Universidad%20de%20Alicante.%20Alicante%20(Spain)

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Modelling the populations of Trans-Neptunian
Objects
Paula G. Benavidez Adriano Campo Bagatin
Departamento de Física, Ingeniería de Sistemas y
Teoría de la Señal

• Universidad de Alicante. Alicante (Spain)

adriano_at_dfists.ua.es
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VII WORKSHOP ON CATASTROPHIC DISRUPTIONS IN THE
SOLAR SYSTEM (CD07)
Alicante (Spain) June 26th to 29th, 2007
Info/mailing list adriano_at_dfists.ua.es
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Modelling the populations of Trans-Neptunian
Objects
Paula G. Benavidez Adriano Campo Bagatin
Departamento de Física, Ingeniería de Sistemas y
Teoría de la Señal

• Universidad de Alicante. Alicante (Spain)

adriano_at_dfists.ua.es
4

• A collisional model for TNOs
• Collisional evolution of TNOs and the
  migration of Neptune
• Results
• Conclusions

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A collisional model for TNOs
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A collisional model for TNOs
(MPC database)
3 populations Plutinos Classical Disk Scattered
Disk
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A collisional model for TNOs
Plutinos Plutinos Classical Disk Classical Disk Scattered Disk Scattered Disk
a (AU) 38-40 38-40 42-48 42-48 35-50 35-50
lt gt s lt gt s lt gt s
e 0.13 0.06 0.05 0.05 0.18 0.10
i (º) 4 3 3 3 17 9
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Zone 1 35(1-0.13) AUlt a lt40(10.13)
AU e0.13 i6º
zone 1
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Zone 2 40(1-0.05) AUlt a lt50(10.05)
AU e0.05 i5.5º
zone 1
zone 2
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zone 1
overlap
zone 2
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Zone 3 40(1-0.18) AUlt a lt50(10.18)
AU e0.18 i25º
zone 1
overlap
zone 3
zone 2
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zone 3
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A collisional model for TNOs

• Collisional evolution for each zone
• PIAB model, with distribution for VRi.
• Interactions in overlapping zones
• Accurately, considering how much lttimegt
• objects spend in common zones.
• Fragmentation/cratering/reaccumulation model
• Petit Farinella (1993), updated.

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A collisional model for TNOs
Some parameters for physics and evolution
Scaling laws for S Gravity, G. strain rate
effect (Davis), Hydrocode (weak mortar)
Zone 1 (Plutinos) Zone 2 (Classical Disk) Zone 3 (Scattered Disk)
a (AU) 35-40 40-50 40-50
ltegt MPC 0.13 0.05 0.18
lti (º)gt 1s MPC 6 5.5 25
ltVgt (km/s) DellOro et al., 2001 1.25 0.93 1.00
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Collisional evolution of TNOs and the migration
of Neptune

• Migration of Neptune? (Ida et al., 1999 Gomes
  et al., 2004 Hahn Malhotra, 2005)
• What about collisional evolution in this
  scenario?
• Was collisional evolution ever efficient enough
  to deplete the mass of the belt to present
  estimates?

4 different evolving scenarios
A Present position and orbital elements. B
Present position, but initially cold (i3º,
e0.01). C Disk between 20 and 35 AU, cold. D
Disk initially as in C, migrating and heating
up to present values.
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Results
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Results
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Results
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Results
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A Present position and orbital elements. B
Present position, but initially cold (i3º,
e0.01). C Disk between 20 and 35 AU, cold. D
Disk initially as in C, migrating and heating
up.
Results
M010 MT A B C D
Mf (MT ) 3.4 3.5 2.8 3.4
slope -0.164 -0.169 -0.168 -0.163
N(Dgt2500 km) 27 27 26 27
Dtr (km) 120 150 160
M030 MT A B C D
Mf (MT ) 8.2 8.2 6.7 8.2
slope -0.166 -0.159
N(Dgt2500 km) 64 65 63 65
Dtr (km) 100 120 130
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Preliminary Conclusions

• Main features are almost independent on
  different initial distributions (with same M0).
• Different strength scaling-laws imply only
  slight variations.
• Change in the power-law distribution around
  100-150 km.
• M reduces quickly (100 Myr) to ½ of its initial
  value.
• Collisional evolution, under different initial
  conditions, may only be responsible for
  65-75 mass depletion
• Other mechanisms are required to get actual mass.

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To be continued...

• Estimate gravitational aggregate (rubble-piles)
  ratios.
• Introduce Neptune migration in a consistent way.
• Re-do simulations with orbital elements from the
  CFEPS.
• Introduce more realistic physics for low
  velocity collisions.
• ...

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Modelling the populations of Trans-Neptunian
Objects
Adriano Campo Bagatin, Paula G.
Beneavidez Departamento de Física, Ingeniería de
Sistemas y Teoría de la Señal

• Universidad de Alicante. Alicante (Spain)

adriano_at_dfists.ua.es
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Results
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Results
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Introduction
Asteroid Population Intrinsic Probability Impact Velocity (km/s) Reference
Main Belt 2.19 3.51 3.93 7.69 Farinella and Davis (1992)
Main Belt 3.97 - Yoshikawa and Nakamura (1994)
Main Belt 2.86 5.2 Bottke et al. (1994)
Main Belt 4.38 4.22 Vedder (1998)
Trojans (L4) 6.37 6.55 4.83 4.97 Marzari et al. (1996)
Trojans (L4) 7.12 8.46 4.66 DellOro et al. (1998)
Trojans (L5) 5.20 5.40 4.79 4.99 Marzari et al. (1996)
Trojans (L5) 6.50 6.86 4.51 DellOro et al. (1998)
Hildas 2.21 2.41 1.62 - 4.56 Dahlgreen (1998)
TNOs Davis and Farinella (1997)
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Observables

• Size distributions
• The Trans-Neptunian Objects

Bernstein et al. (2004)
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Collisional evolution models
CAVEAT What about Q for
gravitational aggregates? And for rotating
bodies? (See Housen et al., in 30)
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Observables

• Size distributions
• The Trans-Neptunian Objects

Bernstein et al. (2004)
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Theoretical studies
Trans-Neptunian Objects
An analytical model
Break confirmed by Davis and Farinella (1997)
collisional model, Krivov et al. (2005)
kinetic model. (Also Kenyon and Bromley, 2004)
Pan and Sari (2005)
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Collisional evolution models
Trans-Neptunian Objects
Zones Transition size km
Plutinos Classical Disk Scattered Disk Total 90-120 90-120 40-50 60-90
Campo Bagatin and Benavidez (POSTER SESSION P6.5)
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Open questions and conclusions
About TNOs

• The Trans-Neptunian region does not look
  collisionally relaxed (and will stay like this)
  above 50-100 km sizes.
• (Similar behaviour seems to apply at least to
  Hildas.)
• We need un-biased data to extrapolate current
  distributions in a reliable way and compare
  models to.

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Open questions and conclusions
About TNOs

• How did the Scattered Disk (and the Centaur
  population?) form and evolve?

• Are TNOs larger than a transition diameter
  mostly pristine bodies?
• What fraction of kmsize populations are
  gravitational aggregates?

• Is (was) the Trans-Neptunian population beyond
  50 AU also a collisional system?

• What was the initial mass of this part of the
  solar system?

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