Spallation l-process (spallation): D, Li, Be, B destroyed in stars: Low binding energies, burn quickly to heavier nuclei. But … D close to Big Bang predictions. Higher Li, Be, B often observed. Why? l-process (spallation): Accelerate nucleus to v ~ c (e.g. cosmic rays) Collide with a stationary nucleus. Splits yield Li, Be, B.

BB 1,2H 3,4He 7Li Intergalactic medium Interstellar medium SN ? Galaxy formation inflow Gal. winds, stripping, mergers Interstellar medium Spallation 6Li, Be, B Cosmic rays Star formation Winds, PN, Novae He, 7Li, C, N D, Li, Be, B Explosive r-process Small stars D, Li Middling stars Big stars SN NS BH WD

X-rays from Supernova remnants Shocked gas hot enough to emit X-rays

More ways to enrich the ISM Stellar winds: radiation pressure blows gas from the surfaces of hot massive stars. Can be very eruptive!

Planetary Nebula: matter ejected from 1-3 solar mass star at end of the AGB phase Animation of the formation of the Helix nebula

Planetary Nebulae

Lecture 9: Supernova Rates Star-Formation Efficiency, Yield How many supernovae per year for each galaxy type? Use power-law IMF, Salpeter slope -7/3 = -2.33 Limits of validity, not well known . . slope = . . 0.1M . 8M 20M Supernova limit

Integrating a Power-Law IMF Number of stars : Fraction of stars with M > 8 M 500 stars --> 1 supernova! . Most stars at low-mass end!

SN Mass Fraction SNe are rare, but each is very massive. What fraction of the mass goes into SNe? Most of mass is in low-mass stars.

Typical SN Mass Median mass: Mean mass: .

SN Rates: Spiral Galaxy: SFR: ~ 8 M yr-1. 7.2% have M > 8M . . . 8 x 0.072 ~ 0.6 M yr-1 go into SNe SN rate: Irregular Galaxy: ~10x this rate during bursts (1 SN per 2 yr)! No SNe between bursts. . . . . .

SNe in Ellipticals t* = 1 Gyr e-folding time t = 10 Gyr age a = 0.95 efficiency M0 = 1011 M total mass = initial gas mass Gas consumption: Star formation: SN rate: 3 SN per 105 yr. Negligible! . . . .

What Efficiency and Yield? X = 0.75 Y = 0.25 Z = 0.00 X = ? Y = ? Z = ? MG = 1 MS = 0 MG = 0 MS = 1 MG = ? MS = ? KABOOM! KABOOM!

Estimates for efficiency a , yield in X, Y, Z Assume: Type-II SNe enrich the ISM. Ignore: Type-I SNe, stellar winds, PNe, .... Ignore: Infall from the IGM. SN 1987A is typical Type-II SN. Better models include these effects. What we know about SN 1987A?

SN 1987A 23 Feb 1987 in LMC Brightest SN since 1604! First SN detected in neutrinos. Visible (14 --> 4.2 mag) to naked eye, in southern sky. Progenitor star visible: ~20 Msun blue supergiant. 3- ring structure (pre-SN wind) Shockwave now hitting inner ring.

SN 1987A

Star Formation Efficiency Use SN 1987A to calculate a and yield. SN 1987A: initial mass = 20 M NS mass = 1.6 M From IMF, 7.2% of MS is in stars with M > 8 M Fraction of MS returned to ISM: Efficiency = fraction of MS retained in stars. . . .

Yields in X, Y, Z Initial mass ~ 20 M NS mass ~ 1.6 M Mass ejected ~ 18.4 M in H 9.0 M He 7.0 M = 18.4 M Z 2.4 M . . . . . . .