Large-Field CO(J = 1→0) Observations of the Starburst Galaxy M82

摘要

We present large-field (15.7 × 16.9 arcmin~2) CO(J = 1→0) observations of the starburst galaxy M82, at an angular resolution of 22″ with the NRO 45-m telescope. The CO emission was detected in the galactic disk, outflow (driven by the galactic wind) up to ~2 kpc above the galactic plane in the halo, and in tidal streams. The kinematics of the outflow (including CO line splitting) suggests that it has the shape of a cylinder that is diverging outwards. The mass and kinetic energy of the molecular gas outflow are estimated to be (0.26–1.0) × 10~9M☉ and (1–4) × 10~(56) erg. A clump of CO gas was discovered 3.5 kpc above the galactic plane; it coincides with a dark lane previously found in X-ray observations, and a peak in HI emission. A comparison with HI, hot molecular hydrogen and dust suggests that the molecular gas shows signatures of warm and cool components in the outflow and tidal streams, respectively.