Galactic Supernova Rate Physis 554 Project December 11, 2007 Satoru Inoue Department of Physics University of Washington What is it? It's the time rate of supernova explosions in the Galaxy. Zwicky (1938) estimated the average time between 2 supernovae in an average “nebula” to be 460yr. Why bother? Stellar evolution − Star formation and death − SN mechanism Why bother? Stellar evolution − Star formation and death − SN mechanism Galactic evolution − Nucleosynthesis − Remnants and other effects on surroundings Why bother? Stellar evolution − Star formation and death − SN mechanism Galactic evolution − Nucleosynthesis − Remnants and other effects on surroundings Guide to Experiments − Neutrinos, cosmic rays − Gravitational waves Strategies and Shortcomings Count the # of events in the Milky Way − Too rare (last known event in late 17th c.) Strategies and Shortcomings Count the # of events in the Milky Way − Too rare (last known event in late 17th c.) Count the # of events in other galaxies − Selection effects Strategies and Shortcomings Count the # of events in the Milky Way − Too rare (last known event in late 17th c.) Count the # of events in other galaxies − Selection effects Count objects that could be SN remnants − How often do SNe turn into pulsars, etc.? Strategies and Shortcomings Count the # of events in the Milky Way − Too rare (last known event in late 17th c.) Count the # of events in other galaxies − Selection effects Count objects that could be SN remnants − How often do SNe turn into pulsars, etc.? Measure the amount of NS output − How much of it does one SN (and its progenitor) produce? Is it constant among galaxies? Is it constant among galaxies? SNe more common in spiral galaxies than in elliptical galaxies Especially type-II, which is closely related to star formation rate Mannucci et. al. (2005) From extragalactic searches You can deduce the SN rate in the Milky Way by plugging in the luminosity for the SN rates for the same galaxy type. 10 Total luminosity is ~2×10 Lʘ Type is (probably) Sb ⇒1.3±0.9/century (Cappellaro et. al. 1999) SN types We can also estimate the relative rates of SNe based on type. 20% Type Ia 10% Type Ib/c 70% Type II The et. al. (2006) The historical data is consistent. (with a small sample) Pulsars Pulsars − Galactic pulsar birth rate ~ 2.8/century − 13~25% of CC SNe leave a black hole, and not a pulsar − Faucher-Giguère and Kaspi (2006) assumed all CC SNe left either a black hole or a pulsar, and derived CC SN rate ~ 3.2-3.7/century − Selection effects and ratio of SNe to pulsars unclear Constraints from NS 60Fe − 8 10 10 Mʘ in the Galaxy, accumulated over 10 yrs − Ia produces about 0.6Mʘ, and CC produces about 0.1Mʘ − Upper limit of ~ 6 SNe/century (Tammann et. al. 1994) Constraints from NS 26Al − Produced mainly by massive stars, and released into the surroundings by a core- collapse SN − β lifetime ~ 7.2×105yrs − CC SN rate = 1.9±1.1/century Diehl et. al. (2006) I said it doesn't work, but... Historically, we haven't seen as many SNe in the Galaxy as these rates indicate. This is most likely due to obscuration by the interstellar medium. With neutrino detectors, this shouldn't be a problem at all. So you CAN count the # of Galactic SNe. Prospects Better optical searches − Understand selection effects 44Ti − Ejected by CC SN − Measurements and theory aren't consistent (The et. al. 2006) Neutrino detection Consistency with models of galaxies and stars Reference Reviews S. van den Bergh and G. A. Tammann, ARA&A 29:363-407 (1991) G. A. Tammann, W. Löffler, and A. Schröder, ApJS 92:487-493 (1994) SN searches E. Cappellaro, R. Evans, and M. Turatto, A&A 351:459-466 (1999) E. Cappellaro et. al., A&A 430:83-93 (2005) F. Mannucci et. Al, A&A 433:807-816 (2005) F. Zwicky, ApJ 88:529-541 (1938) Pulsars C.-A. Faucher-Giguère and V. M. Kaspi, ApJ 643:332-355 (2006) NS output R. Diehl et. al., Nature 439:45-47 (2006) D. Hartmann et. al., A&AS 97:219-220 (1993) L.-S. The et. al. A&A 450:1037-1050 (2006) .