about 1.5. We suggest that those high relative abundances indicate trapping of H into H2 molecules rather than high metallicities. Adopting an initial grain radius of 1 micron, the dust temperatures calculated in the clouds reached by the power-law radiation flux and by the black-body radiation flux are 81 K and 68 K, respectively., Comment: 14 pages, 5 figures, accepted for publication in MNRAS

The latest observations of line and continuum spectra emitted from the extended narrow line region (ENLR) of the Seyfert 2 galaxy NGC 7212 are analysed using models accounting for photoionization from the active nucleus and shocks. The results show that relatively high (500--800 \kms) shock velocities appear on the edge of the cone and outside of it. The model-inferred AGN flux, which is lower than $10^{-11}$ photons cm$^{-2}$ s$^{-1}$ eV$^{-1}$ at the Lyman limit, is more typical of low-luminosity AGN, and less so for Seyfert 2 galaxies. The preshock densities are characteristic of the ENLR and range between 80--150 cm$^{-3}$. Nitrogen and sulphur are found depleted by a factor lower than 2, particularly at the eastern edge. Oxygen is depleted at several locations. The Fe/H ratio is approximately solar, whereas the Ne/H relative abundance is unusually high, 1.5--2 times the solar value. Modelling the continuum spectral energy distribution (SED), we have found radio synchrotron radiation generated by the Fermi mechanism at the shock front, whereas the X-rays are produced by the bremsstrahlung from a relatively high temperature plasma., Comment: 17 pages, 14 figures, accepted for publication in A&A

The discovery of two active black holes in the Seyfert galaxy NGC 3393, separated by about 490 light years, revealed a merging event. This led us to look for other evidences of galaxy collision and merging through the analysis of the observed spectra in different frequency ranges. We found preshock densities higher by a factor of about 10 in the NGC 3393 NLR than in other AGN and patches of ionized matter beyond the observed NLR bulk. They can be explained by compression and heating of the gas downstream of shock waves created by collision. Metallicity in terms of the O/H relative abundance, is about 0.78 solar. Mg/H depletion by a factor of about 3 compared with solar cannot be explained by Mg trapping into dust grains, due to rather high shock velocities. The low O/H and Mg/H abundances indicate mixing with external matter during collision. Twice solar N/H is predicted by modelling the spectra of high shock velocity clouds reached by a Ts =8.6 10^4 K black-body flux. This suggests that Wolf-Rayet stars could be created by galaxy collision in the central region., Comment: 11 pages, 3 figures, 3 tables, accepted for publication in MNRAS

The observations of FIR line and continuum spectra throughout the Galactic centre and in some regions of the disc are analysed in order to determine the physical conditions (densities, shock velocities, radiation parameters, etc.) and the relative abundances of some elements (C, N, and O). The models account for the coupled effect of photoionization and shocks. Consistent model calculations of the line and continuum spectra show that, although the radiation from the stars dominates, an active galactic nucleus (AGN) is clearly present, with a radiation maximum in the Sgr A* region. The flux, similar to that found for low luminosity AGN (LLAGN), is lower by a factor of about 100 than that of AGN., Comment: 11 pages, 8 figures, submitted to MNRAS

The visual magnitude profile of the symbiotic system Z And during the 1984-1986 activity period appears double peaked and the flux intensity is low compared to outbursts in other epochs. The detailed modeling of the observed spectra, accounting for the shells ejected by the red giant star, shows that the outburst is intrinsically single but distorted by the collision at different phases of the white dwarf wind with two close shells., Comment: 16 pages, 3 figs., accepted for publication in New Astr

The spectra emitted from clouds near the Galactic Centre are investigated calculating the UV-optical-IR lines using the physical parameters and the element abundances constrained by the fit of mid-IR observations. The characteristic line ratios are compared with those observed in active galaxies. We have found that the physical conditions in the nebulae near the GC are different from those of starburst galaxies and AGN, namely, gas velocities and densities as well as the photoionization fluxes are relatively low. The geometrical thickness of the emitting nebulae is particularly small suggesting that matter is strongly fragmented by instabilities leading to an underlying shock-generated turbulence., Comment: 16 pages, 11 figures, 4 Tables. MNRAS, accepted

We have collected continuum data of a sample of D-type symbiotic stars. By modelling their spectral energy distribution in a colliding-wind theoretical scenario we have found the common characteristics to all the systems: 1) at least two dust shells are clearly present, one at \sim 1000 K and the other at \sim 400 K; they dominate the emission in the IR; 2) the radio data are explained by thermal self-absorbed emission from the reverse shock between the stars; while 3) the data in the long wavelength tail come from the expanding shock outwards the system; 4) in some symbiotic stars, the contribution from the WD in the UV is directly seen. Finally, 5) for some objects soft X-ray emitted by bremsstrahlung downstream of the reverse-shock between the stars are predicted. The results thus confirm the validity of the colliding wind model and the important role of the shocks. The comparison of the fluxes calculated at the nebula with those observed at Earth reveals the distribution throughout the system of the different components, in particular the nebulae and the dust shells. The correlation of shell radii with the orbital period shows that larger radii are found at larger periods. Moreover, the temperatures of the dust shells regarding the sample are found at 1000 K and <=400 K, while, in the case of late giants, they spread more uniformly throughout the same range., Comment: 14 pages, 7 figures, 5 tables. Accepted for publication in MNRAS

We present consistent modelling of line and continuum IR spectra in the region close to the Galactic center. The models account for the coupled effect of shocks and photoionization from an external source. The results show that the shock velocities range between 65 and 80 km/s, the pre-shock densities between 1 cm-3 in the ISM to 200 cm-3 in the filamentary structures. The pre-shock magnetic field increases from 5. 10^{-6} gauss in the surrounding ISM to ~8. 10^{-5} gauss in the Arched Filaments. The stellar temperatures are ~38000 K in the Quintuplet cluster and ~27000 K in the Arches Cluster. The ionization parameter is relatively low (<0.01) with the highest values near the clusters, reaching a maximum >0.01 near the Arches Cluster. Depletion from the gaseous phase of Si is found throughout the whole observed region, indicating the presence of silicate dust. Grains including iron, are concentrated throughout the Arched Filaments. The modelling of the continuum SED in the IR range, indicates that a component of dust at temperatures of ~100-200 K is present in the central region of the Galaxy. Radio emission appears to be thermal bremsstrahlung in the E2-W1 filaments crossing strip, however a synchrotron component is not excluded. More data are necessary to resolve this questions., Comment: accepted for publication in the MNRAS

MASYS is the AKARI spectroscopic survey of Symbiotic Stars in the Magellanic Clouds, and one of the European Open Time Observing Programmes approved for the AKARI (Post-Helium) Phase-3. It is providing the first ever near-IR spectra of extragalactic symbiotic stars. The observations are scheduled to be completed in July 2009., Comment: 4 pages, 1 table. To appear in the Proceedings of the Conference "AKARI, a light to illuminate the misty Universe", Fukutake Hall, The University of Tokyo, Japan, 16-19 February 2009

We investigate the symbiotic star BI Crucis through a comprehensive and self-consistent analysis of the spectra emitted in three different epochs: 60's, 70's, and late 80's. In particular, we would like to find out the physical conditions in the shocked nebula and in the dust shells, as well as their location within the symbiotic system, by exploiting both photometric and spectroscopic data from radio to UV. We suggest a model which, on the basis of optical imaging, emission line ratios and spectral energy distribution profile, is able to account for collision of the winds, formation of lobes and jets by accretion onto the WD, as well as for the interaction of the blast wave from a past, unrecorded outburst with the ISM. We have found that the spectra observed throughout the years show the marks of the different processes at work within BI Cru, perhaps signatures of a post-outburst evolution. We then call for new infrared and millimeter observations, potentially able to resolve the inner structure of the symbiotic nebula., Comment: 13 pages, 9 figures, 2 tables; accepted for publication in MNRAS

Context. In 1985, at the end of the active phase 1977-1986, a broad (4000 km/s) Ly alpha line appeared in the symbiotic system CH Cygni that had never been observed previously. Aims. In this work we investigate the origin of this anomalous broad Ly alpha line. Methods. We suggest a new interpretation of the broad Ly alpha based on the theory of charge transfer reactions between ambient hydrogen atoms and post-shock protons at a strong shock front. Results. We have found that the broad Ly alpha line originated from the blast wave created by the outburst, while the contemporary optical and UV lines arose from the nebula downstream of the expanding shock in the colliding wind scenario., Comment: 5 pages, 2 figures, accepted for publication in A&A on 7th April 2008

Context. We analyse the line and continuum spectra of the symbiotic system CH Cygni. Aims. To show that the colliding-wind model is valid to explain this symbiotic star at different phases. Methods. Peculiar observed features such as flickering, radio variation, X-ray emission, as well as the distribution of the nebulae and shells throughout the system are investigated by modelling the spectra at different epochs. The models account consistently for shock and photoionization and are constrained by absolute fluxes. Results. We find that the reverse shock between the stars leads to the broad lines observed during the active phases, as well as to radio and hard X-ray emission, while the expanding shock is invoked to explain the data during the transition phases., Comment: 16 pages, 11 figures, 10 tables, submitted to A&A on 5th December 2007

The dust-to-gas ratios in three different samples of luminous, ultraluminous, and hyperluminous infrared galaxies are calculated by modelling their radio to soft X-ray spectral energy distributions using composite models which account for the photoionizing radiation from HII regions, starbursts, or AGNs, and for shocks. The models are limited to a set which broadly reproduces the mid-IR fine structure line ratios of local, IR bright, starburst galaxies. The results show that two types of clouds contribute to the IR emission. Those characterized by low shock velocities and low preshock densities explain the far-IR dust emission, while those with higher velocities and densities contribute to mid-IR dust emission. An AGN is found in nearly all of the ultraluminous IR galaxies and in half of the luminous IR galaxies of the sample. High IR luminosities depend on dust-to-gas ratios of about 0.1 by mass, however, most hyperluminous IR galaxies show dust-to-gas ratios much lower than those calculated for the luminous and ultraluminous IR galaxies., Comment: 19 pages+ 7 figures. in press in AN

In this paper we analyse the spectra of D-type SS H1-36 within a colliding-wind scenario. We aim to analyse the properties of this object taking into account the observational data along the whole electromagnetic spectrum, in order to derive a self-consistent picture able to interpret the nature of the system as a whole. After constraining the relative physical conditions by modelling more than 40 emission lines from radio to UV, we are able to explain the continuum spectral energy distribution by taking into account all the emitting contributions arising from both the stars, the dust shells and the gaseous nebulae. A comprehensive model of the radio spectra allows to reproduce the different slopes of the radio profile and the turnover frequency, as well as the different size of the observed shocked envelope at different frequencies in the light of the different contributions from the expanding and reverse nebulae. The IR continuum unveils the presence of two dust shells with different radii and temperatures, which might be a distinctive feature of D-type symbiotic systems as a class of objects. The broad profiles of IR lines direct us to investigate whether an X-ray jet may be present. This insight leads us to indicate H1-36 as a promising X-ray target and to encourage observations and studies which consistently take into account the complex nature of symbiotic stars throughout the whole electromagnetic spectrum., Comment: 8 pages, 3 figures, 5 tables, accepted for publication in A&A on 2th May 2007

We present a comprehensive and self-consistent modelling of the D' type symbiotic star (SS) HD330036 from radio to UV. Within a colliding-wind scenario, we analyse the continuum, line and dust spectra by means of SUMA, a code that simulates the physical conditions of an emitting gaseous cloud under the coupled effect of ionization from an external radiation source and shocks. We find that the UV lines are emitted from high density gas between the stars downstream of the reverse shock, while the optical lines are emitted downstream of the shock propagating outwards the system. As regards with the continuum SED, three shells are identified in the IR, at 850K, 320 K and 200 K with radii r = 2.8 10^13 cm, 4 10^14$ cm, and 10^15 cm, respectively, adopting a distance to Earth d=2.3 kpc: interestingly, all these shells appear to be circumbinary. The analysis of the unexploited ISO-SWS spectrum reveals that both PAHs and crystalline silicates coexist in HD330036, with PAHs associated to the internal shell at 850 K, and crystalline silicates stored into the cool shells at 320 K and 200 K. Strong evidence that crystalline silicates are shaped in a disk-like structure is derived on the basis of the relative band strengths. Finally, we suggest that shocks can be a reliable mechanism in activating the annealing and the consequent crystallization processes. We show that a consistent interpretation of gas and dust spectra emitted by SS can be obtained by models which accounts for the coupled effect of the photoionizing flux and of shocks. The VLTI/MIDI proposal recently accepted by ESO aims to verify and better constrain some of our results by means of IR interferometric observations., Comment: 11 pages, 5 figures, accepted for publication in A&A on 10th May 2007

We investigate the IR spectral features of a sample of D-type symbiotic stars. Analyzing unexploited ISO-SWS data, deriving the basic observational parameters of dust bands and comparing them with respect to those observed in other astronomical sources, we try to highlight the effect of environment on grain chemistry and physic. We find strong amorphous silicate emission bands at 10 micron and 18 micron in a large fraction of the sample. The analysis of the 10 micron band, along with a direct comparison with several astronomical sources, reveals that silicate dust in symbiotic stars shows features between the characteristic circumstellar environments and the interstellar medium. This indicates an increasing reprocessing of grains in relation to specific symbiotic behavior of the objects. A correlation between the central wavelength of the 10 and 18 micron dust bands is found. By the modeling of IR spectral lines we investigate also dust grains conditions within the shocked nebulae. Both the unusual depletion values and the high sputtering efficiency might be explained by the formation of SiO moleculae, which are known to be a very reliable shock tracer. We conclude that the signature of dust chemical disturbance due to symbiotic activity should be looked for in the outer, circumbinary, expanding shells where the environmental conditions for grain processing might be achieved. Symbiotic stars are thus attractive targets for new mid-infrared and mm observations., Comment: 24 pages, 6 figures, 5 tables - to be published in AJ

We present the first spectroscopic observations in the interval 0.8-4.0 microns, complemented with HST/UV and optical spectroscopy, of the narrow line Seyfert 1 galaxy Mrk766. The NIR spectrum is characterized by permitted lines of HI, HeI, HeII and FeII, and forbidden lines of [SII], [SIII] and [FeII] among others. High ionized species such as [SiIX], [SiX], [SIX] and [MgVII] are also observed. The continuum has a complex shape, with contribution of the central engine, circumnuclear stellar population and dust. This last component is evidenced by the presence of an excess of emission peaking at 2.25 microns, fitted by blackbody function with T_bb=1200K. That temperature is close to the evaporation temperature of graphite grains. As such, it provides strong evidence of hot dust, probably very close to the nucleus. Consistent modeling of the line and broad band continuum spectrum by composite models, which account for the photoionizing flux of the central engine and shocks, shows that the shock velocities are between 100 and 500 km/s, the preshock densities between 100 and 1000 cm^-3 and the radiation fluxes from the active centre between 10^9 and 5x10^12 photons cm^-2 s^-1 eV^-1 at 1 Ryd with spectral indices $\alpha_{UV}$=-1.5 and $\alpha_X$=-0.4. Adopting silicon grains, dust-to-gas ratios are between 10^-{6} and 4x10$^{-4}$ by mass. The emitting clouds are at an average distance of 160 pc from the centre, with high velocity clouds closer and low velocity clouds farther from the centre. The N/H relative abundance could be twice solar. In constrast, Fe is depleted from the gaseous phase by a factor >2. Ratios of calculated to observed line ratios to Hbeta indicate an average contribution of the broad line region to the observed Hbeta of about 40%., Comment: 15 pages, 6 figures. Accepted to MNRAS

Spectroscopic and imaging data of the peculiar galaxy Mkn 298 are presented in this paper. Narrow-band Halpha and broad-band R images are used to study the star formation rate in the galaxy and its morphology, which is typical of a merging system. Long-slit and integral field spectra are used to assess the kinematics of gas and stars, and the nature of the ionizing source at different distances from the nucleus. In particular, the nucleus of Mkn 298 is characterized by peculiar line ratios: [NII] 6583/Halpha is typical of HII-like regions, while [OI] 6300/Halpha could indicate the presence of an active galactic nucleus. We show that models where a shock component is added to photoionization from a starburst allow to reproduce the observed line ratios. Mkn 298 is thus most likely a star forming galaxy, rather than a galaxy hosting an active nucleus., Comment: 9 figures, 12 pages, accepted for publication on Astronomy & Astrophysics

A new method to evaluate the dust-to-gas ratios in the Kepler SNR is presented. Dust emission in the infrared and bremsstrahlung are calculated consistently, considering that dust grains are collisionally heated by the gas throughout the front and downstream of both the expanding and the reverse shocks. The dust-to-gas ratios are determined by the ratio of the dust emission bump and bremsstrahlung in the infrared. A maximum dust mass < 0.16 Mo is calculated., Comment: 12 pages+5 figures, accepted for publication in A&A

We discuss the different physical processes contributing to the infrared continuum of AGN, assuming that both photoionization from the active center and shocks ionize and heat the gas and dust contained in an ensemble of clouds surrounding the nucleus. Radiation transfer of primary and secondary radiation throughout a cloud is calculated consistently with collisional processes due to the shock. We consider that the observed continuum corresponds to reprocessed radiation from both dust and gas in the clouds. The model is applied to the continuum of Seyfert galaxies from which best estimate of the nuclear, stellar subtracted, emission is available. The results show that radiation-dominated high velocity clouds are more numerous in Seyfert 1-1.5 whereas shock-dominated low velocity clouds are dominant in Seyfert type 2 in full agreement with the unified model for AGN. In type 2 objects, radiation is partly suppressed by a central dusty medium with a high dust-to-gas ratio. A grid of models is used to provide a phenomenological analysis of the observed infrared spectral energy distribution., Comment: 14 pages, 10 figures. in press in MNRAS

The correlation between the soft X-ray and near infrared emission from AGN is analysed using composite models by the code SUMA. We find new evidences for differences in ranges of parameters which characterize the NLR of Seyfert galaxies and LINERs. Results obtained by modelling the Einstein and the ROSAT samples of galaxies are in full agreement. In order to fit the infrared and X-ray continua, an eta factor is defined, which accounts for the emitting area of the cloud. If the infrared emission is due to bremsstrahlung and comes from the same cloud producing the soft X-rays, the eta values obtained from both emissions must be the same. Therefore, if eta_IR < eta_soft-X there must be a strong contribution of soft X-rays from the active centre. From the eta values we expect to identify the objects that could present strong variability. \, Comment: 11 pages,13 figures, in press in MNRAS. in press in MNRAS

We present recent results from spectroscopic data and modeling of the biconical ionized gas in the Seyfert-2 galaxy NGC 4388. A field of ~2.6 x 2.4 kpc centered on the nucleus has been observed by means of the modern technique of integral field spectroscopy. The analysis of more than two hundred spectra allowed to study the physical characteristics of the gas in the surroundings of the active nucleus. The South-West ionization cone, revealed by the [O III]5007/H-beta excitation map, shows high emission line ratios not completely supported by simple photoionization. Composite models which account for the combined effects of photoionization and shock show that such high [O III]/H-beta line ratios are emitted by low density (n_0=30 cm^-3) gas inside large (D > 1 pc) shocked clouds (V_s=100 km/s) reached by a relatively low flux from the active nucleus. The data of the VEELR in the North-East cone by Yoshida et al. (2002) have been modeled. The results confirm that photoionization is the prevailing mechanism, but nontheless weak shocks are under way between colliding clouds with small (< 1 pc) sizes and low densities n_0 <= 100 cm^-3, moving outward at relatively low velocities (V_s=100 km/s)., Comment: Accepted for publication in Astronomy & Astrophysics

Detailed modeling of the different regions of NGC 7130 is presented, accounting for its composite nature of AGN and starburst galaxy. Shock waves, created by stellar winds from hot massive stars and by supernova ejecta, are evident in the continuum and line spectra emitted from the clouds. The AGN starburst connection is discussed on the basis of model results, considering in particular the distribution of densities and velocities throughout the galaxy., Comment: 36 pages +10 figures PostScript To appear in The Astrophysical Journal

The multiwavelength emission spectrum and associated velocity field of the Seyfert prototype NGC 4151 is modeled. HST data has impressively revealed the existence of a large range of velocities (100 - 1500 \kms) dominating the emitting clouds in the extended emission line region of the galaxy. Following this observational result, a revision of the photoionization modeling approach applied to NGC 4151 is presented. It is concluded that a mixture of radiation dominated clouds and shock dominated clouds are required to explain the multiwavelength line and continuum spectra of the galaxy., Comment: 16 pages, LaTeX class for Astronomy and Astrophysics (including 3 Tables) + 8 PostScript figures. To appear in "Astronomy and Astrophysics"

The spectra of both the inner and outer nebulae in He2-104 are modelled by composite models which accounts consistently for photoionisation and shocks. The temperature of the hot star results Ts = 130 000 K. We suggest that the characteristic "crab legs" in He2-104 are produced by R-T instability at the shock front. The calculated X-ray flux is below the detection limit of ROSAT., Comment: MS10595.tex (AA vers.), MS10595f1.jpg, MS10595f2.eps. Accepted for publication in A&A

A grid of models for starburst spectra is presented and compared with power-law models which represent AGNs. The models are composite, i.e., they account for the radiation from the starburst and for the shocks created by super-winds. Some interesting fit of models to observations are also discussed. In particular, it is found that [OIII]/Hb ~can reach values as high as for the AGN when the emitting clouds are close to the starburst region. Moreover CIV lines can be high even if SiIV lines are relatively low. It is found that for some line ratios, which have similar values for starburst and AGN models, the width of the lines can distinguish between the two types., Comment: grpaper.tex + 10 tables PostScript + 9 figures PostScript Accepted for publication in ApJS

A grid of composite models for the narrow line region of active galaxies, which consistently account for both the effect of a photoionizing radiation from the active center and of a shock front, is presented. Theoretical results, calculated with the SUMA code, are given for different values of shock velocities, preshock densities, geometrical thickness of the clouds, and, particularly, for the ionizing radiation intensity in a large range. The input parameters are chosen within the ranges indicated by previous fits of several observed emission-line and continuum spectra from active galaxies. Shock velocities from 100 \kms ~to 1500 \kms ~and preshock densities from 100 \cm3 to 1000 \cm3 are considered. The line intensities of the most important ultraviolet, optical and infrared transitions are obtained and are listed in several tables., Comment: 14 pages Latex + 2 Postscript tables + 1 Postscript figures

This paper aims to understand the continuum of Seyfert 2 galaxies. By fitting the single galaxies in the sample of Heckman et al. (1995) with composite models (shock+ photoionization from the active center), we show that five main components characterize the SED of the continuum. Shocks play an important role since they produce a high temperature zone where soft X-rays are emitted. We show that in the optical-UV range, the slope of the NLR emission reproduces the observed values, and may be the main component of the featureless continuum. The presence of star forming regions cannot be excluded in the circumnuclear region of various Seyfert galaxies. An attempt is made to find their fingerprints in the observed AGN spectra. Finally, it is demonstrated that multi-cloud models are necessary to interpret the spectra of single objects, even in the global investigation of a sample of galaxies., Comment: 26 pages, LaTeX (including 5 Tables) + 17 PostScript figures. To appear in "The Astrophysical Journal"

A multi-cloud model is presented which explains the soft X-ray excess in NGC 4051 and, consistently, the optical line spectrum and the SED of the continuum. The clouds are heated and ionized by the photoionizing flux from the active center and by shocks. Diffuse radiation, partly absorbed throughout the clouds, nicely fits the bump in the soft X-ray domain, while bremsstrahlung radiation from the gaseous clouds contribute to the fit of the continuum SED. Debris of high density fragmented clouds are necessary to explain the absorption oxygen throats observed at 0.87 keV and 0.74 keV. The debris are heated by shocks of about 200-300 km/s. Low velocity (100 km/s)-density (100 cm-3) clouds contribute to the line and continuum spectra, as well as high velocity (1000 km/s)-density (8000 cm-3) clouds which are revealed by the FWHM of the line profiles. The SED in the IR is explained by reradiation of dust, however, the dust-to-gas ratio is not particularly high. Radio emission is well fitted by synchrotron radiation created at the shock front by Fermi mechanism., Comment: 19 pages + 3 figures PostScript

Simultaneous modeling of the line and continuum emission from the nuclear region of the Circinus galaxy is presented. Composite models which include the combined effect of shocks and photoionization from the active center and from the circumnuclear star forming region are considered. The effects of dust reradiation, bremsstrahlung from the gas and synchrotron radiation are treated consistently. The proposed model accounts for two important observational features. First, the high obscuration of Circinus central source is produced by high velocity and dense clouds with characteristic high dust-to-gas ratios. Their large velocities, up to 1500 km\s, place them very close to the active center. Second, the derived size of the line emitting region is well in agreement with the observed limits for the coronal and narrow line region of Circinus., Comment: 36 pages, LaTex (including 4 Tables and 9 figures), $$ removed from Abstract To appear in "The Astrophysical Journal"