Preliminary indirect measurement of cosmic-ray proton spectrum using Earth’s γ-ray data from Fermi Large Area Telescope

We report the detection of high-energy γ-ray signal towards the young star-forming region, W40. Using 10-yr Pass 8 data from the Fermi Large Area Telescope (Fermi-LAT), we extracted an extended γ-ray excess region with a significance of ~18σ. The radiation has a spectrum with a photon index of 2.49 ± 0.01. The spatial correlation with the ionized gas content favors the hadronic origin of the γ-ray emission. The total cosmic-ray (CR) proton energy in the γ-ray production region is estimated to be the order of 1047 erg. However, this could be a small fraction of the total energy released in cosmic rays (CRs) by local accelerators, presumably by massive stars, over the lifetime of the system. If so, W40, together with earlier detections of γ-rays from Cygnus cocoon, Westerlund 1, Westerlund 2, NGC 3603, and 30 Dor C, supports the hypothesis that young star clusters are effective CR factories. The unique aspect of this result is that the γ-ray emission is detected, for the first time, from a stellar cluster itself, rather than from the surrounding “cocoons”.

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Measurement of the cosmic ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite

Science Advances ◽

10.1126/sciadv.aax3793 ◽

2019 ◽

Vol 5 (9) ◽

pp. eaax3793 ◽

Cited By ~ 16

Author(s):

◽

Q. An ◽

R. Asfandiyarov ◽

P. Azzarello ◽

P. Bernardini ◽

...

Keyword(s):

Cosmic Rays ◽

Cosmic Radiation ◽

Precise Measurement ◽

Milky Way ◽

Spectral Feature ◽

Dark Matter Particle ◽

Cosmic Ray ◽

Galactic Cosmic Rays ◽

Proton Spectrum ◽

First Time

The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2 1/2 years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.

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A possible radio signal of annihilating dark matter in the Abell 4038 cluster

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz185 ◽

2019 ◽

Vol 495 (1) ◽

pp. L124-L128 ◽

Cited By ~ 2

Author(s):

Man Ho Chan ◽

Chak Man Lee

Keyword(s):

Dark Matter ◽

Cross Section ◽

Radio Signal ◽

Dark Matter Particle ◽

Cosmic Ray ◽

Annihilation Cross Section ◽

Radio Continuum ◽

Test Statistic ◽

Large Area ◽

Dark Matter Annihilation

ABSTRACT In the past decade, some telescopes [e.g. Fermi-Large Area Telescope (LAT), Alpha Magnetic Spectrometer(AMS), and Dark Matter Particle Explorer(DAMPE)] were launched to detect the signals of annihilating dark matter in our Galaxy. Although some excess of gamma-rays, antiprotons, and electrons/positrons have been reported and claimed as dark matter signals, the uncertainties of Galactic pulsars’ contributions are still too large to confirm the claims. In this Letter, we report a possible radio signal of annihilating dark matter manifested in the archival radio continuum spectral data of the Abell 4038 cluster. By assuming the thermal annihilation cross-section and comparing the dark matter annihilation model with the null hypothesis (cosmic ray emission without dark matter annihilation), we get very large test statistic values >45 for four popular annihilation channels, which correspond to more than 6.5σ statistical preference. This provides a very strong evidence for the existence of annihilating dark matter. In particular, our results also support the recent claims of dark matter mass m ≈ 30–50 GeV annihilating via the bb̄ quark channel with the thermal annihilation cross-section.

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Fermi LARGE AREA TELESCOPE DETECTION OF TWO VERY-HIGH-ENERGY ( E > 100 GeV) γ-RAY PHOTONS FROM THE z = 1.1 BLAZAR PKS 0426–380

The Astrophysical Journal ◽

10.1088/2041-8205/777/1/l18 ◽

2013 ◽

Vol 777 (1) ◽

pp. L18 ◽

Cited By ~ 21

Author(s):

Y. T. Tanaka ◽

C. C. Cheung ◽

Y. Inoue ◽

Ł. Stawarz ◽

M. Ajello ◽

...

Keyword(s):

High Energy ◽

Large Area ◽

Very High Energy ◽

Γ Ray ◽

Very High

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Consequences of a Universal Cosmic-ray Theory for γ-ray Astronomy

Nature ◽

10.1038/241109b0 ◽

1973 ◽

Vol 241 (5385) ◽

pp. 109-110 ◽

Cited By ~ 25

Author(s):

A. W. STRONG ◽

A. W. WOLFENDALE ◽

J. WDOWCZYK

Keyword(s):

Cosmic Ray ◽

Ray Theory ◽

Γ Ray

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Molecular Clouds Observed by the EGRET Gamma-Ray Telescope

Symposium - International Astronomical Union ◽

10.1017/s0074180900234013 ◽

1997 ◽

Vol 170 ◽

pp. 22-24 ◽

Cited By ~ 4

Author(s):

Seth. W. Digel ◽

Stanley D. Hunter ◽

Reshmi Mukherjee ◽

Eugéne J. de Geus ◽

Isabelle A. Grenier ◽

...

Keyword(s):

Molecular Mass ◽

Molecular Clouds ◽

Gamma Ray ◽

Angular Resolution ◽

Cosmic Ray ◽

High Energy ◽

Background Rejection ◽

Γ Rays ◽

Γ Ray ◽

Production Mechanisms

EGRET, the high-energy γ-ray telescope on the Compton Gamma-Ray Observatory, has the sensitivity, angular resolution, and background rejection necessary to study diffuse γ-ray emission from the interstellar medium (ISM). High-energy γ rays produced in cosmic-ray (CR) interactions in the ISM can be used to determine the CR density and calibrate the CO line as a tracer of molecular mass. Dominant production mechanisms for γ rays of energies ∼30 MeV–30 GeV are the decay of pions produced in collisions of CR protons with ambient matter and Bremsstrahlung scattering of CR electrons.

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