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Masers as probes of massive star formation in the nuclear disk

Published online by Cambridge University Press:  01 March 2007

F. Yusef-Zadeh
Affiliation:
Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 USA email: zadeh@northwestern.edu, j-hewitt@northwestern.edu, cheinke@northwestern.edu, doug-roberts@northwestern.edu
R. G. Arendt
Affiliation:
CRESST/UMBC/GSFC, Code 665, Greenbelt, MD 20771 USA email: arendt@milkyway.gsfc.nasa.gov
C. O. Heinke
Affiliation:
Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 USA email: zadeh@northwestern.edu, j-hewitt@northwestern.edu, cheinke@northwestern.edu, doug-roberts@northwestern.edu
J. L. Hinz
Affiliation:
Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 USA email: grieke@as.arizona.edu, jhinz@as.arizona.edu
J. W. Hewitt
Affiliation:
Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 USA email: zadeh@northwestern.edu, j-hewitt@northwestern.edu, cheinke@northwestern.edu, doug-roberts@northwestern.edu
P. Pratap
Affiliation:
MIT Haystack Observatory, Westford, MA 01886 USA email: ppratap@haystack.mit.edu
S. V. Ramirez
Affiliation:
IPAC, Cal Tech, Pasadena, CA 91125 USA email: solange@ipac.caltech.edu, stolovy@ipac.caltech.edu
G. H. Rieke
Affiliation:
Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 USA email: grieke@as.arizona.edu, jhinz@as.arizona.edu
D. A. Roberts
Affiliation:
Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 USA email: zadeh@northwestern.edu, j-hewitt@northwestern.edu, cheinke@northwestern.edu, doug-roberts@northwestern.edu
S. R. Stolovy
Affiliation:
IPAC, Cal Tech, Pasadena, CA 91125 USA email: solange@ipac.caltech.edu, stolovy@ipac.caltech.edu
M. Wardle
Affiliation:
Department of Physics, Macquarie University, Sydney NSW 2109, Australia email: wardle@ics.mq.edu.au
B. A. Whitney
Affiliation:
Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 USA email: bwhitney@spacescience.org
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Abstract

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OH(1720 MHz) and methanol masers are now recognized to be excellent probes of the interactions of supernova remnants with molecular clouds and tracers of massive star formation, respectively. To better understand the nature of star formation activity in the central region of the Galaxy, we have used these two classes of masers combined with the IRAC and MIPS data to study prominent sites of ongoing star formation in the nuclear disk. The nuclear disk is characterized by massive GMCs with elevated gas temperatures, compared to their dust temperatures. We note an association between methanol masers and a class of mid-infrared “green sources”. These highly embedded YSOs show enhanced 4.5μm emission due to excited molecular lines.

The distribution of methanol masers and supernova remnants suggest a low efficiency of star formation (with the exception of Sgr B2), which we believe is due to an enhanced flux of cosmic ray electrons impacting molecular clouds in the nuclear disk. We also highlight the importance of cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2008

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