Marcello Giroletti - INAF-Istituto di Radio Astronomia, Bologna

Marcello Giroletti
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Marcello Giroletti
INAF-Istituto di Radio Astronomia, Bologna

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High Energy Astrophysical Phenomena (19)
Cosmology and Nongalactic Astrophysics (16)
Astrophysics of Galaxies (9)
Instrumentation and Methods for Astrophysics (5)
Solar and Stellar Astrophysics (2)
Astrophysics (1)
High Energy Physics - Phenomenology (1)

Publications Authored By Marcello Giroletti

We report on the 1.6 GHz (18 cm) VLBI observations of the unresolved, steady TeV source HESS J1943+213 located in the Galactic plane, performed with the European VLBI Network (EVN) in 2014. Our new observations with a nearly full EVN array provide the deepest image of HESS J1943+213 at the highest resolution ever achieved, enabling us to resolve the long-standing issues of the source identification. Read More

We report on results from new high-sensitivity, high-resolution 86GHz (3.5 millimeter) observations of the jet base in the nearby radio galaxy M87, obtained by the Very Long Baseline Array in conjunction with the Green Bank Telescope. The resulting image has a dynamic range exceeding 1500 to 1, the highest ever achieved for this jet at this frequency, resolving and imaging a detailed jet formation/collimation structure down to ~10 Schwarzschild radii (Rs). Read More

Authors: Fabio Acero, Markus Ackermann, Marco Ajello, Luca Baldini, Jean Ballet, Guido Barbiellini, Denis Bastieri, Ronaldo Bellazzini, E. Bissaldi, Roger Blandford, E. D. Bloom, Raffaella Bonino, Eugenio Bottacini, J. Bregeon, Philippe Bruel, Rolf Buehler, S. Buson, G. A. Caliandro, Rob A. Cameron, R Caputo, Micaela Caragiulo, Patrizia A. Caraveo, Jean Marc Casandjian, Elisabetta Cavazzuti, Claudia Cecchi, A. Chekhtman, J. Chiang, G. Chiaro, Stefano Ciprini, R. Claus, J. M. Cohen, Johann Cohen-Tanugi, L. R. Cominsky, B. Condon, Jan Conrad, S. Cutini, F. D'Ammando, A. Angelis, F. Palma, Rachele Desiante, S. W. Digel, L. Venere, Persis S Drell, Alex Drlica-Wagner, C. Favuzzi, E. C. Ferrara, Anna Franckowiak, Prof. Yasushi Fukazawa, Prof. Stefan Funk, P. Fusco, Fabio Gargano, Dario Gasparrini, Nicola Giglietto, Paolo Giommi, Francesco Giordano, Marcello Giroletti, Tom Glanzman, Gary Godfrey, G A. Gomez-Vargas, I. A. Grenier, M. -H. Grondin, L. Guillemot, Sylvain Guiriec, M Gustafsson, D. Hadasch, A. K. Harding, M. Hayashida, Elizabeth Hays, J. W. Hewitt, A. B. Hill, Deirdre Horan, X. Hou, Giulia Iafrate, Tobias Jogler, G. J'ohannesson, Anthony S. Johnson, T. Kamae, Hideaki Katagiri, Prof. Jun Kataoka, Junichiro Katsuta, Matthew Kerr, J. Knodlseder, Prof. Dale Kocevski, M. Kuss, Helene Laffon, J. Lande, S. Larsson, Luca Latronico, Marianne Lemoine-Goumard, J. Li, L. Li, Francesco Longo, Francesco Loparco, Michael N. Lovellette, Pasquale Lubrano, J. Magill, S. Maldera, Martino Marelli, Michael Mayer, M. N. Mazziotta, Peter F. Michelson, Warit Mitthumsiri, Tsunefumi Mizuno, Alexander A. Moiseev, Maria Elena Monzani, E. Moretti, Aldo Morselli, Igor V. Moskalenko, Prof. Simona Murgia, Prof. Rodrigo Nemmen, Eric Nuss, Takashi Ohsugi, Nicola Omodei, Monica Orienti, Elena Orlando, Jonathan F. Ormes, David Paneque, J. S. Perkins, Melissa Pesce-Rollins, Prof. Vahe' Petrosian, Frederic Piron, Giovanna Pivato, Troy Porter, S. Rain`o, Riccardo Rando, Massimiliano Razzano, Soebur Razzaque, Anita Reimer, Prof. Olaf Reimer, Matthieu Renaud, Thierry Reposeur, Mr. Romain Rousseau, P. M. Parkinson, J. Schmid, A. Schulz, C. Sgr`o, Eric J Siskind, Francesca Spada, Gloria Spandre, Paolo Spinelli, Andrew W. Strong, Daniel Suson, Hiro Tajima, Hiromitsu Takahashi, T. Tanaka, Jana B. Thayer, D. J. Thompson, L. Tibaldo, Omar Tibolla, Prof. Diego F. Torres, Gino Tosti, Eleonora Troja, Yasunobu Uchiyama, G. Vianello, B. Wells, Kent Wood, M. Wood, Manal Yassine, Stephan Zimmer

To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope. Based on the spatial overlap of sources detected at GeV energies with SNRs known from radio surveys, we classify 30 sources as likely GeV SNRs. We also report 14 marginal associations and 245 flux upper limits. Read More

Affiliations: 1INAOE Puebla, Mexico, 2UNAM, Mexico, 3ESA, Madrid- ISAS, Japan, 4INAF-IRA Bologna, Italy, 5INAF-IAPS Roma, Italy, 6SRON Utrecht, The Netherlands, 7ESA, Madrid, 8ESA, Madrid

Winds outflowing from Active Galactic Nuclei (AGNs) may carry significant amount of mass and energy out to their host galaxies. In this paper we report the detection of a sub-relativistic outflow observed in the Narrow Line Seyfert 1 Galaxy IRAS17020+4544 as a series of absorption lines corresponding to at least 5 absorption components with an unprecedented wide range of associated column densities and ionization levels and velocities in the range of 23,000-33,000 km/s, detected at X-ray high spectral resolution (E/Delta E ~1000) with the ESA's observatory XMM-Newton. The charge states of the material constituting the wind clearly indicate a range of low to moderate ionization states in the outflowing gas and column densities significantly lower than observed in highly ionized ultra fast outflows. Read More

The statistical study of the parsec scale properties of radio sources is crucial to get information on the nature of the central engine and to provide the foundations of the current unified theories, suggesting that the appearance of active galactic nuclei depends strongly on orientation. We started a project to observe at sub-arcsec resolution a complete sample of 94 nearby (z<0.1) radio galaxies, the Bologna Complete Sample, which is not affected by any selection effect on the jet velocity and orientation with respect to the line of sight. Read More

The radio-loud BCG at the center of the cool core cluster RBS 797 is known to exhibit a misalignment of its 5 GHz radio emission observed at different VLA resolutions, with the innermost kpc-scale jets being almost orthogonal to the radio lobes which extends for tens of kpc filling the X-ray cavities seen by Chandra. The different radio directions may be caused by rapid jet reorientation due to interaction with a secondary supermassive black hole (SMBH), or to the presence of two AGN, probably in a merging phase, which are emitting radio jets in different directions. We present the results of new 5 GHz observations performed with the EVN in May 2013. Read More

The radio galaxy 3C84 is a representative of gamma-ray-bright misaligned active galactic nuclei (AGN) and one of the best laboratories to study the radio properties of subparsec scale jets. We discuss here the past and present activity of the nuclear region within the central 1pc and the properties of subparsec-sized components C1, C2 and C3. We compare these results with the high resolution space-VLBI image at 5GHz obtained with the RadioAstron satellite and we shortly discuss the possible correlation of radio emission with the gamma-ray emission. Read More

The relativistic jet in M87 offers a unique opportunity for understanding the detailed jet structure and emission processes due to its proximity. In particular, the peculiar jet region HST-1 at ~1 arcsecond (or 80 pc, projected) from the nucleus has attracted a great deal of interest in the last decade because of its superluminal motion and broadband radio-to-X-ray outbursts, which may be further connected to the gamma-ray productions up to TeV energies. Over the last five years, we have been doing an intensive monitoring of HST-1 with EVN at 5GHz in order to examine the detailed structural evolution and its possible connection to high-energy activities. Read More

Relativistic jets in active galactic nuclei (AGN) are among the most powerful astrophysical objects discovered to date. Indeed, jetted AGN studies have been considered a prominent science case for SKA, and were included in several different chapters of the previous SKA Science Book (Carilli & Rawlings 2004). Most of the fundamental questions about the physics of relativistic jets still remain unanswered, and await high-sensitivity radio instruments such as SKA to solve them. Read More


Adding VLBI capability to the SKA arrays will greatly broaden the science of the SKA, and is feasible within the current specifications. SKA-VLBI can be initially implemented by providing phased-array outputs for SKA1-MID and SKA1-SUR and using these extremely sensitive stations with other radio telescopes, and in SKA2 by realising a distributed configuration providing baselines up to thousands of km, merging it with existing VLBI networks. The motivation for and the possible realization of SKA-VLBI is described in this paper. Read More

Affiliations: 1SISSA, Trieste, 2INAF-Istituto di Radio Astronomia, Bologna, 3INAF - Osservatorio Astrofisico di Torino, 4INAF-Istituto di Radio Astronomia, Bologna, 5INAF-Istituto di Radio Astronomia, Bologna, 6Instituto de Astrofisica de Andalucia, Granada, 7University of Tsukuba

Aims. We want to study the amount of molecular gas in a sample of nearby early-type galaxies (ETGs) which host low-luminosity Active Galactic Nuclei (AGN). We look for possible differences between the radio-loud (RL) and radio-quiet (RQ) AGN. Read More

To obtain a better understanding of the location and mechanisms for the production of the gamma-ray emission in jets of AGN we present a detailed study of the HST-1 structure, 0.8 arcsec downstream the jet of M87, previously identified as a possible candidate for TeV emission. HST-1 shows a very peculiar structure with superluminal as well as possible stationary sub-components, and appears to be located in the transition from a parabolic to a conical jet shape, presumably leading to the formation of a recollimation shock. Read More

Abridged: We investigated the detailed radio structure of the nucleus of the Sombrero galaxy using high-resolution, quasi-simultaneous, multi-frequency, phase-referencing VLBA observations. We obtained the VLBI images toward this nucleus, with unprecedented sensitivities and resolutions, at the seven frequencies between 1.4 and 43 GHz, where those at 15, 24 and 43 GHz are the first clear VLBI detections. Read More

An international consortium is presently constructing a beamformer for the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile that will be available as a facility instrument. The beamformer will aggregate the entire collecting area of the array into a single, very large aperture. The extraordinary sensitivity of phased ALMA, combined with the extremely fine angular resolution available on baselines to the Northern Hemisphere, will enable transformational new very long baseline interferometry (VLBI) observations in Bands 6 and 7 (1. Read More

We present {\it Gemini} longslit optical spectroscopy and VLA radio observations of the nuclear region of NGC 4178, a late-type bulgeless disk galaxy recently confirmed to host an AGN through infrared and X-ray observations. Our observations reveal that the dynamical center of the galaxy is coincident with the location of the {\it Chandra} X-ray point source discovered in a previous work, providing further support for the presence of an AGN. While the X-ray and IR observations provide robust evidence for an AGN, the optical spectrum shows no evidence for the AGN, underscoring the need for the penetrative power of mid-IR and X-ray observations in finding buried or weak AGNs in this class of galaxy. Read More

We investigated the detailed inner jet structure of M87 using the Very Long Baseline Array data at 2, 5, 8.4, 15, 23.8, 43, and 86 GHz, especially focusing on the multi-frequency properties of the radio core at the jet base. Read More

We present a census of sub-pc scale properties of the VLBI cores in a complete sample of local Seyfert galaxies. Seventeen out of 23 sources with a VLA detection are detected also with VLBI at 1.7 GHz and/or 5 GHz, with an average monochromatic radio luminosity log [P (5\, GHz) W Hz^{-1} = 19. Read More

We report on the detailed radio status of the M87 jet during the Very-High-Energy (VHE) gamma-ray flaring event in April 2010, obtained from high-resolution, multi-frequency, phase-referencing VLBA observations. We especially focus on the properties for the jet base (the radio core) and the peculiar knot HST-1, which are currently favored as the gamma-ray emitting sites. During the VHE flaring event, the HST-1 region remains stable in terms of its structure and flux density in the optically thin regime above 2GHz, being consistent with no signs of enhanced activities reported at X-ray for this feature. Read More

We introduce the GENJI program (Gamma-ray Emitting Notable AGN Monitoring by Japanese VLBI), which is a monitoring program of gamma-ray bright AGNs with the VERA array (VLBI Exploration of Radio Astrometry). The GENJI programme aims a dense monitoring at 22 GHz towards the $\gamma$-ray emitting active galactic nuclei (AGNs) to investigate the radio time variation of the core and possible ejection of new radio component, motion of jets, and their relation with the emission at other wavelengths especially in $\gamma$-rays. Currently we are monitoring 8 $\gamma$-ray-emitting notable AGNs (DA 55, 3C 84, M 87, PKS 1510-089, DA 406, NRAO 530, BL Lac, 3C 454. Read More

The radio galaxy 3C 84 is a representative of gamma-ray-bright misaligned active galactic nuclei (AGNs) and one of the best laboratories to study the radio properties of the sub-pc jet in connection with the gamma-ray emission. In order to identify possible radio counterparts of the gamma-ray emissions in 3C 84, we study the change in structure within the central 1 pc and the light curve of sub-pc-size components C1, C2, and C3. We search for any correlation between changes in the radio components and the gamma-ray flares by making use of VLBI and single dish data. Read More

Following the discovery of a new radio component right before the GeV \gamma-ray detection since 2008 August by Fermi Gamma-ray Space Telescope, we present a detailed study of the kinematics and lightcurve on the central sub-pc scale of 3C 84 using the archival VLBA 43-GHz data covering the period between 2002 January to 2008 November. We find that the new component "C3", previously reported by the observations with the VLBI Exploration of Radio Astrometry (VERA), was already formed in 2003. The flux density of C3 increases moderately until 2008, and then it becomes brighter rapidly after 2008. Read More

The detection of gamma-ray emission by Fermi-LAT from the radio loud Narrow Line Seyfert 1 PMN J0948+0022 (Abdo et al. 2009, ApJ 699, 976) triggered a multi-wavelength campaign between March and July 2009. Given its high compactness (Doi et al. Read More

Affiliations: 1INAF Istituto di Radioastronomia, 2IASF/INAF

In this letter, we report on dual-frequency European VLBI Network (EVN) observations of the faintest and least luminous radio cores in Seyfert nuclei, going to sub-mJy flux densities and radio luminosities around 10^19 W/Hz. We detect radio emission from the nuclear region of four galaxies (NGC 4051, NGC 4388, NGC 4501, and NGC 5033), while one (NGC 5273) is undetected at the level of ~100 microJy. The detected compact nuclei have rather different radio properties: spectral indices range from steep (alpha>0. Read More

We show preliminary results from a sample of Luminous and Ultra-Luminous Infrared Galaxies (LIRGs and ULIRGs, respectively) in the local universe, obtained from observations using the Very Large Array (VLA), the Multi-Element Radio Link Interferometer Network (MERLIN), and the European VLBI Network (EVN). The main goal of our high-resolution, high-sensitivity radio observations is to unveil the dominant gas heating mechanism in the central regions of local (U)LIRGs. The main tracer of recent star-formation in (U)LIRGs is the explosion of core-collapse supernovae (CCSNe), which are the endproducts of the explosion of massive stars and yield bright radio events. Read More