Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-25T19:31:52.307Z Has data issue: false hasContentIssue false
  • English
  • Français

Revisiting the helium abundance in globular clusters with multiple main sequences

Published online by Cambridge University Press:  23 April 2010

Luca Casagrande ,
Laura Portinari  and
Chris Flynn
Luca Casagrande
Affiliation:
Max Planck Institue for Astrophysics, Karl Schwartzschild Straße 1, Garching, Germany email: luca@mpa-garching.mpg.de
Laura Portinari
Affiliation:
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Finland email: lporti@utu.fi, cflynn@utu.fi
Chris Flynn
Affiliation:
Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Finland email: lporti@utu.fi, cflynn@utu.fi
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.

For nearby K dwarfs, the broadening of the observed Main Sequence at low metallicities is much narrower than expected from isochrones with the standard helium–to–metal enrichment ratio ΔY/ΔZ~2. A much higher value, of order 10, is formally needed to reproduce the observed broadening, but it returns helium abundances in awkward contrast with Big Bang Nucleosynthesis. This steep enrichment ratio resembles, on a milder scale, the very high ΔY/ΔZ estimated from the multiple Main Sequences observed in some metal-poor Globular Clusters. We argue that a revision of low Main Sequence stellar models, suggested from nearby stars, could help to reduce the overwhelmingly high ΔY/ΔZ deduced so far for those clusters. Under the most favourable assumptions, the estimated helium content for the enriched populations may decrease from Y ≃ 0.4 to as low as Y ≃ 0.3, with intermediate values being plausible.

Keywords

Stars: fundamental parameterslate-type – subdwarfs – globular clusters: individual (ωCen, NGC 2808, 47 Tuc)
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S268: Light Elements in the Universe , November 2009 , pp. 129 - 134
Copyright
Copyright © International Astronomical Union 2010

References

Anderson, J., Piotto, G., King, I. R., Bedin, L. R., & Guhathakurta, P. 2009, ApJ, 697, L58CrossRefGoogle Scholar
Asplund, M., Grevesse, N., Sauval, A. J., & Scott, P. 2009, ARA&A, 47, 481Google Scholar
Bertelli, G., Girardi, L., Marigo, P., & Nasi, E. 2008, A&A, 484, 815Google Scholar
Carigi, L. & Peimbert, M. 2008, RMxAA, 44, 341Google Scholar
Carretta, E., Bragaglia, A., Gratton, R. G. et al. 2006, A&A, 450, 523Google Scholar
Casagrande, L. 2008, PhD Thesis, Annales Universitatis Turkuensis, Ser. A1 t., 382Google Scholar
Casagrande, L., Portinari, L., & Flynn, C. 2006, MNRAS, 373, 13CrossRefGoogle Scholar
Casagrande, L., Flynn, C., Portinari, L., Girardi, L., & Jimenez, J. 2007, MNRAS, 382, 1516CrossRefGoogle Scholar
Casagrande, L., Ramírez, I., Meléndez, J., Bessell, M., & Asplund, M. 2010, A&A, in pressGoogle Scholar
Catelan, M., Valcarce, A. A. R., & Sweigart, A. V. 2009, IAU Symp. 266, (arXiv:0910.1367)Google Scholar
Cox, J. P. & Giuli, R. T. 1968, Principles of Stellar Structure, Gordon & Breach, New YorkGoogle Scholar
D'Antona, F., Bellazzini, M., Caloi, V., Pecci, F. F., Galleti, S., & Rood, R. T. 2005, ApJ, 631, 868Google Scholar
Faulkner, J. 1967, ApJ 147, 617CrossRefGoogle Scholar
Fernandes, J., Lebreton, Y., & Baglin, A. 1996, A&A, 311, 127Google Scholar
Jimenez, R., Flynn, C., McDonald, J., & Gibson, B. 2003, Science, 299, 1552CrossRefGoogle Scholar
Lebreton, Y., Perrin, M.-N., Cayrel, R., Baglin, A., & Fernandes, J. 1999, A&A, 350, 587Google Scholar
Lee, Y.-W., Joo, S.-J., Han, S.-I. et al. 2005, ApJ, 621, L57CrossRefGoogle Scholar
Norris, J. E. 2004, ApJ, 612, 25CrossRefGoogle Scholar
Pagel, B. E. J. & Portinari, L. 1998, MNRAS, 298, 747CrossRefGoogle Scholar
Peimbert, M., Luridiana, V., & Peimbert, A. 2007, ApJ, 666, 636CrossRefGoogle Scholar
Piotto, G. 2009, in The Ages of Stars IAU Symp. 258, 233CrossRefGoogle Scholar
Piotto, G., Villanova, S., Bedin, L. R., Gratton, R., Cassisi, S. et al. 2005, ApJ, 621, 777Google Scholar
Piotto, G., Bedin, L. R., Anderson, J., King, I. R., Cassisi, S. et al. 2007, ApJ, 661, L53CrossRefGoogle Scholar
Portinari, L., Casagrande, L., & Flynn, C. 2010, submittedGoogle Scholar
Romano, D., Tosi, M., & Cignoni, M. et al. 2009, MNRAS, in press (arXiv:0910.1299)Google Scholar
Sollima, A., Ferraro, F. R., Bellazzini, M. et al. 2007, ApJ, 654, 915CrossRefGoogle Scholar
Villanova, S., Piotto, G., & Gratton, R. G. 2009, A&A, 499, 755Google Scholar
Yi, S.-K. 2009, in The Ages of Stars IAU Symp. 258, 253Google Scholar