Synthetic observations of clumpy ISM: Implications on the seed CO clouds and CO-dark molecular gas

立原　研悟（Kengo TACHIHARA）
名古屋大学大学院理学研究科

We carried out synthetic observations of a theoretical model of interstellar carbon in CO, C I and C II including H2 formation. The theoretical model based on numerical simulations of H I gas converging at a velocity of 20km/s by Inoue & Inutsuka (2012) is employed in the present study. The gas model, which is fairy realistic and consistent with the observations of the local gas located at high b, is turbulent and inhomogeneous with magnetic field. We focus on the evolution of the rare species, CO, C I and C II from 0.3 Myr to 9 Myr since the converging flows collided. In the early phase within 1 Myr, the Cold Neutral Medium (CNM) clumps of sub-pc scales are the formation sites of H2, CO and C I, and in the late phase from 3 Myr to 9 Myr the CNM clumps merge together to form pc-scale molecular clouds. The results show that C I and CO are well mixed at pc scales, and mark a significant disagreement with the classic picture which predicts layered C I and CO distributions according to Av. The total mass budget of the local ISM indicates the fraction of H I is about 70% and the CO-dark H2 is small, less than a few percent, contrary to the usual assumption. The results of high resolution CO observations by the Nobeyama 45m telescope, ASTE, and ALMA obtained at a cloud edge are consistent with this picture, and future high resolution CI observations by ALMA/ACA will reveal small- scale structures of molecular clouds and PDRs.

Place: A 2F Conf. room（1236） / 研究管理棟２階会議場（1236号室）