The Discovery of Radio Stars within 10 arcseconds of Sgr A* at 7mm

Abstract

Very Large Array observations of the Galactic Center at 7 mm have produced an image of the 30 arcseconds surrounding Sgr A* with a resolution of 82x42 milliarcseconds (mas). A comparison with IR images taken simultaneously with the Very Large Telescope (VLT) identifies 41 radio sources with L-band (3.8 microns) stellar counterparts. The well-known young, massive stars in the central Sgr A* cluster (e.g., IRS 16C, IRS 16NE, IRS 16SE2, IRS 16NW, IRS 16SW, AF, AFNW, IRS 34W and IRS 33E) are detected with peak flux densities between 0.2 and 1.3 mJy. The origin of the stellar radio emission in the central cluster is discussed in terms of ionized stellar winds with mass-loss rates in the range 0.8-5x10^{-5} solar mass per year. Radio emission from eight massive stars is used as a tool for registration between the radio and infrared frames with mas precision within a few arcseconds of Sgr A*. This is similar to the established technique of aligning SiO masers and evolved stars except that radio stars lie within a few arcseconds of Sgr A*. Our data show a scatter of ~6.5 mas in the positions of the eight radio sources that appear in both the L-band and 7 mm images. Lastly, we use the radio and IR data to argue that members of IRS 13N are Young Stellar Objects rather than dust clumps, supporting the hypothesis that recent star formation has occurred near Sgr A*.

arXiv comment15 pages, 3 figures, ApJL (in press)

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Cited by in corpus (12)

• Radio Continuum Observations of the Galactic Center: Photoevaporative Proplyd-like Objects near Sgr A*
• The Second Galactic Center Black Hole?; A Possible Detection of Ionized Gas Orbiting around an IMBH embedded in the Galactic Center IRS13E complex
• Compact Radio Sources within 30" of Sgr A*: Proper Motions, Stellar Winds and the Accretion Rate onto Sgr A*
• Multiwavelength study of the flaring activity of Sgr A* in 2014 February-April
• Galactic Center IRS13E: Colliding Stellar Winds or an Intermediate Mass Black Hole?
• Signatures of Young Star Formation Activity Within Two Parsecs of Sgr A*
• ALMA and VLA observations of emission from the environment of Sgr A*
• Sgr A* and its Environment: Low Mass Star Formation, the Origin of X-ray Gas and Collimated Outflow
• Radio Continuum Emission from the Magnetar SGR J1745-2900: Interaction with Gas Orbiting Sgr A*
• Detection of a dense group of hyper-compact radio sources in the central parsec of the Galaxy
• Sub-millimeter Detection of a Galactic Center Cool Star IRS 7 by ALMA
• ALMA Astrometry of the Objects within 0.5 pc of Sagittarius A${}^{\ast }$