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Warm Gas and Spatial Variations of Molecular Excitation in the Nuclear Region of IC342

Published online by Cambridge University Press:  14 August 2015

A. Eckart ,
D. Downes ,
R. Genzel ,
A.I. Harris ,
D.T. Jaffe  and
W. Wild
A. Eckart
Affiliation:
Max-Planck-Institut für extraterrestrische Physik, München, West-Germany
D. Downes
Affiliation:
Institut de Radioastronomie Millimetrique (IRAM), Grenoble, France
R. Genzel
Affiliation:
Max-Planck-Institut für extraterrestrische Physik, München, West-Germany
A.I. Harris
Affiliation:
Max-Planck-Institut für extraterrestrische Physik, München, West-Germany
D.T. Jaffe
Affiliation:
Department of Astronomy, University of Texas at Austin, USA
W. Wild
Affiliation:
Max-Planck-Institut für extraterrestrische Physik, München, West-Germany

Extract

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Using the IRAM 30m millimeter radio telescope we mapped the line emission of the J=1-0 and J=2-1 transitions of 12C0, 13C0, and C180 in the nuclear region of the spiral galaxy IC342. This study demonstrates the value of multi line studies to investigate the neutral interstellar medium in extragalactic sources. Our observations as well as calculations of simple models of CO excitation and radiative transport show that the molecular gas in the nucleus is warm and that physical conditions vary with position in the galaxy. The molecular gas in the central kiloparsec of IC342 has a kinetic temperature of at least 30K and a molecular hydrogen density of about 3xl03 cm”3. At distances more than 500pc north and south of the center the kinetic temperature is significantly less (≥13K). About 500 pc north east of the center we find evidence for optically thin CO emission originating in a component of warm gas with a temperature of at least 40 K. Our model calculations result in conversion factors between the H2 column density and the 12CO (1-0) line intensity close to the value of 3–4×1020 cm-2/K km s-1 derived for molecular clouds in the Galaxy. The molecular mass contained in the central two kpc of IC342 is of the order of 2×108 M⊙.

Type
Joint Commission Meeting
Information
Highlights of Astronomy , Volume 8: Highlights of Astronomy. As presented at the XXth General Assembly of the IAU, 1988 , 1989 , pp. 589 - 590
Copyright
Copyright © Kluwer 1989

References

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