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CO and H2 in Local Group Galaxies

Published online by Cambridge University Press:  03 August 2017

F.P. Israel*
Affiliation:
Sterrewacht Postbus 9513 2300 RA Leiden The Netherlands

Extract

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Since the detection of molecular line emission from Galactic sources in the seventies, the importance of molecular clouds as a major constituent of the interstellar medium in the Galaxy has become clear. A major problem in Galactic research has been the overall distribution of the molecular component and position-related variations in this distribution. Studies of this problem are greatly hampered by our eccentric location inside the Galaxy. The global view offered by external galaxies eliminates this problem, but now limitations on linear resolution take its place. Only the nearby Local Group galaxies (Magellanic Clouds: 54 and 63 kpc; M31, M33 and NGC 6822: 500 − 700 kpc) combine acceptable linear resolutions with a global view. Their angular size and the low brightness of their molecular component makes mapping of these galaxies slow process. Yet, this is a worthwile undertaking: not only the global properties of the molecular interstellar medium emerge, but also interesting physical differences due to variations in metallicity and ambient radiation field strength in the galaxies of the Local Group. This paper presents a brief review on molecules in the Local Group and preliminary results from ongoing projects.

Type
I- Local Group Galaxies
Copyright
Copyright © Kluwer 1991 

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