γ Rays from the cosmic ray irradiation of local molecular clouds

Issa, M. R.; Wolfendale, A. W.

doi:10.1038/292430a0

Cited by 56 publications

(28 citation statements)

References 23 publications

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“…If cosmic rays can freely penetrate the clouds, the high energy gamma ray spectrum is expected to mimic the slope of the cosmic ray spectrum and the total gamma ray luminosity depends only on the cloud total mass. For this reason, molecular clouds can be used to probe the cosmic ray energy spectrum and its absolute flux in different parts of the Galaxy [5,3,4]. The condition for the detectability of these passive clouds with EGRET is M 5 /d kpc ≥ 10, where M 5 is the cloud mass in units of 10 5 M ⊙ and d kpc is the source distance in kpc [4].…”

Section: Introductionmentioning

confidence: 99%

Gamma rays from molecular clouds

Gabici

Aharonian

Blasi

2007

Astrophys Space Sci

194

204

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It is believed that the observed diffuse gamma ray emission from the galactic plane is the result of interactions between cosmic rays and the interstellar gas. Such emission can be amplified if cosmic rays penetrate into dense molecular clouds. The propagation of cosmic rays inside a molecular cloud has been studied assuming an arbitrary energy and space dependent diffusion coefficient. If the diffusion coefficient inside the cloud is significantly smaller compared to the average one derived for the galactic disk, the observed gamma ray spectrum appears harder than the cosmic ray spectrum, mainly due to the slower penetration of the low energy particles towards the core of the cloud. This may produce a great variety of gamma ray spectra.PACS First · Second · More

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Section: Introductionmentioning

confidence: 99%

Gamma rays from molecular clouds

Gabici

Aharonian

Blasi

2007

Astrophys Space Sci

194

204

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“…[60,61,62]). If the MC is embedded in the galactic CR background (sometimes referred to as CR sea), then the expected gamma-ray flux is proportional to the quantity M cl /d 2 , where M cl is the cloud mass and d is its distance, and the MC is called passive.…”

Section: Molecular Clouds With Cta: Probing the Intensity Of Cosmic Rmentioning

confidence: 99%

Gamma-ray signatures of cosmic ray acceleration, propagation, and confinement in the era of CTA

Acero

Bamba

Casanova

et al. 2013

Astroparticle Physics

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Galactic cosmic rays are commonly believed to be accelerated at supernova remnants via diffusive shock acceleration. Despite the popularity of this idea, a conclusive proof for its validity is still missing. Gamma-ray astronomy provides us with a powerful tool to tackle this problem, because gamma rays are produced during cosmic ray interactions with the ambient gas. The detection of gamma rays from several supernova remnants is encouraging, but still does not constitute a proof of the scenario, the main problem being the difficulty in disentangling the hadronic and leptonic contributions to the emission. Once released by their sources, cosmic rays diffuse in the interstellar medium, and finally escape from the Galaxy. The diffuse gamma-ray emission from the * Principal corresponding author, stefano.gabici@apc.univ-paris7.fr, tel. +33157277024, fax. +33157276071 * * Corresponding author Galactic disk, as well as the gamma-ray emission detected from a few galaxies is largely due to the interactions of cosmic rays in the interstellar medium. On much larger scales, cosmic rays are also expected to permeate the intracluster medium, since they can be confined and accumulated within clusters of galaxies for cosmological times. Thus, the detection of gamma rays from clusters of galaxies, or even upper limits on their emission, will allow us to constrain the cosmic ray output of the sources they contain, such as normal galaxies, AGNs, and cosmological shocks. In this paper, we describe the impact that the Cherenkov Telescope Array, a future ground-based facility for very-high energy gamma-ray astronomy, is expected to have in this field of research.

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“…In recent work (Issa and Wolfendale, 1981) we assumed that the cosmic-ray intensity within about 2 kpc of the Sun is the same as that locally and compared the observed and expected 7-ray fluxes from the known molecular clouds in this region. There is no doubt that the procedure is rather uncertain for many reasons (not least the difficulties in deriving 7-ray fluxes) -and is strictly premature -but the principle is sound and the results have some value.…”

Section: Determination Of Cloud Massesmentioning

confidence: 99%

“…The 2CG source 353 + 16 associated with the pOph cloud complex, which had been claimed previously to be discrete, has now been shown to be extended (COS-B group, private communication) and to mirror rather well the distribution of gas in that vicinity. It remains to be seen whether a significantly enhanced value of ICR iS needed; previously (Issa et al, 198 lb;Issa and Wolfendale, 1981) we needed an enhancement factor F~ 1.5 which cannot be regarded as significantly greater than unity and we know of no reason yet to increase this value, Another feature of the analysis by Li and Wolfendale was the demonstration that the lumpy ISM coupled with the limited number of 7-rays detected in the COS-B experiment (typically 80 above 100 MeV for a flux of 1.0 x 10 -6 cm -2 s-1) causes the appearance of many apparently significant 7-ray 'sources'. Specifically, at the threshold of significance C~/a~ = 4.75 adopted in the 2CG catalogue the probability of a 'spurious' source appearing is increased by a factor of about 500.…”

Section: Gamma-ray Sourcesmentioning

confidence: 99%

Cosmic gamma rays and molecular gas in the galaxy

1983

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A brief analysis is made of the interrelation of the intensity of cosmic-ray particles, the column density of gas and the intensity of cosmic 7-rays. It is shown that, locally, 7-ray data enable the calibration ofH 2 densities to be inferred from CO data and elsewhere the variation of cosmic-ray intensity with position to be assessed. Finally, the importance of cosmic-ray irradiated molecular clouds in simulating y-ray 'sources' is reiterated.

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γ Rays from the cosmic ray irradiation of local molecular clouds

Cited by 56 publications

References 23 publications

Gamma rays from molecular clouds

Gamma rays from molecular clouds

Gamma-ray signatures of cosmic ray acceleration, propagation, and confinement in the era of CTA

Cosmic gamma rays and molecular gas in the galaxy

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