Models of emission line profiles and spectral energy distributions to characterize the multi-frequency properties of active galactic nuclei

The spectra of Active Galactic Nuclei (AGNs) are often characterized by a wealth of emission lines with different profiles and intensity ratios that led to a complicated classification. Their electro-magnetic radiation spans more than 10 orders of magnitude in frequency. In spite of the differences between various classes, the origin of their activity is attributed to a combination of emitting components, surrounding an accreting Super Massive Black Hole, in the so called Unified Model. Currently, the execution of sky surveys, with instruments operating at various frequencies, provides the possibility to detect and to investigate the properties of AGNs on very large statistical samples. Thanks to the spectroscopic surveys that allow investigation of many objects, we have the opportunity to place new constraints on the nature and evolution of AGNs. In this contribution we present the results obtained by working on multi-frequency data and we discuss their relations with the available optical spectra. We compare our findings with the AGN Unified Model predictions, and we present a revised technique to select AGNs of different types from other line emitting objects. We discuss the multi-frequency properties in terms of the innermost structures of the sources.Comment: 11 pages, 4 figures. Proceedings of the XI Serbian Conference on Spectral Line Shapes in Astrophysics. Accepted for publication on Atom

An orientation-based unification of young jetted AGN: the case of 3C 286

In recent years, the old paradigm according to which only high-mass black holes can launch powerful relativistic jets in active galactic nuclei (AGN) has begun to crumble. The discovery of $\gamma$-rays coming from narrow-line Seyfert 1 galaxies (NLS1s), usually considered young and growing AGN harboring a central black hole with mass typically lower than 10$^8$ M$_\odot$, indicated that also these low-mass AGN can produce powerful relativistic jets. The search for parent population of $\gamma$-ray emitting NLS1s revealed their connection with compact steep-spectrum sources (CSS). In this proceeding we present a review of the current knowledge of these sources, we present the new important case of 3C 286, classified here for the fist time as NLS1, and we finally provide a tentative orientation based unification of NLS1s and CSS sources.Comment: 12 pages, 3 figures. Proceeding of the conference "Quasars at all cosmic epochs", held in Padova, April 2-7, 2017, published on Frontiers in Astronomy and Space Science

Extended narrow-line region in Seyfert galaxies

We present our recent results about the extended narrow-line region (ENLR) of two nearby Seyfert 2 galaxies (IC 5063 and NGC 7212) obtained by modelling the observed line profiles and spectra with composite models (photoionization+shocks) in the different regions surrounding the AGN. Then, we compare the Seyfert 2 ENLRs with the very extended one recently discovered in the narrow-line Seyfert 1 (NLS1) galaxy Mrk 783. We have found several evidences of interaction between the ISM of the galaxies and their radio jets, such as a) the contribution of shocks in ionizing the high velocity gas, b) the complex kinematics showed by the profile of the emission lines, c) the high fragmentation of matter, etc. The results suggest that the ENLR of IC 5063 have a hollow bi-conical shape, with one edge aligned to the galaxy disk, which may cause some kind of dependence on velocity of the ionization parameter. Regarding the Mrk 783 properties, it is found that the extension of the optical emission is almost twice the size of the radio one and it seems due to the AGN activity, although there is contamination by star formation around 12 arcsec from the nucleus. Diagnostic diagrams excluded the contribution of star formation in IC 5063 and NGC 7212, while the shock contribution was used to explain the spectra emitted by their high velocity gas.Comment: 9 pages, 2 figures, proceeding of the conference "Quasars at all cosmic epochs", accepted for publication in Front. Astron. Space Sci. - Milky Way and Galaxie

Compact steep-spectrum sources as the parent population of flat-spectrum radio-loud NLS1s

Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active galactic nuclei (AGN), which tipically does not exhibit any strong radio emission. Seven percent of them, though, are radio-loud and often show a flat radio-spectrum (F-NLS1s). This, along to the detection of $\gamma$-ray emission coming from them, is usually interpreted as a sign of a relativistic beamed jet oriented along the line of sight. An important aspect of these AGN that must be understood is the nature of their parent population, in other words how do they appear when observed under different angles. In the recent literature it has been proposed that a specific class of radio-galaxies, compact-steep sources (CSS) classified as high excitation radio galaxies (HERG), can represent the parent population of F-NLS1s. To test this hypothesis in a quantitative way,in this paper we analyzed the only two statistically complete samples of CSS/HERGs and F-NLS1s available in the literature. We derived the black hole mass and Eddington ratio distributions, and we built for the first time the radio luminosity function of F-NLS1s. Finally, we applied a relativistic beaming model to the luminosity function of CSS/HERGs, and compared the result with the observed function of F-NLS1s. We found that compact steep-spectrum sources are valid parent candidates and that F-NLS1s, when observed with a different inclination, might actually appear as CSS/HERGs.Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in Astronomy & Astrophysic

A new approach to produce calcium-phosphate coatings on titanium

In the study, hydroxyapatite-gelatin composite powders were synthesized from simulated body fluid (SBF) with gelatin content ranging from 1 to 3 wt. %. It was established that all the samples were single-phase and represented hydroxyapatite. The surface and morphological characteristics of the produced hydroxyapatite-gelatin (HAG) based coatings were studied. Uniform deposition of the composite on the titanium substrate surface (VT1-0) was found to occur on etched titanium samples. It is shown that exposure of titanium substrates with hydroxyapatite-gelatin (HAG) based coating to powerful ion beam can stimulate further growth of crystals and regeneration of the surface

Modeling the Extended narrow line Region in the era of Integral Field surveys

The Extended Narrow Line Region (ENLR) of Active Galactic Nuclei (AGN) is a region of highly ionized gas with conical or bi-conical shape, extending from the Narrow Line Region (~ 100 pc) up to 15-20 kpc with the apexes pointing towards the nucleus. At the moment ~ 50 galaxies have been found showing evidence of ENLR, the vast majority of which are nearby Seyfert galaxies. The presence of these cones is interpreted in the framework of the Unified Model of AGN thatpredicts an anisotropic radiation field escaping from the nucleus, collimated by a dusty torus. The strong non-thermal radiation produced by the accretion disk seems indeed to be the main responsible of the ionization in the ENLR, although the contribution of shocks cannot always be neglected. The ionized gas however does not reside entirely inside the cones. There is evidence of several Seyfert galaxies (e.g. NGC 4151, Mrk 3, NGC 3393) showing low-ionization lines emission, identifiable in BPT diagnostic diagrams as LINERs emission, located in the outskirts of the cones or even in the cross-cone region. It is argued that these spatial variation of the ionization in the ENLR may be a new channel in the study of the collimation by the torus and could provide valuable information on the torus structure (e.g. clumpiness, edge features). Moreover, recent advances in integral field spectroscopy and the start of the first integral field survey could provide an unprecedented advantage in a more thorough characterization of this phenomenon. The theoretical study of ionized gas in AGN is mainly carried out through photo-ionization models realized with dedicated codes. The radiative transfer, ionization and chemistry calculations are solved numerically due to the complexity of the problem. The state of the art of these models still relies on an ad hoc single-zone or two-zone approach, able to reproduce the gas spectral features in detail, however not suited to study spatial effects in the ENLR. The aim of this work is to explore a new method to realize photo-ionization models of ENLR, taking into account both a cloud-based distributions of gas and the effects of the torus structure on the collimation of the nuclear radiation and on the ionization of gas inside and outside the cones. For the first time the models will be bi-dimensional in order to provide a useful tool to be compared with integral field data. To achieve this goal we developed a python code able to perform a procedural generation of the gas distribution in different regions of space, i.e. the cloud parameters as their position, dimension and mass are randomly drawn from a probability distribution determined by the user. This multi-cloud approach is intended to avoid the simple assumption typical of traditional photo-ionization models and at the same time to reproduce the observation with a more realistic ansatz on the distribution of gas. The user can, for instance, generate clouds of gas in the galactic disk and ionize them with a chosen Spectral Energy Distribution (SED). To collimate the radiation we included a simple torus model, either clumpy, smooth or composite. The code interfaces with Cloudy, the photo-ionization code, through the pyCloudy libraries, and it is able to define a set of models, write the input files and, after the calculations are over, read and plot the results.La Extended Narrow Line Region (ENLR) dei Nuclei Galattici Attivi (AGN) è una regione di gas altamente ionizzato di forma conica o di cono bifalde, che si estende dalla Narrow Line Region (~ 100 pc) fino a 15-20 kpc con gli apici che puntano verso il nucleo. Al momento circa 50 galassie hanno mostrato evidenza di una ENLR, di queste la maggior parte sono galassie di Seyfert nell'Universo locale. La presenza di questi coni viene interpretata nel contesto del modello unificato degli AGN, il quale predice che la radiazione uscente dal nucleo sia anisotropa, poiché collimata da un toro di gas e polveri. L'intensa radiazione non termica prodotta dal disco di accrescimento sembra a tutti gli effetti la principale responsabile della ionizzazione della ENLR, anche se il contributo degli shock non può essere sempre ignorato. Il gas ionizzato tuttavia non si limita solamente ai coni. Alcune galassie (e.g. NGC 4151, Mrk 3, NGC 3393) sono state osservate emettere righe di bassa ionizzazione ai margini dei coni o persino in direzione perpendicolare al cono stesso. Le variazioni spaziali della ionizzazione della ENLR potrebbero essere un nuovo canale per lo studio della collimazione della radiazione da parte del toro e fornire importanti informazioni sulla sua struttura. Inoltre i recenti progressi nella spettroscopia integral field e la comparsa delle prime survey con questi strumenti permetterano una sempre miglior caratterizzazione di questi fenomeni. Lo studio teorico del gas ionizzato negli AGN viene condotto principalmente attraverso i modelli di fotoionizzazione, realizzati con codici dedicati. Questi calcolano numericamente il trasporto radiativo, laionizzazione e la chimica del gas. Lo stato dell'arte di questi modelli consiste su un approcio ad hoc con una o due nubi di gas, in grado di riprodurre in dettaglio le caratteristiche dello spettro. Questi modelli non sono tuttavia adatti allo studio degli effetti su grande scala nella ENLR. Lo scopo di questa tesi è esplorare un nuovo metodo per realizzare modelli di fotoionizzazione della ENLR che siano in grado di considerare gli effetti della struttura del toro sulla collimazione della radiazione utilizzando al contempo una distribuzione del gas frammentata in nubi, realizzando così modelli bidimensionali. Per raggiungere questo scopo abbiamo sviluppato un codice in python in grado di generare proceduralmente una distribuzione di gas in diverse regioni dello spazio. La posizione, la dimensione e la massa di ogni nube viene estratta casualmente da una distribuzione di probabilità decisa dall'utente. Questo metodo con multi nube è pensato per evitare le assunzioni tipiche dei modelli tradizionali e allo stesso tempo riprodurre le osservazioni con ipotesi più realistiche sulla distribuzione del gas. L'utente può, ad esempio, generare nubi di gas nel disco galattico e ionizzarle con una emissione di sua scelta. Per collimare la radiazione è stato incluso un semplice modello di toro: liscio, frammentato o composito. Il codice si interfaccia con Cloudy, il codice di fotoionizzazione, attraverso le librerie pyCloudy ed è in grado di definire un insieme di modelli, scrivere i file di input e, una volta che i calcoli sono terminati, leggere e mostrare i risultati

Exploring the parent population of beamed NLS1s: from the black hole to the jet

The aim of this work is to understand the nature of the parent population of beamed narrow-line Seyfert 1 galaxies (NLS1s), by studying the physical properties of three parent candidates samples: steep-spectrum radio-loud NLS1s, radio-quiet NLS1s and disk-hosted radio-galaxies. In particular, we focused on the black hole mass and Eddington ratio distribution and on the interactions between the jet and the narrow-line region