Tails of Gravity: Persistence of Star Formation in the Central Molecular Zone

Abstract We characterize star-forming gas in six molecular clouds (Sgr B1-off, Sgr B2, Sgr C, the 20 and 50 km s −1 molecular clouds, and the Brick) in the Galactic central molecular zone (CMZ), and compare their star-forming activities with those in molecular clouds outside the CMZ. Using multiband continuum observations taken from Planck, Herschel, James Clerk Maxwell Telescope/SCUBA-2, and Caltech Submillimeter Observatory/SHARC2, we derived 8 . ″ 5 resolution column density maps for the CMZ clouds and evaluated the column density probability distribution functions (N-PDFs). With the archival Atacama Large Millimeter/submillimeter Array 1.3 mm dust continuum data, we further evaluated the mass of the most massive cores ( M core ma x ). We find that the N-PDFs of four of the selected CMZ clouds are well described by a piecewise log-normal+power-law function, while the N-PDFs of the remaining two can be approximated by log-normal functions. In the first four targets, the masses in the power-law component ( M gas bound ), M core max , and star formation rate are correlated. These correlations are very similar to those derived from low-mass clouds in the solar neighborhood and massive star-forming regions on the Galactic disk. These findings lead to our key hypotheses: (1) in the extreme environment of the CMZ, the power-law component in the N-PDF also represents self-gravitationally bound gas structures, and (2) evolution and star-forming activities of self-gravitationally bound gas structures may be self regulated, insensitive to the exterior environment on ≳5–10 pc scales.