Hostname: page-component-cd9895bd7-dk4vv Total loading time: 0 Render date: 2024-12-26T03:12:01.276Z Has data issue: false hasContentIssue false
  • English
  • Français

Massive Stars in the MCs: What They Tell Us about the IMF, Stellar Evolution, and Upper Mass “Cutoffs”

Published online by Cambridge University Press:  25 May 2016

Philip Massey
Philip Massey*
Affiliation:
National Optical Astronomy Observatories, P.O. 26732, Tucson, AZ 85726-6732, USA

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.

Studies over the past decade have shown that the initial mass function (IMF) is the same for massive stars born in the OB associations of the LMC and SMC as in the associations of the Milky Way: the slope of the IMF is essentially Salpeter (Γ ~ −1.3), despite the factor of 4 difference in metallicity between these systems, and despite a factor of several hundred in stellar density between the sparsest and richest OB associations. However, there does appear to be a number of massive stars that are born in relative isolation, and the IMF of this mixed-age, field population is quite different than that of OB associations, with Γ ~ −4 in all three galaxies. The distribution of stars in the HR diagram is in excellent agreement with the Geneva group's evolutionary models for stars with masses with no “main-sequence widening problem” left to be solved. The massive stars born in clusters are formed quite coevally (Δτ < 1–2Myr), which allows us to use the “turn-off masses” to determine what mass objects become Wolf-Rayet stars of various types, and new results are briefly described. For the LMC, WNEs come from a wide range of masses, WCs come only from the highest mass stars, and Ofpe/WN9 “slash” stars come from lower mass OBs. Recent work on the R136a cluster (described in Hunter's review talk) suggest that there is no such thing as an upper mass cutoff to the IMF, at least not one that has been found observationally: for the youngest clusters (2 Myr and younger), the mass of the highest mass star present is simply dependent upon how populous the cluster is; i.e., the IMF is truncated by statistics, not physics.

Type
Part 3. Massive Stars and 30 Doradus
Information
Symposium - International Astronomical Union , Volume 190: New Views of the Magellanic Clouds , 1999 , pp. 173 - 180
Copyright
Copyright © Astronomical Society of the Pacific 1999 

References

Azzopardi, M., & Vigneau, J. 1975, A&AS, 22, 285 Google Scholar
Azzopardi, M., & Vigneau, J. 1982, A&AS, 50, 291 Google Scholar
DeGioia-Eastwood, K., Throop, H., Walker, G., & Cudworth, K. M. 1999, AJ, submitted Google Scholar
Esteban, D., & Peimbert, M. 1995, Rev. Mex. A&A, Ser. Conf. 3, 133 Google Scholar
Fitzpatrick, E. L., & Garmany, C. D. 1990, ApJ, 363, 119 Google Scholar
Garmany, C. D., Conti, P. S., & Chiosi, C. 1982, ApJ, 263, 777 Google Scholar
Hill, R. J., Madore, B. F., & Freedman, W. L. 1994, ApJ, 429, 204 Google Scholar
Hillenbrand, L. A., Massey, P., Strom, S. E., & Merrill, K. M. 1993, AJ, 106, 1906.Google Scholar
Hunter, D. A., & Massey, P. 1990, AJ, 99, 846 Google Scholar
Lucke, P. B., & Hodge, P. W. 1970, AJ, 75, 171 CrossRefGoogle Scholar
Massey, P. 1998a, in The Stellar Initial Mass Function , ed. by Gilmore, G. & Howell, D. (San Francisco, ASP), 17 Google Scholar
Massey, P. 1998b, in Stellar Astrophysics for the Local Group , ed. Aparicio, A., Herrero, A., & Sanchez, F. (Cambridge, Cambridge Univ. Press), 95 Google Scholar
Massey, P., & Hunter, D. A. 1998, ApJ, 493, 180 Google Scholar
Massey, P., Johnson, K. E., & DeGioia-Eastwood, K. 1995a, ApJ, 454, 151 CrossRefGoogle Scholar
Massey, P., Lang, C. C., DeGioia-Eastwood, K., & Garmany, C. D. 1995b, ApJ, 438, 188 Google Scholar
Rousseau, J., Martin, N., Prevot, L., Rebeirot, E., Robin, A., & Brunet, J. P. 1978, A&AS, 31, 243 Google Scholar
Russell, S. C., & Dopita, M. A. 1990, ApJS, 74, 93 Google Scholar
Sanduleak, N. 1969, Contr. Cerro Tololo Inter-American Obs., 89 Google Scholar
Scalo, J. 1998, in The Stellar Initial Mass Function , ed. Gilmore, G. & Howell, D. (San Francisco, ASP), 201 Google Scholar
Shields, G. A., & Tinsley, B. M. 1976, ApJ, 203, 66 Google Scholar
St-Louis, N., Moffat, A. F. J., Turbide, L., & Bertrand, J.-F. 1998, in Boulder-Munich II: Properties of Hot, Luminous Stars , ed. Howarth, I. D. (San Francisco, ASP), 326 Google Scholar
Walborn, N. R., & Blades, J. C. 1987, ApJL, 323, 65 Google Scholar