Accurate OH maser positions II. the Galactic Center region

Abstract

We present high spatial resolution observations of ground-state OH masers, achieved using the Australia Telescope Compact Array (ATCA). These observations were conducted towards 171 pointing centres, where OH maser candidates were identified previously in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) towards the Galactic Center region, between Galactic longitudes of $355^{\circ }$ and $5^{\circ }$ and Galactic latitudes of $-2^{\circ }$ and $+2^{\circ }$. We detect maser emission towards 162 target fields and suggest that 6 out of 9 non-detections are due to intrinsic variability. Due to the superior spatial resolution of the follow-up ATCA observations, we have identified 356 OH maser sites in the 162 of the target fields with maser detections. Almost half (161 of 356) of these maser sites have been detected for the first time in these observations. After comparing the positions of these 356 maser sites to the literature, we find that 269 (76\%) sites are associated with evolved stars (two of which are planetary nebulae), 31 (9\%) are associated with star formation, four are associated with supernova remnants and we were unable to determine the origin of the remaining 52 (15\%) sites. Unlike the pilot region (\citealt{Qie2016a}), the infrared colors of evolved star sites with symmetric maser profiles in the 1612 MHz transition do not show obvious differences compared with those of evolved star sites with asymmetric maser profiles.

arXiv comment24 pages, 12 figures, accepted by ApJS

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• Accurate OH Maser Positions From The SPLASH Survey III: The Final 96 Square Degrees
• The Evolutionary Status of Protostellar Clumps Hosting Class II Methanol Masers
• ATLASGAL -- Relationship between dense star forming clumps and interstellar masers
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• 86 GHz SiO masers in Galactic Centre OH/IR stars