In the past twenty years, the reconnaissance of 12CO and 13CO emission in the Milky Way by single-dish millimeter-wave telescopes has expanded our view and understanding of interstellar molecular gas. We enumerate the major surveys of CO emission along the Galactic plane and summarize the various approaches that leverage these data to determine the large-scale distribution of molecular gas: its radial and vertical distributions, its concentration into clouds, and its relationship to spiral structure. The integrated properties of molecular clouds are compiled from catalogs derived from the CO surveys using uniform assumptions regarding the Galactic rotation curve, solar radius, and the CO-to-H conversion factor. We discuss the radial variations of cloud surface brightness, the distributions of cloud mass and size, and scaling relations between velocity dispersion, cloud size, and surface density that affirm that the larger clouds are gravitationally bound. Measures of density structure and gas kinematics within nearby, well-resolved clouds are examined and attributed to the effects of magnetohydrodynamic turbulence. We review the arguments for short, intermediate, and long molecular lifetimes based on the observational record. The review concludes with questions that shall require further observational attention.


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Literature Cited

  1. Acharyya K, Fuchs GW, Fraser HJ, van Dishoeck EF, Linnartz H. 2007. Astron. Astrophys. 466:1005–12
  2. Ackermann M, Ajello M, Atwood WB. et al. 2012. Ap. J. 750:3
  3. Aguirre JE, Ginsburg AG, Dunham MK. et al. 2011. Ap. J. Suppl. 192:4
  4. Allen RJ, Rodríguez MI, Black JH, Booth RS. 2012. Astron. J. 143:97
  5. Alves J, Lombardi M, Lada CJ. 2007. Astron. Astrophys. 462:L17–21
  6. Anderson LD, Bania TM, Balser DS, Rood RT. 2012. Ap. J. 754:62
  7. André P, Men'shchikov A, Bontemps S. et al. 2010. Astron. Astrophys. 518:L102
  8. Arnaud K, Riley PA, Wolfendale AW. et al. 1982. MNRAS 201:745–58
  9. Arzoumanian D, André P, Peretto N, Könyves V. 2013. Astron. Astrophys. 553:A119
  10. Ballesteros-Paredes J, Hartmann L. 2007. Rev. Mex. Astron. Astrofis. 43:123–36
  11. Ballesteros-Paredes J, Hartmann LW, Vázquez-Semadeni E, Heitsch F, Zamora-Avilés MA. 2011. MNRAS 411:65–70
  12. Bally J, Langer WD, Stark AA, Wilson RW. 1987. Ap. J. Lett. 312:L45–49
  13. Balser DS, Rood RT, Bania TM, Anderson LD. 2011. Ap. J. 738:27
  14. Bania TM. 1977. Ap. J. 216:381–403
  15. Bania TM. 1980. Ap. J. 242:95–111
  16. Barnard EE, Frost EB, Calvert MR. 1927. A Photographic Atlas of Selected Regions of the Milky Way. Washington, DC: Carnegie Inst. Wash.
  17. Barnes PJ, Muller E, Indermühle B. et al. 2015. Ap. J. In press

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