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Paper: CO in M51
Volume: 320, The Neutral ISM in Starburst Galaxies
Page: 152
Authors: Rydbeck, G.; Thomasson, M.; Aalto, S.; Johansson, L.; Huttemeister, S.
Abstract: The spiral galaxy M51 has been mapped in the J = 1 → 0 line of CO with the Onsala 20 m antenna. The telescope resolution was 33″ and the map spacing 11″. The present map consists of old data plus recent extensions large radii. The data have been reduced using a statistical image analysis method. The map now covers an area of 11.7′ × 6.7′ and includes the satellite galaxy NGC 5195. CO is detected at large (>12 kpc) galactocentric radii. The CO emission is compared to HI, 15 μm (dust) and Hα emission. The integrated CO to HI ratio remains constant with radius in the outer parts of the galaxy. The CO emission follows the 15 μm emission, but the 15 μm to CO ratio increases on spiral arms and its maximum is shifted towards the Hα bright stellar arm somewhat outside the molecular arm. In the far south, what appears to be counter-rotating or out-of-plane moving molecular gas is detected in addition to gas following the general rotation of the galaxy.
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