On the nearest molecular clouds. II - MBM 12 and 16

The distance to an individual cloud in the MBM group can be determined at optical wavelengths by mapping the interstellar absorption lines toward a set of stars at different distances in the direction of the cloud. The distance to MBM 16 is estimated by this method to 60 ⪉ d ⪉ 95 pc. MBM 16 is only 11° away from MBM 12, previously placed by the same method at d ≈ 65 pc. The relation of clouds 12 and 16 to the local, hot, low-density, interstellar gas is discussed. Upper limits on the interstellar λ4300 line of CH toward three of the background stars projected on or near MBM 12 and MBM 16 suggest that no extremely large overabundances of CH molecules exist in these clouds. It is indicated that MBM 16 and at least the outer regions of MBM 12 in fact are CO rich diffuse clouds.