The structure of the high galactic latitude Cometary Globule 12 ( CG 12 ) has been investigated by means of radio molecular line observations .
Detailed , high signal to noise ratio maps in C ^ { 18 } O ( 1–0 ) , C ^ { 18 } O ( 2–1 ) and molecules tracing high density gas , CS ( 3–2 ) , \mathrm { DCO ^ { + } } ( 2–1 ) and \mathrm { H ^ { 13 } CO ^ { + } } ( 1–0 ) , are presented .
The C ^ { 18 } O line emission is distributed in a 10 \arcmin long North-South elongated lane with two strong maxima , CG 12-N ( orth ) and CG 12-S ( outh ) .
In CG 12-S the high density tracers delineate a compact core , \mathrm { DCO ^ { + } } core , which is offset by 15″ from the \mathrm { C ^ { 18 } O } maximum .
The observed strong \mathrm { C ^ { 18 } O } emission traces the surface of the \mathrm { DCO ^ { + } } core or a separate , adjacent cloud component .
The driving source of the collimated molecular outflow detected by [ White ( 1993 ) ] is located in the \mathrm { DCO ^ { + } } core .
The \mathrm { C ^ { 18 } O } lines in CG 12-S have low intensity wings possibly caused by the outflow.The emission in high density tracers is weak in CG 12-N and especially the \mathrm { H ^ { 13 } CO ^ { + } } , \mathrm { DCO ^ { + } } and \mathrm { N _ { 2 } H ^ { + } } lines are +0.5 \mathrm { km s ^ { -1 } } offset in velocity with respect to the \mathrm { C ^ { 18 } O } lines .
Evidence is presented that the molecular gas is highly depleted .
The observed strong \mathrm { C ^ { 18 } O } emission towards CG 12-N originates in the envelope of this depleted cloud component or in a separate entity seen in the same line of sight .
The \mathrm { C ^ { 18 } O } lines in CG 12 were analyzed using Positive Matrix Factorization , PMF .
The shape and the spatial distribution of the individual PMF factors fitted separately to the \mathrm { C ^ { 18 } O } ( 1–0 ) and ( 2–1 ) transitions were consistent with each other .
The results indicate a complex velocity and line excitation structure in the cloud .
Besides separate cloud velocity components the \mathrm { C ^ { 18 } O } line shapes and intensities are influenced by excitation temperature variations caused by e.g , the molecular outflow or by molecular depletion .
Assuming a distance of 630 pc the size of the CG 12 compact head , 1.1 pc by 1.8 pc , and the \mathrm { C ^ { 18 } O } mass larger than 100 M _ { \sun } are comparable to those of other nearby low/intermediate mass star formation regions .