The Effect of Progenitor Age and Metallicity on Luminosity and [sup]56[/sup]Ni Yield in Type Ia Supernovae

Timmes et al. found that metallicity variations could theoretically account for a 25% variation in the mass of 56Ni synthesized in Type Ia supernovae (SNe Ia), and thus account for a large fraction of the scatter in observed SN Ia luminosities. Higher-metallicity progenitors are more neutron rich, producing more stable burning products relative to radioactive 56Ni. We develop a new method for estimating bolometric luminosity and 56Ni yield in SNe Ia and use it to test the theory with data from the Supernova Legacy Survey. We find that the average 56Ni yield does drop in SNe Ia from high-metallicity environments, but the theory can only account for 7%-10% of the dispersion in SN Ia 56Ni mass, and thus luminosity. This is because the effect is dominant at metallicities significantly above solar, whereas we find that SN hosts have predominantly subsolar or only moderately above-solar metallicities. We also show that allowing for changes in O/Fe with the metallicity [Fe/H] does not have a major effect on the theoretical prediction of Timmes et al., so long as one is using the O/H as the independent variable. Age may have a greater effect than metallicity—we find that the luminosity-weighted age of the host galaxy is correlated with 56Ni yield, and thus more massive progenitors give rise to more luminous explosions. This is hard to understand if most SNe Ia explode when the primaries reach the Chandrasekhar mass. Finally, we test the findings of Gallagher et al. that the residuals of SNe Ia from the Hubble diagram are correlated with host galaxy metallicity, and we find no such correlation.
Paper Reference: 
Howell, D. A. et al. 2009, ApJ, 691, 661
Paper Authors: 

THE EFFECT OF PROGENITOR AGE AND METALLICITY ON LUMINOSITY AND 56Ni YIELD IN TYPE Ia SUPERNOVAE

D. A. Howell et al 2009 ApJ 691 661-671   doi: 10.1088/0004-637X/691/1/661  Help


D. A. Howell1,2,3, M. Sullivan1,4, E. F. Brown5, A. Conley1, D. Le Borgne6, E. Y. Hsiao7, P. Astier8, D. Balam7, C. Balland8,9, S. Basa10, R. G. Carlberg1, D. Fouchez11, J. Guy8, D. Hardin8, I. M. Hook4, R. Pain8, K. Perrett1, C. J. Pritchet7, N. Regnault8, S. Baumont8, J. Le Du11, C. Lidman12, S. Perlmutter13,14, N. Suzuki13, E. S. Walker4 and J. C. Wheeler15

1 Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H8, Canada
2 Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Goleta, CA 93117, USA
3 Department of Physics, University of California, Santa Barbara, Broida Hall, Mail Code 9530, Santa Barbara, CA 93106-9530, USA
4 University of Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
5 Department of Physics & Astronomy, National Superconducting Cyclotron Laboratory, and the Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824, USA
6 Institut d'Astrophysique de Paris, UMR7095 CNRS, UPMC, 98 bis Boulevard Arago, 75014 Paris, France
7 Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC V8W 3P6, Canada
8 LPNHE, CNRS-IN2P3 and University of Paris VI & VII, 75005 Paris, France
9 Univ. Paris-Sud, Orsay, F-91405, France
10 Laboratoire d'Astrophysique de Marseille, Pôle de l'Etoile Site de Château-Gombert, 38, rue Frédéric Joliot-Curie, 13388 Marseille cedex 13, France
11 CPPM, CNRS-Luminy, Case 907, 13288 Marseille Cedex 9, France
12 ESO, Alonso de Cordova, 3107, Vitacura Casilla 19001, Santiago 19, Chile
13 Lawrence Berkeley National Laboratory, Mail Stop 50-232, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
14 Department of Physics, University of California, 366 LeConte Hall MC 7300, Berkeley, CA 94720-7300, USA
15 Department of Astronomy, University of Texas, RLM 5.208, Austin, TX 78712-1081, USA

Downloadable version: 
http://www.iop.org/EJ/abstract/0004-637X/691/1/661
Publication Date: 
16 January, 2009
Tags: 
Metallicity
supernova
Type Ia
Age
Cosmology