Suzaku Observation of the Fermi Cygnus Cocoon: Search for a Signature of Young Cosmic-Ray Electrons

Abstract

The origin of Galactic cosmic rays remains unconfirmed, but promising candidates for their sources are found in star-forming regions. We report a series of X-ray observations, with Suzaku, toward the nearby star-forming region of Cygnus X. They aim at comparing diffuse X-ray emissions on and off the $\gamma$-ray cocoon of hard cosmic rays revealed by Fermi LAT. After excluding point sources and small-scale structures and subtracting the non-X-ray and cosmic X-ray backgrounds, the 2--10~keV X-ray intensity distribution is found to monotonically decrease with increasing Galactic latitude. This indicates that most of the extended emission detected by Suzaku originates from the Galactic ridge. In two observations, we derive upper limits of $3.4\times 10^{-8}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}\mathrm{s}{\mathrm{r}}^{-1}$ and $1.3\times 10^{-8}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}\mathrm{s}{\mathrm{r}}^{-1}$ to X-ray emission in the 2--10 keV range from the gamma-ray cocoon. These limits exclude the presence of cosmic-ray electrons with energies above about 50 TeV at a flux level capable of explaining the gamma-ray spectrum. They are consistent with the emission cut-off observed near a TeV in gamma rays. The properties of Galactic ridge and local diffuse X-rays are also discussed.

accepted by the ApJ

References in corpus (6)

• TeV Gamma-Ray Sources from a Survey of the Galactic Plane with Milagro
• Suzaku observations of the diffuse x-ray emission across the fermi bubbles' edges
• Identification of the TeV Gamma-ray Source ARGO J2031+4157 with the Cygnus Cocoon
• The K-shell Line Distribution of Heavy Elements along the Galactic Plane Observed with Suzaku
• Discovery of TeV Gamma-ray Emission Toward Supernova Remnant SNR G78.2+2.1
• Is the Cygnus Superbubble a Hypernova Remnant?

Cited by in corpus (6)

• Science with e-ASTROGAM (A space mission for MeV-GeV gamma-ray astrophysics)
• HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon
• Is The Gamma-Ray Source 3FGL J2212.5+0703 A Dark Matter Subhalo?
• Multiple emission components in the Cygnus cocoon detected from Fermi-LAT observations
• X-ray Studies of the Extended TeV Gamma-Ray Source VER J2019+368
• Limits on Leptonic TeV Emission from the Cygnus Cocoon with Swift-XRT