http://arxiv.org/abs/1907.07358
We report radio continuum and molecular line observations of the Galactic super star cluster RCW38, obtained from the Atacama Large Millimeter/Submillimeter Array with a minimum angular resolution of $0”17\times0”15$ ($\simeq289\,{\rm AU}\times255\,{\rm AU}$). The C$^{18}$O image reveal many massive condensations embedded within filamentary structures extending along the northwest-southeast direction in the center of cluster. The condensations have sizes of 0.01–0.02pc, H$2$ column densities of $10^{23}$–$10^{24}$\,cm$^{-2}$, and H$_2$ masses of 10–130$M\odot$. In addition, the 233-GHz continuum image discovered that two dense, small millimeter-sources with radii of 460 and 200 AU (SourceA and SourceB). SourceA is embedded within the most massive C$^{18}$O condensation, whereas no counterpart is seen for SourceB. The masses of SourceA and SourceB are estimated as 13 and 3$M_\odot$ at the optically-thin limit, respectively. The C$^{18}$O emission shows a velocity gradient of 2km/s at the central 2000AU of SourceA, which could be interpreted as a Keplerian rotation with a central mass of a few $M_\odot$ or infall motion of gas. Further, the ALMA $^{12}$CO data reveal that SourceA and SourceB are associated with molecular outflows exhibiting maximum velocities of $\sim$30–70km/s. The outflows have short dynamical timescales of $<$1000yr and high mass outflow rates of $\sim10^{-4}$–$10^{-3}\,M_\odot$/yr. These observational signatures suggest an early evolutionary phase of the massive star formation in SourceA and SourceB, although further investigation based on the high-resolution observations are needed to reach a firm conclusion.
K. Torii, K. Tokuda, K. Tachihara, et. al.
Thu, 18 Jul 19
51/64
Comments: 24 pages, 6 figures, 6 tables
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