Galactic center mini-spiral by ALMA: Possible origin of the central cluster

Abstract

We present continuum images of the Galactic center mini-spiral in the 100, 250, and 340 GHz bands with analysis of the Cy.0 data acquired from the Atacama Large Millimeter/submillimeter Array (ALMA) archive. Good u-v coverage of the data and the self-calibration method give us the opportunity to obtain dynamic ranges of over 2 104 in the resultant maps of the 250 and 340 GHz bands. In particular, the image of the 340 GHz band has high dynamic ranges unprecedented in sub-millimeter waves. The angular resolutions attained are 1. 57 1. 33 in the 100 GHz band, 0. 63 0. 53 in the 250 GHz band, and 0. 44 0. 38 in the 340 GHz band, respectively. The continuum images clearly depict the mini-spiral, which is an ionized gas stream in the vicinity of SgrA. We found a tight correlation between the dust emission peaks and the OB/WR stars in the northern arm of the mini-spiral. The core mass function of the dust cores identified by the clumpfind algorithm would obey the flat power-law dN/dM M1.5±0.4 on the high-mass side. These support the scenario that the star-forming cloud has fallen into the immediate vicinity of SgrA for the origin of the central cluster.