The Physical And Chemical Envriment Of Massive Star Formation Region W51 North

We present the Submillimeter Array (SMA) observations of molecular lines at 217 and 227 GHz toward massive star forming region, W51 North. We have identified molecular line transitions from seventeen species and their isotopo-logues. In addition to commonly detected nitrogen and oxygen-bearing species, thirteen (CH3)2CO transitions are confirmed in W51 North which is proven as a new source of searching for (CH3)2CO. The molecular gas distribution-s show that compact core peaked around the continuum peak position with east-west extension. There are no obvious difference in gas distribution be-tween the oxygen-bearing and nitrogen-bearing molecules. Under the assump-tion of LTE, with XCLASS tool, the molecular column densities and rotation temperatures are estimated. The oxygen-bearing molecules have higher colum-n densities of 4.3×1016-2.3×1018 cm-2 than the nitrogen-bearing molecules of 2.8×1015-2.6×1016 cm-2. The rotation temperatures of most of molecules range from 100 to 200 K, which suggests that the molecular emissions origi-nate from warm environment. The H2 column density of 6.4×1024 cm-2 is derived from the millimeter continuum, and then the fractional abundance of all molecules relative to H2 are estimated. The oxygen-bearing molecules have high-er fractional abundance than the nitrogen-bearing molecules. Based on the gas distributions, fractional abundances and the rotation temperatures of molecules, we conclude that the complex molecules in W51 North originate from hot core environments with well-mixed N and O-bearing species.