Transitions of methyl formate toward Orion KL

Using extensive ALMA data, we determined the rotational and vibrational temperatures for the Compact Ridge and Hot Core by the conventional rotation diagram method. The rotational temperature and vibrational temperatures agree for the Hot Core and for one component of the Compact Ridge. At the 7.3 km/s velocity component for the Compact Ridge, the rotational temperature was found to be higher than the vibrational temperature.

This is different from what we obtained from the results by using the single-dish observation. The difference might be explained by the beam dilution effect of the single-dish data and/or the smaller number of observed transitions within the limited range of energy levels (<=30 K) of E_u_ in the previous study.