Prediction of stellar mass in star formation: Theory and its application to the orion a cloud

  • T. Nakano
  • T. Hasegawa
  • C. Norman
Part III: Young Stellar Objects and Their Environment
Part of the Lecture Notes in Physics book series (LNP, volume 465)


We have developed a way to estimate the mass of a star from the physical quantities of the cloud core in which it forms. Because matter falls onto a stellar core mainly through an accretion disk, a significant fraction of the mass outflow and ultraviolet radiation escapes from the inner region without interacting with the infalling matter and disturbs the cloud core matter which has not yet contracted much. A highvelocity mass outflow gradually pushes out the surrounding matter forming a thin dense shell. On the other hand, as the central star grows, a compact HII region develops and pushes out the surrounding matter also forming a thin dense shell. A considerable fraction of the initial core matter is blown off when the radius of the bubble or the HII region inside the shell grows to the initial radius of the cloud core, and the remaining matter disperses because it is no longer gravitationally bound. In this way the supply of matter from the cloud core to the disk stops. Consequently accretion onto the star also stops, and the mass of the forming star is fixed. The stellar mass determined in this way is a function of the core density n c, the mass inflow rate M I, M o/M I, and M c/M j, or a function of n c, M c, M o/M I, and M c/M J, where M o is the mass outflow rate, M c is the cloud core mass, and M j is the generalized Jeans mass for the core. When the mass outflow is dominant, we have M * α M c 7/6 n c 1/12 with the proportionality coefficient dependent on M o/M I, and thus the stellar mass is almost independent of n c. Therefore, the star formation efficiency M */M c is mainly determined by M o/M I and is only weakly dependent on the core parameters M c and n c; we obtain M */M c≈0.04 for M o/M I=0.1 around M c≈100M . Applying this result to the observed cloud cores in the Orion A molecular cloud by assuming that each core does not contain subclumps we estimate the stellar mass and the initial mass function of stars (IMF) expected in this cloud. As long as M o/M I≳0.02, the mass outflow is more efficient than the HII region in determining the stellar mass for all the Orion A cores. The IMF at M *≳4M can be approximated by a power law dN */dlogM *αM * −1.7 for M o/M I=0.1, which is in reasonable agreement with the IMF of field stars α M * −1.5 at M *≳3M .


Star Formation Accretion Disk Molecular Cloud Stellar Mass Core Mass 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Anthony, D. M., & Carlberg, R. G. 1988, ApJ, 332, 637CrossRefADSGoogle Scholar
  2. Blitz, L. 1993, Protostars & Planets III, eds. E. H. Levy & J. I. Lunine (Univ. Arizona Press, Tucson), p. 125Google Scholar
  3. Boss, A. P. 1984, MNRAS, 209, 543ADSzbMATHGoogle Scholar
  4. Carpenter, J. M., Snell, R. L., Schloerb, F. P., & Skrutskie, M. F. 1993, ApJ, 407, 657CrossRefADSGoogle Scholar
  5. Chen, H., Tokunaga, A. T., Strom, K. M., & Hodapp, K.-W, 1993, ApJ, 407, 639CrossRefADSGoogle Scholar
  6. Edwards, S., Ray, T., & Mundt, R. 1993, Protostars & Planets III, eds. E. H. Levy & J. I. Lunine (Univ. Arizona Press, Tucson) p. 567Google Scholar
  7. Genzel, R., & Stutzki, J. 1989, Ann. Rev. A. Ap., 27, 41CrossRefADSGoogle Scholar
  8. hayashi, C., & Nakano, T. 1965. Prog. Theor. Phys., 34, 754CrossRefADSGoogle Scholar
  9. Heyvaerts, J., & Norman, C. 1989, ApJ, 347, 1055CrossRefADSMathSciNetGoogle Scholar
  10. Heyvaerts, J., 1995, in preparationGoogle Scholar
  11. Lada, E.A., Bally, J., & Stark, A. A. 1991, ApJ, 368, 432CrossRefADSGoogle Scholar
  12. Larson, R.B. 1969, MNRAS, 145, 271ADSGoogle Scholar
  13. 1972, MNRAS, 157, 121ADSGoogle Scholar
  14. 1981, MNRAS, 194, 809ADSGoogle Scholar
  15. 1984, MNRAS, 206, 197ADSGoogle Scholar
  16. Larson, R.B., & Starrfield, S. 1971, A&A, 13, 190ADSGoogle Scholar
  17. Lin, D. N. C., & Pringle, J. E. 1987, MNRAS, 225, 607ADSGoogle Scholar
  18. Nakano, T. 1989, ApJ, 345, 464CrossRefADSGoogle Scholar
  19. Nakano, T., Ohyama, N., & Hayashi, C. 1968, Prog. Theor. Phys., 49, 1448CrossRefADSGoogle Scholar
  20. 1970, Prog. Theor. Phys., 43, 672CrossRefADSGoogle Scholar
  21. Narita, S., Nakano, T., & Hayashi, C. 1970, Prog. Theor. Phys., 43, 942CrossRefADSGoogle Scholar
  22. Norman, C., & Silk, J. 1980, ApJ, 238, 158CrossRefADSGoogle Scholar
  23. Nozawa, S., Mizuno, A., Teshima, Y., Ogawa, H., & Fukui, Y. 1991, ApJ Suppl, 77, 647CrossRefADSGoogle Scholar
  24. Scalo, J.M. 1986, Fundam. Cosmic Phys., 11, 1ADSGoogle Scholar
  25. Shu, F. H., Lizano, S., Ruden, S. P. & Najita, J 1988, ApJ, 328, L19CrossRefADSGoogle Scholar
  26. Stahler, S. W., Shu, F.H. & Taam, R.E. 1980, ApJ, 241, 637CrossRefADSGoogle Scholar
  27. Tatematsu, K., Umemoto, T., Kameya, O., Hirano, N., Hasegawa, T., Hayashi, M., Iwata, T., Kaifu, N. Mikami, H., Murata, Y., Nakano, M., Nakano, T., Ohashi, N., Sunada, K., Takaba, H., & Yamamoto, S. 1993, ApJ, 404, 643CrossRefADSGoogle Scholar
  28. Wolfire, M.G., & Cassinelli, J. P. 1987, ApJ, 319, 850CrossRefADSGoogle Scholar
  29. Wynn-Williams, C. G., Genzel, R., Becklin E. E., & Downes, D. 1984, ApJ, 281, 172CrossRefADSGoogle Scholar

Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • T. Nakano
    • 1
  • T. Hasegawa
    • 2
  • C. Norman
    • 3
  1. 1.Nobeyama Radio ObservatoryNational Astronomical ObservatoryNaganoJapan
  2. 2.Institute of AstronomyUniversity of TokyoTokyoJapan
  3. 3.Department of Physics and AstronomyJohns Hopkins University and Space Telescope Science InstituteBaltimoreUSA

Personalised recommendations