Resolving The Northern Arm Sources at the Galactic Center

Abstract

Diffraction limited images obtained with the W. M. Keck telescopes have spatially resolved the cool luminous Galactic Center sources IRS 21, 1W, 2, 5, and 10W at wavelengths ranging from 2 to 25 μm. Their gaussian convolved sizes (∼ 2000 AU or 0″. 25 in diameter), along with their mid-infrared color temperatures, favor the hypothesis that they are centrally heated stellar sources rather than externally heated dust clumps. The near-infrared Keck speckle and AO images as well as 2.2 μm Gemini AO images of IRS 8 reveal asymmetric structures indicative of bow shock structures around all the Northern Arm sources. The presence of such large bow shocks around these objects suggests that their central heating sources have large winds requiring them to be young, massive stars like those observed in the nearby IRS 16 cluster. This number of windy stars is expected considering the a 10% volume coverage of the Northern Arm and the number of windy stars detected over a smaller region of the central parsec by Paumard et al (2001). This increases the total population of such stars to fifteen, which is comparable to the number of similar stars found in the nearby Quintuplet cluster.