Volume 654, October 2021
|Number of page(s)||48|
|Section||Planets and planetary systems|
|Published online||12 October 2021|
Aix Marseille Université, CNRS, CNES, Laboratoire d’Astrophysique de Marseille,
2 Institute of Astronomy, Charles University, Prague, V Holešovičkách 2, 18000 Prague 8, Czech Republic
3 Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
4 Department of Earth, Atmospheric and Planetary Sciences, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
5 Mathematics and Statistics, Tampere University, 33720 Tampere, Finland
6 SETI Institute, Carl Sagan Center, 189 Bernado Avenue, Mountain View CA 94043, USA
7 IMCCE, CNRS, Observatoire de Paris, PSL Université, Sorbonne Université, Paris, France
8 Astronomical Institute of the Romanian Academy, 5-Cuţitul de Argint, 040557 Bucharest, Romania
9 Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
10 NASA Goddard Space Flight Center, University of Maryland College Park, USA
11 Space sciences, Technologies and Astrophysics Research Institute, Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium
12 Institut de Planetologie et d’Astrophysique de Grenoble, UGA-CNRS, France; Institut Universitaire de France, Paris, France
13 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
14 European Space Agency, ESTEC - Scientific Support Office, Keplerlaan 1, Noordwijk 2200 AG, The Netherlands
15 TMT Observatory, 100 W. Walnut Street, Suite 300, Pasadena, CA 91124, USA
16 Open University, School of Physical Sciences, The Open University, MK7 6AA, UK
17 Laboratoire Atmosphères, Milieux et Observations Spatiales, CNRS & Université de Versailles Saint-Quentin-en-Yvelines, Guyancourt, France
18 Departamento de Fisica, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Alicante, Spain
19 Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Martí Franquès 1, E08028 Barcelona, Spain
20 European Southern Observatory (ESO), Alonso de Cordova 3107, 1900 Casilla Vitacura, Santiago, Chile
21 Observatoire des Hauts Patys, 84410 Bédoin, France
22 Observatoire de Chinon, Mairie de Chinon, 37500 Chinon, France
23 Aix Marseille Université, CNRS, OHP (Observatoire de Haute Provence), Institut Pythéas (UMS 3470), 04870 Saint-Michel-l’Observatoire, France
24 Geneva Observatory, 1290 Sauverny, Switzerland
25 High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
26 B74, Avinguda de Catalunya 34, 25354 Santa Maria de Montmagastrell (Tarrega), Spain
27 I39, Cruz del Sur Observatory, San Justo city, Buenos Aires, Argentina
28 Observatoire du Bois de Bardon, 16110 Taponnat, France
29 Association T60, Observatoire Midi-Pyrénées, 14 avenue Edouard Belin, 31400 Toulouse, France
30 Hong Kong Space Museum, Tsimshatsui, Hong Kong, PR China
31 I64, SL6 1XE Maidenhead, UK
32 Korea Astronomy and Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea
33 Chungbuk National University, 1, Chungdae-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do 28644, Korea
34 Faculty of Physics, Astronomical Observatory Institute, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
35 Observatoire OPERA, 33820 Saint Palais, France
36 Uranoscope, Avenue Carnot 7, 77220 Gretz-Armainvilliers, France
37 Institut d’Astrophysique de Paris, 98 bis boulevard Arago, UMR 7095 CNRS et Sorbonne Universités, 75014 Paris, France
38 Anunaki Observatory, Calle de los Llanos, 28410 Manzanares el Real, Spain
39 Club d’Astronomie de Lyon Ampere (CALA), Place de la Nation, 69120 Vaulx-en-Velin, France
40 Kingsgrove, NSW, Australia
41 Planetary Science Institute, 1700 East Fort Lowell Road, Tucson, AZ 85719, USA
42 Rio Cofio Observatory, Robledo de Chavela (Madrid), Spain
43 Cicha 43, 44-144 Nieborowice, Poland
Accepted: 3 September 2021
Context. Until recently, the 3D shape, and therefore density (when combining the volume estimate with available mass estimates), and surface topography of the vast majority of the largest (D ≥ 100 km) main-belt asteroids have remained poorly constrained. The improved capabilities of the SPHERE/ZIMPOL instrument have opened new doors into ground-based asteroid exploration.
Aims. To constrain the formation and evolution of a representative sample of large asteroids, we conducted a high-angular-resolution imaging survey of 42 large main-belt asteroids with VLT/SPHERE/ZIMPOL. Our asteroid sample comprises 39 bodies with D ≥ 100 km and in particular most D ≥ 200 km main-belt asteroids (20/23). Furthermore, it nicely reflects the compositional diversity present in the main belt as the sampled bodies belong to the following taxonomic classes: A, B, C, Ch/Cgh, E/M/X, K, P/T, S, and V.
Methods. The SPHERE/ZIMPOL images were first used to reconstruct the 3D shape of all targets with both the ADAM and MPCD reconstruction methods. We subsequently performed a detailed shape analysis and constrained the density of each target using available mass estimates including our own mass estimates in the case of multiple systems.
Results. The analysis of the reconstructed shapes allowed us to identify two families of objects as a function of their diameters, namely “spherical” and “elongated” bodies. A difference in rotation period appears to be the main origin of this bimodality. In addition, all but one object (216 Kleopatra) are located along the Maclaurin sequence with large volatile-rich bodies being the closest to the latter. Our results further reveal that the primaries of most multiple systems possess a rotation period of shorter than 6 h and an elongated shape (c∕a ≤ 0.65). Densities in our sample range from ~1.3 g cm−3 (87 Sylvia) to ~4.3 g cm−3 (22 Kalliope). Furthermore, the density distribution appears to be strongly bimodal with volatile-poor (ρ ≥ 2.7 g cm−3) and volatile-rich (ρ ≤ 2.2 g cm−3) bodies. Finally, our survey along with previous observations provides evidence in support of the possibility that some C-complex bodies could be intrinsically related to IDP-like P- and D-type asteroids, representing different layers of a same body (C: core; P/D: outer shell). We therefore propose that P/ D-types and some C-types may have the same origin in the primordial trans-Neptunian disk.
Key words: minor planets, asteroids: general / methods: observational / techniques: high angular resolution
Tables A.2 and A.3 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/654/A56
Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 199.C-0074 (PI: P. Vernazza).
The reduced and deconvolved images as well as the 3D shape models are available at https://observations.lam.fr/astero/
© P. Vernazza et al. 2021
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