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Date and Time of the Query: 2019-05-22 T16:32:12 PDT
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For refcode 1993A&AS...97..887B:
Retrieve 81 NED objects in this reference.
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NED Abstract

Copyright by European Southern Observatory (ESO). Reproduced by permission
1993A&AS...97..887B A co(1-0) and CO (2-1) survey of nearby spiral galaxies. I. data and observations J. Braine, F. Combes, F. Casoli, C. Dupraz, M. Gerin, U. Klein, R. Wielebinski and N. Brouillet Observatoire de Meudon, DEMIRM, F-92195 Meudon Cedex, France Ecole Normale Superieure 24, rue Lhomond, F-75005 Paris, France Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-5300 Bonn 1, Germany Radioastronomisches Institut der Universitat Bonn, Auf dem Hugel 71, D-5300 Bonn 1, Germany Observatoire de Bordeaux, B.P. 89, F-33270 Floirac, France Received June 5, 1991; accepted June 26, 1992 Abstract. - High angular resolution observations of ^12^CO(1-0) and ^12^CO(2-1) at the IRAM 30m telescope are for 81 galaxies in a survey of the molecular gas in an optically selected sample of nearby spiral galaxies. The presented goal is threefold: (a) to determine the excitation conditions of the molecular gas in galactic centers; (b) to observe radial distribution of CO(1-0) and CO(2-1) at high angular resolution; and (c) to estimate the effect of environment on the above. In 36 galactic centers both the CO(1-0) and CO(2-1) lines were detected and a small central map made in CO(2-1) to enable a real comparison of the CO(2-1) and CO(1-0) data. The overall detection rate is 75% but the upper limits are inhomogeneous. The previously unobserved or undetected galaxies yielded 18 new detections (including 4 marginal detections) and 12 new upper limits; two previous detections were not confirmed. The average (and median) CO(2-1) to CO(1-0) line intensity ratio, after convolution of the data to the same angular resolution, is 0.89 +/- 0.06. This is consistent with optically thick gas with equal excitation temperatures in both transitions. Only one true exception exists out of the 36 galactic centers: NGC 3310. The line ratio in this highly starbursting galaxy is 2.6, higher than in M82, implying that the gas is warm and possibly optically thin. Off-center maxima, generally corresponding with optical and/or H{alpha} rings, were found in 1/3 of the galaxies. The previously observed exponential disk image thus breaks down at higher angular resolution. A detailed analysis and discussion of the survey results is presented in companion papers. Key words: galaxies: interstellar matter - galaxies: spiral galaxies: interaction - radiolines: molecular: interstellar
Retrieve 81 NED objects in this reference.
Please click here for ADS abstract

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