GeV Gamma-ray Emission and Molecular Clouds towards Supernova Remnant G35.6$-$0.4 and the TeV Source HESS J1858+020

Abstract

It is difficult to distinguish hadronic process from the leptonic one in $\gamma$-ray observation, which is however crucial in revealing the origin of cosmic rays. As an endeavor in the regard, we focus in this work on the complex $\gamma$-ray emitting region, which partially overlaps with the unidentified TeV source HESS~J1858+020 and includes supernova remnant (SNR) G35.6$-$0.4 and HII region G35.6$-$0.5. We reanalyze CO-line, HI, and Fermi-LAT GeV $\gamma$-ray emission data of this region. The analysis of the molecular and HI data suggests that SNR G35.6$-$0.4 and HII region G35.6$-$0.5 are located at different distances. The analysis the GeV $\gamma$-rays shows that GeV emission arises from two point sources: one (SrcA) coincident with the SNR, and the other (SrcB) coincident with both HESS J1858+020 and HII region G35.6$-$0.5. The GeV emission of SrcA can be explained by the hadronic process in the SNR-MC association scenario. The GeV-band spectrum of SrcB and the TeV-band spectrum of HESS J1858+020 can be smoothly connected by a power-law function, with an index of $\sim$2.2. The connected spectrum is well explained with a hadronic emission, with the cutoff energy of protons above 1 PeV. It thus indicates that there is a potential PeVatron in the HII region and should be further verified with ultra-high energy observations with, e.g., LHAASO.

arXiv comment19 pages, 9 figures, accepted for publication in ApJ

References in corpus (39)

• Astropy: A Community Python Package for Astronomy
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The ATNF Pulsar Catalogue
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• Fermi Large Area Telescope Fourth Source Catalog
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• The H.E.S.S. Galactic plane survey
• The VLA Galactic Plane Survey
• Pulsar rotation measures and the large-scale structure of Galactic magnetic field
• The 1st Fermi Lat Supernova Remnant Catalog
• Analytical solutions for energy spectra of electrons accelerated by nonrelativistic shock-waves in shell type supernova remnants
• HESS VHE Gamma-Ray Sources Without Identified Counterparts
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) I: Project Overview and Initial Results
• The Parkes Multibeam Pulsar Survey -- II. Discovery and Timing of 120 Pulsars
• Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field
• HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon
• Kinematic Distances: A Monte Carlo Method
• Identification of the TeV Gamma-ray Source ARGO J2031+4157 with the Cygnus Cocoon
• Mechanism for spectral break in cosmic ray proton spectrum from Supernova remnant W44
• The Distance and Age of the SNR Kes 73 and AXP 1E 1841-045
• Revised Distances to 21 Supernova Remnants
• New Distances to Four Supernova Remnants
• Gamma-rays from molecular clouds illuminated by accumulated diffusive protons. II: interacting supernova remnants
• Escape of cosmic-ray electrons from supernova remnants
• The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and HI overview
• Observations of the unidentified gamma-ray source TeV J2032+4130 by VERITAS
• A possible approach to three-dimensional cosmic-ray propagation in the Galaxy IV. Electrons and electron-induced gamma-rays
• Gamma-ray Observation of the Cygnus Region in the 100 TeV Energy Region
• Detection of very-high-energy γ-ray emission from the colliding wind binary η Car with H.E.S.S
• Re-identification of G35.6-0.4 as a supernova remnant
• GeV γ-ray Emission Detected by Fermi-LAT Probably Associated with the Thermal Composite Supernova Remnant Kesteven 41 in a Molecular Environment
• Kinematic distance study of the planetary nebulae-supernova remnant-HII region complex at G35.6-0.5
• Cosmic rays in the surroundings of SNR G35.6-0.4
• Identifying the counterpart of HESS J1858+020
• Deep GMRT radio observations and a multi-wavelength study of the region around HESS J1858+020
• Study of the molecular clump associated with the high-energy source HESS J1858+020
• Search for galactic Pevatron candidates in a population of unidentified gamma-ray sources
• HESS J1858+020: A GeV-TeV source possibly powered by CRs from SNR G35.6-0.4

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