Bibcode
Licandro, J.; Alí-Lagoa, V.; Tancredi, G.; Fernández, Y.
Bibliographical reference
Astronomy and Astrophysics, Volume 585, id.A9, 12 pp.
Advertised on:
1
2016
Journal
Citations
25
Refereed citations
22
Description
Context. Determining whether asteroids in cometary orbits (ACOs) are
dormant or extinct comets is relevant for understanding the end-states
of comets and the sizes of the comet population. Aims: We intend
to study the value distributions of effective diameter (D), beaming
parameter (η), and visible geometric albedo (pV) of ACO
populations, which can be derived from NASA's Wide-field Infrared
Explorer (WISE) observations, and we aim to compare these with the same,
independently determined properties of the comets. Methods: The
near-Earth asteroid thermal model (NEATM) is used with WISE data and the
absolute magnitude (H) of the ACOs to compute the D, pV and
η. Results: We obtained D and pV for 49 ACOs in
Jupiter family cometary orbits (JF-ACOs) and 16 ACOs in Halley-type
cometary orbits (Damocloids). We also obtained the infrared beaming
parameter η for 45 of them. All but three JF-ACOs (95% of the
sample) present a low albedo compatible with a cometary origin. The
pV and η distributions of both ACO populations are very
similar. For the entire sample of ACOs, the mean geometric albedo is
p̅V = 0.05±0.02, (p̅V =
0.05±0.01 and p̅V = 0.05±0.02 for JF-ACOs
and for Damocloids, respectively) compatible with a narrow albedo
distribution similar to that of the Jupiter family comets (JFCs), with a
p̅V ~ 0.04. The mean beaming parameter is η̅ =
1.0±0.2. We find no correlations between D, pV, or
η. We also compare the cumulative size distribution (CSD) of ACOs,
Centaurs, and JFCs. Although the Centaur sample contains larger objects,
the linear parts in their log-log plot of the CSDs presents a similar
cumulative exponent (β = 1.85 ± 0.30 and 1.76 ± 0.35,
respectively). The CSD for Damocloids presents a much shallower exponent
β = 0.89 ± 0.17. Conclusions: The pV- and
η-value distributions of ACOs are very similar to those of JF comet
(JFCs) nuclei. The ACOs in Tancredi's list are the best possible
candidates to be dormant/inactive comets. The CSD for JF-ACOs is
shallower and shifted towards larger diameters with respect to the CSD
of active JFCs, which suggests that the mantling process has a size
dependency whereby large comets tend to reach an inactive stage faster
than small comets. Finally, the population of JF-ACOs is comparable in
number with the population of JFCs, although there are more tens-km
JF-ACOs than JFCs.