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Chamaeleon Dance P Chamaeleon DANCe P. A. B. Galli, H. Bouy, J. Olivares, N. Miret-Roig, L. M. Sarro, D. Barrado, A. Berihuete, E. Bertin, J.-C. Cuillandre To cite this version: P. A. B. Galli, H. Bouy, J. Olivares, N. Miret-Roig, L. M. Sarro, et al.. Chamaeleon DANCe: Re- visiting the stellar populations of Chamaeleon I and Chamaeleon II with Gaia-DR2 data. Astronomy and Astrophysics - A&A, EDP Sciences, 2021, 646, pp.A46. 10.1051/0004-6361/202039395. hal- 03132243 HAL Id: hal-03132243 https://hal.archives-ouvertes.fr/hal-03132243 Submitted on 4 Feb 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. A&A 646, A46 (2021) Astronomy https://doi.org/10.1051/0004-6361/202039395 & c P. A. B. Galli et al. 2021 Astrophysics Chamaeleon DANCe Revisiting the stellar populations of Chamaeleon I and Chamaeleon II with Gaia-DR2 data? P. A. B. Galli1, H. Bouy1, J. Olivares1, N. Miret-Roig1, L. M. Sarro2, D. Barrado3, A. Berihuete4, E. Bertin5, and J.-C. Cuillandre6 1 Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hillaire, 33615 Pessac, France e-mail: [email protected] 2 Depto. de Inteligencia Artificial, UNED, Juan del Rosal, 16, 28040 Madrid, Spain 3 Centro de Astrobiología, Depto. de Astrofísica, INTA-CSIC, ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain 4 Dpto. Estadística e Investigación Operativa, Universidad de Cádiz, Campus Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain 5 Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France 6 AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot, Orme des Merisiers, France Received 11 September 2020 / Accepted 21 November 2020 ABSTRACT Context. Chamaeleon is the southernmost low-mass star-forming complex within 200 pc from the Sun. Its stellar population has been extensively studied in the past, but the current census of the stellar content is not complete yet and deserves further investigation. Aims. We take advantage of the second data release of the Gaia space mission to expand the census of stars in Chamaeleon and to revisit the properties of the stellar populations associated to the Chamaeleon I (Cha I) and Chamaeleon II (Cha II) dark clouds. Methods. We perform a membership analysis of the sources in the Gaia catalogue over a field of 100 deg2 encompassing the Chamaeleon clouds, and use this new census of cluster members to investigate the 6D structure of the complex. Results. We identify 188 and 41 high-probability members of the stellar populations in Cha I and Cha II, respectively, including 19 and 7 new members. Our sample covers the magnitude range from G = 6 to G = 20 mag in Cha I, and from G = 12 to G = 18 mag in +0:8 +1:0 Cha II. We confirm that the northern and southern subgroups of Cha I are located at different distances (191:4−0:8 pc and 186:7−1:0 pc), +1:0 but they exhibit the same space motion within the reported uncertainties. Cha II is located at a distance of 197:5−0:9 pc and exhibits a space motion that is consistent with Cha I within the admittedly large uncertainties on the spatial velocities of the stars that come from radial velocity data. The median age of the stars derived from the Hertzsprung-Russell diagram and stellar models is about 1−2 Myr, suggesting that they are somewhat younger than previously thought. We do not detect significant age differences between the Chamaeleon subgroups, but we show that Cha II exhibits a higher fraction of disc-bearing stars compared to Cha I. Conclusions. This study provides the most complete sample of cluster members associated to the Chamaeleon clouds that can be produced with Gaia data alone. We use this new census of stars to revisit the 6D structure of this region with unprecedented precision. Key words. open clusters and associations: individual: Chamaeleon – stars: formation – stars: distances – methods: statistical – parallaxes – proper motions 1. Introduction example Ophiuchus (Cambrésy 1999). The modest extinction, proximity, compact structure and isolated location with respect The molecular cloud complex in the southern constellation of to other young stellar groups led to Chamaeleon being one of Chamaeleon hosts one of the richest populations of T Tauri the most targeted regions over the past decades for the study of stars in the Solar neighbourhood. It consists of three molecu- lar clouds with angular sizes of a few degrees: Chamaeleon I low-mass star formation. (Cha I), Chamaeleon II (Cha II), and Chamaeleon III (Cha III). The first young stellar objects associated to the Chamaeleon Star formation activity is restricted to Cha I and Cha II as no clouds were mostly classical T Tauri stars (CTTSs) identified young stars have been detected in Cha III (see Luhman 2008). from objective prism surveys based on their strong Hα emis- The cloud morphology has been investigated in previous studies sion (Henize & Mendoza 1973; Schwartz 1977; Hartigan 1993). from star counts and extinction maps (see e.g., Gregorio Hetem Deeper Hα surveys conducted in the years that followed added et al. 1988; Cambresy et al. 1997; Mizuno et al. 2001; Dobashi a number of very low-mass members and brown dwarfs to the et al. 2005) revealing moderate extinction levels in Chamaeleon region (Comerón et al. 1999, 2000; Neuhäuser & Comerón 1999). as compared to other nearby star-forming regions such as for ROSAT X-ray pointed observations led to the discovery of a sig- nificant number of weak-emission-line T Tauri stars (WTTSs) in ? Full Tables A.1–A.7 are only available at the CDS via anony- this region (Feigelson et al. 1993; Alcala et al. 1995; Alcalá et al. mous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http: 2000) and the first brown dwarf detected in X-rays (Neuhauser & //cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/646/A46 Comeron 1998). Additional members were later discovered from A46, page 1 of 19 Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A&A 646, A46 (2021) data collected with the XMM-Newton (Stelzer et al. 2004; Robrade that this dispersed population could be larger, but more accu- & Schmitt 2007) and Chandra X-ray observatories (Feigelson rate data would be required to confirm this hypothesis. Indeed, & Lawson 2004). Several optical and infrared surveys followed the scarcity of trigonometric parallaxes and radial velocity (RV) by ground-based spectroscopic observations expanded the cen- information for most stars in Chamaeleon has been the main lim- sus of Chamaeleon stars and confirmed the most likely members itation to studying the kinematic properties of this region. This associated to the molecular clouds (see e.g., Hughes & Hartigan situation has dramatically changed with the advent of the Gaia- 1992; Prusti et al. 1992; Cambresy et al. 1998; Persi et al. 2000; DR2 catalogue combined with the spectroscopic observations Vuong et al. 2001; Carpenter et al. 2002; Barrado y Navascués & conducted by the Gaia-ESO Survey (Gilmore et al. 2012) in the Jayawardhana 2004; Comerón & Claes 2004; López Martí et al. Chamaeleon region (see e.g., Sacco et al. 2017). Altogether, this 2004, 2005; Luhman 2004, 2007; Luhman et al. 2004; Allers et al. puts us in a timely position to investigate the 3D structure and 2007). The most recent census of the stellar population of Cha I is 3D space motion of the Chamaeleon star-forming complex with given by Esplin et al.(2017) and contains 250 stars. Analogously, unprecedented precision as discussed throughout this study. the list of 63 stars studied by Alcalá et al.(2008) and Spezzi et al. This paper is one in a series conducted in the context of (2008) represents the most complete sample of stars in Cha II to the Dynamical Analysis of Nearby Clusters project (DANCe, date. Bouy et al. 2013). Here, we investigate the census of stars, and The distance to Chamaeleon has undergone extensive revi- the structure and kinematic properties of the Chamaeleon star- sion in recent decades. Early studies reported distance estimates forming region in light of Gaia-DR2 data. The paper is organ- to Cha I in the range from 115 to 215 pc (Grasdalen et al. 1975; ised as follows. In Sect.2 we compile the lists of stars in Cha I Rydgren 1980; Hyland et al. 1982; Schwartz 1992), and sug- and Cha II published in the literature, and perform a new mem- gested that the distance to Cha II could be as large as 400 pc bership analysis to confirm the historical members associated (Fitzgerald et al. 1976; Graham & Hartigan 1988). Franco(1991) with these clouds and discover new ones. In Sect.3 we revisit investigated the interstellar extinction of field stars projected the distance, spatial velocity, and age of the Chamaeleon sub- towards the Chameleon clouds and estimated distances of 140 pc groups based on our new sample of cluster members selected in and 158 ± 40 pc to Cha I and Cha II, respectively.
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