C~(18)O Observations of the Dark Molecular Cloud L134 and Gas Depletion onto Dust

We map the dark molecular cloud core of L134 in the C18O (J = 1 - 0) emission line using the PMO 13.7m telescope, and present a contour map of integrated intensity of C18O (J = 1 - 0) emission. The C18O cloud is inside the distribution of extinction AB, the visual extinction of blue light, as well as inside the 13CO cloud in the L134 region. The depletion factors in this C18O cloud are generally greater than unity, which means there is gas depletion onto dust. Since only a minimum AB = 9.7 mag is available, and our observations measure both undepleted and depleted regions along the line of sight, the depletion factors could very likely be larger in the central core than the calculated value. So we conclude that depletion does occur in the bulk of the C18O cloud through a comparison between the C18O and blue extinction maps in the L134 region. There is no direct evidence as yet for star formation in L134, and so cores on the verge of collapse will not be visible in CO and other gas molecules.

C18O Observations of the Dark Molecular Cloud L134 and Gas Depletion onto Dust

We map the dark molecular cloud core of L134 in the C^18O (J=1-0) emission line using the PMO 13.7 m telescope, and present a contour map of integrated intensity of C^18O (J=1-0) emission. The C^18O cloud is inside the distribution of extinction As, the visual extinction of blue light, as well as inside the ^13CO cloud in the L134 region. The depletion factors in this C^18O cloud are generally greater than unity, which means there is gas depletion onto dust. Since only a minimum AB=9.7 mag is available, and our observations measure both undepleted and depleted regions along the line of sight, the depletion factors could very likely be larger in the central core than the calculated value. So we conclude that depletion does occur in the bulk of the C^18O cloud through a comparison between the C^18O and blue extinction maps in the L134 region. There is no direct evidence as yet for star formation in L134, and so cores on the verge of collapse will not be visible in CO and other gas molecules.