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

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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