Evidence for the detection of gamma rays from Centaurus A at gamma-ray energies above 300 GeV

Grindlay, J. E.; Helmken, H. F.; Brown, R. H.; Davis, J.; Allen, L. R.

doi:10.1086/181764

Cited by 114 publications

(77 citation statements)

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“…Moreover, EGRET measurements [21] of the gamma ray flux for energies > 100 MeV allow an estimate L γ ∼ 10 41 erg s −1 for the source [22]. This value of L γ is consistent with an earlier observation in the TeV-range during a period of elevated activity [23], and is considerably smaller than the estimated bolometric luminosity L bol ∼ 10 43 erg s −1 [16].CR "lore" convinces us that the TeV γ-ray emission is a result of synchrotron radiation of electrons or pro-1 …”

supporting

confidence: 86%

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Anchordoqui

Goldberg²,

Weiler³

2001

Phys. Rev. Lett.

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If, as recently proposed by Farrar and Piran, Cen A is the source of cosmic rays detected above the Greisen-Zatsepin-Kuz'min cutoff, neutrons are ≈ 140 more probable than protons to be observed along its line of sight. This is because the proton flux is rendered nearly isotropic by O(µG) intergalactic magnetic fields. With the anticipated aperture of the Southern Auger Observatory, one may expect on the order of 2 neutron events/year above 10 20 eV in the line of sight of Cen A.The energy spectrum of cosmic rays (CRs) is well fitted by power laws with increasing index for energies above 4 × 10 15 eV (the "knee") flattening again above 5 × 10 18 eV (the "ankle"), yielding the overall shape of a leg. Over the last third of the century, ingenious installations with large effective areas and long exposure times-needed to overcome the steep falling flux-have raised the tail of the spectrum up to an energy of 3 × 10 20 eV, with no evidence that the highest energy recorded thus far is Nature's upper limit [1]. The origin of these extraordinarily energetic particles continues to present a major enigma to high energy physics [2].The main problem posed by the detection of CRs of such energy (if nucleons, gammas, and/or nuclei) is energy degradation through inelastic collisions with the universal radiation fields permeating the universe. Therefore, if the CR sources are all at cosmological distances, the observed spectrum must virtually end with the Greisen-Zatsepin-Kuz'min (GZK) cutoff at E ≈ 8 × 10 19 eV [3]. The spectral cutoff is less sharp for nearby sources (within 50 Mpc or so). The arrival directions of the trans-GZK events are distributed widely over the sky, with no plausible counterparts (such as sources in the Galactic Plane or in the Local Supercluster). Furthermore, the data are consistent with an isotropic distribution of sources in sharp constrast to the anisotropic distribution of light within 50 Mpc [4]. The difficulties encountered by conventional acceleration mechanisms in accelerating particles to the highest observed energies have motivated suggestions that the underlying production mechanism could be of non-acceleration nature. Namely, charged and neutral primaries, mainly light mesons (pions) together with a small fraction (3%) of nucleons, might be produced at extremely high energy by decay of supermassive elementary X particles (m X ∼ 10 22 − 10 28 eV) [5]. However, if this were the case, the observed spectrum should be dominated by gamma rays and neutrinos, in contrast to current observation [6]! Alternative explanations involve undiscovered neutral hadrons with masses above a few GeV [7], neutrinos producing nucleons and photons via resonant Z-production with the relic neutrino background [8], or else neutrinos attaining cross sections in the millibarn range above the electroweak scale [9]. A controversial correlation between the arrival direction of CRs above 10 20 eV and high redshift compact radio quasars seems to support these scenarios [10].Over the last few years, it has become evident tha...

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supporting

confidence: 86%

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Anchordoqui

Goldberg²,

Weiler³

2001

Phys. Rev. Lett.

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“…Note that nearly 30 years ago the radio galaxy Centaurus A was reported to be a TeV source observed with a non-imaging instrument (Grindlay et al 1975).…”

Section: Discussionmentioning

confidence: 99%

Is the giant radio galaxy M 87 a TeV gamma-ray emitter?

Aharonian¹,

Akhperjanian²,

Beilicke³

et al. 2003

A&A

181

126

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Abstract. For the first time an excess of photons above an energy threshold of 730 GeV from the giant radio galaxy M 87 has been measured at a significance level above 4 σ. The data have been taken during the years 1998 and 1999 with the HEGRA stereoscopic system of 5 imaging atmospheric Cherenkov telescopes. The excess of 107.4 ± 26.8 events above 730 GeV corresponds to an integral flux of 3.3% of the Crab flux or N γ (E > 730 GeV) = (0.96 ± 0.23) × 10 −12 phot cm −2 s −1 . M 87 is located at the center of the Virgo cluster of galaxies at a relatively small redshift of z = 0.00436 and is a promising candidate among the class of giant radio galaxies for the emission of TeV γ-radiation. The detection of TeV γ-rays from M 87 -if confirmed -would establish a new class of extragalactic source in this energy regime since all other AGN detected to date at TeV energies are BL Lac type objects.

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“…We detected gamma rays from Cen A (Grindlay et al 1975) and, on one night, I detected what appeared to be a clear and unambiguous signal from the Crab Nebula. Unfortunately, the signal could not be detected on subsequent nights and it had to be regarded as a highly unlikely but spurious event.…”

Section: Personal Remarksmentioning

confidence: 78%

Forty Years of Progress in Long-Baseline Optical Interferometry: 2005 Robert Ellery Lecture

Davis

2006

Publ. – Astron. Soc. Aust

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The development of long-baseline optical interferometry in Australia from the Narrabri Stellar Intensity Interferometer (NSII) to the Sydney University Stellar Interferometer (SUSI) and the resulting technical and scientific achievements are described. Three examples of results from the SUSI programme, for a single star, a double-lined spectroscopic binary, and a Cepheid variable, are presented to illustrate the advances made in the past four decades. The leading role that Australia has played in the development of the field worldwide is discussed from a personal viewpoint. Long-baseline optical interferometry has promised much, has been slow to deliver, and has been restricted to black-belt interferometrists, but it has now matured to the point where it is becoming an observational technique for astronomers in general.

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Evidence for the detection of gamma rays from Centaurus A at gamma-ray energies above 300 GeV

Cited by 114 publications

References 0 publications

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Is the giant radio galaxy M 87 a TeV gamma-ray emitter?

Forty Years of Progress in Long-Baseline Optical Interferometry: 2005 Robert Ellery Lecture

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