ALMA and VLA observations of emission from the environment of Sgr A*

Abstract

We present 44 and 226 GHz observations of the Galactic center within 20$"$ of Sgr A*. Millimeter continuum emission at 226 GHz is detected from eight stars that have previously been identified at near-IR and radio wavelengths. We also detect a 5.8 mJy source at 226 GHz coincident with the magnetar SGR~J1745-29 located 2.39$"$ SE of Sgr A* and identify a new 2.5$"\times 1.5"$ halo of mm emission centered on Sgr A*. The X-ray emission from this halo has been detected previously and is interpreted in terms of a radiatively inefficient accretion flow. The mm halo surrounds an EW linear feature which appears to arise from Sgr A* and coincides with the diffuse X-ray emission and a minimum in the near-IR extinction. We argue that the millimeter emission is produced by synchrotron emission from relativistic electrons in equipartition with a $\sim 1.5$mG magnetic field. The origin of these is unclear but its coexistence with hot gas supports scenarios in which the gas is produced by the interaction of winds either from the fast moving S-stars, the photo-evaporation of low-mass YSO disks or by a jet-driven outflow from Sgr A*. The spatial anti-correlation of the X-ray, radio and mm emission from the halo and the low near-IR extinction provides compelling evidence for an outflow sweeping up the interstellar material, creating a dust cavity within 2$"$ of Sgr A*. Finally, the radio and mm counterparts to eight near-IR identified stars within $\sim$10\arcs\ of Sgr A* provide accurate astrometry to determine the positional shift between the peak emission at 44 and 226 GHz.

22 pages, 9 figures, MNRAS, in press

References in corpus (15)

• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• An Update on Monitoring Stellar Orbits in the Galactic Center
• An Improved Distance and Mass Estimate for Sgr A* from a Multistar Orbit Analysis
• The structure of the nuclear stellar cluster of the Milky Way
• Dynamics of Ionized Gas at the Galactic Center: VLA Observations of the 3D Velocity Field and Location of the Ionized Streams in Sagittarius A West
• How to hide large scale outflows: size constraints on the jets of Sgr A*
• The Galactic Center cloud G2 and its gas streamer
• First proper motions of thin dust filaments at the Galactic Center
• Monitoring the Dusty S-Cluster Object (DSO/G2) on its Orbit towards the Galactic Center Black Hole
• Detection of the magnetar SGR J1745-2900 up to 291 GHz with evidence of polarized millimetre emission
• Asymmetric structure in Sgr A* at 3mm from closure phase measurements with VLBA, GBT and LMT
• Properties of bow-shock sources at the Galactic center
• The enigma of GCIRS 3 - Constraining the properties of the mid-infrared reference star of the central parsec of the Milky Way with optical long baseline interferometry
• The Discovery of Radio Stars within 10 arcseconds of Sgr A* at 7mm
• ALMA and VLA Observations: Evidence for Ongoing Low-mass Star Formation near Sgr A*

Cited by in corpus (7)

• Monitoring dusty sources in the vicinity of Sgr A*
• Evidence for a jet and outflow from Sgr A*: a continuum and spectral line study
• Near- and mid-infrared observations in the inner tenth of a parsec of the Galactic center -- Detection of proper motion of a filament very close to Sgr~A*
• First observed interaction of the circumstellar envelope of an S-star with the environment of Sgr A*
• Detection of a dense group of hyper-compact radio sources in the central parsec of the Galaxy
• Mapping the aliphatic hydrocarbon content of interstellar dust in the Galactic plane
• Stability of planetary systems within the S-star cluster: the Solar system analogues