Yu-Hsuan Teng (NTU/ASIAA); Naomi Hirano (ASIAA)
Using the N2H+(3-2) observed with the SMA and CSO, and N2H+(1-0) observed with the NRO 45m telescope and ALMA, we study the structure and kinematics of the Orion Molecular Cloud 1 (OMC1), which is the most active star forming region near our solar system. Unlike other molecular lines such as HCO+ or HCN, the observations in N2H+ are less affected by the expansion or explosion originated from the Orion KL, and can trace the dense gas distribution. By conducting non-LTE analysis with the ratio of N2H+ (3-2) and N2H+ (1-0) data, we derived the physical parameters of these three regions. The north-eastern part of Orion KL has a typical density of 3*10^6 cm-3, and a temperature of ~35K. The western part has a similar density to the north-eastern part, but a lower temperature of ~10K. The southern part, OMC1-S, has a higher density of 3*10^7 cm-3, and a temperature of ~35K. These three regions have different velocities; the velocity of the north-eastern part is 10~12 km/s, that of the western part is 8~10 km/s, and that of the southern part is 6~8 km/s. Especially, there is a clear velocity jump at the boundary of the north-eastern and the western part. This velocity structure of OMC1 is similar to a global collapse scenario. The high-resolution N2H+ (3-2) image reveals multiple filamentary structure, having a typical width of 0.02-0.03 pc. We analyze the velocity fields along both the major and minor axis of these filaments. The velocity patterns along some of the filaments may indicate the local motion related to the clumpy, dense cores in those filaments.