Very Large Array Observations of Galactic Center OH 1720 MHz Masers in Sagittarius A East and in the Circumnuclear Disk

Abstract

We present Very Large Array (VLA) radio interferometry observations of the 1720 MHz OH masers in the Galactic Center (GC). Most 1720 MHz OH masers arise in regions where the supernova remnant Sgr A East is interacting with the interstellar medium. The majority of the newly found 1720 MHz OH masers are located to the northeast, independently indicating and confirming an area of shock interaction with the +50 km/s molecular cloud (M-0.02-0.07) on the far side of Sgr A East. The previously known bright masers in the southeast are suggested to be the result of the interaction between two supernova remnants, instead of between Sgr A East and the surrounding molecular clouds as generally found elsewhere in the Galaxy. Together with masers north of the circumnuclear disk (CND) they outline an interaction on the near side of Sgr A East. In contrast to the interaction between the +50 km/s cloud and Sgr A East, OH absorption data do not support a direct interaction between the CND material and Sgr A East. We also present three new high-negative velocity masers, supporting a previous single detection. The location and velocities of the high-negative and high-positive velocity masers are consistent with being near the tangent points of, and physically located in the CND. We argue that the high velocity masers in the CND are pumped by dissipation between density clumps in the CND instead of a shock generated by the supernova remnant. That is, the CND masers are not coupled to the supernova remnant and are sustained independently.

arXiv commentaccepted to ApJ, 9 pages 3 figures

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Cited by in corpus (24)

• The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline
• Molecular gas kinematics within the central 250 pc of the Milky Way
• Simulations of the Milky Way's central molecular zone -- I. Gas dynamics
• The Excitation of HCN and HCO+ in the Galactic Center Circumnuclear Disk
• Interstellar gas within $\sim 10$ pc of Sgr A${}^{\ast }$
• Discovery of New Interacting Supernova Remnants in the Inner Galaxy
• ISM Processing in the Inner 20 pc in Galactic center
• Mapping photodissociation and shocks in the vicinity of Sgr A*
• Expanded VLA Detection of 36.2 GHz Class I Methanol Masers in Sagittarius A
• OH (1720 MHz) Masers: A Multiwavelength Study of the Interaction between the W51C Supernova Remnant and the W51B Star Forming Region
• Expanded Very Large Array Detection of 44.1 GHz Class I Methanol Masers in Sagittarius A
• Properties of the Compact HII Region Complex G-0.02-0.07
• An analysis of HCN observations of the Circumnuclear Disk at the galactic centre
• Statistical Properties of Molecular Clumps in the Galactic Center 50 km s${}^{-1}$ Molecular Cloud
• An OH(1720 MHz) Maser and a Nonthermal Radio Source in Sgr B2(M): A SNR--Molecular Cloud Interaction Site?
• 44 GHz Class I Methanol (CH${}_3$OH) Maser Survey in the Galactic Center
• The X-ray footprint of the CircumNuclear Disk
• The connecting molecular ridge in the Galactic center
• Very Large Array monitoring of 1720 MHz OH masers toward the Galactic Center
• Atomic Carbon in the Central Molecular Zone of the Milky Way : Possible Cosmic-ray Induced Chemistry or Time-Dependent Chemistry Associated with SNR Sagittarius A East
• Hot Molecular Core Candidates in the Galactic Center 50 km/s Molecular Cloud
• OH Masers and Supernova Remnants
• A 95 GHz Methanol Emission Survey Toward Eight Small Supernova Remnants
• Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the Sgr A complex