scholarly journals Hadronic origin of multi-TeV gamma rays and neutrinos from low-luminosity active galactic nuclei: Implications of past activities of the Galactic center

2015 ◽  
Vol 92 (2) ◽  
Author(s):  
Yutaka Fujita ◽  
Shigeo S. Kimura ◽  
Kohta Murase
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Galactic Center ◽  
Galactic Nuclei ◽  
Tev Gamma Rays

scholarly journals TeV Gamma Rays from Ultrahigh Energy Cosmic Ray Interactions in the Cores of Active Galactic Nuclei: Lessons from Centaurus A

2010 ◽  
Vol 27 (4) ◽  
pp. 482-489 ◽  
Author(s):  
M. Kachelrieß ◽  
S. Ostapchenko ◽  
R. Tomàs
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Galactic Nuclei ◽  
Cosmic Ray ◽  
Far Infrared ◽  
High Energy ◽  
Ultrahigh Energy ◽  
Very High Energy ◽  
Tev Gamma Rays ◽  
Centaurus A

AbstractTeV gamma rays have been observed from blazars as well as from radio galaxies like M 87 and Centaurus A. In leptonic models, gamma rays above the pair production threshold can escape from the ultrarelativistic jet, because large Lorentz factors reduce the background photon densities compared to those required for isotropic emission. Here we discuss an alternative scenario, where very high energy photons are generated as secondaries from ultrahigh energy cosmic rays interactions in the cores of active galactic nuclei. We show that TeV gamma-rays can escape from the core despite large infrared and ultraviolet backgrounds. For the special case of Centaurus A, we study whether the various existing observations from the far infrared to the ultrahigh energy range can be reconciled within this picture.

scholarly journals PHYSICS INSIGHTS FROM RECENT MAGIC AGN OBSERVATIONS

2009 ◽  
Vol 18 (10) ◽  
pp. 1489-1492
Author(s):  
◽  
ROBERT WAGNER
Keyword(s):  
Energy Spectrum ◽  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Radio Galaxy ◽  
Galactic Nuclei ◽  
New Physics ◽  
Spectrum Radio ◽  
Tev Gamma Rays ◽  
Radio Quasar

The total set of the 14 active galactic nuclei detected by MAGIC so far includes well-studied bright blazars like Mkn 501, the giant radio galaxy M 87, but also the distant flat-spectrum radio quasar 3C 279, and an intriguing gamma-ray source in the 3C 66A/B region, whose energy spectrum is not compatible with the expectations from 3C 66A. Besides scheduled observations, so far MAGIC succeeded in discovering TeV gamma rays from three blazars following triggers from high optical states. I report selected highlights from recent MAGIC observations of extragalactic TeV gamma-ray sources, emphasizing and discussing the new physics insights the MAGIC observations were able to contribute.

Radiative wind from a luminous star cluster

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Jun Fukue
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Source Distribution ◽  
Radiative Force ◽  
Mass Reduction ◽  
Central Mass ◽  
Point Analysis ◽  
Thermally Driven

Abstract We reexamine the steady spherical wind from distributed sources, such as star clusters and a galactic center, taking into account the radiative force from distributed sources and mass reduction via orbital motions. We consider a cold dusty wind, an isothermal gaseous flow, and a nonisothermal general one without/with a central mass and a stagnation radius for various powers of source distributions. We perform singular point analysis for each case, and obtain a transonic solution, if one exists. We find that thermally driven outflows can emerge in limited situations, such that the source distribution is rather steep in the isothermal flow. On the other hand, under the appropriate conditions radiatively driven winds can easily be produced. Radiative cluster winds without a central mass could emerge from newly born star clusters or neutron star clusters, whereas those with a central mass could appear from active galactic nuclei. Radiative cluster winds would also operate in first star clusters.

scholarly journals Study of the Galactic Center with a High Resolution Gamma Ray Telescope

1989 ◽  
Vol 136 ◽  
pp. 639-643
Author(s):  
Ervin J. Fenyves ◽  
Stephen N. Balog ◽  
David B. Cline ◽  
M. Atac
Keyword(s):  
Black Holes ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Center ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Hole Formation ◽  
Massive Black Holes ◽  
General Outcome ◽  
Enormous Amount

It is generally accepted that massive black holes are the most likely source for the energy radiated from active galactic nuclei, and may explain the enormous amount of energy emitted by quasars, radio galaxies, Seyfert galaxies, and BL Lacertid objects. Although the detailed mechanisms of the black hole formation in galactic nuclei are not clear at present, it seems to be quite possible that the formation of massive black holes is a general outcome of the evolution of galactic nuclei.

scholarly journals Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

2020 ◽  
Vol 6 (27) ◽  
pp. eaay9711 ◽  
Author(s):  
D. Krishnarao ◽  
R. A. Benjamin ◽  
L. M. Haffner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Hydrogen Gas ◽  
Emission Lines ◽  
Neutral Gas ◽  
Optical Line ◽  
Tilted Disk

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius “Tilted Disk” of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

scholarly journals NONTHERMAL EMISSIONS FROM SHOCKED SHELLS DRIVEN BY POWERFUL AGN JETS

2010 ◽  
Vol 19 (06) ◽  
pp. 893-899
Author(s):  
HIROTAKA ITO ◽  
MOTOKI KINO ◽  
NOZOMU KAWAKATU ◽  
SHOICHI YAMADA
Keyword(s):  
Synchrotron Radiation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Cherenkov Telescopes ◽  
Inverse Compton ◽  
Radiative Output ◽  
Radiation Processes ◽  
Tev Gamma Rays ◽  
Nonthermal Emissions ◽  
Compact Sources

We explore the emissions by accelerated electrons in shocked shells driven by jets in active galactic nuclei (AGNs). Focusing on powerful sources which host luminous quasars, the synchrotron radiation and inverse-Compton (IC) scattering of various photons that are mainly produced in the core are considered as radiation processes. We show that the radiative output is dominated by the IC emission for compact sources (≲ 30 kpc), whereas the synchrotron radiation is more important for larger sources. It is predicted that, for powerful sources (L j ~ 1047 ergs s -1), GeV – TeV gamma-rays produced via the IC emissions can be detected by the Fermi satellite and modern Cherenkov telescopes such as MAGIC, HESS and VERITAS if the source is compact.

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