Young radio sources at high-energies and the γ-ray CSO PKS 1718–649

2018 ◽  
Vol 14 (S342) ◽  
pp. 176-179
Author(s):  
Giulia Migliori
Keyword(s):  
Radio Galaxy ◽  
Radio Galaxies ◽  
High Energy ◽  
Radio Sources ◽  
Host Galaxies ◽  
X Ray ◽  
High Energies ◽  
Γ Rays ◽  
Γ Ray ◽  
High Energy Emission

AbstractObservations at high-energies are important to define the first stages of the evolution of extragalactic radio sources and to characterize the interstellar medium of their host galaxies. In some of the X-ray-observed Compact Symmetric Objects (CSOs, among the youngest and most compact radio galaxies), we measured values of the total hydrogen column densities large enough to slow or prevent the radio source growth. The γ-ray window has the potential to constrain the non-thermal contribution of jets and lobes to the total high-energy emission. However, so far, young radio sources remain elusive in γ-rays, with only a handful of detections (or candidates) reported by Fermi. I present our γ-ray study of the CSO PKS 1718–649, and draw comparison with the restarted, γ-ray detected, radio galaxy 3C 84.

scholarly journals Cosmic rays and high energy emission from starburst galaxies

2011 ◽  
Vol 7 (S284) ◽  
pp. 393-396
Author(s):  
Brian C. Lacki ◽  
Todd A. Thompson
Keyword(s):  
Cosmic Rays ◽  
High Energy ◽  
Starburst Galaxies ◽  
Electron Cooling ◽  
X Ray ◽  
Inverse Compton ◽  
Γ Rays ◽  
Γ Ray ◽  
High Energy Emission ◽  
The Magnetic Field

AbstractThe nearby starburst galaxies M82 and NGC 253 are now detected in GeV and TeV γ-rays, allowing us to directly study cosmic rays (CRs) in starburst galaxies. Combined with radio observations, the detections constrain the propagation and density of CRs in these starbursts. We discuss the implications for “proton calorimetry”, whether CR protons cool through pion losses before escaping these galaxies. The ratio of γ-ray and radio luminosities constrains how much of the CR electron cooling is due to synchrotron losses. As for leptonic emission, we predict that synchrotron and Inverse Compton emission make up ~1–10% of the unresolved hard X-ray emission from M82, and a few percent or less of the total X-ray emission from starbursts. A detection of these components would inform us of the magnetic field strength and 10 – 100 TeV electron spectrum. We conclude by discussing the prospects for detecting leptonic MeV γ-rays from starbursts and the cosmic γ-ray background.

scholarly journals Pulsed γ-ray emission from magnetar 1E 2259+586

2012 ◽  
Vol 8 (S291) ◽  
pp. 555-557
Author(s):  
J. H. K. Wu ◽  
C. Y. Hui ◽  
R. H. H. Huang ◽  
A. K. H. Kong ◽  
K. S. Cheng ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Theoretical Models ◽  
High Energy ◽  
Large Area ◽  
Strong Magnetic Fields ◽  
X Ray ◽  
Γ Rays ◽  
Γ Ray ◽  
High Energy Emission ◽  
Intensive Search

AbstractAnomalous X-ray pulsars (AXPs) are thought to be magnetars which are young isolated neutron stars with extremely strong magnetic fields of >1014 Gauss. Their tremendous magnetic fields inferred from the spin parameters provide a huge energy reservoir to power the observed X-ray emission. High-energy emission above 0.3 MeV has never been detected despite intensive search. Here, we present the possible Fermi Large Area Telescope (LAT) detection of γ-ray pulsations above 200 MeV from the AXP, 1E 2259+586, which puts the current theoretical models of γ-ray emission mechanisms of magnetars into challenge. We speculate that the high-energy γ-rays originate from the outer magnetosphere of the magnetar.

scholarly journals NGC 3894: a young radio galaxy seen by Fermi-LAT

2020 ◽  
Vol 635 ◽  
pp. A185 ◽  
Author(s):  
G. Principe ◽  
G. Migliori ◽  
T. J. Johnson ◽  
F. D’Ammando ◽  
M. Giroletti ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Radio Galaxies ◽  
High Energy ◽  
Apparent Velocity ◽  
Large Area ◽  
Long Baseline ◽  
Full Period ◽  
Very Long Baseline Array ◽  
High Energy Emission ◽  
First Time

Context. According to radiative models, radio galaxies may produce γ-ray emission from the first stages of their evolution. However, very few such galaxies have been detected by the Fermi Large Area Telescope (LAT) so far. Aims. NGC 3894 is a nearby (z = 0.0108) object that belongs to the class of compact symmetric objects (CSOs, i.e., the most compact and youngest radio galaxies), which is associated with a γ-ray counterpart in the Fourth Fermi-LAT source catalog. Here we present a study of the source in the γ-ray and radio bands aimed at investigating its high-energy emission and assess its young nature. Methods. We analyzed 10.8 years of Fermi-LAT data between 100 MeV and 300 GeV and determined the spectral and variability characteristics of the source. Multi-epoch very long baseline array (VLBA) observations between 5 and 15 GHz over a period of 35years were used to study the radio morphology of NGC 3894 and its evolution. Results. NGC 3894 is detected in γ-rays with a significance >9σ over the full period, and no significant variability has been observed in the γ-ray flux on a yearly time-scale. The spectrum is modeled with a flat power law (Γ = 2.0 ± 0.1) and a flux on the order of 2.2 × 10−9 ph cm−2 s−1. For the first time, the VLBA data allow us to constrain with high precision the apparent velocity of the jet and counter-jet side to be βapp, NW = 0.132 ± 0.004 and βapp, SE = 0.065 ± 0.003, respectively. Conclusions. Fermi-LAT and VLBA results favor the youth scenario for the inner structure of this object, with an estimated dynamical age of 59 ± 5 years. The estimated range of viewing angle (10° < θ <  21°) does not exclude a possible jet-like origin of the γ-ray emission.

scholarly journals A New Chapter in Hard X-rays of the M87 AGN

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 9
Author(s):  
Ka-Wah Wong ◽  
Rodrigo S. Nemmen ◽  
Jimmy A. Irwin ◽  
Dacheng Lin
Keyword(s):  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Accretion Flow ◽  
Relativistic Jet ◽  
Very High Energy ◽  
Γ Ray ◽  
High Energy Emission ◽  
First Time ◽  
Very High

The nearby M87 hosts an exceptional relativistic jet. It has been regularly monitored in radio to TeV bands, but little has been done in hard X-rays ≳10 keV. For the first time, we have successfully detected hard X-rays up to 40 keV from its X-ray core with joint Chandra and NuSTAR observations, providing important insights to the X-ray origins: from the unresolved jet or the accretion flow. We found that the hard X-ray emission is significantly lower than that predicted by synchrotron self-Compton models introduced to explain very-high-energy γ -ray emission above a GeV. We discuss recent models to understand these high energy emission processes.

scholarly journals Tracing the high energy emission of γ-ray detected radio loud quasars

2014 ◽  
Vol 10 (S313) ◽  
pp. 225-230
Author(s):  
Giulia Migliori
Keyword(s):  
Spectral Energy Distribution ◽  
High Energy ◽  
Host Galaxy ◽  
Spectral Energy ◽  
X Ray ◽  
Relativistic Jet ◽  
Quasar Jets ◽  
Γ Ray ◽  
High Energy Emission ◽  
Jet Power

AbstractWe present a multiwavelength study of the core and relativistic jet of the radio loud (RL) quasar RGB J1512+020A (z=0.20). We report the discovery of a bright, 13” extended X-ray jet with a short Chandra observation. We discuss the origin of the jet X-ray emission and its properties in comparison with sample of X-ray quasar jets. The broadband core spectrum is contributed by the emission of the central quasar, by a blazar component, responsible for the γ-ray emission detected by Fermi, and by the host galaxy. We model the non-thermal blazar spectral energy distribution (SED) and constrain the total jet power. The jet power inferred from the blazar SED modeling is in agreement with the values obtained from the total radio power, pointing to a jet that efficiently carries its power up to kiloparsec scales. The quasar emission appears intrinsically weak in the optical-UV band. The disk luminosity estimated from the broad emission lines is lower than the jet power, in agreement with recent results from observations and theory.

Steep-Spectrum Radio Sources in Clusters of Galaxies—The Southern Sample

1984 ◽  
Vol 5 (4) ◽  
pp. 516-529 ◽  
Author(s):  
O. B. Slee ◽  
J. E. Reynolds
Keyword(s):  
Radio Galaxies ◽  
High Energy ◽  
Radio Spectrum ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Detailed Review ◽  
X Ray ◽  
High Energy Electrons ◽  
Spectrum Radio ◽  
Inverse Compton

It is well established (e.g. Slee et al. 1983) that radio galaxies near the centres of rich clusters of galaxies tend to have steeper radio spectra than field radio galaxies. The fact that the sources with the steepest spectra occur in clusters that are highly luminous X-ray emitters has generally been interpreted in terms of the confining influence of a hot (~108 K), relatively dense (10-2 to 10-3 electrons cm-3) intra-cluster gas; the confined relativistic plasma then preferentially loses its high-energy electrons through synchrotron and inverse Compton losses, resulting in a steepening of the radio spectrum. A more detailed review of the evidence for this process is given by Robertson (1983).

The spectrum of γ rays in the energy range 1011 to 1013 eV at an atmospheric depth of 200 g/cm2, and pion generation in high-energy nucleon interactions

1968 ◽  
Vol 46 (10) ◽  
pp. S700-S705 ◽  
Author(s):  
A. V. Apanasenko ◽  
L. T. Baradzei ◽  
E. A. Kanevskaya ◽  
V. V. Rykov ◽  
Yu. A. Smorodin ◽  
...  
Keyword(s):  
Energy Range ◽  
High Energy ◽  
Nucleon Interaction ◽  
Nuclear Emulsions ◽  
X Ray ◽  
Black Spots ◽  
Γ Rays ◽  
Γ Ray ◽  
Using Data ◽  
Electron Photon

The problem of the existence of a change of slope in the γ-ray spectrum in the atmosphere is of considerable interest in connection with conclusions about the change in the character of the nucleon interaction. Up to now this problem has not been solved experimentally. In this report the γ-ray spectrum in the 1011–1013 eV energy range has been obtained using data from X-ray films and nuclear emulsions exposed on board an airplane at a pressure of 200 g/cm2. The total exposure was 425 hours∙m2. The energies of the electron–photon cascades initiated by γ rays were determined in the X-ray films by measuring the photometric densities of the black spots, and in nuclear emulsions by counting the electron tracks near the cascade axis. The integral spectrum has a power-law form with an exponent of 1.7–1.9. A change in slope in the spectrum was not found. Thus, a mechanism generating pions with energies proportional to the initial nucleon energies exists up to nucleon energies of ~1014 eV. The analysis of the accompaniment of γ rays by "families" shows that in one-third of the cases the energy of the most energetic π0 meson is at least five times that of the next π0 meson. In the remaining two-thirds of the cases the π0 mesons have comparable energies.

scholarly journals VHE GAMMA-RAYS FROM GALACTIC X-RAY BINARY SYSTEMS

2008 ◽  
Vol 17 (10) ◽  
pp. 1849-1858 ◽  
Author(s):  
J. M. PAREDES
Keyword(s):  
Gamma Rays ◽  
Binary Systems ◽  
High Energy ◽  
X Ray ◽  
Very High Energy ◽  
Γ Rays ◽  
Γ Ray ◽  
Tev Gamma Rays ◽  
X Ray Binaries ◽  
Very High

The detection of TeV gamma-rays from LS 5039 and the binary pulsar PSR B1259–63 by HESS, and from LS I +61 303 and the stellar-mass black hole Cygnus X-1 by MAGIC, provides clear evidence of very efficient acceleration of particles to multi-TeV energies in X-ray binaries. These observations demonstrate the richness of nonthermal phenomena in compact galactic objects containing relativistic outflows or winds produced near black holes and neutron stars. I review here some of the main observational results on very high energy (VHE) γ-ray emission from X-ray binaries, as well as some of the proposed scenarios to explain the production of VHE γ-rays. I put special emphasis on the flare TeV emission, suggesting that the flaring activity might be a common phenomena in X-ray binaries.

scholarly journals A strong radio brightening at the jet base of M87 during the elevated very-high-energy γ-ray state in 2012

2014 ◽  
Vol 10 (S313) ◽  
pp. 340-345
Author(s):  
K. Hada ◽  
M. Giroletti ◽  
M. Kino ◽  
G. Giovannini ◽  
F. D' Ammando ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
High Energy ◽  
Jet Formation ◽  
Radio Monitoring ◽  
Linear Resolution ◽  
Very High Energy ◽  
Γ Rays ◽  
Γ Ray ◽  
Flux Increase ◽  
Very High

AbstractThe nearby radio galaxy M87 offers a unique opportunity for exploring the connection between γ-ray production and jet formation at an unprecedented linear resolution. However, the origin and location of the γ-rays in this source is still elusive. Based on previous radio/TeV correlation events, the unresolved jet base (radio core) and the peculiar knot HST-1 at >120 pc from the nucleus are proposed as candidate site(s) of γ-ray production. Here we report our intensive, high-resolution radio monitoring observations of the M87 jet with the VLBI Exploration of Radio Astrometry (VERA) and the European VLBI Network (EVN) from February 2011 to October 2012. During this period, an elevated level of the M87 flux is reported at TeV with VERITAS. We detected a remarkable flux increase in the radio core with VERA at 22/43 GHz coincident with the VHE activity. Meanwhile, HST-1 remained quiescent in terms of its flux density and structure at radio. These results strongly suggest that the TeV γ-ray activity in 2012 originates in the jet base within 0.03 pc (projected) from the central supermassive black hole.

scholarly journals GAMMA RAYS FROM RADIO GALAXIES: FERMI/LAT OBSERVATIONS

2012 ◽  
Vol 08 ◽  
pp. 25-30 ◽  
Author(s):  
◽  
PAOLA GRANDI
Keyword(s):  
Low Power ◽  
Gamma Rays ◽  
High Power ◽  
Detection Rate ◽  
Radio Galaxies ◽  
High Energy ◽  
Radio Sources ◽  
Structural Differences ◽  
Γ Ray

We review the high energy properties of Misaligned AGNs associated with γ-ray sources detected by Fermi in 24 months of survey. Most of them are nearby emission low power radio galaxies (i.e FRIs) which probably have structured jets. On the contrary, high power radio sources (i.e FRIIs) with GeV emission are rare. The small number of FRIIs does not seem to be related to their higher redshifts. Assuming proportionality between the radio core flux and the γ-ray flux, several of them are expected to be bright enough to be detected above 100 MeV in spite of their distance. We suggest that beaming/jet structural differences are responsible for the detection rate discrepancy observed between FRIs and FRIIs.

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