scholarly journals JD6 - The Connection between Radio Properties and High Energy Emission in AGNs

2012 ◽  
Vol 10 (H16) ◽  
pp. 187-198
Author(s):  
Gabriele Giovannini ◽  
Teddy Cheung
Keyword(s):  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Jet Physics ◽  
Spectral Energy ◽  
Essential Information ◽  
Multi Wavelength ◽  
Radio Band ◽  
High Energy Emission ◽  
Wavelength Monitoring

AbstractWhile observations in the radio band are providing essential information on the innermost structures of relativistic jets in active galactic nuclei (AGN), the recent detection byFermiof gamma-ray emission from many hundreds of blazars shows that the maximum jet power is emitted at high energies. Multi-wavelength monitoring observations further allow variability studies of the AGN spectral energy distributions over 13 orders of magnitude in frequency. The Joint Discussion offered the possibility for a comprehensive discussion of advances in the observational domain and stimulated theoretical discussion about our current understanding of jet physics.

scholarly journals HIGH-ENERGY EMISSION FROM JET–CLOUD INTERACTIONS IN AGNs

2010 ◽  
Vol 19 (06) ◽  
pp. 931-936 ◽  
Author(s):  
ANABELLA T. ARAUDO ◽  
VALENTÍ BOSCH-RAMON ◽  
GUSTAVO E. ROMERO
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Small Region ◽  
High Energy ◽  
Energy Emission ◽  
Central Regions ◽  
High Energy Emission

Active galactic nuclei present continuum and line emission. The emission lines are originated by gas located close to the central supermassive black hole. Some of these lines are broad, and would be produced in a small region called broad-line region. This region could be formed by clouds surrounding the central black hole. In this work, we study the interaction of such clouds with the base of the jets in active galactic nuclei, and we compute the produced high-energy emission. We focus on sources with low luminosities in the inner jet regions, to avoid strong gamma-ray absorption. We find that the resulting high-energy radiation may be significant in Centaurus A. Also, this phenomenon might be behind the variable gamma-ray emission detected in M87, if very large dark clouds are present. The detection of jet–cloud interactions in active galactic nuclei would give information on the properties of the jet base and the very central regions.

scholarly journals Radio Galaxies - The TeV Challenge

2018 ◽  
Author(s):  
Bindu Rani
Keyword(s):  
Gamma Ray ◽  
Radio Galaxies ◽  
High Energy ◽  
Energy Emission ◽  
Long Baseline ◽  
Multi Wavelength ◽  
Emission Models ◽  
Radiation Processes ◽  
High Energy Emission ◽  
Near Future

Over the past decade, our knowledge of the $\gamma$-ray sky has been revolutionized by ground- and space-based observatories by detecting photons up to several hundreds of tera-electron volt (TeV) energies. A major population of the $\gamma$-ray bright objects are active galactic nuclei (AGN) with their relativistic jets pointed along our line-of-sight. Gamma-ray emission is also detected from nearby mis-aligned AGN such as radio galaxies. While the TeV-detected radio galaxies ($TeVRad$) only form a small fraction of the $\gamma$-ray detected AGN, their multi-wavelength study offers a unique opportunity to probe and pinpoint the high-energy emission processes and sites. Even in the absence of substantial Doppler beaming $TeVRad$ are extremely bright objects in the TeV sky (luminosities detected up to $10^{45}~erg~s^{-1}$), and exhibit flux variations on timescales shorter than the event-horizon scales (flux doubling timescale less than 5 minutes). Thanks to the recent advancement in the imaging capabilities of high-resolution radio interferometry (millimeter very long baseline interferometry, mm-VLBI), one can probe the scales down to less than 10 gravitational radii in $TeVRad$, making it possible not only to test jet launching models but also to pinpoint the high-energy emission sites and to unravel the emission mechanisms. This review provides an overview of the high-energy observations of $TeVRad$ with a focus on the emitting sites and radiation processes. Some recent approaches in simulations are also sketched. Observations by the near-future facilities like Cherenkov Telescope Array, short millimeter-VLBI, and high-energy polarimetry instruments will be crucial for discriminating the competing high-energy emission models.

scholarly journals The unique case of the AGN core of M87: a misaligned low power blazar?

2019 ◽  
Author(s):  
M Lucchini ◽  
F Krauß ◽  
S Markoff
Keyword(s):  
Spectral Energy Distribution ◽  
Large Mass ◽  
High Energy ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Zone Model ◽  
Multi Wavelength ◽  
General Relativistic ◽  
Unique Source ◽  
High Energy Emission

Abstract M87 hosts one of the closest jetted active galactic nucleus (AGN) to Earth. Thanks to its vicinity and to the large mass of is central black hole, M87 is the only source in which the jet can be directly imaged down to near-event horizon scales with radio very large baseline interferometry (VLBI). This property makes M87 a unique source to isolate and study jet launching, acceleration and collimation. In this paper we employ a multi-zone model designed as a parametrisation of general relativistic magneto-hydrodynamics (GRMHD); for the first time we reproduce the jet’s observed shape and multi-wavelength spectral energy distribution (SED) simultaneously. We find strong constraints on key physical parameters of the jet, such as the location of particle acceleration and the kinetic power. However, we under-predict the (unresolved) γ-ray flux of the source, implying that the high-energy emission does not originate in the magnetically-dominated inner jet regions. Our results have important implications both for comparisons of GRMHD simulations with observations, and for unified models of AGN classes.

scholarly journals NON-THERMAL EMISSION FROM GALACTIC JETS

2012 ◽  
Vol 08 ◽  
pp. 84-95
Author(s):  
VALENTÍ BOSCH-RAMON
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Galactic Nuclei ◽  
High Energy ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Thermal Emitters ◽  
Thermal Sources ◽  
High Energy Emission ◽  
The Universe

Jets are ubiquitous in the Universe. They are collimated outflows whose origin is associated to an accretion disc and a central object, and can be very powerful non-thermal emitters. Jets form in active galactic nuclei, gamma-ray bursts, microquasars, and young stellar objects. Galactic jets emitting non-thermal emission are typically associated to microquasars, although the jets of massive young stellar objects are also non-thermal sources. The production of non-thermal radiation, in particular radio synchrotron emission, is a clear indication that particle acceleration is taking place in the source, which hints to the generation of photons even at high energies. In this work, we will discuss the emitting sites in, or related to, microquasar jets, and briefly comment on the possibility of high-energy emission in jets from young stellar objects.

scholarly journals A model for high-energy emission of the Intrabinary shock in pulsar binaries

2018 ◽  
Vol 168 ◽  
pp. 04013
Author(s):  
Hongjun An
Keyword(s):  
Neutron Star ◽  
Inclination Angle ◽  
Binary Systems ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Plasma Properties ◽  
Energy Emission ◽  
High Energy Emission

We present our studies of intrabinary shock emission for astrophysical binary systems with a neutron star. We construct a model for the shock emission and compare the model calculation with the light curve and the spectral energy distribution of the gamma-ray binary 1FGL J1018.6-5856. The model assumes a slow and a fast population of particles accelerated in the shock, and computes the high-energy emission spectra and orbital light curves produced by synchrotron, self-Compton and external Compton processes of the high-energy particles in the shock. The model allows one to study plasma properties and to constrain the binary geometry, most importantly the inclination angle (i). We discuss potential use of this model for other pulsar binaries to determine the inclination angle of the binary hence the mass of the neutron star.

scholarly journals ASCA Observations of Blazars

1998 ◽  
Vol 11 (2) ◽  
pp. 812-815
Author(s):  
T. Takahashi ◽  
H. Kubo ◽  
G. Madejski
Keyword(s):  
Active Galactic Nuclei ◽  
Time Scales ◽  
Small Angle ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Galactic Nuclei ◽  
High Energy ◽  
Energetic Particles ◽  
Energy Emission ◽  
High Energy Emission

During the last years it has become evident that blazar class of AGN emit a lot of energy in the gamma-ray regime. It is generally thought that the non-thermal emission from blazars, observed from radio to GeV/TeV 7-rays, is radiation of very energetic particles via both synchrotron and Compton processes. This underlines the importance of high-energy emission for models of the blazar class of active galactic nuclei. Most of the gamma-bright AGN are variable, and flares with time scales as short as a day have been observed. This suggests that the site of gamma-ray emission is very compact and situated in a fluid which moves relativistically at a small angle towards the observer. It is generally assumed that the emission originates from the jet of these objects.

scholarly journals The mid-2016 flaring activity of the flat spectrum radio quasar PKS 2023-07

2018 ◽  
Vol 616 ◽  
pp. A65 ◽  
Author(s):  
G. Piano ◽  
P. Munar-Adrover ◽  
L. Pacciani ◽  
P. Romano ◽  
S. Vercellone ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Emission Region ◽  
Massive Black Hole ◽  
Line Region ◽  
Entire Duration ◽  
Spectrum Radio ◽  
High Energy Emission

Context. Flat spectrum radio quasars (FSRQs) can suffer strong absorption above E = 25∕(1 + z) GeV, due to gamma–gamma interaction if the emitting region is at sub-parsec scale from the super-massive black hole (SMBH). Aims. Gamma-ray flares from these astrophysical sources can be used to investigate the location of the high-energy emission region and the physics of the radiating processes. Methods. We present an episode of remarkable gamma-ray flaring activity from FSRQ PKS 2023-07 during April 2016, as detected by both the AGILE and Fermi satellites. An intensive multiwavelength campaign, triggered by Swift, covered the entire duration of the flaring activity, including the peak gamma-ray activity. Results. We report the results of multiwavelength observations of the blazar. We found that during the peak emission, the most energetic photon had an energy of 44 GeV, putting strong constraints on the opacity of the gamma-ray dissipation region. The overall spectral energy distribution (SED) is interpreted in terms of leptonic models for blazar jets, with the emission site located beyond the broad line region (BLR).

THE OPTICAL-X-RAY–GAMMA-RAY SPECTRAL ENERGY DISTRIBUTIONS OF GEV GAMMA-RAY LOUD BLAZARS AND CONNECTION AMONG LBLs, HBLs AND FSRQs

2003 ◽  
Vol 12 (05) ◽  
pp. 781-789 ◽  
Author(s):  
G. Z. XIE ◽  
S. X. DING ◽  
H. DAI ◽  
E. W. LIANG ◽  
H. T. LIU
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Spectral Energy ◽  
Spectral Indices ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
X Ray ◽  
Γ Ray ◽  
High Energy Emission ◽  
Bl Lacs

In this paper, we introduce a new composite spectral indices αγxγ = αxγ - αγ, and prove [Formula: see text], that means αγxγ is intrinsic. We plot a αxox - αγxγ diagram for 25 Gev γ-ray blazars for which αx and αγ have been provided in the literature, where αxox = αox - αx which was introduced by Sambruna et al. (1996) and proved that it is intrinsic by our previous paper (Xie et al. 2001). Using this new composite color–color (αxox - αγxγ) diagram, we investigated the nature of the HBLs–LBLs relationship, and the BL Lacs–FSRQs relationship, in high-energy emission. The results show that the spectral energy distributions of three subclasses of Gev γ-ray loud blazars are different, but essentially continuous: HBLs and FSRQs occupy separated regions while LBLs bridge the gap between HBLs and FSRQs. The results are consistent with that derived from a low energy color–color(αxox - αoro) diagram by Sambruna et al. (1996) and Xie et al. (2001). However, on the αox - αxγ diagram, FSRQs, LBLs and HBLs occupy same region. Because both αγxγ and αxox are intrinsic, thus, the new connection among HBLs, LBLs and FSRQs obtained by us is intrinsic.

scholarly journals Multiwavelength study of potential blazar candidates among Fermi-LAT unidentified gamma-ray sources

2019 ◽  
Vol 15 (S356) ◽  
pp. 326-328
Author(s):  
Jean Damascène Mbarubucyeye ◽  
Felicia Krauß ◽  
Pheneas Nkundabakura
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Peak Position ◽  
Spectral Energy ◽  
Synchrotron Emission ◽  
Parabolic Model ◽  
X Ray ◽  
Single Radio ◽  
High Energy Emission

AbstractStudying unidentified γ-ray sources is important as they may hide new discoveries. We conducted a multiwavelength analysis of 13 unidentified Fermi-LAT sources in the 3FGL catalogue that have no known counterparts (Unidentified Gamma-ray Sources, UnIDs). The sample was selected for sources that have a single radio and X-ray candidate counterpart in their uncertainty ellipses. The purpose of this study is to find a possible blazar signature and to model the Spectral Energy Distribution (SED) of the selected sources using an empirical log parabolic model. The results show that the synchrotron emission of all sources peaks in the infrared (IR) band and that the high-energy emission peaks in MeV to GeV bands. The SEDs of sources in our sample are all blazar like. In addition, the peak position of the sample reveals that 6 sources (46.2%) are Low Synchrotron Peaked (LSP) blazars, 4 (30.8%) of them are High Synchrotron Peaked (HSP) blazars, while 3 of them (23.0%) are Intermediate Synchrotron Peaked (ISP) blazars.

scholarly journals Radio Galaxies—The TeV Challenge

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 23 ◽  
Author(s):  
Bindu Rani
Keyword(s):  
Gamma Ray ◽  
Radio Galaxies ◽  
High Energy ◽  
Energy Emission ◽  
Long Baseline ◽  
Multi Wavelength ◽  
Emission Models ◽  
Γ Ray ◽  
Radiation Processes ◽  
High Energy Emission

Over the past decade, our knowledge of the γ -ray sky has been revolutionized by ground- and space-based observatories by detecting photons up to several hundreds of tera-electron volt (TeV) energies. A major population of the γ -ray bright objects are active galactic nuclei (AGN) with their relativistic jets pointed along our line-of-sight. Gamma-ray emission is also detected from nearby misaligned AGN such as radio galaxies. While the TeV-detected radio galaxies ( T e V R a d ) only form a small fraction of the γ -ray detected AGN, their multi-wavelength study offers a unique opportunity to probe and pinpoint the high-energy emission processes and sites. Even in the absence of substantial Doppler beaming T e V R a d are extremely bright objects in the TeV sky (luminosities detected up to 10 45 erg s − 1 ), and exhibit flux variations on timescales shorter than the event-horizon scales (flux doubling timescale less than 5 min). Thanks to the recent advancement in the imaging capabilities of high-resolution radio interferometry (millimeter very long baseline interferometry, mm-VLBI), one can probe the scales down to less than 10 gravitational radii in T e V R a d , making it possible not only to test jet launching models but also to pinpoint the high-energy emission sites and to unravel the emission mechanisms. This review provides an overview of the high-energy observations of T e V R a d with a focus on the emitting sites and radiation processes. Some recent approaches in simulations are also sketched. Observations by the near-future facilities like Cherenkov Telescope Array, short millimeter-VLBI, and high-energy polarimetry instruments will be crucial for discriminating the competing high-energy emission models.

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