9-12 October 2018
Europe/Rome timezone

Poster list

The posters will be displayed next to the conference room and will have an assigned maximum space of 70 (width) x 100 (height) cm. Please, respect the limit size for the poster.


The Chandra and XMM-Newton view of the Einstein Cross

 Elena Bertola 

Co-author: M. Dadina, M. Cappi, C. Vignali, G. Chartas, B. De Marco, G. Lanzuisi, M. Giustini, E., Torresi

Out of the known gravitationally lensed systems, Q2237+0305 (the Einstein Cross) is perhaps the most studied, due to its brightness/vicinity and configuration (quasar at redshift z=1.695, lensing galaxy at z=0.0305). This system shows both macrolensing and microlensing effects, which offer a unique tool to investigate the innermost structure of the quasar.
I present the preliminary results obtained analyzing thirty-five observations carried out over the last seventeen years by Chandra, and three XMM-Newton observations, among which only one has been published so far. 
The aim of this work is to study the X-ray variability of the quasar, investigate the regions where the high-energy photons originate and how they interact with the matter surrounding the black hole.


FERMI transient J1544-0649: a flaring radio-weak BL Lac

Gabriele Bruni

Co-author: Francesca Panessa

On May 15th, 2017, the FERMI/LAT γ-ray telescope observed a transient source not present in any previous high-energy catalogue: J1544-0649. It was visible for two consecutive weeks, with a flux peak on May 21st. Subsequently observed by a Swift/XRT follow-up starting on May 26, the X-ray counterpart position was coincident with the optical transient ASASSN- 17gs = AT2017egv, detected on May 25, with a potential host galaxy at z=0.171. We conducted a 4-months follow-up in radio (Effelsberg-100m) and optical (San Pedro Martir, 2.1m) bands, in order to build the overall Spectral Energy Distribution (SED) of this object. The radio data from 5 to 15 GHz confirmed the flat spectrum of the source, favoring a line of sight close to jet axis, not showing significant variability in the explored post-burst time-window. The Rx ratio, common indicator of radio loudness, gives a value at the border between the radio-loud and radio-quiet AGN populations. The CaII H&K break value (0.29±0.05) is compatible with the range expected for the long-sought intermediate population between BL Lacs and FRI radio galaxies. An overall SED fitting from Radio to γ-ray band shows properties typical of a low-power BL Lac. As a whole, these results suggest that this transient could well be a new example of the recently discovered class of radio-weak BL Lac, showing for the first time a flare in the γ/X-ray bands.


Molecular gas in Low Luminosity Radio Galaxies in (proto-)cluster at z=0.4-2.6

Gianluca Castignani

Co-authors: F. Combes, P. Salomé, C. Benoist, M. Chiaberge, J. Freundlich, G. De Zotti 

We investigate the role of the environment in processing molecular gas in radio galaxies (RGs). We observed five RGs at z=0.4-2.6 in dense Mpc-scale environment with the IRAM-30m telescope. We set four upper-limits and report a CO(7-6) detection for COSMOS-FRI~70 at z=2.63, which is the most distant brightest cluster galaxy (BCG) candidate detected in CO. We speculate that the cluster environment might have played a role in preventing the refueling via environmental mechanisms such as galaxy harassment, strangulation, ram-pressure, or tidal stripping. The RGs of this work are excellent targets for ALMA as well as next generation telescopes such as the James Webb Space Telescope.



Dispersion and variability of the X-ray/UV ratio in active galactic nuclei

 Elia Chiaraluce

Co-authors: Fausto Vagnetti, Francesco Tombesi, Maurizio Paolillo

The well established negative correlation between the αOX spectral slope and the optical/UV luminosity is affected by a relatively large dispersion, which can be affected by variability in the X-ray/UV ratio and/or by changes in fundamental physical parameters. We want to quantify the contribution of variability of single sources (intra-source dispersion) and that due to variations of other quantities different from source to source (inter-source dispersion). We use archival data from the XMM-Newton Serendipitous Source Catalog (XMMSSC) and from the XMM-OM Serendipitous Ultra-violet Source Survey (XMMOM-SUSS3). We select a sub-sample in order to decrease the dispersion of the relation due to the presence of Radio-Loud and Broad Absorption Line objects, and to absorptions in both X-ray and optical/UV bands. Our reference sub-sample is constitued by 1095 observations corresponding to 636 unique sources. For 273 sources observed at multiple epochs, we use the structure function to estimate the contribution of variability to the dispersion. We analyse the dependence of the residuals of the relation on various physical parameters in order to characterise the inter-source dispersion. We find a total dispersion of σ∼0.118 and find that variability contributes for approximately the 60% to the variance of the αOX−LUV relation. We find no evidence of a dependence of the residuals of the relation either on black hole mass or on Eddington ratio. We find a weak positive correlation of both αOX index and the residuals of the relation with the FWHM(Hβ), suggesting a weak increase of αOX with the viewing angle.


Radio cores in low-luminosity AGN

 Elia Chiaraluce

Co-authors: Gabriele Bruni, Francesca Panessa, Marcello Giroletti, Fausto Vagnetti, Francesco Tombesi

It is commonly established that low-luminosity AGN (LLAGN) are radio-emitters at some level, being characterised by low radio flux densities, compact cores sometimes accompanied by low power jet components. However the origin of such radio emission is often unknown. Multi-frequency, high-sensitivity and high-resolution observations are a powerful tool to unveil the source of emission. 
We selected ten nuclei which have been undetected in a complete, distance limited sample of 27 nearby Seyfert nuclei. In order to isolate their nuclear radio emission, we used high-resolution (≤1 arcsec), multi-frequency (1.4, 5, 10 and 15 GHz) Expanded Very Large Array (EVLA) observations. We were able to estimate flux densities for six sources down to luminosities of ∼1018 W Hz−1, while for four sources were undetected at a level as low as 27 uJy/beam. The morphology of the detected sources is predominantly compact, either unresolved or marginally resolved. Three sources exhibits spectral slopes compatible with flat/inverted spectra, hint for compact cores associated to synchrotron self-absorbed (SSA) radiation, as originating from the base of a jet, ruling out a possible free-free emission/absorption origin. However, the emission could also originate from an advection-dominated accretion flows (ADAF), plus a jet component. 
The four undetected sources force us to revise the paradigm according to which radio-quiet AGN are not radio-silent. We will discuss the radio versus X-ray correlation in these faint sources and make predictions about low power cores that will be the dominant AGN population of the Square Kilometre Array sky.


Probing accretion/ejection flows in AGN by characterizing Fe K emission/absorption lines variability with residual maps

 Deborah Costanzo  

Co-authors: M. Cappi, M. Dadina, B. De Marco, C. Vignali

The dynamics and geometry of the material close to the SMBH in AGN are still largely uncertain, both as regards the inflows via accretion disk and the outflows. The latter phenomena may have a fundamental role in the AGN feedback on the host galaxy, so it is important to understand their properties and extent. A simultaneous investigation of inflows and outflows may highlight some kind of correlation, that shall help to unravel the driving mechanisms of massive winds from the disk, still an open issue. Time-resolved spectral analysis is a key tool to investigate these phenomena. The 4.0-10.0 keV energy band is the most suitable for these aims, because it includes the Fe Kα fluorescence emission line at 6.4 keV, a fundamental proxy of the motions around the SMBH, and possibly Fe resonant absorption lines, features that indicate the presence of massive, relativistic (<v>∼0.1c) disk winds (Ultra Fast Outflows, Tombesi et al. 2010), observed in about 50% of local AGN for which good quality data exist.

We use a technique, Residual maps, that couples time and spectral analysis to the two X-ray brightest Seyfert 1 observed to date: NGC 3783 and Mrk 509. It allows to identify spectral features and trace their evolution in time. Residual maps can be used to detect potentially interesting time intervals, on which a deep spectral analysis can be (and will be) carried out to characterize the physical phenomena in act.


Super-critical accretion of supermassive black holes

Massimo Dotti

Co-authors: R. Decarli, D. Fiacconi, F. Haardt, A. Lupi, P. Madau, L. Mayer, T. Sbarrato

The observation of extremely massive black holes shining as quasars up to z~7.5 requires either large BH seeds or episodes of supercritical accretion. I will comment on the current and future constraints on supercritical accretion, on how it can be triggered, and on the possibility of observing supercritically growing MBHs.


Spectral evolution of Hydra A jets

Mohammad Nawaz

Co-author: Alex Wagner, Elisabete de Gouveia Dal Pino, Falceta-Gonçalves,Geoffrey Bicknell


We present our study of the spectral evolution of bright jet knots and flaring zones of an iconic radio source Hydra A. We focus on the gradually increasing brightness of knots along downstream and significantly bright flaring zones. We developed an axisymmetric jet-intracluster medium interaction model utilising RMHD simulations. The parameter space of the jet and the cluster environment is set based on our previous study of the source. The key feature of our model is that the bright jet knots of Hydra A are formed when over-pressured supersonic jets interact with the environment through a series of reconfinement shocks. In order to produce realistic emission map, we further developed a spectral evolution code. Here, we track the evolution of a distribution of non-thermal particles both spatially due to advection along the jet and energetically due to adiabatic process and synchrotron cooling. Preliminary results of the calculation of surface brightness of the simulated Hydra A jets show that in the early stage the knots are gradually brighter due to increasing downstream magnetic pressure.


ZBLLAC : A spectroscopic library of BL Lac objects

Renato Falomo

Co-authors: M. Landoni, S. Paiano, A. Treves

BL Lac objects are active nuclei, hosted in massive elliptical galaxies, the emission of which is dominated by a relativistic jet closely aligned with the line of sight. A most distinctive characteristic of the class is the weakness or absence of spectral lines, that historically hindered the identification of their nature and ever there after proved to be a hurdle in the determination of their distance. We present a database (http://www.oapd.inaf.it/zbllac/) of high quality optical spectra of several BL Lac objects. All the spectra are also available for downloads. 


Extreme BL Lacs at multi-TeV energies with the CTA 

Giorgio Galanti

Co-authors: F. Tavecchio, M. Landoni, P. Romano, S. Vercellone, for the CTA Consortium

Extreme BL Lacs (EHBL) are a subclass of blazars with unique properties, such as synchrotron peaks in the hard X-ray band and extremely hard TeV spectra peaking above 10 TeV. Their exceptional properties make them interesting sources for current Cherenkov telescopes and a major topic for the upcoming Cherenkov Telescope Array (CTA), the next-generation ground-based gamma-ray observatory. In particular, quite interesting is the possibility that, despite the strong gamma-gamma absorption, EHBL will be detected above 10 TeV. We explore two potential scenarios discussed in literature: 1) the possibility that photon-axion like particles oscillations give rise to an effective decrease of the opacity; 2) that EHBL are sources of ultra-high energy cosmic ray beams. With dedicated simulations we study and discuss the implications of both cases for observations with CTA. 


Multi-frequency polarimetry of a complete sample of PACO radio sources

Vincenzo Galluzzi

Co-authors: Marcella Massardi, Loretta Gregorini 

The high-frequency (> 20 GHz), bright flux density (> 200 mJy) radio population is dominated by blazars. Their polarization properties are invaluable to study magnetic fields and plasma in the inner and unresolved regions of relativistic jets. For Cosmology, these objects are important contaminant of CMB at scales smaller than 30' up to 100 GHz, hence they hamper the detection of primordial B-modes associated to inflation. However, their properties are still poorly constrained: results in literature are easily affected by spectral, detection and variability-related biases.
We present an unbiased analysis of high sensitivity (0.6 mJy, with a detection rate above 90% at 5σ) multi-frequency (and multi-epoch) polarimetric observations for a complete sample of 104 compact extragalactic radio sources drawn from the faint (> 200 mJy at 20 GHz in total intensity) Planck-ATCA Coeval Observations (PACO) catalogue, performed with ATCA at 7 frequencies, over the 1.1-39 GHz frequency range. An ALMA project extends the analysis up to 100 GHz for a (complete) sub-sample of 32 objects. We classified our sources in terms of stuctural complexity, finding different behaviours in polarization fractions (both linear and circular) and position angles (PPA). We produce polarization differential source counts and assess forecasts for CMB studies.


A MUSE analysis of the A2667 BCG

 Edoardo Iani

Co-authors: Giulia Rodighiero, Piero Rosati, Gabriel Bartosh Caminha,  Giovanni Cresci, Jacopo Fritz, Paolo Tozzi , Chiara Mancini, Lucìa Rodrìguez-Munoz

On the basis of data from the state-of-the-art ESO IFU instrument MUSE, we present an extensive analysis of the visual properties of the radio-loud brightest cluster galaxy (BCG) sitting at the centre of the X-ray luminous cluster Abell 2667 (z=0.234).
By means of both well-known and newly-developed fitting codes, we probe both the stellar and gas properties (i.e. kinematics, dust extinction, stellar mass, star formation rate) of the BCG, from its core to the outskirts.
We retrieve stellar kinematic maps which show no sign of a coherent pattern (e.g. rotation), with the stars maximum velocity <150 km s−1 but mean velocity dispersion ∼230 km s−1, thus suggesting the galaxy is dispersionally supported.
Although the star formation history (SFH) maps show a building history for the BCG almost completed for tlb>6×108yr, the presence of a young stellar population in knots and in an extended clump north-east of the galaxy suggests recent star formation (SF) possibly taking place within the cooling-flow that feeds the BCG central supermassive black hole (SMBH). 
By studying the [OIII]λ5007 spatial distribution in different velocity channels, we detect an extended redshifted component (Δv=+100÷+500 km s−1) consistent with infalling gas, i.e. the cooling-flow, and a blueshifted component (Δv=−500÷−100 km s−1) that could be connected to a large ionized gas outflow originating from the SMBH. 
From the analysis of the gas emission lines (predominantly Hβ, [OIII], Hα, [NII] and [SII]) thanks to spectroscopic diagnostic diagrams, we infer the presence of a multiphase gas within the galaxy, with the BCG core consistent with a Low-Ionization Nuclear Emission-line Region (LINER) while star-forming and shocked in the outer regions.


Unveiling the origin of the gamma‐ray emission in NGC 1068 with the Cherenkov Telescope Array    

 Alessandra Lamastra 

Co-authors: F. Tavecchio, P. Romano, M. Landoni, S. Vercellone, for the CTA Consortium

Several observations are revealing the widespread occurrence of mildly relativistic wide-angle AGN winds strongly interacting with the gas of their host galaxy. Such winds are potential cosmic-ray accelerators, as supported by gamma-ray observations of the nearby Seyfert galaxy NGC 1068 with the Fermi gamma-ray space telescope. The shocks produced by the interaction of AGN winds with the surrounding interstellar medium are expected to accelerate particles to relativistic energies.
We present a physical model for the gamma-ray emission produced by relativistic particles accelerated by the AGN-driven shocks observed in the circum-nuclear molecular disk of the Seyfert galaxy NGC 1068. The AGN wind model predicts a hard spectrum that extend in the VHE band which differs significantly from those corresponding to other models discussed in the literature, like starburst or AGN jet.
With dedicated simulations in the context of the Cherenkov Telescope Array (CTA) we study and discuss the implications of particle acceleration models in active galaxies for observations with CTA.


An X-Ray analysis of high-z blazar candidates

Luca Ighina

Co-authors: A. Caccianiga, A. Moretti, S. Belladitta, L. Ballo, C. Cicone, R. Della Ceca, P. Severgnini, D. Dallacasa 

We present the results of a systematic X-ray analysis of a complete and well-defined sample of 21 high-z (z=4-5.5) blazar candidates selected from the CLASS radio survey. In particular, we have complemented the existing archival data (mostly Chandra) with dedicated Swift-XRT observations reaching an almost complete X-ray coverage of the sample. Our goal is to use the X-ray data to assess the blazar nature of these objects since a strong and flat (Gamma<1.5) X-ray emission is a striking signature of the presence of an oriented relativistic jet.




A Cloud-Based architecture for the Cherenkov Telescope Array observation simulations

 Marco Landoni

Co-authors: P. Romano, S. Vercellone, J. Knodlseder, A. Bianco, F. Tavecchio, A. Corina

We review the current cloud architecture based on Amazon Web Services (AWS) adopted to perform scientific simulations in the context of the Cherenkov Telescope Array (CTA). This kind of tasks require thousands of CPU/hours (especially for population studies or faint sources) to be completed and, for this reason, a new computational approach is needed to secure results in a reasonable amount of time. The AWS-based cloud architecture allows to parallelize and distribute across many nodes and CPUs the ctools suite (a native sequential software tools built for the analysis of Imaging Air Cherenkov Telescope event data) by exploiting efficiently the computational power (offered at low cost) by the AWS platform. We made use of Elastic Cloud Computing (EC2) to obtain the required CPUs to run our jobs and Simple Storage Service (S3) as baseline for storing the huge amount of data (various TBs) processed by simulations. We took advantage of this proposed solution to run thousands of ctools-based scientific simulations in minutes, decreasing the computation time with respect to the on premises (local machines) capabilities by a factor > 200.


Constraining the geometry and the dynamics of the ultra-fast outflow in PDS 456 using a new wind emission model

Alfredo Luminari

Co-authors: E. Piconcelli, F. Tombesi, L. Zappacosta, F. Fiore, L. Piro, F. Vagnetti

Ultra-fast outflows (UFO) in the X-rays are observed in an increasing number of active galactic nuclei. They are a powerful tool to shed new light on the innermost region surrounding the supermassive black hole (SMBH), as well as on the feedback mechanism and hence on the SMBH-host galaxy co-evolution. The nearby (z=0.184), luminous (L~10^47 erg/s) quasar PDS 456 hosts a well-known UFO, with velocities of ~0.25c, and is mainly detected through a characteristic P-Cygni profile between ~5 and ~10 keV.
We analyzed the combined XMM-Newton and NuSTAR spectra using a novel wind emission (WINE) model. This model allowed us to constrain some of the fundamental characteristics of the outflow, such as the wind covering fraction, the angular dependence with respect to the accretion disk plane and the velocity range.
We found an opening angle of the wind of 70 deg, a covering fraction of 0.7 and a mean velocity of the wind of 0.23c. We derived a mass outflow rate ~20 M_sun / yr (i.e., 0.3 times the Eddington mass) and an energy transfer rate ~3*10^46 erg/s, 30% of the AGN luminosity. These values are consistent with the results in Nardini et al. (2015), but a factor of ~1.5 higher.
Moreover, we simulated observations with the next generation X-ray observatory ATHENA, and we found a significant improvement in the determination of the free parameters of the model.
Our wind emission model can be easily adapted to include an accurate treatment of the radiative transfer by the outflow. It can also be generalized to different kind of sources and different scales, up to galaxy-scales, thus following the outflow all along its journey to the host galaxy.


Tracking the Iron Kα line and the Ultra Fast Outflow in NGC 2992

Andrea Marinucci

Co-authors: S. Bianchi, V. Braito, G. Matt, E. Nardini, J. Reeves

Variability is one of the best tools to investigate the emission mechanisms in Active Galactic Nuclei (AGN). We report on the 2010 XMM-Newton monitoring of the highly variable Seyfert 2 Galaxy NGC 2992, which was subsequently targeted by Swift and NuSTAR in 2015. XMM-Newton always caught the source in a faint state but NuSTAR observed a brightening of the source, with evidence of an Ultra Fast Outflow with velocity v=0.21±0.01c. The UFO in NGC 2992 is consistent with being ejected at a few tens of gravitational radii only at accretion rates greater than 2% of the Eddington luminosity.
The analysis of the XMM data also allowed us to determine that the Iron Kα emission line complex in this object is likely the sum of three distinct components: a constant, narrow one due to reflection from cold, distant material (likely the molecular torus); a narrow, but variable one which is more intense in brighter observations and a broad relativistic one emitted in the innermost regions of the accretion disk.


Are AGN special? The NuSTAR and Chandra point of view

Alberto Masini

Co-authors: R. C. Hickox, and the NuSTAR team

We report the result of a detailed analysis from a deep simultaneous 130ks \xmmnu observation of the nearby (z=0.0315) and bright starburst-AGN system: MCG-03-58-007. Rapid X-ray spectral variability has been detected, which may be caused by an obscuration event. We show that most of the observed variability may be caused by an inhomogeneous, highly ionized fast (vw,1∼−0.10c and vw,2∼−0.35c) disc-wind rather than a neutral absorber embedded in the clumpy torus. Such dramatic and fast variability of the wind, places MCG-3-58-007 among the unique objects such as the luminous quasar PDS456, which is considered the prototype of fast disc-wind. We also show that most of the scattered soft X-ray emission in MCG--03--58--007 originates form the larger scale photoionized plasma, possibly associated with NLR gas, as seen from the presence of several narrow emission lines in the RGS spectra.


Evidence of a clumpy disc-wind in the star forming galaxy MCG–03–58–007

Gabi Matzeu

Co-authors: V. Braito, J. Reeves, P. Severgnini, L. Ballo, A. Caccianiga, S. Campana, C. Cicone, R. Della Ceca, M. L. Parker, M. Santos-Lléo, N. Schartel

We report the result of a detailed analysis from a deep simultaneous 130ks \xmmnu observation of the nearby (z=0.0315) and bright starburst-AGN system: MCG-03-58-007. Rapid X-ray spectral variability has been detected, which may be caused by an obscuration event. We show that most of the observed variability may be caused by an inhomogeneous, highly ionized fast (vw,1∼−0.10c and vw,2∼−0.35c) disc-wind rather than a neutral absorber embedded in the clumpy torus. Such dramatic and fast variability of the wind, places MCG--3--58-007 among the unique objects such as the luminous quasar PDS\,456, which is considered the prototype of fast disc-wind. We also show that most of the scattered soft X-ray emission in MCG--03--58--007 originates form the larger scale photoionized plasma, possibly associated with NLR gas, as seen from the presence of several narrow emission lines in the RGS spectra.


The unusual suspects. A new population of X-ray weak quasars.

Emanuele Nardini 

Co-authors: Elisabeta Lusso, Guido Risaliti, Susanna Bisogni 

In order to further test the suitability of AGN as standard candles for cosmological studies, we have recently obtained deep XMM-Newton observations of 30 bright quasars, selected in the optical from the SDSS-DR7 to be representative of the most luminous, intrinsically blue quasars at z∼3. Despite the uniform selection in terms of optical/UV spectral properties and the narrow range of luminosity, black-hole mass and accretion rate probed by our sample, two distinct populations surprisingly emerge from the X-ray analysis: about two thirds of the targets perfectly follow the well-established UV vs. X-ray luminosity relation, while the remaining one third lie significantly below the expectations. The spectra of the latter sources are flatter and show no clear evidence of absorption, suggesting a different disc/coronal state. This result provides novel insights into the nature and incidence of X-ray weak quasars. We argue that X-ray weakness might be associated with an ongoing blow-out phase, as our sample picks the objects where the physical conditions are most favourable for the presence of powerful winds and radiative feedback is supposed to be most intense, shaping the galaxies as we see them in the present-day Universe.


Optical-Gamma-ray correlation in the blazar S5 1803+78

Roberto Nesci 

Co-authors: A. Maselli, V. M. Lipunov, F. Martinelli, A. Siviero, M. Giroletti, M. Orienti

Near simultaneous, multiwavelength observations of BL Lac objects are a key to understand the physical mechanisms responsible for their emission.

We present here the optical and Gamma-ray light curve of the blazar S5 1803+78 since the beginning of the Fermi-LAT mission in August 2008 until December 2016. X-ray data from SWIFT and radio data from VLBA and EVN are also analyzed.

We reanalised all the data collected by Fermi-LAT instrument regarding the source, taking into account the presence of nearby sources, and collected optical data from our own observations and public archive data to build an optical light curve as complete as possible. We also obtained two Swift ToO observations during the strong flare of 2015.
Eight major Gamma-ray flares (F>2.5E-7ct/cm2/s) with optical coverage were detected, all save one with corresponding optical enhancement. We also found an optical flare without a Gamma-ray counterpart. 
The optical/Gamma-ray flux ratio at the flare peak was 0.4 with large (0.4) dispersion. No significant optical V-I color changes were detected during the flares. The X-ray emission was well fitted by a power law with energy spectral index 1.5, independently from the flux level. No clear correlation with the optical or the Gamma-ray emission was found. The Gamma-ray spectral slope was well fitted by a power law with photon index 2.2, with very small variations despite large changes in flux level. These findings are as expected for an Inverse Compton origin for the high-energy emission of the source, nearly co-spatial to the optically emitting region.


Multi-wavelength follow-up of a large flare of PKS0346-27

Roberto Nesci 

Co-authors: R. Angion, S. Buson

A large gamma-ray flare of the FSRQ PKS0346-27 was detected by Fermi-LAT in February 2018. This enhanced activity signed the first awakening of the blazar since the satellite is operational. Follow-up with REM and Swift reported the source at very high flux level also in the optical and X-rays bands. We investigate the object’s properties thanks to the gamma-ray and NIR data collected, together with additional available radio, optical and mm-band data. The time variability patterns and the overall SED are briefly discussed.


Gamma-ray flaring FSRQs: correlation with accretion disk luminosity, and the relevance of high energy component

Luigi Pacciani 

I show here a study of gamma-ray flaring FSRQs. Candidate flares are reveled using a photometric unbinned peak detection method (Pacciani 2018, 2018arXiv180311540P); fake flares are removed from the sample by comparing the photometric results with the standard likelihood analysis performed within the identified peak activity period.
The aim of this study is to show up similarities as well as differences among the gamma-ray flaring states, and to compare the whole sample with the high-energy flares (flares with relevant emission above 25 GeV/(1+z) ).
Even though several engines proposed for the "distant scenario" does not require to be connected with accretion disk, we will show and discuss that jet luminosities and disks correlate not only on years averaged time-scales, but also during High-Energy gamma-ray flares (time-resolved within this investigation with time-scale of the order of 10 days or less). For the whole sample I will show and discuss the spectral and temporal properties, and the average distribution of gamma-ray luminosity during flares.


Obscured AGN in the field of J1030: the X-ray and optical/infrared perspective

Alessandro Peca 

Co-authors: C. Vignali, R. Gilli, M. Mignoli

I will present an X-ray spectral analysis of 30 candidate obscured AGN in the 17'x17' field surrounding the bright z=6.31 QSO SDSS J1030+0524. 
The sample is selected from a 500ks Chandra observation campaign, on the basis of a positive hardness ratio, suggestive of the presence of obscuration, and a range of net counts from a few tens to hundreds, with a median of ∼100.

The goal is to place constraints on the redshifts of the sources, using a multiwavelength approach. Firstly, the analysis has been carried out using X-ray spectroscopy, searching for strong features like the iron 6.4 keV emission line or the 7.1 keV absorption edge, that is expected to be very deep for this type of objects. Due to the low photon statistics, the resulting redshift solutions have also been verified using state-of-the art simulations. Then, using the large photometric coverage in optical/NIR/MIR (LBT, CFHT, CTIO and Spitzer), independent solutions are calculated performing photometric redshifts.

The comparison between the X-ray and photometric methods can be an efficient tool to estimate redshifts of high-z obscured AGN, which are usually weak in optical/NIR, possibly making the spectroscopic identification challenging. Furthermore, I will show the properties of the host galaxies in which this sample of obscured AGN candidate resides.


Bulding a Hubble Diagram of Quasars

Guido Risaliti

Co-authors: Elisabeta Lusso, Susanna Bisogni

We describe the procedure to build a Hubble diagram of quasars based on the non-linear X-ray to UV luminosity relation. We show the sample selection and discuss the main possible systematic effects and measurement errors. We conclude that the method is solid and can be used to determine the expansion of the Universe in the so-far poorly explored z=1.5-6 redshift range.


Narrow-line Seyfert 1 galaxies and the Cherenkov Telescope Array: simulations and perspectives

Patrizia Romano 

Co-authors: L. Foschini, F. Tavecchio, S. Vercellone, M. Landoni, J. Knodlseder, for the CTA Consortium

In the last decade, narrow-line Seyfert 1 (NLSy1) galaxies have been discovered to be gamma-ray emitting sources, with extreme properties of flux and spectral variability in the gamma-ray energy band. This points toward a jetted, blazar-like nature. These same properties, therefore, can be investigated with the the next-generation ground-based gamma-ray observatory, the Cherenkov Telescope Array (CTA), which will potentially be about two orders of magnitude more sensitive with respect to Fermi-LAT at the overlapping energy of 25 GeV for transients/flaring events (time-scales of ~1 day or shorter). We present the results of our simulations of all currently known gamma-ray emitting NLS1s, performed using the CTA public ctools software and the public instrument response files. We investigate their possible detection and spectral properties, taking into account both the effect of the extra-galactic background light in the propagation of gamma-rays and intrinsic absorption components.


The Environment of Low Redshift BL Lac Objects

 Angela Sandrinelli

Co-authors: Renato Falomo, Aldo Treves

We constructed a sample of ~50 BL Lac objects at 0.1 < z < 0.3 extracted from the BZCAT for which SDSS images are available, in order to characterize the distribution of galaxies (up to ~ M*+2 ) in the Mpc scale environment . The BL Lac classification and the redshift was verified through the analysis of their spectra. On the basis of the SDSS classification and photometry of all galaxies in the fields we estimate the galaxy overdensity around the BL Lac objects.
On average we found a modest galaxy overdensity with respect to the local galaxy background. We compare the galaxy overdensity of BL Lacs with a large sample of inactive elliptical galaxies in the same redshift range and with absolute magnitude comparable to that of the host galaxies of BL Lac objects .


An Inventory of Quasar Physical Pairs

 Angela Sandrinelli

Co-authors: Renato Falomo, Aldo Treves

Quasar physical pairs are rare objects and are of particular interest since they can probe the connection between the galaxy environment and the QSO activation. We search for quasars pairs candidates from large databases of QSO up to z ~2. On the basis of the projected separation and their redshift difference we evaluate the probability that a pair is a bound system. For each qso pair candidate we performed a detailed analysis of the optical spectra when available. Moreover we are carried out a spectroscopic campaign at GTC + OSIRIS for the remaining objects. This allowed us to validate or reject the nature of quasar pairs. We present the inventory of this sample of quasar pairs and their properties.


AGN winds in PG 1114+445: feedback from nuclear to galaxy scales

Roberto Serafinelli

Co-authors: F. Tombesi,  F. Vagnetti, E. Piconcelli, M. Gaspari, F. G. Saturni 

Extensive evidence in the last few decades suggests that the evolution of supermassive black holes (SMBHs) and that of their host galaxies are tightly related. Powerful winds driven by Active Galactic Nuclei (AGNs) are often invoked as a fundamental mechanism by which the SMBH transfers its energy on the surrounding environment, possibly halting star formation by clearing out the galaxy from its gas and dust. Mildly relativistic (v∼0.05−0.4c) ultra-fast outflows (UFOs) are now commonly detected in the X-ray spectra of many Seyfert galaxies and quasars. Here, we present the spectral analysis of 12 XMM-Newton EPIC archival observations of PG 1114+445, a type-1 quasar at z=0.144, showing the presence of three layers of ionized absorbing material with outflow velocities ranging from 500 km s−1 up to 0.15c. Together with a UFO and a slow, moderately ionized warm absorber, we detect the presence of a "low-ionization UFO", that we interpret as the possible observational evidence of the interaction between the nuclear UFO and the ambient medium surrounding the AGN.


Morphology of AGN host galaxies using deep learning

Diego Tuccillo

Fundamental relationships between the AGNs and their host galaxies properties have been found, catching the attention of the scientific community on the connection between galaxy evolution and AGN activity.Understanding this connection is critical in any attempt to map out the evolutionary pathways of both galaxies and AGNs over cosmic time. In this context the study of the galaxies morphologies represent one of the most accessible indicators of the galaxy’s physical structure and can provide valuable clues about star formation and interaction histories. 

In this work we study using samples and high-quality multi-wavelength data from HST we study the morphological properties of galaxies hosting an AGNs, using a deep neural network. In particular we study if different AGN selections criteria catch objects in a different stage of the evolutionary path, and if this is reflected into the morphology of their host galaxy.


Soft γ-ray selected radio galaxies: a high-energy view of jetted AGNs

Francesco Ursini

Co-authors: L. Bassani, A. Malizia, A. Bazzano, G. Bruni, F. Pamessa, P. Ubertini, A. J. Bird 

We discuss results of a multiwavelength study of a sample of ~70 radio galaxies, selected in the soft gamma-ray band from INTEGRAL and Swift/BAT catalogues (Bassani et al. 2016), focusing on the X-ray view. This ongoing study is aimed at characterizing for the first time the broad-band emission of a statistically significant sample of radio galaxies, thus constraining the accretion/ejection mechanisms at play in AGNs. The sample contains a significantly larger fraction of giant radio galaxies (linear size > 0.7 Mpc) than typically found in radio surveys; a talk focused on the radio properties of these peculiar objects is also proposed at this meeting (Bruni et al.). Concerning the X-ray absorption properties of the whole sample (Panessa et al. 2016), an intriguing result is the lack of heavily absorbed (Compton-thick) sources, which could hint for a discrepancy between the average absorption properties of radio-loud and radio-quiet AGNs. We also study the relation between X-ray absorption and 21 cm HI absorption, finding a higher probability of 21 cm detection among X-ray absorbed sources. This might in turn suggest that at least part of the X-ray obscuration is due to atomic hydrogen seen at radio frequencies, and that could reside at distances larger than the classical pc-scale torus.



Heavy X-ray obscuration in the most-luminous galaxies discovered by WISE

Fabio Vito

Co-authors: W.N. Brandt, D. Stern, R.J. Assef, C.-T. J. Chen, M. Brightman, A. Comastri, P. Eisenhardt, G.P. Garmire,  R. Hickox, G. Lansbury, C.-W. Tsai, D.J. Walton, J. W. Wu

Hot Dust-Obscured Galaxies (Hot DOGs) are hyperluminous (L_IR>10^{13} Lsun) infrared galaxies with extremely high (up to hundreds of K) dust temperatures. The sources powering both their extremely high luminosities and dust temperatures are thought to be deeply buried and rapidly accreting supermassive black holes (SMBHs). Hot DOGs could therefore represent a key evolutionary phase in which the SMBH growth peaks. X-ray observations can be used to study their obscuration levels and luminosities. I will discuss the X-ray properties of the 20 most-luminous (Lbol>10^{14} Lsun) known Hot DOGs at z=2-4.6, presented in Vito et al. (2018). We investigated the individual properties of the 3 sources detected with enough counts to perform basic spectral analysis. One of these sources (W0116-0505) is a Compton-thick candidate. We applied a stacking analysis to investigate the average emission of the remaining individually undetected sources. From hardness-ratio analysis, we constrained the average obscuring column density and intrinsic luminosity to be logNH>23.5 and logLx>44, which are consistent with results for individually detected sources. We also investigated the Lx-L6um and Lx-Lbol relations, finding hints that Hot DOGs are typically X-ray weaker than expected, although larger samples of luminous obscured QSOs are needed to derive solid conclusions. I will also compare our results with other samples of red quasars.