Title page for 952209003


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Student Number 952209003
Author Jhen-Kuei Guo()
Author's Email Address m959003@astro.ncu.edu.tw
Statistics This thesis had been viewed 1977 times. Download 618 times.
Department Graduate Institute of Astronomy
Year 2007
Semester 2
Degree Master
Type of Document Master's Thesis
Language English
Title Physical Properties of Molecular Clouds in Active Galaxies
Date of Defense 2008-06-19
Page Count 43
Keyword
  • active galactic nuclei
  • active galaxies
  • cosmic rays
  • molecular clouds
  • Abstract We study the physical properties of molecular clouds in active galaxies. Recent SMA observations have discovered several high temperature molecular clouds around the center regions of some active galaxies. The origin of the heating mechanism for these high temperature clouds is unclear. We analyze the thermal properties of these high temperature molecular clouds by considering various cooling and heating mechanisms within these clouds. We consider the cooling of several different atomic and molecular species, including CI, CII, OI, H2, and CO. We consider three heating mechanisms in the active galaxies: dust heating, X-ray heating, and cosmic-ray heating. By considering the thermal balance between cooling and heating, we find that the cooling rates in these active galaxies are about three order or more higher than that in the Milky Way. Our results indicate that the heating from dust grains and X-ray could not account for the total cooling in the active galaxies. If the cooling is balanced by the heating of cosmic rays in the active galaxies, the ionization rates due to the cosmic rays can be as high as 10 to the power of -13 to -15. Studying the cosmic ray from the supernova remnants, we find that these cosmic rays contribute at most 5% of the total cosmic rays and can not account for the amount of cosmic rays required. We suggest that these cosmic rays are from the AGN activities, such as jets or shocks.
    Table of Content 1 Introduction 1
    2 Cooling Rates 6
    2.1 Cooling Rate of Carbon . . . . . . . . . . . . . . . . . . . . . . . . . 7
    2.2 Cooling Rate of Hydrogen . . . . . . . . . . . . . . . . . . . . . . . . 11
    2.3 Cooling Rate of CO . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
    2.4 Other Cooling Processes . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3 Heating Rate 13
    3.1 Heating by Dust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
    3.2 Cosmic Ray Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
    4 Comparison with Observations 15
    5 Results 18
    6 Discussion 35
    7 Summary 40
    8 Bibliography 41
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    Date of Submission 2008-06-24

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