Metallicity Dependence of Winds from
Red SuperGiants and
Asymptotic Giant Branch Stars
Jacco van LoonKeele
University
Jacco van LoonKeele
University
Dust wind structure
Radiative equilibrium + continuity equation:
Spectral Energy Distribution
Spectral Energy Distribution
• Integral luminosity
Spectral Energy Distribution
• Integral luminosity• Shape optical depth
Spectral Energy Distribution
• Integral luminosity• Shape optical depth
… but measuring mass-loss rate requires:
• Dust-to-gas ratio
Spectral Energy Distribution
• Integral luminosity• Shape optical depth
… but measuring mass-loss rate requires:
• Dust-to-gas ratio• Wind speed
Dust wind structure
Momentum equation:
Gail & Sedlmayr (1986)
Dust wind structure
Large Magellanic Cloud
Parkes radio observatory
Wind speed from OH masers
Wood et al. (1992)
Marshall et al. (2004)
Wind speed
Wind speed
For oxygen-rich stars
LMC versus the Milky Way
Van Loon (2000)
Mass-loss rate
Mass-loss rate
For oxygen-rich stars
van Loon et al. (1999) + new MSX sample
Superwind mass-loss ratesConversion of radiative momentum:
Superwind mass-loss ratesConversion of radiative momentum:
Multiple scattering:
Gail & Sedlmayr (1986)
Superwind mass-loss rates
Multiple scattering limit predicts:
Superwind mass-loss rates
Multiple scattering limit predicts:
LMC versus galactic bulge
Alard et al. (2001)
Temperature and evolution
Alard et al. (2001)
Galactic bulge observations:
Temperature and evolution
Alard et al. (2001)
Galactic bulge observations:
Hydrodynamic models (carbon stars):
Arndt, Fleischer & Sedlmayr (1997)
Wachter et al. (2002)
Superwind stars in the LMC
luminosity, metallicity (20-25% solar), mass
Cluster superwind carbon star LI-LMC 1813:
Van Loon et al. (2003)
Superwind stars in the LMC
luminosity, metallicity (20-25% solar), mass
Cluster superwind carbon star LI-LMC 1813:
Van Loon et al. (2003)
Wachter et al. (2002)
Compare with solar metallicity model:
Superwind stars in the LMC
Van Loon et al. (2005)
Superwind stars in the LMC
For oxygen-rich stars
LMC prediction applied to Milky Way
Van Loon et al. (2005)
Small Magellanic Cloud
Small Magellanic Cloud
47 Tucanae
SMC versus the LMC
Mass-loss rate
For oxygen-rich and carbon stars
LMC + corrected SMC from Groenewegen et al. (2000)
Z-independent mass-loss rate?
Z-independent mass-loss rate?
(above ~0.1 solar metallicity)
Z-independent mass-loss rate?
(above ~0.1 solar metallicity)
WHY ?
Pulsation in LMC superwind stars
Whitelock et al. (2003)
Pulsational energy
Absolute maximum = 0.5
Pulsation during the superwind
Similar limit for Milky Way, LMC, SMC
Pulsation during the superwind
Similar limit for Milky Way, LMC, SMC
Pulsation during the superwind
Similar limit for Milky Way, LMC, SMC
Hence similar (maximum) mass-loss rates?
Molecule formation
Van Loon et al. (1998)
Molecule formation
• LMC: AGB up to M10; RSG up to M7
Molecule formation
• LMC: AGB up to M10; RSG up to M7
• SMC: AGB up to M8; RSG up to M5Groenewegen & Blommaert (1998)
ESO-VLT
Magellanic carbon stars
Magellanic carbon stars
Van Loon, Zijlstra & Groenewegen (1999)Matsuura et al. (2002, 2005)
Magellanic carbon stars
Large(r?) molecular abundances at low Z
Magellanic carbon stars
Large(r?) molecular abundances at low Z
Especially C2 and C2H2 (not CN and HCN)
Magellanic carbon stars
Large(r?) molecular abundances at low Z
Especially C2 and C2H2 (not CN and HCN)
Due to lower O (and N) abundances
Metal-poor carbon star winds
What if in metal-poor carbon stars...
Metal-poor carbon star winds
What if in metal-poor carbon stars...
… the dust-to-gas ratio were higher...
Metal-poor carbon star winds
What if in metal-poor carbon stars...
… the dust-to-gas ratio were higher...
… their winds would be faster...
Metal-poor carbon star winds
What if in metal-poor carbon stars...
… the dust-to-gas ratio were higher...
… their winds would be faster...
… but their mass-loss rates the same (?)
Spitzer Space Telescope
Molecules in magellanic winds
Spitzer GO programme 3505 (Peter Wood)
CO in magellanic winds
• measure dust-to-CO ratio
• measure carbon star wind speed
Conclusions (to be continued)
above ~0.1 solar metallicity:
Conclusions (to be continued)
• mass-loss rates independent of Z
above ~0.1 solar metallicity:
Conclusions (to be continued)
• mass-loss rates independent of Z• metal-poor O-rich stars are less dusty
above ~0.1 solar metallicity:
Conclusions (to be continued)
• mass-loss rates independent of Z• metal-poor O-rich stars are less dusty• slower winds of metal-poor O-rich
stars
above ~0.1 solar metallicity:
Conclusions (to be continued)
• mass-loss rates independent of Z• metal-poor O-rich stars are less dusty• slower winds of metal-poor O-rich
stars• … smaller momentum injection rate
above ~0.1 solar metallicity:
Conclusions (to be continued)
• mass-loss rates independent of Z• metal-poor O-rich stars are less dusty• slower winds of metal-poor O-rich stars• … smaller momentum injection rate• are metal-poor carbon stars less dusty?
above ~0.1 solar metallicity:
Conclusions (to be continued)
• mass-loss rates independent of Z• metal-poor O-rich stars are less dusty• slower winds of metal-poor O-rich stars• … smaller momentum injection rate• are metal-poor carbon stars less dusty?• wind speed of metal-poor carbon stars: ?
above ~0.1 solar metallicity:
Conclusions (to be continued)
• mass-loss rates independent of Z• metal-poor O-rich stars are less dusty• slower winds of metal-poor O-rich stars• … smaller momentum injection rate• are metal-poor carbon stars less dusty?• wind speed of metal-poor carbon stars: ?
above ~0.1 solar metallicity:
Below ~0.1 solar metallicity: ?