E. Torresi

THE γ-RAY EMISSION REGION IN THE FANAROFF-RILEY II RADIO GALAXY 3C 111

The broad-line radio galaxy 3C 111, characterized by a Fanaroff-Riley II (FRII) radio morphology, is one of the sources of the misaligned active galactic nucleus sample, consisting of radio galaxies and steep spectrum radio quasars, recently detected by the Fermi Large Area Telescope (LAT). Our analysis of the 24 month {gamma}-ray light curve shows that 3C 111 was only occasionally detected at high energies. It was bright at the end of 2008 and faint, below the Fermi-LAT sensitivity threshold, for the rest of the time. A multifrequency campaign of 3C 111, ongoing in the same period, revealed an increase of the millimeter, optical, and X-ray fluxes in 2008 September-November, interpreted by Chatterjee et al. as due to the passage of a superluminal knot through the jet core. The temporal coincidence of the millimeter-optical-X-ray outburst with the GeV activity suggests a cospatiality of the events, allowing, for the first time, the localization of the {gamma}-ray dissipative zone in an FRII jet. We argue that the GeV photons of 3C 111 are produced in a compact region confined within 0.1 pc and at a distance of about 0.3 pc from the black hole.

Extended soft X-ray emission in 3CR radio galaxies at z < 0.3: high excitation and broad line galaxies

We analyze Chandra observations of diffuse soft X-ray emission associated with a complete sample of 3CR radio galaxies at z < 0.3. We focus on the properties of the spectroscopic sub-classes of high excitation galaxies (HEGs) and broad line objects (BLOs). Among the 33 HEGs we detect extended (or possibly extended) emission in about 40% of the sources; the fraction is even higher (8/10) when restricting the analysis to the objects with exposure times larger than 10 ks. In the 18 BLOs, extended emission is seen only in two objects; this lower detection rate can be ascribed to the presence of their bright X-ray nuclei that easily outshine any genuine diffuse emission. A very close correspondence between the soft X-ray and optical line morphology emerges. We also find that the ratio between [O III] and extended soft X-ray luminosity is confined within a factor of 2 around a median value of 5. Both results are similar to what is seen in Seyfert galaxies. We discuss different processes that could explain the soft X-ray emission and conclude that the photoionization of extended gas, coincident with the narrow line region, is the favored mechanism.

Unveiling the nature of the γ-ray emitting active galactic nucleus PKS 0521−36

PKS 0521−36 is an Active Galactic Nucleus (AGN) with uncertain classi fication. We investigate the properties of this source from radio to γ rays. The broad emission lines in the optical and UV bands and steep radio spectrum indicate a possible cla ssific tion as an intermediate object between broad-line radio galaxies (BLRG) and steep s p ctrum radio quasars (SSRQ). On pc-scales PKS 0521 −36 shows a knotty structure similar to misaligned AGN. The co re dominance and the γ-ray properties are similar to those estimated for other SSR Q and BLRG detected inγ rays, suggesting an intermediate viewing angle with respec t to the observer. In this context the flaring activity detected from this source b y Fermi-LAT between 2010 June and 2012 February is very intriguing. We discuss the γ-ray emission of this source in the framework of the structured jet scenario, comparing the spe ctral energy distribution (SED) of the flaring state in 2010 June with that of a low state. We prese nt three alternative models corresponding to three different choices of the viewing angles θv = 6, 15, and 20. We obtain a good fit for the the first two cases, but the SED obtained with θv = 15 if observed at a small angle does not resemble that of a typical blazar since the syn chrotron emission should dominate by a large factor ( ∼ 100) the inverse Compton component. This suggests that a vie wing angle between 6 ◦ and 15 is preferred, with the rapid variability observed during γ-ray flares favouring a smaller angle. However, we cannot rule out that P KS 0521−36 is the misaligned counterpart of a synchrotron-dominated blazar.

The On-Site Analysis of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) observatory will be one of the largest ground-based very high-energy gamma-ray observatories. The On-Site Analysis will be the first CTA scientific analysis of data acquired from the array of telescopes, in both northern and southern sites. The On-Site Analysis will have two pipelines: the Level-A pipeline (also known as Real-Time Analysis, RTA) and the level-B one. The RTA performs data quality monitoring and must be able to issue automated alerts on variable and transient astrophysical sources within 30 seconds from the last acquired Cherenkov event that contributes to the alert, with a sensitivity not worse than the one achieved by the final pipeline by more than a factor of 3. The Level-B Analysis has a better sensitivity (not be worse than the final one by a factor of 2) and the results should be available within 10 hours from the acquisition of the data: for this reason this analysis could be performed at the end of an observation or next morning. The latency (in particular for the RTA) and the sensitivity requirements are challenging because of the large data rate, a few GByte/s. The remote connection to the CTA candidate site with a rather limited network bandwidth makes the issue of the exported data size extremely critical and prevents any kind of processing in real-time of the data outside the site of the telescopes. For these reasons the analysis will be performed on-site with infrastructures co-located with the telescopes, with limited electrical power availability and with a reduced possibility of human intervention. This means, for example, that the on-site hardware infrastructure should have low-power consumption. A substantial effort towards the optimization of high-throughput computing service is envisioned to provide hardware and software solutions with high-throughput, low-power consumption at a low-cost.

Radio/X-ray monitoring of the broad-line radio galaxy 3C 382. High-energy view with XMM–Newton and NuSTAR

We present the analysis of five joint XMM–Newton/NuSTARobservations, 20 ks each and separated by 12 days, of the broad-line radio galaxy 3C 382. The data were obtained as part of a campaign performed in September-October 2016 simultaneously with VLBA. The radio data and their relation with the X-ray ones will be discussed in a following paper. The source exhibits a moderate flux variability in the UV/X-ray bands, and a limited spectral variability especially in the soft X-ray band. In agreement with past observations, we find the presence of a warm absorber, an iron Kα line with no associated Compton reflection hump, and a variable soft excess well described by a thermal Comptonization component. The data are consistent with a “two-corona” scenario, in which the UV emission and soft excess are produced by a warm (kT ≃ 0.6 keV), optically thick (τ ≃ 20) corona consistent with being a slab fully covering a nearly passive accretion disc, while the hard X-ray emission is due to a hot corona intercepting roughly 10% of the soft emission. These results are remarkably similar to those generally found in radio-quiet Seyferts, thus suggesting a common accretion mechanism.

Yet another UFO in the X-ray spectrum of a high-z lensed QSO

Ultra-fast outflows (UFO) appear to be common in local active galactic nuclei (AGN) and may be powerful enough (

Radio galaxies with the Cherenkov Telescope Array

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Faint γ-ray sources at low redshift: the radio galaxy IC 1531

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The MURALES survey. I. A dual AGN in the radio galaxy 3C 459

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