Asteroid families age determination: the role of the physical effects
- 1National Institute for Astrophysics - Arcetri Astrophysical Observatory, Italy (aldo.delloro@inaf.it)
- 2University of Pisa, Italy
- 3Harvard & Smithsonian Center for Astrophysics, USA
- 4Serbian Academy of Sciences and Arts, Serbia
The availability of large data set of asteroids proper elements made
possible in recent years a deeper and deeper analysis of the structure
of the asteroid dynamical families in the Main Belt (Milani et al.,
2014). At the same time the Yarkovsky effect, the importance of which
has been largely recognized, has imposed a new data interpretation
paradigm. Precisely the Yarkovsky effect is the basis of one
estimation method of the age of the asteroid families analyzing the
shape of the family members distribution in the plane diameter versus
proper semimajor axes, the so called V-shape (Spoto et al., 2015).
This very important goal has been achieved under the assumption that
the post-formation evolution of the semimajor axes producing the
V-shape structure was linear in time and dominates their present
dispersion. In particular the impact of the initial values of the
fragments ejection velocities, determining the initial dispersion of
the semimajor axes, is supposed to be marginal, assumption probably
correct for old enough families. If this is not the case, the initial
ejection velocity field introduces a more or less large bias in the
age determination. We conducted a series of numerical experiments
simulating the formation and dynamical evolution of the asteroid
families in order to evaluate the extent of this bias.
Moreover in our model we included a series of mechanisms concerning
the initial break-up outcomes. In particular two aspects have been
taken into account: the effect of the initial gravitational
re-accumulation on the structure of the V-shape and the effect of
possible correlations between spin direction and ejection velocity
direction (Milani et al., 2019). We show how the former effect could
be responsible of some systematic features of the V-shape structure,
while the second can in some cases mitigate the bias in the age
determination introduced by the initial ejection field.
Finally we discuss the role of the family members spin axes evolution
due to non destructive collisions, affecting the efficiency of the
Yarkovsky-driven semimajor axis mobility. We show how this latter
mechanism modifies the determination of the age.
References:
Milani A., Cellino A., Knezevic Z., Novakovic B., Spoto F., Paolicchi P.
2014.
Asteroid families classification: Exploiting very large datasets.
Icarus, 239, 46-73.
Spoto F., Milani A., Knezevic Z.
2015.
Asteroid family ages.
Icarus, 257, 275-289.
Milani A., Knezevic Z., Spoto F., Paolicchi P.
2019.
Asteroid cratering families: recognition and collisional interpretation.
Astronomy and Astrophysics, 622, A47.
How to cite: Dell'Oro, A., Boccenti, J., Spoto, F., Paolicchi, P., and Knezevic, Z.: Asteroid families age determination: the role of the physical effects, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-90, https://doi.org/10.5194/epsc2020-90, 2020