The Galactic Center Lobe Filled with Thermal Plasma

Abstract

An observational result of a radio continuum and H92$\alpha$ radio recombination line of the Galactic Center Lobe (GCL), using the Yamaguchi 32 m radio telescope, is reported. The obtained spatial intensity distribution of the radio recombination line shows two distinctive ridge-like structures extending from the galactic plane vertically to the north at the eastern and western sides of the galactic center, which are connected to each other at a latitude of $1.2^{\circ }$ to form a loop-like structure as a whole. This suggests that most of the radio continuum emission of the GCL is free-free emission, and that the GCL is filled with thermal plasma. The east ridge of the GCL observed with the radio recombination line separates 30 pc from the radio arc, which has been considered as a part of the GCL, but coincides with a ridge of the radio continuum at a galactic longitude of $0^{\circ }$. The radial velocity of the radio recombination line is found to be between $-4$ and $+10$ km s${}^{-1}$ across the GCL. This velocity is much smaller than the one expected from the galactic rotation, and hence indicates that the GCL exists apart from the galactic center. These characteristics of the GCL suggest that the long-standing hypothesis that the GCL was created by an explosive activity in the galactic center is unlikely, but favor that the GCL is a giant HII region.

References in corpus (18)

• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Galactic Winds
• A Robotic Wide-Angle H-Alpha Survey of the Southern Sky
• The Large-scale Bipolar Wind in the Galactic Center
• Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive YSOs
• Jet- and Wind-Driven Ionized Outflows in the Superbubble and Star-Forming Disk of NGC 3079
• The Vertical Distribution and Kinematics of HI and Mass Models of the Galactic Disk
• Wild at Heart:-The Particle Astrophysics of the Galactic Centre
• The Vertical Equilibrium of Molecular Gas in the Galactic Disk
• The HIPASS survey of the Galactic plane in Radio Recombination Lines
• A Wide-area VLA Continuum Survey near the Galactic Center at 6 and 20 cm Wavelengths
• Far-Infrared [C II] Line Survey Observations of the Galactic Plane
• GBT Multiwavelength Survey of the Galactic Center Region
• A Multiwavelength View of a Mass Outflow from the Galactic Center
• Radio Recombination Lines toward the Galactic Center Lobe
• A Constraint on the Organization of the Galactic Center Magnetic Field Using Faraday Rotation
• The Mid-Infrared Colors of the ISM and Extended Sources at the Galactic Center
• High-Velocity Molecular Gas in the Galactic Center Radio Lobe

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• Chandra large-scale mapping of the Galactic center: Probing high-energy structures around the central molecular zone
• Galactic Centre Threads as Nuclear MHD Waves
• Where is the Western Part of the Galactic Center Lobe Located really?
• SDSS-V LVM: Verifying what, and where, the 'Galactic Center' Lobe is