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COSMIC RATE OF SNIa

COSMIC RATE OF SNIa. Laura Greggio INAF, Padova Astronomical Observatory. SNIa are relevant to the study of:. Chemical evolution of galaxies Chemical evolution of the ICM and IGM Gas flows in Ellipticals The determination of cosmological parameters.

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COSMIC RATE OF SNIa

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  1. COSMIC RATE OF SNIa Laura Greggio INAF, Padova Astronomical Observatory Ringberg, July 8, 2005

  2. SNIa are relevant to the study of: • Chemical evolution of galaxies • Chemical evolution of the ICM and IGM • Gas flows in Ellipticals • The determination of cosmological parameters To study # 1,2 and 3we needthe SNIa rate following a burst of SF To address # 4 we need to understand the nature of the SNIa progenitor The cosmic evolution of the SNIa rate helps constraining both Ringberg, July 8, 2005

  3. Dahlen et al. 2004: SNII trace the recent SF  use the rate of type II to trace the cosmic SFR SNIa come from longer lived progenitors: At a cosmic epoch t the SNIa rate is • τ is the delay time (interval between the birth • of the stellar system and its explosion) • fIa is the distribution function of the delay • times • AIa is the realization probability of the • SNIa event out of one stellar generation • kα is the number of stars per unit Mass of • one stellar generation Ringberg, July 8, 2005

  4. (1984) SD DD Close Binary Evolution provides two main cathegories of SNIa precursors: Single Degenerate Systems a CO WD accretes from a living companion Double Degenerate Systems the companion is another WD • Explosion may occur when • the WD mass reaches the • Chandrasekhar limit • (Ch-exploders) • a Helium layer of ≈0.1 MO, accumulated • on top of the WD, detonates • (Sub-Ch exploders) Ringberg, July 8, 2005

  5. Pros and Cons Single Degenerates: Candidate precursors observed (SSXRS, Symbiotic, CV) Fine tuning of accretion rate is needed to avoid nova and/or CE (small volume in the phase space) Absence of H in the spectra Double Degenerates: Absence of H in the spectra Theoretical likelyhood accounts for current rate in the MW Theoretical explosion leads to neutron star Observed DDs are not massive enough CHANDRA exploders : uniform light curves and better spectra BUT few of them SUB-CHANDRA : many of them BUT variety of Ni56 produced and high velocity of ejected Ni Ringberg, July 8, 2005

  6. Population Synthesis of Binaries Monte Carlo simulations of a population of binaries with n(m1), n(q), n(A0), following the evolution of each system through the RLOs and determining the outcome (CVs, RCBor, sdO,all varieties of DD.., sometimes SNIa) Tutukov & Yungelson , Ruiz-Lapuente,Burket & Canal, Han et al., Nelemans et al. Yungelson and Livio 2000 The results are: (highly) model dependent ( aCE, mass loss, criterion for mass transfer stability …) hard to implement in other computations (for galaxy evolution, cosmic evolution…) BUT the distribution function of the delay times can be characterized on general grounds … Ringberg, July 8, 2005

  7. Single Degenerates:Clock is the nuclear timescale of the secondary + limits on primary mass: Evolutionary clock and Distribution of the secondaries in systems which give rise to a SNIa Ringberg, July 8, 2005

  8. Double Degenerates Double CO WDs: m1, m2 2 then tn≤ 1Gyr Clock is the nuclear timescale of the secondary + the gravitational delay MDD=2 τgw ranges in 5Myr – 15 Gyr A ranges from 0.5 to 3.8 Ro The distribution function of the separations of the DD systems is crucial for the distribution of the gravitational delays • Shrinkage at RLO: • Start from: • 100 R0 <A0 < 1000 R0 • Go through RLO: • standard CE: (A/AO)≈few 10-3 • heavier systems have smaller A/AO & shortertgw • Nelemans et al. : • large range of (A/AO) • no correlation between mass and tgw WIDE DDs CLOSE DDs A small dispersion in DD masses and/or final separations yield a wide distribution of delay times Ringberg, July 8, 2005

  9. The distribution function of the delay times for DDs mainly controlled by: maximum nuclear delay (minimum m2 of a successful system) whether evolution leads to WIDE or CLOSE DD distribution function of the separations of the DD whether favouring larger or smaller A Ringberg, July 8, 2005

  10. The distribution function of the delay times All models normalized at 12 Gyr : Main Parameters : SD: minimum mass of the primary for a successful SNIa (distribution of mass ratios) DD: 1) minimum mass of the secondary (fix maximum nuclear delay) 2) distribution function of the separations after II RLO 3) whether WIDE or CLOSE • Different models have: • different • different Fe production Ringberg, July 8, 2005

  11. The Cosmic SNIa rate Ringberg, July 8, 2005

  12. Results of the convolution: The results of the convolution are rather sensitive to the adopted cosmic SFR: A steep increase from z=0 to 1 favors a steep increase of the cosmic SNIa rate A decrease from z=1 upward Could explain the low SNIa rate at z=1.6 Ringberg, July 8, 2005

  13. SNIa rate in different galaxy types Another way to constrain the distribution function of the delay times • Younger stellar populations sample the peak of • the distribution function of the delay times • Younger stellar populations are bluer •  Bluer galaxies have larger SPECIFIC SNIa rates Ringberg, July 8, 2005 Data from Mannucci et al. 2005

  14. CONCLUSIONS • I illustratedhow the SFR and the distribution function of the delay times compose to determine the SNIa rate in galaxies The current SNIa rate in Spirals mostly constrains the realization probability of the SNIa scenario; in Ellipticals it scales as the fIafunction The ratio between the current SNIa rates in Spirals and Ellipticals constrains the shape of the function • I presented analytic expressions, describing the distribution function of the delay times for Single and Double Degenerate progenitors These expressions are based on general stellar evolution arguments, which result into a fIafunction controlled by a few main parameters • Representing Es as instantaneous burst of SF, and using their current rate to calibrate the fIa function, I showed that: SD models greatly overproduce Fe in Galaxy Clusters and overpredict the current rate in Spiral galaxies The data are met with either CLOSE DDs with flat n(A) or WIDE DDs with steep n(A) Ringberg, July 8, 2005

  15. NORMALIZATION Horizontal levels derived from rate in galaxies Points derived from cosmic rate Ringberg, July 8, 2005

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