Hostname: page-component-586b7cd67f-dsjbd Total loading time: 0 Render date: 2024-11-20T15:24:21.172Z Has data issue: false hasContentIssue false
  • English
  • Français

Molecular cloud turbulence and the star formation efficiency: enlarging the scope

Published online by Cambridge University Press:  01 August 2006

Enrique Vázquez-Semadeni
Enrique Vázquez-Semadeni*
Affiliation:
Centro de Radioastronomía y Astrofísica, UNAM, Campus Morelia, P.O. Box 3-72, Morelia, Michoacán, 58088, México
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We summarize recent numerical results on the control of the star formation efficiency (SFE), addressing the effects of turbulence and the magnetic field strength. In closed-box numerical simulations, the effect of the turbulent Mach number depends on whether the turbulence is driven or decaying: In driven regimes, increasing with all other parameters fixed decreases the SFE, while in decaying regimes the converse is true. The efficiencies in non-magnetic cases for realistic Mach numbers 10 are somewhat too high compared to observed values. Including the magnetic field can bring the SFE down to levels consistent with observations, but the intensity of the magnetic field necessary to accomplish this depends again on whether the turbulence is driven or decaying. In this kind of simulations, a lifetime of the molecular cloud (MC) needs to be assumed, being typically a few free-fall times. Further progress requires determining the true nature of the turbulence driving and the lifetimes of the clouds. Simulations of MC formation by large-scale compressions in the warm neutral medium (WNM) show that the generation of the clouds' initial turbulence is built into the accumulation process that forms them, and that the turbulence is driven for as long as accumulation process lasts, producing realistic velocity dispersions and also thermal pressures in excess of the mean WNM value. In simulations including self-gravity, but neglecting the magnetic field and stellar energy feedback, the clouds never reach an equilibrium state, but rather evolve secularly, increasing their mass and gravitational energy until they engage in generalized gravitational collapse. However, local collapse events begin midways through this process, and produce enough stellar objects to disperse the cloud or at least halt its collapse before the latter is completed. Simulations of this kind including the missing physical ingredients should contribute to a final resolution of the MC lifetime and the origin of the low SFE problems.

Keywords

ISM: Cloudsstars:formationturbulencemagnetic fields
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S237: Triggered Star Formation in a Turbulent ISM , August 2006 , pp. 292 - 299
Copyright
Copyright © International Astronomical Union 2007

References

Ballesteros-Paredes, J., Hartmann, L. & Vázquez-Semadeni, E. 1999, ApJ 527, 285CrossRefGoogle Scholar
Ballesteros-Paredes, J. 2004, ApSS 289, 243Google Scholar
Ballesteros-Paredes, J. & Hartmann, L. 2006, RMAA submitted (astro-ph/0605268)Google Scholar
Ballesteros-Paredes, J., Klessen, R. S., Mac Low, M.-M. & Vázquez-Semadeni, E. 2006, in: Reipurth, B., Jewitt, D. & Keil, K. (eds.), Protostars and Planets V (Tucson: Univ. of Arizona), in press (astro-ph/0603357)Google Scholar
Bate, M. R., Bonnell, I. A. & Bromm, V. 2003, MNRAS 339, 577CrossRefGoogle Scholar
Blitz, L. 1993, in: Levy, E. H. & Lunine, J. I. (eds.), Protostars and Planets III (Tucson: Univ. of Arizona), p. 125Google Scholar
Bonnell, I. A. & Bate, M. R. 2006, MNRAS 370, 488CrossRefGoogle Scholar
Folini, D. & Walder, R. 2006, A&A in press (astro-ph/0606753)Google Scholar
Franco, J. & Cox, D. P. 1986, PASP 98, 1076CrossRefGoogle Scholar
Franco, J., Shore, S. N. & Tenorio-Tagle, G. 1994, ApJ 436, 795CrossRefGoogle Scholar
Goldreich, P. & Kwan, J. 1974, ApJ 189, 441CrossRefGoogle Scholar
Goldsmith, P. F. & Li, D. 2005, ApJ 622, 938CrossRefGoogle Scholar
Hartmann, L., Ballesteros-Paredes, J. & Bergin, E. A. 2001, ApJ 562, 852 (HBB01)CrossRefGoogle Scholar
Hartmann, L. 2003, ApJ 585, 398CrossRefGoogle Scholar
Hartmann, L. & Burkert, A. 2006, ApJ in pressGoogle Scholar
Heitsch, F., Mac Low, M. M. & Klessen, R. S. 2001, ApJ 547, 280CrossRefGoogle Scholar
Heitsch, F., Burkert, A., Hartmann, L., Slyz, A. D. & Devriendt, J. E. G. 2005, ApJ 633, L113CrossRefGoogle Scholar
Heitsch, F., Slyz, A. D., Devriendt, J. E. G.Hartmann, L. W. & Burkert, A. 2006, ApJ, submitted (astro-ph/0605435)Google Scholar
Heyer, M. H. & Brunt, C. M. 2004, ApJ 615, L45CrossRefGoogle Scholar
Inutsuka, S. & Koyama, H. 2004, in Revista Mexicana de Astronomia y Astrofisica Conference Series, p. 26Google Scholar
Klessen, R. S., Heitsch, F. & MacLow, M. M. 2000, ApJ 535, 887CrossRefGoogle Scholar
Koyama, H. & Inutsuka, S.-I. 2002, ApJ 564, L97.CrossRefGoogle Scholar
Krumholz, M. R., Matzner, C. D. & McKee, C. F. 2006, ApJ submitted (astro-ph/0608471)Google Scholar
Lada, C. J. & Lada, E. A. 2003, ARAA 41, 57CrossRefGoogle Scholar
Larson, R. B. 1981, MNRAS 194, 809CrossRefGoogle Scholar
Lesieur, M., Turbulence in Fluids 2nd. ed. (Kluwer, Dordrecht 1990)CrossRefGoogle Scholar
Li, Z.-Y. & Nakamura, F. 2006, ApJ 640, L187CrossRefGoogle Scholar
Mac, Low M.-M. & Klessen, R. S. 2004, Rev. Mod. Phys. 76, 125CrossRefGoogle Scholar
Maddalena, R. J. & Thaddeus, P. 1985, ApJ 294, 231CrossRefGoogle Scholar
Matzner, C. D. 2002, ApJ 566, 302CrossRefGoogle Scholar
Mestel, L. & Spitzer, L. Jr. 1956, MNRAS 116, 503CrossRefGoogle Scholar
Mouschovias, T. C. 1976b, ApJ 206, 753CrossRefGoogle Scholar
Mouschovias, T. C., Tassis, K. & Kunz, M. W. 2006, ApJ 646, 1043CrossRefGoogle Scholar
Myers, P. C., Dame, T. M., Thaddeus, P., Cohen, R. S., Silverberg, R. F., Dwek, E. & Hauser, M. G. 1986, ApJ 301, 398CrossRefGoogle Scholar
Nakamura, F. & Li, Z.-Y. 2005, ApJ 631, 411CrossRefGoogle Scholar
Nakano, T. & Nakamura, T. 1978, PASJ 30, 671Google Scholar
Ostriker, E. C., Gammie, C. F. & Stone, J. M. 1999, ApJ 513, 259CrossRefGoogle Scholar
Palla, F. & Stahler, S. W. 2000, ApJ 540, 255CrossRefGoogle Scholar
Palla, F. & Stahler, S. W. 2002, ApJ 581, 1194CrossRefGoogle Scholar
Shu, F. H., Adams, F. C. & Lizano, S. 1987, ARA&A 25, 23.Google Scholar
Stahler, S. W. & Palla, F. 2004, The Formation of Stars (New York: Wiley)CrossRefGoogle Scholar
Tan, J. C., Krumholz, M. R. & McKee, C. F. 2006, ApJ 641, L121CrossRefGoogle Scholar
Tassis, K. & Mouschovias, T. Ch. 2004, ApJ 616, 283CrossRefGoogle Scholar
Vázquez-Semadeni, E. & Passot, T. 1999, in: Franco, J. & Carraminana, A. (eds.), Interstellar Turbulence (Cambridge: Cambridge Univ.), p. 223CrossRefGoogle Scholar
Vázquez-Semadeni, E., Ballesteros-Paredes, J. & Klessen, R. S. 2003, ApJ 585, L131CrossRefGoogle Scholar
Vázquez-Semadeni, E. 2005, in: Corbelli, E., Palla, F., & Zinnecker, H. (eds.), IMF@50: The Initial Mass Function 50 years later (Dordrecht: Springer), p. 371CrossRefGoogle Scholar
Vázquez-Semadeni, E.Kim, J., Shadmehri, M. & Ballesteros-Paredes, J. 2005, ApJ 618, 344CrossRefGoogle Scholar
Vázquez-Semadeni, E., Ryu, D., Passot, T., González, R. F. & Gazol, A. 2006, ApJ 643, 245CrossRefGoogle Scholar
Vázquez-Semadeni, E.Gómez, G. C., Jappsen, K. A.Ballesteros-Paredes, J.González, R. F. & Klessen, R. S. 2006, ApJ submitted (astro-ph/0608375)Google Scholar
Zuckerman, B. & Evans, N. J. II 1974, ApJ 192, L149CrossRefGoogle Scholar
Zuckerman, B. & Palmer, P. 1974, ARAA 12, 279CrossRefGoogle Scholar