Efficiency of Mixing of Supernova Ejecta into Nearby Protoplanetary Disks Nicolas Ouellette & Steve...
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Transcript of Efficiency of Mixing of Supernova Ejecta into Nearby Protoplanetary Disks Nicolas Ouellette & Steve...
Efficiency of Mixing of Supernova Ejecta into Nearby
Protoplanetary Disks
Nicolas Ouellette & Steve Desch
Arizona State University
Motivation•The origin of the short-lived radionuclides (26Al, 60Fe, etc.) inferred from meteorites is a major unsolved problem.
•We hypothesize a nearby (< 1 pc) supernova injected them into the Solar System’s already-formed protoplanetary disk.
•This same process will happen to disks in regions like NGC 6611, the Carina Nebula, and the Orion Nebula:
disks 1 Ori C
~ 0.2 pc
HST
MotivationInitial abundance of 26Al (26Al/27Al = 5 x 10-5) is explained by homogeneous injection of 5 x 10-6 M of a 25 M supernova’s ejecta into a minimum-mass (0.01 M) disk.
5 x 10-6 M is the ejecta mass intercepted by a 40 AU-radius disk 0.2 pc from a 25 M supernova
But will a disk this close survive? Will ejecta be mixed in?
Note: abundance of 60Fe is plausibly explained only by injection by supernova, not by continuous Galactic nucleosynthesis nor AGB star injection nor X-winds.
Note: if the supernova ejecta is injected inhomogeneously, abundances of all the short-lived radionuclides can be explained (Desch et al., submitted)
PERSEUS• PERSEUS: 2-D hydrodynamics code written to
study the effect of supernova ejecta on a proto-planetary disk
• Algorithms based on Zeus (Stone and Norman 1992)
• Time-explicit program solves the fluid equations in finite-difference form, using consistent transport
• Van-Leer (2nd-order) interpolation for advection• Tensor artificial viscosity used to smoothe out
discontinuities (shocks)• Cylindrical (axisymmetric) geometry assumed
PERSEUS• Added energy loss term due to radiative cooling.
Cooling rate in range T = 104 - 107 K taken from Sutherland & Dopita (1993)
• Added non-uniform grid: – R = 4 AU to 80 AU, R = 1 AU – Z = -40 AU to +100 AU, Z = 0.2 AU at disk
midplane, Z = 5 AU far from disk midplane• Added color field to track mixing of ejecta gas• Gravity due to central star only.
• Disk– Minimum mass (0.01 M) disk truncated at 30 AU– Disk allowed to dynamically relax for 1000 years– Final radius ~ 40 AU
• Supernova – 0.3 pc away– 1051 ergs (1 foe) explosion energy– 20 M ejected isotropically with time dependence of
density and velocity from Matzner & McKee (1999)– Isotopic composition assumed homogeneous, that of 25
M supernova from Woosley & Weaver (1995)
Canonical Simulation
Relaxed Disk
Canonical Run
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Reverse Shock
Disk Stripping
Stripping and Mixing: KH Rolls
• Negligible mass loss from disk (<1%)• Low mixing efficiency of supernova ejecta into disk
– Roughly 0.7% of the intercepted ejecta is injected into the disk
– If 26Al mixed in as gas, final 26Al/27Al ~ 1.4 x 10-7
• Efficiency does not depend much on distance, disk mass or explosion energy
Simulation Results
Distance (or Density) Injection efficiency 26Al/27Al0.1 pc 2.4% 4.3 x 10-6
0.3 pc (canonical) 0.7% 1.4 x 10-7
0.5 pc 0.5% 3.6 x 10-8
Energy Injection efficiency 26Al/27Al0.25 foe 0.9% 1.8 x 10-7
1 foe (canonical) 0.7% 1.4 x 10-7
4 foe 0.6% 1.2 x 10-7
Disk mass Injection efficiency 26Al/27Al0.1 x min. mass 1.2% 2.4 x 10-6
Min. mass (canonical) 0.7% 1.4 x 10-7
10 x min. mass 0.8% 1.6 x 10-8
• Protoplanetary disks will survive nearby supernova explosions
• Gas-phase supernova ejecta is mixed into the disk, but with low efficiency (~ 1%), too low to explain SLR ratios
• Dust injection is the best candidate for SLR injection and will be the subject of future work– Preliminary calculations show the dust will travel
roughly 100 AU before being deviated by the bow shock, and will be mixed in with ~ 100% efficiency
Conclusions