Alma Spectroscopic Observations Of The 13co/C18o Intensity Ratios In NGC602 And N22 Of The Small Magellanic Cloud

Abstract

This research sought to observe C18O in the Small Magellanic Cloud (SMC) in regions NGC602 and N22 using data taken by the Atacama Large Millimeter/ Submillimeter Array (ALMA). C18O has been used as a dense gas tracer and has been observed in both the Milky Way (MW) and the Large Magellanic Cloud (LMC). There was no direct detection of C18O (J: 2 ! 1 line emission in either NGC602 or N22 based on the integrated intensity images. A lower bound of the 13CO/C18O integrated intensity ratio is calculated to be  60 for NGC602 and  58 for N22 is set based on spectral line stacking analysis. These integrated intensity ratios are about twice as large as LMC values and 20 times larger MW ratios. The large integrated intensity ratio indicates that emission of C18O is lower than what would be expected from metallicity scaling of Milky Way and LMC observations, which may be a consequence of a low abundance of the isotope 18O because of reduced massive star nucleosynthesis in comparison to the MW and LMC.