The Chemical Variation in the Orion A Cloud Cores

In order to investigate whether the column density ratios of carbon chain molecules (CCS, and HC3N) to N-bearing molecules (N2H+ and NH3) can be indicators of the chemical evolution in giant molecular clouds or not, we examined chemical characteristics of dense cores. As a results, we found that the column density ratio, N(NH3)/N(CCS) and N(NH3)/N(HC3N), are high in star-forming cores and low in starless cores in the Orion A cloud. It may be suggested that the N(NH3)/N(CCS) and N(NH3)/N(HC3N) ratios are indicators of chemical evolution even in GMCs. We also found that the N(NH3)/N(CCS) ratio increases with the dissipation of turbulence. This means that the chemical evolution may be an indicator of the dynamical evolution of the core.