A&A 617, A72 (2018) Astronomy https://doi.org/10.1051/0004-6361/201832780 & © ESO 2018 Astrophysics Color study of asteroid families within the MOVIS catalog David Morate1,2, Javier Licandro1,2, Marcel Popescu1,2,3, and Julia de León1,2 1 Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain e-mail: [email protected] 2 Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain 3 Astronomical Institute of the Romanian Academy, 5 Cu¸titulde Argint, 040557 Bucharest, Romania Received 6 February 2018 / Accepted 13 March 2018 ABSTRACT The aim of this work is to study the compositional diversity of asteroid families based on their near-infrared colors, using the data within the MOVIS catalog. As of 2017, this catalog presents data for 53 436 asteroids observed in at least two near-infrared filters (Y, J, H, or Ks). Among these asteroids, we find information for 6299 belonging to collisional families with both Y J and J Ks colors defined. The work presented here complements the data from SDSS and NEOWISE, and allows a detailed description− of− the overall composition of asteroid families. We derived a near-infrared parameter, the ML∗, that allows us to distinguish between four generic compositions: two different primitive groups (P1 and P2), a rocky population, and basaltic asteroids. We conducted statistical tests comparing the families in the MOVIS catalog with the theoretical distributions derived from our ML∗ in order to classify them according to the above-mentioned groups. We also studied the background populations in order to check how similar they are to their associated families. Finally, we used this parameter in combination with NEOWISE and SDSS to check for possible bimodalities in the data. We found 43 families with MLerr∗ < 0:071 and with at least 8 asteroids observed: 5 classified as P1, 10 classified as P2, 19 families associated with the rocky population, and 9 families that were not linked to any of the previous populations. In these cases, we compared our samples with different combinations of these theoretical distributions to find the one that best fits the family data. We also show, using the data from MOVIS and NEOWISE, that the Bapistina family presents a two-cluster distribution in the near-infrared albedo vs. ML∗ parameter space that might be related to a common differentiated parent body. Finally, we show that the backgrounds we defined seem to be linked to their associated families. Key words. minor planets, asteroids: general – methods: data analysis – techniques: photometric 1. Introduction effect of space weathering or the presence of inhomogeneities in asteroid family composition. Related to this last point, one Asteroid families are the remnants of catastrophic collisional of the most prominent questions is the apparent absence of col- episodes in the solar system. After such events, a large aster- lisional families generated from the complete disruption of a oid (commonly known as parent body) leaves behind dozens, differentiated parent body. hundreds, or even thousands of fragments that share similar In 2009, using the Visible and Infrared Survey Telescope orbital properties. These fragments, referred to as family mem- for Astronomy (VISTA), several near-infrared surveys started bers, experienced dynamical processes under the gravitational to collect data in five broadband filters: Z, Y, J, H, and Ks forces dominating the solar system and also via the Yarkovsky (Sutherland et al. 2015). Among these, the VISTA Hemisphere effect, gradually evolving to their current locations in the main Survey (VHS) aims to image almost the entire southern hemi- 1 asteroid belt (Bottke et al. 2002). By analyzing the physical prop- sphere, i.e., 19 000− (McMahon et al. 2013). Using the third erties of the family members, we can investigate the composition data release∼ of this survey (VISTA VHS-DR3), Popescu et al. of the original bodies, and we can study the processes that these (2016) compiled their Moving Objects from VISTA Survey cat- objects have experienced through the history of the solar system. alog (MOVIS), with a total of 39 947 solar system objects, At the beginning of the 21st century, several all-sky sur- including NEAs, main-belt asteroids, TNOs, comets, and other veys were carried out: SDSS (York et al. 2000) and Pan- bodies. This catalog presents colors for those objects observed STARRS (Kaiser et al. 2010) at optical wavelengths, and WISE in at least two of the Y, J, H, and Ks infrared filters. See Fig.1 (Wright et al. 2010), AKARI (Ishihara et al. 2010), and 2MASS for the response curves of these filters. (Skrutskie et al. 2006) at different infrared wavelengths. Initially, The work presented here aims to enhance the current knowl- these surveys were mainly of cosmological or stellar interest. edge about overall family composition and physical properties, However, their sky coverage offers the opportunity to study a and to complement the available information of the families with large number of solar system objects. Using data from some of near-infrared photometry. To achieve this, we have used the lat- these databases, combined with data from visible and infrared est version of the MOVIS database. This paper is organized as spectroscopic surveys, light curves, and polarimetry, Masiero follows: we describe the latest version of the MOVIS catalog in et al.(2015) carried out an analysis of 109 out of the 122 families Sect.2, as well as the datasets used for family identification and identified by Nesvorný et al.(2015). In their paper, they outlined data comparison; in Sect.3 we define a near-infrared parame- some key questions that still remain unanswered, such as the ter that will be used to classify those families with a significant Article published by EDP Sciences A72, page 1 of 24 A&A 617, A72 (2018) 2.00 Table 1. Central wavelengths and passbands for the different filters used Primitives in the SDSS (Bessell 2005), VISTA-VHSa, and NEOWISE (Jarrett et al. Rocky 2011) surveys. 1.75 Basaltic 1.50 Filter Effective central Width wavelength (µm) (µm) 1.25 SDSS 1.00 u0 0.3596 0.057 g0 0.4639 0.128 Reflectance 0.75 r0 0.6122 0.115 i0 0.7439 0.123 0.50 z0 0.8896 0.107 0.25 Y J H Ks VISTA-VHS Y 1.021 0.093 0.00 1.00 1.25 1.50 1.75 2.00 2.25 2.50 J 1.254 0.172 Wavelength (microns) H 1.646 0.291 Ks 2.149 0.309 Fig. 1. Response curves of the Y, J, H, and Ks VISTA filters (blue), together with the DeMeo et al.(2009) template spectra of the asteroid NEOWISE populations in our study. We averaged the templates for the B-, C-, and W1 3.3526 0.66256 X-types and subclasses (primitives); the S-types and subclasses (rocky); W2 4.6028 1.0423 and V-types (basaltic). The template spectra have been normalized to unity at 1.25 µm (central wavelength of the J filter) for representation W3 11.5608 5.5069 purposes. W4 22.0883 4.1013 Notes. (a)Filter information available at http://casu.ast.cam.ac. number of members observed within the catalog; in Sect.4 we uk/surveys-projects/vista/technical/filter-set discuss the results for individual families; finally, in Sect.5 we summarize the obtained results and we address some important 2.2. Family lists questions to be investigated in the near future. In order to look for family members within the objects present in the MOVIS catalog, we used the lists from Nesvorný et al. 2. Dataset description (2015). For the family identification process the authors took To conduct our analysis we used several databases with physical into account many past publications (Mothé-Diniz et al. 2005; data of thousands of asteroids. Here follows a brief description Nesvorný et al. 2005; Gil-Hutton 2006; Parker et al. 2008; of each of these datasets. Nesvorny 2010, 2012; Novakovic´ et al. 2011; Brož et al. 2013; Masiero et al. 2011, 2013; Carruba et al. 2013; Milani et al. 2014), as well as data from SDSS and NEOWISE, to finally define 2.1. Infrared colors from the MOVIS catalog 122 asteroid families. These lists were created using numerically The main dataset that we use throughout this paper is the latest computed proper orbital elements for 384 337 numbered aster- version of the Moving Objects from VISTA Survey (MOVIS) oids and 4016 Jupiter trojans. The dataset, publicly available in catalog1. It was compiled from data in the VISTA Hemisphere the Small Bodies Node of the NASA Planetary Data System2, Survey (VHS), obtained using the VISTA telescope, a 4 m class provides the synthetic proper orbital elements used to compute telescope located at the ESO Cerro Paranal Observatory (Chile). family membership, as well as values for the absolute magnitude Thanks to this survey, which aims to cover almost the whole sky of the asteroids (Hv). Some asteroids are included in more than of the southern hemisphere (McMahon et al. 2013), it was pos- one family; for example, all the members of the Beagle family sible to retrieve spectro-photometric data in four near-infrared are also included in the Themis family. In these cases we consid- filters, Y, J, H, and Ks (see Fig.1 and Table1), and also accu- ered those asteroids as members of the smallest family (i.e., we rate astrometry, for a very large number of solar system objects. removed the Beagle family members from the Themis family). A complete description of the creation of the MOVIS catalog can We found 6299 asteroids belonging to 104 families among the be found in Popescu et al.(2016).