On the Galactic Center Being the Main Source of Galactic Cosmic Rays as Evidenced by Recent Cosmic Ray and Gamma Ray Observations

TL;DR

This paper presents evidence supporting the Galactic center as the main source of galactic cosmic rays, proposing a unified model that explains cosmic ray spectra, gamma-ray bubbles, microwave haze, and positron annihilation through GC activity.

Contribution

It introduces a comprehensive model linking GC activity to various cosmic ray and gamma-ray phenomena, unifying multiple observational signals.

Findings

GC activity accelerates cosmic rays and explains the knee in spectra.

Pair production in GC radiation fields accounts for gamma-ray and microwave signals.

Positron production and annihilation explain the 511 keV line observed by INTEGRAL.

Abstract

We revisit the idea that the Galactic center (GC) is the dominant source of Galactic cosmic rays (GCRs), based on a series of new observational evidence. A unified model is proposed to explain the new phenomena of GCRs and $\gamma$-rays simultaneously. The GCRs are thought to be accelerated during past activities of the GC. The pair production process of GCRs in the strong radiation field due to the GC activity is responsible for the knee structure of the cosmic ray spectra. A f raction of $e^+e^-$ produced by pair production interactions, can be reaccelerated in the induced bipolar jets and be transported into the halo, leaving the Fermi $\gamma$-ray bubbles and WMAP microwave haze as the remnant signal. Finally, the CRs diffuse in the bulge could further interact with the interstellar medium to produce low energy $e^+e^-$. After cooling down, these positrons may annihilate to produce the 511 keV line emission as discovered by INTEGRAL.