We present the results of mapping observations toward an outflow-shocked region , OMC-2 FIR 4 using the Nobeyama 45-m telescope .
We observed the area in ^ { 13 } CO ( J = 1 - 0 ) , C ^ { 18 } O ( J = 1 - 0 ) , N _ { 2 } H ^ { + } ( J = 1 - 0 ) , CCS ( J _ { N } = 8 _ { 7 } -7 _ { 6 } ) , HCO ^ { + } ( J = 1 - 0 ) , H ^ { 13 } CO ^ { + } ( J = 1 - 0 ) , HN ^ { 13 } C ( J = 1 - 0 ) , H ^ { 13 } CN ( J = 1 - 0 ) , DNC ( J = 1 - 0 ) , N _ { 2 } D ^ { + } ( J = 1 - 0 ) , and DC _ { 3 } N ( J = 9 - 8 ) .
We detected a dense molecular clump that contains FIR 4/5 .
We also detected in ^ { 13 } CO blueshifted and redshifted components driven presumably by protostellar outflows in this region .
The axes of the FIR 3 and VLA 13 outflows , projected on the plane of the sky , appear to point toward the FIR 4 clump , suggesting that the clump may be compressed by protostellar outflows from Class I sources , FIR 3 and VLA 13 .
Applying the hyperfine fit of N _ { 2 } H ^ { + } lines , we estimated the excitation temperature to be \sim 20 K. The high excitation temperature is consistent with the fact that the clump contains protostars .
The CCS emission was detected in this region for the first time .
Its abundance is estimated to be a few \times 10 ^ { -12 } , indicating that the region is chemically evolved at \sim 10 ^ { 5 } years , which is comparable to the typical lifetime of the Class I protostars .
This timescale is consistent with the scenario that star formation in FIR 4 is triggered by dynamical compression of the protostellar outflows .
The [ HNC ] / [ HCN ] ratio is evaluated to be \sim 0.5 in the dense clump and the outflow lobes , whereas it is somewhat larger in the envelope of the dense clump .
The small [ HNC ] / [ HCN ] ratio indicates that the HNC formation was prevented due to high temperatures .
Such high temperatures seem to be consistent with the scenario that either protostellar radiation or outflow compression , or both , affected the thermal properties of this region .