Proper motions of young stars in Chamaeleon. I. A Virtual Observatory study of spectroscopically confirmed members
Belén López Martí, Francisco Jiménez-Esteban, Amelia Bayo, David Barrado, Enrique Solano, Carlos Rodrigo
AAstronomy & Astrophysics manuscript no. lopezMarti˙cham c (cid:13)
ESO 2018August 13, 2018
Proper motions of young stars in Chamaeleon
I. A Virtual Observatory study of spectroscopically confirmed members
Bel´en L´opez Mart´ı , Francisco Jim´enez-Esteban , , , Amelia Bayo , David Barrado , , Enrique Solano , , and CarlosRodrigo , Centro de Astrobiolog´ıa (INTA-CSIC), Departamento de Astrof´ısica, P.O. Box 78, E-28261 Villanueva de la Ca˜nada, Madrid, Spaine-mail: [email protected] Spanish Virtual Observatory, Spain Saint Louis University, Madrid Campus, Division of Science and Engineering, Avenida del Valle 34, E-28003 Madrid, Spain European Southern Observatory, Alonso de C´ordova 3107, Vitacura, Santiago, Chile Calar Alto Observatory, Centro Astron´omico Hispano-Alem´an, C / Jes´us Durb´an Rem´on 2-2, E-04004 Almer´ıa, SpainReceived; accepted
ABSTRACT
Context.
The study of the motion of the members of a given open cluster or stellar association provides key information about theirformation and early evolution. The Chamaeleon cloud complex constitutes one of the closest and best studied low-mass star-formingregions in the Galaxy.
Aims.
We want to provide further evidence of the origin of the proposed stellar members of Chamaeleon and to identify interlopersfrom the foreground (cid:15)
Cha and η Cha associations.
Methods.
We compile lists of spectroscopically confirmed members of Chamaeleon I and II, (cid:15)
Cha and η Cha, and of backgroundobjects in the same line of sight. Using Virtual Observatory tools, we cross-match these lists with the UCAC3 catalogue to get theproper motions of the objects. In the vector point diagram, we identify the di ff erent moving groups, and use this information tostudy the membership of proposed candidate members of the associations from the literature. For those objects with available radialvelocities, we compute their Galactic space velocities. We look for correlations between the known properties of the objects and theirproper motions. Results.
The members of the dark clouds exhibit clearly di ff erent proper motions from those of the foreground associations and ofthe background stars. The data suggest that Chamaeleon II could have di ff erent dynamical properties from Chamaeleon I. Althoughthe two foreground clusters (cid:15) and η Chamaeleontis constitute two di ff erent proper motion groups, they have similar spatial motions,which are di ff erent from the spatial motion of Chamaeleon I. On the other hand, the space motions of the Chamaeleon II stars lookmore similar to those of the foreground clusters than to the Chamaeleon I stars, but the numbers are low. We find no correlationsbetween the proper motions and the properties of the objects in either of the clouds. Conclusions.
On the basis of proper motion, Chamaeleon I and II constitute two physical entities unrelated to the foreground (cid:15) and η Chamaeleontis clusters, but with the available data it is unclear to what extent the stellar populations in both clouds are physicallyconnected to each other.
Key words. stars:low-mass, brown dwarfs − stars: kinematics and dynamics − stars: formation − stars: luminosity function, massfunction − astronomical databases: miscellaneous − astronomical databases: virtual observatory tools
1. Introduction
The kinematic properties of the members of a given stellar asso-ciation hold important clues to its history. Some formation mod-els predict that the early dynamical evolution of the parent proto-stellar cluster should lead to mass-dependent kinematic distribu-tions, and, eventually, to an e ffi cient mass segregation (Kroupa& Bouvier 2003), while other numerical simulations predict sim-ilar kinematic properties over the whole mass spectrum ( ? Bate2012). Various authors have used radial velocity measurementsto study the kinematic properties of young low-mass objects (e.g.Je ff ries et al. 2006; Maxted et al. 2008), and a number of sur-veys have used proper motions to identify and confirm new low-mass members in young associations and clusters (e.g. Morauxet al. 2001; Kraus & Hillenbrand 2007; Bouy & Mart´ın 2009;Caballero 2010). In particular, our recent proper motion studyof the Lupus star-forming region shows that it is possible to dis-tinguish between probable low-mass members of the complex and likely contaminants using kinematic information from avail-able astrometric catalogues (L´opez Mart´ı et al. 2011, hereafterLJS11).The Chamaeleon complex is one of the closest and best stud-ied low-mass star-forming regions. At an estimated distance inthe range 115-215 pc, it is composed of three dark clouds, namedChamaeleon I, II and III (Schwartz 1977; Schwartz et al. 1991).The oldest one is Chamaeleon I, with a mean age of about 2 Myr;it contains more than 300 known young stars (see Luhman 2008,for the latest census), most of them clustered in two cloudcores containing two intermediate-mass stars, HD 97048 andHD 97300. Chamaeleon II seems to be at an earlier stage of evo-lution than Chamaeleon I, because it contains more embeddedthan visual objects (Gauvin & Strom 1992). Surveys by severalauthors have identified more than 60 stars in this cloud (Spezziet al. 2007, 2008; Alcal´a et al. 2008, and references therein). Noactive star formation seems to be taking place in Chamaeleon III. a r X i v : . [ a s t r o - ph . S R ] F e b el´en L´opez Mart´ı et al.: Proper motions of young stars in Chamaeleon The Chamaeleon clouds have also been the target of kine-matic studies, generally based on radial velocities and fo-cused on the brightest stars in the complex (e.g. Dubath et al.1996). The exceptions are a few very low-mass stars and browndwarf candidates in Chamaeleon I (Joergens 2006, and refer-ences therein). Proper motion and parallax information fromHipparcos has been used to assess the origin of the star formationin the clouds and their relation to other neighbouring associa-tions (Sartori et al. 2003). X-ray observations during the past twodecades, combined with Hipparcos astrometry, have shown thatthe young stars observed towards the Chamaeleon sky area canbe grouped into several distinct associations: the Chamaeleondark cloud complex itself, and the foreground (at around 100 pc) (cid:15)
Chamaeleontis ( (cid:15)
Cha) and η Chamaeleontis ( η Cha) young as-sociations (Feigelson et al. 2003; Mamajek et al. 1999). The ob-servations have shown that these two associations are older thanthe Chamaeleon star-forming complex ( ∼ (VO) toolsto investigate the kinematic properties of members and candi-date members of the Chamaeleon dark clouds. Our goals are toprovide further evidence of a common origin for all these objectsand to test their association with the dark clouds and between theclouds themselves.
2. Available data
We compiled a list of Chamaeleon confirmed members (throughspectroscopy) from the literature. For Chamaeleon I, we re-trieved the list from the most recent census by Luhman (2007),and completed it with the eight new members reported byLuhman & Muench (2008a). The final list contained 304 ob-jects down to R =
24 mag, with extinctions in the range A V (cid:39) R -band magnitudes downto about 23 mag and extinctions in the range A V (cid:39) ff erent popula-tions based on the available proper motions, and to check thepossible presence of interlopers from the foreground clusters inour Chamaeleon I and II lists, we compiled two lists of mem-bers for the (cid:15) Cha and η Cha associations, merging the cata-logues provided by Luhman (2004) and Fern´andez et al. (2008)for both groups, and adding the objects from the lists by Luhman& Steeghs (2004) in η Cha and by da Silva et al. (2009) in (cid:15)
Cha. Membership of these objects in the corresponding clusterhas been confirmed by several di ff erent means, including spec-troscopy and proper motions. The final compiled lists contained36 stars in (cid:15) Cha and 20 in η Cha down to R ∼
18 mag. Noestimations of extinction are available for these stars, but theirlocation outside areas of dense dust suggests that it is very lowin most cases.For control purposes, we also considered the list of 88 back-ground sources from Table 4 of Luhman (2007). These objects The VO is a project designed to provide the astronomical commu-nity with the data access and the research tools needed to enable theexploration of the digital, multiwavelength universe resident in the as-tronomical data archives. http: // were initially proposed in the literature as Chamaeleon I mem-bers, but they were later discarded through spectroscopy.We note that the magnitude limit of most of these compi-lations is much fainter than the UCAC3 magnitude limit (seeSect. 2.2 below); therefore, a significant fraction of objects arenot expected to have counterparts in that catalogue. Since thefaintest objects are also the lowest mass ones, and given thatthe substellar mass limit is estimated to be around R ∼
21 magat the age and distance of the Chamaeleon clouds, this impliesthat only stellar members of the associations will have measuredproper motions. In particular, the objects at the substellar bound-ary studied by L´opez Mart´ı et al. (2004) in Chamaeleon I andBarrado y Navascu´es & Jayawardhana (2004) in Chamaeleon IIare not included in UCAC3.In a second step in our study, we also investigated those can-didate members of the Chamaeleon associations from the liter-ature whose true nature is still unclear. This list included 63 X-ray emitting stars unveiled by the ROSAT mission (Alcal´a et al.1995) that remained unclassified, as well as some objects fromother previous works still lacking spectroscopic confirmation ofyouth: the list of uncertain objects provided by Luhman et al.(2004, his Table 8; 21 objects) for Chamaeleon I, and the can-didate members of Chamaeleon II without spectroscopic confir-mation of membership from Spezzi et al. (2008, 11 objects) andthe DENIS survey (Vuong et al. 2001, 41 objects).In total, our list of unconfirmed candidates amounted to 136objects (63 ROSAT stars and 73 objects from other works), butthe vast majority of them are too faint to be included in theproper motion study, and only a handful of them have proper mo-tion measurements available in UCAC3, as explained in Sect. 4.
To get proper motion measurements, we cross-matched our com-piled catalogues with the UCAC3 catalogue, available within theVirtual Observatory. This is an all-sky survey containing about100 million objects, 95% of them with proper motions, coveringa dynamical range of about 8-16 mag in a single bandpass be-tween V and R. Its positional accuracy is about 15 to 100 masper coordinate, depending on magnitude. The proper motion er-rors range from 1 to 10 mas / yr, depending on magnitude andobserving history.As in our previous work on Lupus (LJS11), we followed aVO-based methodology to cross-match and analyse the data. Wemade use of the Multiple Cone Search utility of TOPCAT . Amatching radius of 2 (cid:48)(cid:48) was used. We retained all sources whoseproper motion errors were not set to zero, which had been com-puted using more than two epoch positions, and which had anobject classification flag (ot) between 0 and 3. After purging thedata in this way, the number of counterparts with proper mo-tion data in Chamaeleon I and II were 81 and 25 (correspondingto the 27% and 61% of the total number of stars included inour compiled lists), respectively. In addition, UCAC3 providedproper motions for 19 objects in (cid:15) Cha and 12 in η Cha, re-spectively (53% and 60% of the compiled lists, respectively). Asfor the background sources, the number of objects with avail-able proper motions was 52 (59%). These samples were furthercleaned by removing bad proper motion measurements and in-terlopers identified during the analysis (see Sect. 3 for details).The proper motion data for the members of the dark clouds, TOPCAT is an interactive graphical viewer and editor for tabulardata that allows the user to examine, analyse, combine, and edit astro-nomical tables. http: // / ∼ mbt / topcat / the foreground clusters, and the contaminants are presented inTables 1, 2, and 3, respectively.In LJS11, a comparison of the cross-matching results of theLupus catalogues with di ff erent astrometric catalogues (USNO-B1, SuperCOSMOS, PPMX) led to the conclusion that UCAC3provided the best compromise between the number of counter-parts (dependent among others on the magnitude limit of thecatalogue) and the typical proper motion errors. For the presentwork, we further compared the analysis presented in Sect. 3.1with the results obtained using the recently released PPMXL cat-alogue (R¨oser et al. 2010). Although this catalogue is deeper inmagnitude than UCAC3, and thus included much more sourcesfrom our initial member lists, it was not possible to distin-guish the di ff erent populations due to the larger errors in theproper motions for most of the objects. Thus, we concluded thatUCAC3 is still the best option available for our study. Aiming at better insight into the kinematics of the members ofthe Chamaeleon associations, we combined the UCAC3 propermotions with radial velocity measurements from the literature(Covino et al. 1997; Joergens & Guenther 2001; Biazzo et al.2012) and from the SIMBAD database. We only consideredmeasurements with errors better than about 30%. If several mea-surements were available for the same star, the average was com-puted. Known and suspected spectroscopic binaries were dis-carded.Our final sample contains radial velocity information for 18stars in Chamaeleon I and nine in Chamaeleon II. These data aresummarized in Table 1. We also retrieved radial velocity data for15 stars in the (cid:15)
Cha association and four stars in the η Cha as-sociation, which are listed in Table 2. We also considered radialvelocities from Covino et al. (1997) for the candidate membersof the associations discussed in Sect. 4.1.
We compiled multiwavelength photometry for the confirmedmembers and candidate members of the Chamaeleon associa-tions discussed in this work. Most of the data were retrieved us-ing the latest version of the VO SED Analyzer tool (VOSA;Bayo et al. 2008, submitted). They include ultraviolet photome-try from GALEX (Bianchi & GALEX Team 2000), optical pho-tometry ( B , V and I ) from the Tycho-2 and DENIS catalogues(Høg et al. 2000; DENIS Consortium 2005), near-infrared pho-tometry from 2MASS (Skrutskie et al. 2006), and mid-infraredphotometry from AKARI and WISE (Ishihara et al. 2010; Cutri& et al. 2012).More photometry data from the literature were retrievedthrough the VizieR catalogue service (Ochsenbein et al. 2000).For Chamaeleon II members and candidate members, we re-trieved the compilation of optical and infrared photometry byAlcal´a et al. (2008), which includes Johnson U -band data fromHughes & Hartigan (1992), Cousins R C I C and Sloan z photome-try from Spezzi et al. (2007), and mid- and far-infrared photome-try from IRAS and from the “cores to disks” ( c2d ) Spitzer legacyprogramme (Evans et al. 2003). For Chamaeleon I members and http: // svo2.cab.inta-csic.es / svo / theory / vosa / The c2d data are now retrievable through VOSA (Bayo et al. sub-mitted). candidate members, we retrieved the
Spitzer / IRAC and MIPS24 µ m photometry provided by Luhman & Muench (2008a).Optical photometry from the survey by L´opez Mart´ı et al. (2004)was also included in the data compilation for this cloud, as wellas IRAS fluxes for three objects. The photometric information issummarized in Table 4.
3. Kinematic groups towards Chamaeleon
Figure 1 shows the vector point diagram for the young sourcesseen towards the Chamaeleon sky area that are included in theUCAC3 astrometric catalogue. In Fig. 2 we can see the his-tograms of the total proper motion modulus for the Chamaeleon Iand II members, for the members of the foreground associations,and for the known background contaminants. As expected, theyoung objects are clearly separated from the older backgroundobjects in these plots, and several distinct kinematic groups canbe seen, which correspond to di ff erent spatial locations in thesky (see Fig. 3).The spectroscopically confirmed members of Chamaeleon I(hereafter “the Cha I moving group”) are clustered in the samearea of the vector-point diagram, roughly around the position( − , +
2) mas / yr. The Chamaeleon II objects, on the other hand,are seen mostly clustered around the position ( − , −
7) mas / yr,slightly shifted from the Chamaeleon I sources (Fig. 1). Thisseems to suggest that these objects (hereafter “the Cha II movinggroup”) are moving, on average, faster than the Chamaeleon Istars in the tangential direction. This is also seen in theshift of the peak of the total proper motion distribution inChamaeleon II with respect to Chamaeleon I (Fig. 2). If real,this result is interesting, because all estimations in the literatureplace Chamaeleon II at the same distance or further away thanChamaeleon I; hence, the di ff erence in proper motion betweenboth populations cannot be attributed to distance. However, thedi ff erence in mean proper motions is of little significance ow-ing to the low number of Chamaeleon II sources with measuredproper motions, and to the large dispersion.The two foreground associations form in turn two distinctkinematic groups in the vector point diagram, which are clearlydi ff erent from those in the dark clouds. The mean UCAC3 propermotions for these two groups are in good agreement with previ-ously published values (Kharchenko et al. 2005; Wu et al. 2009).Interestingly, the total proper motion is very similar in both as-sociations, as shown by the histograms in Fig. 2. As shown laterin Sect. 3.3, the radial velocities of the stars in both clusters arealso very similar.Finally, with a few exceptions, the objects classified as back-ground contaminants have lower proper motion values than anyof the young moving groups and are clustered in a di ff erent lo-cation of the vector point diagram. This confirms our ability todistinguish members and non-members of the Chamaeleon asso-ciations with the UCAC3 data. Even so, the separation betweenthe groups is not complete, and there is some overlapping be-tween young stars and contaminants and between young starsfrom di ff erent groups.A few spectroscopically confirmed members from bothChamaeleon clouds present UCAC3 proper motions that areclearly discrepant from those of their attributed associations. Tocheck the reliability of the reported measurements, we followedthe same procedure as in LJS11: Using Aladin , we visually in-spected these objects, blinking and comparing two sets of images Available online. 3el´en L´opez Mart´ı et al.: Proper motions of young stars in Chamaeleon
Fig. 1.
UCAC3 vector point diagram for the objects seen towards the Chamaeleon sky area. Only spectroscopically confirmed members areconsidered. Sources belonging to di ff erent kinematic associations and to the background have been plotted with di ff erent symbols and colours.Objects with reliable and dubious proper motions have been indicated with solid and open symbols, respectively (see Sect. 3.1 for details). To helpthe eye, the moving groups have been labelled and marked with ellipses. Some interlopers (objects with discrepant proper motions that are morelikely members of other associations) are identified (see discussion in Sect. 3.4). separated several decades in time, from the optical POSS andthe near-infrared 2MASS surveys (Skrutskie et al. 2006). The2MASS sources and the UCAC3 counterparts were superim-posed on the images to assess the reliability of the cross-match.Besides, we used other available astro-photometric databases,namely the Astrographic Catalogue AC2000.2 (Urban et al.1998) and the SuperCOSMOS Sky Survey (Hambly et al. 2001)to verify the peculiar proper motions, and the USNO-B Catalog(Monet et al. 2003) and the PPMX and PPMXL catalogues(R¨oser et al. 2008, 2010) for comparison. This procedure showedthat the clearly discrepant proper motions were mostly causedby errors in the measurements, mainly from centroiding errorsor source confusion. A rough estimation of the proper motionsof the objects, based on the comparison of the positions mea-sured by the di ff erent catalogues, and with the motion of othernearby cloud members, suggests that most of them have propermotions in relatively good agreement with the correspondingmoving groups.The reliability of the proper motions is di ffi cult to assess insome cases (e.g. HD 104237D and E) because these sources arepart of visual binaries or multiples not always resolved in theimages. And in a few cases (e.g. CW Cha), we could not test theproper motions in this way because SuperCOSMOS provides nodata for the stars, or else the data were wrong. The sources with clearly wrong proper motions (7 from Chamaeleon I and 2 fromChamaeleon II) were removed from the vector point diagram ofFig. 1. They were also excluded from Tables 1 and 2. Objectswith dubious proper motions (because they could not be testedor the checks were unconclusive) were not removed from thetables, but a flag was added.We also identified four spectroscopically confirmed mem-bers (2MASS J11183572-7935548, CM Cha, Sz 60W, and CP-68 1388) whose UCAC3 proper motions seem to be right but donot agree with the means of their attributed associations; theseinterlopers are discussed in Sect. 3.4 below. Five Chamaeleon I and three (cid:15)
Cha bona fide members from ourUCAC3 samples have proper motion and parallax measurementsprovided by the latest Hipparcos reduction (van Leeuwen 2007).In addition, six (cid:15)
Cha and two η Cha members have proper mo-tions from the Tycho catalogue (Høg et al. 1998). These data aresummarized in Table 5, together with the parallax, if available,and the distance derived from it. We used this information as afurther check of the accuracy of the UCAC3 measurements.We note that the proper motions of bright stars in UCAC3 arebased on about 140 catalogues, including Hipparcos and Tycho.
Fig. 3.
Current spatial location of the members of the Chamaeleon associations (circles) and of the ROSAT sources discussed in Sect. 4.1 (squares).Colours as in Fig. 1. Also shown are the expected displacement of these objects within 10 Myr. The background image is a dust map by Schlegelet al. (Schlegel et al. 1998). Only objects with reliable proper motions are considered.
Therefore, we generally expect good agreement between theUCAC3 measurements and the proper motions listed in Table 5,as is indeed found. However, problems may have a ff ected themeasurements in some of the images used by UCAC3, either dueto saturation, nebulosity, or the presence of nearby fainter stars.This seems to be the case for two Chamaeleon I stars (HD 97300and CW Cha). For these two objects, the Hipparcos proper mo-tions are in much better agreement with membership in the Cha Imoving group than the UCAC3 values.In particular, the membership in the dark cloud of HD 97300(the intermediate-mass star seen towards the northern core ofChamaeleon I) and its evolutionary status have sometimes beenquestioned. However, most authors agree that this is most likelya Herbig Ae / Be star similar to HD 97048 in the southern Chamaeleon I core. The proper motion seems to confirm thatthis star is a member of the Chamaeleon I cloud.It is also interesting to note that HD 97048 has been in-cluded in the catalogue of potential young runaway stars byTetzla ff et al. (2011), albeit with not very high probability (61%).However, we notice that the selection by these authors is onlybased on Hipparcos stars, which are relatively bright. Therefore,the sample used by Tetzla ff et al. (2011) included only a hand-ful of Chamaeleon I members. Indeed, Table 5 shows that theproper motion of this object is lower, in modulus, than the restof Chamaeleon I stars with Hipparcos or Tycho measurements,what could be interpreted as a hint for a di ff erent motion pattern.However, when the larger sample of cloud members provided bythe UCAC3 catalogue are considered, HD 97048 does not standup as having remarkably di ff erent kinematical properties from Table 5.
Hipparcos and Tycho proper motions and Hipparcos parallaxes for Chamaeleon stars
UCAC3 Hipparcos / TychoName µ α cos δ µ δ µ α cos δ µ δ π d Reference a Remarks b (mas / yr) (mas / yr) (mas / yr) (mas / yr) (mas) (pc)Chamaeleon I cloudHD 93828 –25.2 ± ± − . ± . − . ± .
84 5 . ± .
96 175 ±
30 HHD 97048 –17.8 ± ± − . ± . + . ± .
62 6 . ± .
62 158 ±
16 HHD 97300 –17.7 ± ± − . ± . − . ± .
78 5 . ± .
88 178 ±
28 H dCV Cha –21.3 ± ± − . ± . + . ± .
78 6 . ± .
86 143 ±
59 HCW Cha –13.6 ± ± − . ± . − . ± .
55 3 . ± .
56 255 ±
232 H d (cid:15)
Chamaeleontis clusterCP-68 1388 –35.8 ± ± − . ± . + . ± . ± ± − . ± . − . ± .
97 6 . ± . c ±
79 H dDW Cha –40.4 ± ± − . ± . + . ± . . ± .
52 90 ±
12 HRX J1159.7-7601 –40.9 ± ± − . ± . − . ± .
49 9 . ± .
72 101 ±
18 HHD 104467 –41.3 ± ± − . ± . − . ± . ± ± − . ± . − . ± . ± ± − . ± . − . ± . ± ± − . ± . − . ± . ± ± − . ± . − . ± . η Chamaeleontis clusterEG Cha − ± ± − . ± . . ± . − ± ± − . ± . . ± . Notes. a H = Hipparcos (van Leeuwen 2007); T = Tycho (Høg et al. 1998) b d = discrepant proper motion respect to UCAC3 c The 1997 Main Hipparcos Catalogue provides a parallax π = .
06 mas for this object (d ∼
66 pc).
Fig. 2.
Total proper motion histograms for the di ff erent moving groups:Cha I (blue hashed histogram), Cha II (filled red histogram), (cid:15) Cha(green empty histogram), η Cha (orange hashed histogram) and back-ground sources (black dashed-line histogram). Only objects with reli-able proper motions are considered. the rest (see also the discussion in Sect. 6.1). In view of ouranalysis, we think it unlikely that HD 97048 is actually runningaway from its birth place.There is also overall good agreement between the individualparallaxes of the stars in Table 5 and the usually quoted distances to the associations.The only possible exception is T Cha, whoseHipparcos parallax suggests a greater distance. However, giventhe large error, this estimation is still consistent with membershipto the (cid:15)
Cha cluster (but see also discussion in Sect. 5).
Figure 4 shows two plots of the radial velocities versus theproper motion components of the stars. With a couple of excep-tions, all the objects from the same proper motion group displaysimilar radial velocities, and are therefore clustered in these dia-grams. The radial velocity data therefore confirm that there is aphysical relationship between these stars. However, given that allthe associations have similar mean radial velocities, in the range10-20 km / s, it is not possible to distinguish between members ofthe dark clouds and of the foreground associations on the basisof radial velocity alone.The largest individual deviations from the mean group valuesare observed for EM Cha in the η Cha cluster ( V r = . ± / s)and GSC 9420-0948 in the (cid:15) Cha cluster ( V r = ± / s).The radial velocities of these stars di ff er by more than 3 σ fromthe mean cluster values, which challenges their membershipto the quoted associations. We therefore flag these objects inTable 2. Also, T Cha has a reported radial velocity discrepantin more than 2 σ from the mean value for the (cid:15) Cha association( V r = . ± . / s). The discrepancy may be related to thepresence of an unresolved companion, as there is indeed one re-ported in the literature (Hu´elamo et al. 2011). We discuss thisobject further in Sect. 5. Fig. 4.
Plots of radial velocity vs. proper motion components for stars in the Chamaeleon associations. Only objects with reliable proper motionsare considered. Symbols and colours as in Fig. 1.
Table 6.
Mean and weighted mean proper motion components and radial velocities for the moving groups identified towards theChamaeleon sky area a Group Arithmetic means Weighted means < µ α cos δ > < µ δ > < µ > < V r > < µ α cos δ > < µ δ > < µ > < V r > (mas / yr) (mas / yr) (mas / yr) (km / s) (mas / yr) (mas / yr) (mas / yr) (km / s)Cha I − ± + ± ± ± − ± + ± ± ± − ± − ± ± ± − ± − ± ± ± (cid:15) Cha − ± − ± ± ± − ± − ± ± ± η Cha − ± + ± ± ± − ± + ± ± ± Notes. a Interlopers and objects with uncertain proper motion measurements have been excluded from the calculations.
Once the proper motion lists are purged from inaccu-rate measurements, three true interlopers remain, namelyone Chamaeleon I object (2MASS J11183572-7935548) andtwo Chamaeleon II objects (2MASS J11183572-7935548 andCM Cha), whose proper motions seem to be in better agreementwith membership to the (cid:15)
Cha group.The source 2MASS J11183572-7935548 was included as aChamaeleon I member in the list of Luhman (2007). However,in a later work, Luhman et al. (2008) reclassified it as an (cid:15)
Chamember on the basis of its UCAC2 proper motion. Our analysisof the UCAC3 data confirms their result. This object is thereforeincluded in Table 2 as a probable member of the (cid:15)
Chamaeleontiscluster.CM Cha had been listed as a Chamaeleon II member bySpezzi et al. (2008). However, it has UCAC3 proper motioncomponents µ α cos δ = − . ± . µ δ = . ± . / yr.These values are only marginally compatible with the Cha IImoving group, and seem to be in better agreement with mem-bership in the foreground (cid:15) Cha association. Unfortunately,AC2000.2 provides no data for this star, and the data providedby SuperCOSMOS are wrong, probably because this object ap-pears blended with other star in the POSS image, so we cannottest its proper motion directly in the way explained above. In theliterature we find a reported proper motion of ( − ,
21) mas / yrfor this object, with a quoted accuracy of 5-10 mas / yr (Teixeira et al. 2000). The PPMXL catalogue reports a similar value of( − ,
9) mas / yr. These measurements are quite discrepant fromthe UCAC3 measurement, even when the large errors are con-sidered, but indicate in any case that CM Cha is probably lo-cated closer to the Sun than the Chamaeleon II members. Onthe other hand, there is spectroscopic evidence that the object isyoung: Spezzi et al. (2008) report an equivalent width for theLi I absorption line of 0 .
38 Å, which is similar to many othercloud members, but close to the lowest values measured by theseauthors. (Their range encompasses 0.35 to 0.61 Å, and typi-cal values in star forming regions are in the range 0.3-0.8 Å.)They also report an H α equivalent width of −
29 Å, which isconsistent with low accretion. This suggests that, though young,CM Cha is among the most evolved objects in the Spezzi et al.sample. On the other hand, the reported radial velocity for thisstar (15 . ± . / s; Torres et al. (2006) quite well agrees withthe values measured for other stars in the Chamaeleon clouds,but also with the radial velocities reported for (cid:15) Cha members(see Sect. 3.3). The space motion of this star (as computed usingthe UCAC3 proper motions) also seems to be in better agree-ment with this cluster (see Sect. 5 below). Taking all this intoaccount, we tentatively reclassify CM Cha as a member of the (cid:15)
Cha young association, and list it accordingly in Table 2. Wenote, however, that if the proper motion reported by Teixeiraet al. (2000) were correct, this star would probably be located even closer to the Sun than the (cid:15)
Cha members, and thus couldbe an unrelated young star from the solar neighbourhood.The situation is also ambiguous for Sz 60W, because thelarge error in µ δ makes its UCAC3 proper motion compatiblewith both the (cid:15) Cha and the Cha II moving groups. This star ispart of a binary object with a separation of 3.6 (cid:48)(cid:48) , and the sec-ondary has no UCAC3 counterpart. This may a ff ect the propermotion measurement of the primary, if the system is not com-pletely resolved in the images used by UCAC3 to compute theproper motion, or if source confusion has occurred at some stage.Indeed, secondaries at separations lower than 10 (cid:48)(cid:48) are often notresolved in UCAC3. More precise measurements are required toclarify the nature of Sz 60W, but we note that the spatial locationof this source, within the dark cloud (in contrast with CM Chathat is located in the outskirts), suggests a physical connectionwith Chamaeleon II. For the time being, Sz 60W is listed inTable 1 as a member of this cloud.In addition, we identify one object, namely CP-68 1388,whose reported UCAC3 proper motion di ff ers from the rest of (cid:15) Chamaeleontis members, and is seen detached from mov-ing group in the vector-point diagram of Fig. 1. This is dueto the value of the proper motion in the δ direction ( µ δ = . ± . / yr), because its µ α cos δ value ( − . ± . / yr)and its radial velocity (15.9 km / s) are in good agreement withthose of other cluster members. This star was observed by Tycho,and the proper motions reported in Table 5 agree closely with theUCAC3 values (although the Tycho µ δ value is somewhat lower, µ δ = .
70 mas / yr). The di ff erent proper motion and the spa-tial location of CP-68 1388, to the North of Chamaeleon I andmore than 6 ◦ away from the closest (cid:15) Chamaeleontis member,makes its membership to the cluster dubious. It is interesting,however, that this object is placed halfway between the (cid:15) and η Chamaeleontis cluster in the vector point diagram. As shownlater in Sect. 5, the space velocities of CP-68 1388 agree wellwith other stars in both clusters. We therefore keep this object inthe list of (cid:15)
Cha members for the time being.VW Cha also deserves some comments. This star hasbeen listed in the literature both as a Chamaeleon I member(Luhman 2007) and as a member of the (cid:15)
Cha group (Fern´andezet al. 2008). We find that both its spatial location within theChamaeleon I southern cloud core and its UCAC3 proper mo-tion ( µ α cos δ = − . ± . / yr, µ δ = − . ± . / yr) arein better agreement with VW Cha belonging to the dark cloud.The proper motion values reported by SIMBAD ( µ α cos δ = −
23 mas / yr and µ δ = − / yr; Teixeira et al. (2000) agreewell with our classification. This star also has a reported radialvelocity ( V r = . ± . / s; Torres et al. 2006) that is slightlyhigher than the mean value for Chamaeleon I, but similar to thevalues reported for other member stars (see Sect. 3.3). Once the proper motion lists are purged of incorrect measure-ments, and once the interlopers assigned to the associations theyare likely to belong to, the definitive member lists for the Cha I,Cha II, (cid:15)
Cha and η Cha contain 73, 22, 21, and 12 stars, respec-tively. These are the objects presented in Tables 1 and 2. Theselists still contain objects with dubious measurements that couldnot be proved wrong, as discussed in Sect. 3.1.After this analysis, we computed the means of the propermotion and values for the di ff erent kinematic groups, which arelisted in Table 6. Interlopers and objects with wrong or dubiousproper motion measurements were not considered in the calcula-tions. Because of the large proper motion errors for some of the objects, we also computed the weighted means, which are alsogiven in Table 6. The values of both the arithmetic and weightedmeans for each parameter are fully consistent with each other,within the estimated errors.Table 6 also lists the arithmetic and weighted mean radial ve-locities that we derive for three of the four groups. For the (cid:15) and η Cha clusters, the mean radial velocities are in good agreementwith previously published values (Kharchenko et al. 2005; Wuet al. 2009).
4. Proper motions of candidate Chamaeleonmembers
In the next step, we made an attempt to confirm candidate mem-bers of Chamaeleon I and II on the basis of their proper mo-tion. As in our Lupus study, we compared the proper motions ofcandidate members proposed in the literature with those of theconfirmed members.
In the 1990s, the ROSAT mission unveiled a dispersed popula-tion of X-ray emitting stars towards the Chamaeleon area, butnot confined to the dark clouds (Alcal´a et al. 1995). Alcal´a et al.(1997) provided the first spectroscopic evidence that these starswere young. Covino et al. (1997) performed radial velocity mea-surements for most of these stars, showing that the sample in-cluded objects belonging to di ff erent kinematical populations.This result was confirmed for a subsample of these objects byFrink et al. (1998) combining information from several propermotion catalogues. In addition, these authors used the Hipparcosparallaxes available for some of the stars to show that they werelocated at di ff erent distances(from 60 to about 200 pc). The dif-ferent stellar populations identified by these authors were thusassigned to the Chamaeleon I cloud, the foreground (cid:15) Cha clus-ter, or to an undetermined field population. However, many starsremained unclassified owing to the lack of proper motions. Only18 out of the 81 stars studied by Covino et al. (1997) are includedin our compilations of members of the associations seen towardsthe Chamaeleon area. These objects are flagged in Tables 1 and2. To clarify the nature of the remaining ROSAT sources, weperformed the same proper motion analysis on them described inSect. 3.1. UCAC3 provides proper motion measurements for 38of these objects, listed in Table 7. The radial velocities and evo-lutionary status of these stars according to Covino et al. (1997)are also indicated. We show the vector point diagram for theseobjects in Fig. 5, compared to the loci of the known young popu-lations in the Chamaeleon area. We also show the spatial locationof the ROSAT sources in Fig. 3.The UCAC3 vector point diagram confirms that the ROSATstars are a mixture of di ff erent kinematical populations. Fromtheir position on this diagram, some sources present completelydiscrepant proper motions from any of the moving groups identi-fied in Sect. 3.1. The radial velocity measurements from Covinoet al. (1997) confirm that these stars follow a completely dif-ferent motion pattern with respect to the Chamaeleon associa-tions. Other sources can be nicely assigned to one of the mov-ing groups in the Chamaeleon sky area; however, a few of themare also discarded because their radial velocities, as provided byCovino et al. (1997), are in complete disagreement with mem-bership to any of the associations, or because their location inthe sky does not coincide with that of the group with similar Fig. 5.
Vector point diagram for Chamaeleon candidate members from the literature. The ellipses indicate the approximate location of the kine-matical groups identified in Fig. 1. proper motion (especially in the case of the dark clouds). All theROSAT objects with discrepant proper motions and / or radial ve-locities are classified as zero-age main sequence (ZAMS) starsor stars of unclear nature by these authors.This left us with 13 stars (11 PMS stars and two stars ofunclear nature) whose spatial location, proper motions and ra-dial velocities (except for RXJ1150.4-7704, which has no avail-able radial velocity measurement) all overlap with one of theChamaeleon moving groups. We assigned two of these objects tothe Cha I moving group. The eleven other sources are classifiedas candidate members of the (cid:15) Cha association (three objects) orthe η Cha association (eight objects). We do not find any goodChamaeleon II candidate members. The membership of all thesesources is indicated in Table 7.In two cases, namely RXJ1123.2-7924 and RX J1158.5-7913, membership in a single association cannot be clearly at-tributed. The spatial location of these two objects (two PMS starsaccording to the study by Covino et al. (1997) seems more con-sistent with membership in the (cid:15)
Cha moving group than in ei-ther of the dark clouds. However, this is not so straightforwardfrom their UCAC3 proper motions. RXJ1123.2-7924 is locatedin the vector point diagram closer to the Cha II moving groupthan to the (cid:15)
Cha members, but its proper motion values arestill marginally consistent with membership in this group. Givenits location in the sky, in the area between the Chamaeleon Iand the Chamaeleon III clouds, and about 5 ◦ from the known Chamaeleon II members, we tentatively assign this object to the (cid:15) Cha moving group, and list it in Table 7.RX J1158.5-7913 is seen towards the small cloud[DB2002b] G300.23-16.89, located halfway between theChamaeleon I and II clouds and about 2.8 ◦ south-east of theformer. The star T Cha and other members and candidatemembers of the (cid:15) Cha association are also seen in this area.However, the proper motion components of RX J1158.5-7913( µ α cos δ = − . ± . / yr, µ δ = − . ± . / yr)place this star in the overlapping area between Chamaeleon Iand II members in the vector point diagram, but closer tothe Chamaeleon I mean value given in Table 6. This lookscompletely incompatible with membership in the (cid:15) Cha cluster,even though the radial velocity reported by Covino et al.( V = . ± / s) is very close to the mean value we obtainfor the (cid:15) Cha members (see Table 6). Because the proper motionand radial velocity look consistent with the mean values derivedfor the Cha I moving group, we tentatively assign RX J1158.5-7913 to this cloud for the time being. More accurate kinematicdata will help clarify the nature of this object.
Several works have provided lists of candidate members in theChamaeleon clouds that still lack spectroscopic confirmation ofyouth. Unfortunately, most of the postulated objects are too faint
Fig. 6.
Histograms of space velocities, uncorrected and corrected for the solar reflex motion with respect to the LSR (left and right panels,respectively) for stars in the di ff erent Chamaeleon associations. Symbols as in Fig. 2. to be included in the UCAC3 catalogue and, therefore, we cannottest their membership on the basis of their proper motion. Thereare, however, a few exceptions, which we discuss in this section.The UCAC3 proper motions for these candidates are listed inTable 8, and they are plotted in the vector point diagram shownin Fig. 5.Luhman et al. (2004) provides a list of objects whose mem-bership in Chamaeleon I is uncertain (cf. his Table 8), 21 ofthem lacking confirmation in later works. Only one of these ob-jects has a valid UCAC3 counterpart, namely C1-14, an infraredsource first quoted by Prusti et al. (1991), and also identified withthe X-ray source CHX 15a. This object is located within thenorthern cloud core of Chamaeleon I and, as shown in Fig. 5, itsproper motion is compatible with the Cha I moving group. Thespectral type of this source is badly constrained, but quoted in therange F0-A7, which would make it one of the most massive ob-jects in the dark cloud, together with HD 97300 and HD 97048.In addition to the confirmed Chamaeleon II members, Spezziet al. (2008) list a number of objects still lacking spectroscopicconfirmation of membership to the cloud, but considered likelymembers on the basis of the multiwavelength photometric anal-ysis reported in a previous work (Alcal´a et al. 2008). Only two ofthese sources have UCAC3 counterparts, namely IRAS 12589-7646 (ISO-Cha II 89) and IRAS 12448-7650. The proper motionfor the latter object clearly disagrees with membership in theCha II moving group, and strongly suggests that IRAS 12448-7650 belongs to the background. As for IRAS 12589-7646, itsproper motion ( µ α cos δ = − . ± . / yr, µ δ = . ± . / yr) places this source in the area of the Cha I mov-ing group rather than Cha II. From our own check, however,the proper motion seems to be around (5, 1.1) mas / yr, whichwould place it in the same area as the background objects in thevector-point diagram. In view of these results, the classificationof IRAS 12589-7646 as a Chamaeleon II member is dubious,and we conservatively flag it as “rejected” in Table 8. In addition to C1-14, SIMBAD lists three other sources within 2 (cid:48)(cid:48) (the value of our cross-matching radius) from the UCAC3 position: CD-75 522, Glass R, and WKK F 32. The former has a reported proper mo-tion suggesting ia foreground star. From the intercomparison of theirproperties as listed in SIMBAD, we are led to think that Glass R,WKK F 32, and C1-14 must actually be the same object.
Vuong et al. (2001) performed a search for candidate mem-bers of Chamaeleon II based on DENIS
I JK s photometry. Onlyfive objects from their list are included in UCAC3, namelytheir sources [VCE2001] C18, C29, C64, X3, and X4. As seenin Fig. 5, their proper motions do not agree with membershipin the Cha II moving group. Therefore, it seems unlikely thatthese objects belong to the Chamaeleon II dark cloud. The onlypossible exception is the X-ray source [VCE2001] X4, whoselocation in the vector point diagram is marginally compatiblewith those of the Chamaeleon II members. While deceiving,this result is not totally surprising, since spectroscopic stud-ies of about 30 sources from the Vuong et al. (2001) selectionalso failed to confirm most of them as Chamaeleon II mem-bers (Barrado y Navascu´es & Jayawardhana 2004; Spezzi et al.2008), thus showing the high contamination of the original sam-ple (which amounted to 76 sources). None of the five DENISsources discussed above with available proper motions was ob-served in these works. To date, there have only been five con-firmed young stars from the Vuong et al. (2001)) list (see com-piled list in Spezzi et al. 2008), but only one, [VCE2001] C61, isincluded in UCAC3 and listed in Table 1. The proper motion ofthis object is compatible with Chamaeleon II membership.
5. Space velocities
We computed the galactic space velocities for the stars (mem-bers and candidate members) with available radial velocity mea-surements. For this purpose we made use of an IDL routine re-trieved from the IDL Astronomy Library, originally written byW. Landsman and later modified by S. Koposov. The procedurefollows the formulation in Johnson & Soderblom (1987), exceptfor two details: the U component is positive toward the Galactic anticentre , and the Hipparcos transformation matrix is used. Wemodified the routine to include the computation of the velocityerrors in the way prescribed by Johnson & Soderblom (1987).Since most of the stars lack parallax measurements, we as-sumed the canonical distances to the associations for this cal-culation: 160 ±
15 pc and 178 ±
18 pc to Chamaeleon I and II,respectively (Whittet et al. 1997), and 111 ± ± (cid:15) Cha and η Cha clusters, respectively (Feigelson et al. http: // idlastro.gsfc.nasa.gov / ftp / pro / astro / gal uvw.pro10el´en L´opez Mart´ı et al.: Proper motions of young stars in Chamaeleon Fig. 7. ( U , V ) and ( V , W ) planes for stars in the di ff erent Chamaeleonassociation. The big crosses indicate the location of known nearby mov-ing groups. Rest of symbols and colours as in Fig. 1. U (cid:12) , V (cid:12) , W (cid:12) ) = ( − .
5, 13.38, 6.49) km / s. Figure 6 shows the his-tograms for the space velocities of the stars in the di ff erent asso-ciations.Although this exercise is certainly a ff ected by lots of uncer-tainties, especially in the stellar distances, the resulting spacevelocities confirm the membership of the stars in the di ff erentChamaeleon associations to the young disk population, accord-ing to the prescriptions listed in Leggett (1992). The histogramsdisplayed in Fig. 6 further confirm the presence of di ff erent kine-matical populations towards Chamaeleon. In particular, the starsin the Chamaeleon I cloud seem to display, as a sample, a dif-ferent motion pattern from the rest. This is most evident in theGalactic centre-anticentre direction ( U component), especiallywhen the velocities are corrected with respect to the LSR (upperright panel of Fig. 6): While the mean U LS R -component of theCha I moving group is negative (i.e. pointing to the Galactic cen-tre), for the rest of associations this component is positive (i.e.pointing to the Galactic anticentre).The stars in the two foreground clusters seem to have verysimilar space velocities, so the di ff erences in proper motion ob-served in the vector point diagram of Fig. 1 seem to be mostlyrelated to the di ff erent spatial location of both groups in the pro-jected sky (separated by about 8.5 ◦ ). This fact, together with thesimilar ages and distances of both associations, hints at a con- nection between them, as already suggested in the literature (e.g.Feigelson et al. 2003). Indeed, the space velocities we obtainare in good agreement with published values (e.g. Zuckerman& Song 2004), and with the membership of both clusters to theso-called “Local Association” (or “Pleiades moving group”), acoherent kinematic stream of young stars (ages ∼ α Per or Scorpius-Centaurus) first postulated by Eggen (1975).This is shown in Fig. 7, where we show the location of the starsfrom Table 9 in the ( U , V ) and ( V , W ) planes, together with thelocation of the mean space velocities for several nearby youngmoving groups (ages 20-600 Myr; Montes et al. 2001).Interestingly, the stars in Chamaeleon II seem to have spacevelocities more similar to those of the foreground clusters thanto the Chamaeleon I stars. However, the numbers are low, andthe errors for most stars are large, as is the dispersion in the data.Better precision and statistics with larger samples are requiredto investigate the eventual relation of Chamaeleon II with the (cid:15) and η Cha associations, and to other young moving groups.We close this section with some remarks on particular ob-jects. First of all, we note that the usually quoted parallax forT Cha is 15 ± ±
15 pc. This is the value included in the Hipparcos MainCatalogue (ESA 1997). However, the new reduction performedby (van Leeuwen 2007) provides a parallax of 6 ± ±
80 pc. The first value wouldplace this star closer to the Sun than most of the members ofthe (cid:15)
Cha association, and with quite discrepant space velocities,even when the errors are considered. In contrast, the most recentdistance value is compatible, within the error, with the canonicaldistance to the cluster, and provides space velocities in relativelygood agreement with T Cha being an (cid:15)
Cha member. The sametrend is observed if the space velocities are computed using theHipparcos proper motions from Table 5 instead of the UCAC3ones. Nevertheless, T Cha is seen detached from the group of (cid:15)
Cha members in both planes represented in Fig. 7, and, giventhe large uncertainties in the distance (i.e. in the space veloc-ities), the membership of this star to the (cid:15)
Cha moving groupcannot be assigned with certainty.Second, we note that the space velocities of CM Cha showrelatively good agreement with those of other (cid:15)
Cha members,when the mean distance to this cluster is used in the calcula-tion. If the distance to Chamaeleon II is used instead, the re-sulting space velocities are quite discrepant from those of theonly confirmed Cha II member with available space velocities.This further supports the hypothesis that CM Cha is a memberof the (cid:15)
Cha association, as suggested in Sect. 3.4. Even so, itmust be noted that the velocity component in the direction of theGalactic poles ( W ) of CM Cha is quite di ff erent from the rest of (cid:15) Cha members, as it is pointing towards the northern instead ofthe southern Galactic pole. We note, though, that a handful of η Cha cluster members are also located in the same area of the( V , W ) plane.We made the same check with the two ROSAT sources dis-cussed at the end of Sect. 4.1. RX J1158.5-7913, a potentialinterloper from the Chamaeleon I cloud in the sky area of the (cid:15) Cha members, has space velocities that are fully consistentwith membership in the dark cloud, if the mean distance to itis used in the calculation. In contrast, the resulting space veloc-ities when the distance to (cid:15)
Cha is used are not consistent withmembership in this cluster. On the other hand, RXJ1123.2-7924,whose proper motion looks compatible with both the (cid:15)
Cha clus-ter and the Chamaeleon II cloud, has space velocities fully com-patible with the foreground association.
6. Properties of the kinematic populations of theChamaeleon dark clouds
Fig. 8.
Enlargements of the map from Fig. 3 showing the Chamaeleon Iand II areas in more detail (upper and lower panels, respectively).
Figure 8 shows two enlargements of Fig. 3 in the location ofthe Chamaeleon I and II clouds. As noted in previous works,the sources belonging to the Cha I moving group tend to clus-ter around the two main cores containing the intermediate-massstars HD 97300 (the northern core) and HD 97048 (the south-ern core). Luhman (2007) reports on a di ff erence in isochronalages of a few Myr between both cores, which he interprets asthe result of two di ff erent bursts of star formation. We there-fore checked whether any proper motion di ff erence could beseen between the two cores. To this purpose, all the stars withina radius of 50 (cid:48) from one of the intermediate-mass star weredefined as members of the corresponding core. This distancewas chosen after inspecting the distance distributions from bothintermediate-mass stars. At the UCAC3 precision, we found noobvious di ff erence between the proper motions of both groups.No evident di ff erence is seen either between the in- and theo ff -cloud populations, neither in proper motion moduli nor inproper motion directions. This seems to confirm that both sam-ples belong to the same structure. It also suggests that the loca-tion of the outer sources is not the consequence of these objectsbeing ejected from their parental birth sites.We performed a similar analysis in Chamaeleon II, dividingthe population in a northern group, located north-west of a densecore in the northern part of the cloud, and a southern group,located in and around a smallest core to the south. Again, wefound no obvious di ff erence between the proper motions of bothgroups. A comparison between the in- and o ff -cloud populationis not possible in this case due to the low number of objects andthe dubious proper motions of most of the sources located o ff -cloud (leftmost sources in the lower panel of Fig. 8). As a next step, we investigated the possible correlations be-tween the proper motions and the physical parameters of theobjects. Luhman et al. (2008) performed an analysis of thespectral energy distributions (SEDs) of confirmed members ofChamaeleon I. A similar study of Chamaeleon II was presentedby Alcal´a et al. (2008) and Spezzi et al. (2008). These worksprovide a classification of the confirmed members of the darkclouds into class III (diskless) sources, class II (disk) sourcesand so-called “flat-spectrum sources”, which are thought to behalfway between class I (envelope) sources and class II sources.They also provide estimations of the e ff ective temperature andbolometric luminosity of the objects. In total, we compiled val-ues of physical parameters for 47 stars in Cha I and 14 stars inCha II, whose properties are summarized in Table 10. Only ob-jects with reliable UCAC3 proper motions are included.We used this information to look for correlations betweenthe proper motions and the physical parameters of the objects.Figures 9 and 10 show the plots of the proper motion compo-nents versus T e f f and log L / L (cid:12) for the objects in both clouds.No trends are seen in the proper motion with either of the con-sidered parameters. Since these properties are directly correlatedwith mass in young low-mass stars, this result suggests that themotion of the objects does not depend on their mass to the pre-cision that we can prove with the UCAC3 data.In Chamaeleon I, where this can be investigated, we do notfind any correlation either between proper motion and the pres-ence of a (primordial) circumstellar disk, or for objects with andwithout disks (class II and class III sources) separately. Fig. 9.
Proper motion components versus bolometric luminosity (left) and e ff ective temperature (right) for Chamaeleon I members with andwithout disks (red circles and blue asterisks, respectively). We note that similar studies in other star-forming regionsalso failed to find any correlation between the proper motion andthe properties of the objects (e.g. Bouy & Mart´ın 2009, LSJ11).More accurate proper motion measurements and better statisticsare required to reveal any eventual trend with the physical prop-erties of young low-mass stars in these regions.
7. Conclusions
We have performed a kinematic study of the Chamaeleon cloudsbased on UCAC3 proper motions and radial velocities from theliterature. Our analysis has led to the following conclusions: – With the UCAC3 data, we were able to separate the severaldistinct kinematic groups that coexist in the Chamaeleon skyarea: the Chamaeleon I and II dark clouds, the young (cid:15)
Chaand η Cha associations, and the field contaminants. – Compiled radial velocity data from the literature showedthat all the young stars have similar radial velocities, regard-less of the association the objects belong to. It is not possi-ble to discern membership to the di ff erent groups seen to-wards Chamaeleon on the basis of radial velocity informa-tion alone. – The stars in Chamaeleon I and II may have di ff erent kinemat-ical properties, but this result must be confirmed with moreprecise proper motions. If true, the Chamaeleon II mem-bers would be moving faster in the tangential direction thanthe Chamaeleon I members. Because they are located at thesame or a further distance, this would question the physicalconnection between both clouds. – The kinematical analysis confirmed the membership of al-most all the studied objects to the corresponding associa- tions. We only identified two possible interlopers from the (cid:15)
Cha association in our list of Chamaeleon II members:CM Cha and Sz 60W. With the available data, we reclas-sified CM Cha as an (cid:15)
Cha member. The nature of Sz 60W ismore uncertain due to the big proper motion error, but givenits spatial location and its isochronal age (2 Myr) we think itmore likely that this object belongs to Chamaeleon II. – We reanalysed a sample of X-ray detected stars towards theChamaeleon sky area and confirmed that they constitute amixture of di ff erent populations. After purging the sample offoreground and background contaminants and excluding theobjects previously classified in the literature, we identifiedtwo stars as likely Chamaeleon I members, three as (cid:15) Chamembers, and eight as η Cha members. We did not identifyany Chamaeleon II members in this sample. – We checked the proper motions of candidate members of theChamaeleon dark clouds from the literature, and confirmedone object, C1-14, as a probable member of Chamaeleon I.This would be one of the earliest type (i.e. most massive)stars in this dark cloud. In Chamaeleon II, we checked theproper motions of two candidate members listed by Spezziet al. (2008) and of five candidate members from the list byVuong et al. (2001), and found it unlikely that any of thembelongs to the dark cloud. – For those objects with available radial velocities, we com-puted the corresponding Galactic space motions. Our resultsconfirm the di ff erent spatial motion of Chamaeleon I fromthe foreground associations. The data also hint at a di ff erencein spatial motion between Chamaeleon I and II, further sug-gesting di ff erent origins for the populations in both clouds,but this has to be confirmed with better datasets. Fig. 10.
Same as Fig. 9 for Chamaeleon II. – The space velocities for the (cid:15) and η Cha members and can-didate members are in very good agreement with previousestimations in the literature, which identify these two clus-ters as part of the Local Association. Interestingly, the spacemotions of most of the Cha II members with available ra-dial velocity measurements also look quite similar to thoseof the Local Association stars. It would be highly desirableto have a larger sample of stars with estimated space veloc-ities in this dark cloud, in order to investigate the eventualrelation between Chamaeleon II and the Local Associationand to confirm or discard the di ff erent motion pattern fromChamaeleon I. – We investigated the relation between the proper motions andthe published properties of the members and candidate mem-bers of Chamaeleon I and II, such as spatial location, thepresence of circumstellar material, e ff ective temperature, orluminosity, but we found no evident correlations. More ac-curate proper motions, combined with radial velocity infor-mation, may unveil possible hidden trends with the physicalproperties of the stars, undetectable with the precision of theproper motions used here.Our work has shown how the use of kinematical informationcan complement photometric and spectroscopic data to constrainthe selection of members of young star-forming clusters, mini-mizing the contamination of the samples. Currently available as-trometric catalogues are deep enough to provide proper motionsfor a significant number of candidate members of nearby star-forming regions precisely enough to disentangle true members,not only from background sources, but also from young stars inclusters overlapping in the line of sight. In a forthcoming paper(L´opez Mart´ı et al. in preparation), we will report on a search for new candidate members of the Chamaeleon clouds based onproper motion.Furthermore, the results obtained both in the present workand in our previous Lupus study illustrate the potential of usinga VO methodology for analysing heterogeneous datasets in ane ffi cient manner.Most of the issues left unsolved in the present study are ex-pected to get a definitive answer with the advent of the Gaia mis-sion of the European Space Agency, whose launch is foreseen in2013.
Gaia will provide astrometric information with unprece-dented precision for most of the stars in the samples studiedhere, remarkably improving our understanding of the kinemat-ics, physical properties and formation process of the objects inthe Chamaeleon associations.
Acknowledgements.
This work was funded by the Spanish MICINN throughgrant Consolider-CSD2006-00070. It also benefitted from funding from theSpanish government through grants ESP2007-65475-C02-02, AYA2008-02156,AYA2010-21161-C02-02, and AyA2011-24052, and from the Madrid regionalgovernment through grant PRICIT-S2009ESP-1496. A. B. was co-funded underthe Marie Curie Actions of the European Commission (FP7-COFUND).This publication made use of VOSA, developed under the Spanish VirtualObservatory project supported by the Spanish MEC through grants AyA2008-02156 and AyA2011-24052. It greatly benefitted from the use of the SIMBADdatabase and the VIZIER Catalogue Service, both operated at the CDS(Strasbourg, France). We used the VO-compliant tools Aladin, developed at theCDS, and TOPCAT, currently developed within the AstroGrid project.This publication makes use of data products from the Two Micron All SkySurvey (2MASS), which is a joint project of the University of Massachusetts andthe Infrared Processing and Analysis Center / California Institute of Technology,funded by the US National Aeronautics and Space Administration and NationalScience Foundation, and from the Wide-field Infrared Survey Explorer (WISE),which is a joint project of the University of California, Los Angeles, and theJet Propulsion Laboratory / California Institute of Technology, funded by the USNational Aeronautics and Space Administration.
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H., Cambr´esy, L., & Epchtein, N. 2001, A&A, 379, 208Whittet, D. C. B., Prusti, T., Franco, G. A. P., et al. 1997, A&A, 327, 1194Wright, E. L., Eisenhardt, P. R. M., Mainzer, A. K., et al. 2010, AJ, 140, 1868Wu, Z.-Y., Zhou, X., Ma, J., & Du, C.-H. 2009, MNRAS, 399, 2146Zacharias, N., Finch, C., Girard, T., et al. 2010, AJ, 139, 2184Zuckerman, B. & Song, I. 2004, ARA&A, 42, 685 T a b l e . C on fi r m e d m e m b e r s o f C h a m ae l e on I a nd II w it h U C A C r op e r m o ti on s ( e x c l ud i ng w r ong m ea s u r e m e n t s a nd i n t e r l op e r s ) M A SS J O t h e r n a m e s U C A C µ α c o s δ µ δ V r R I J HKN o t e s ( m a s / y r)( m a s / y r)( k m / s )( m a g )( m a g )( m a g )( m a g )( m a g ) C h a m ae l e on I C l oud10463795 - HD - . ± . . ± . . . . ± . . ± . . ± . - T A - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - S Y C h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . - S z , T - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - T - . ± . . ± . . . . ± . . ± . . ± . - S W C h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . - CRC h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R C - . ± . . ± . . . . ± . . ± . . ± . - C S C h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - C T C h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . - C HX R N - . ± . . ± . . . . ± . . ± . . ± . - C HX R S - . ± . . ± . . . . ± . . ± . . ± . - - . ± . . ± . . . . ± . . ± . . ± . - H n4026 - . ± . . ± . . . . ± . . ± . . ± . - - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - [ LE S ] C h a I , I S O - . ± . . ± . . . . ± . . ± . . ± . - D I C h a , T - . ± . . ± . . ± . . ± . . ± . . ± . - VV C h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - V W C h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - HD , T - . ± . . ± . . ± . . ± . . ± . - T A - . ± . . ± . . . . ± . . ± . . ± . ( ) - T - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - P U C a r - . ± . . ± . . ± . . ± . . ± . ( ) - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R , R X J . - - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - V Z C h a , T - . ± . . ± . . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - HD , T - . ± . . ± . . ± . . ± . . ± . ( ) - T - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . T a b l e . ( c on ti nu e d ) M A SS J O t h e r n a m e s U C A C µ α c o s δ µ δ V r R I J HKN o t e s ( m a s / y r)( m a s / y r)( k m / s )( m a g )( m a g )( m a g )( m a g )( m a g ) - T a - . ± . . ± . . ± . . ± . . ± . - T - . ± . . ± . . ± . . ± . . ± . . ± . - I S O - . ± . . ± . . ± . . ± . . ± . - C HX R , W KK F - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - T - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - C HX N - . ± . . ± . . . . . ± . . ± . . ± . ( ) - C HX R N E - . ± . . ± . . . . ± . . ± . . ± . - C HX , T , R X J . - - . ± . . ± . . ± . . ± . . ± . . ± . ( , ) - C V C h a , T - . ± . . ± . . ± . . . . ± . . ± . . ± . - C W C h a , T - . ± . . ± . . ± . . ± . . ± . ( , ) - C HX R - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . ± . . ± . . ± . - C HX R - . ± . . ± . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - - . ± . . ± . . . . ± . . ± . . ± . - H n18028 - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - C HX R - . ± . . ± . . . . ± . . ± . . ± . - B Y B - . ± . . ± . . . . ± . . ± . . ± . - - . ± . . ± . . . . ± . . ± . . ± . - T - . ± . . ± . . . . ± . . ± . . ± . - - . ± . . ± . . . . ± . . ± . . ± . ( ) - - . ± . . ± . . . . ± . . ± . . ± . ( ) - - . ± . . ± . . . . ± . . ± . . ± . ( ) C h a m ae l e on II C l oud12563364 - S z N - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - S z - . ± . . ± . . . . ± . . ± . . ± . ( ) - I R A S - , C H II X R - . ± . . ± . . ± . . . . ± . . ± . . ± . - I R A S - - . ± . . ± . . . . ± . . ± . . ± . ( ) - S z , I s o - C h a II , C H II X R - . ± . . ± . . . ± . . ± . . ± . - S z , I s o - C h a II , C H II X R - . ± . . ± . . ± . . . . ± . . ± . . ± . - W F I J - - . ± . . ± . . . . ± . . ± . . ± . - R X J . - a - . ± . . ± . . . . ± . . ± . . ± . - S z - . ± . . ± . . . . ± . . ± . . ± . - R X J . - - . ± . . ± . . ± . . . . ± . . ± . . ± . - H n23027 - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - H n24025 - . ± . . ± . . . . ± . . ± . . ± . - B F C h a , S z - . ± . . ± . . . . ± . . ± . . ± . - S z - . ± . . ± . . . . ± . . ± . . ± . - S z , I R A S - , [ V C E ] C - . ± . . ± . . ± . . . . ± . . ± . . ± . - S z - . ± . . ± . . ± . . . . ± . . ± . . ± . - S z W - . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - H n26025 - . ± . . ± . . . . ± . . ± . . ± . - S z - . ± . . ± . . ± . . . . ± . . ± . . ± . - S z - . ± . . ± . . . . ± . . ± . . ± . - S z - . ± . . ± . . . . ± . . ± . . ± . T a b l e . ( c on ti nu e d ) M A SS J O t h e r n a m e s U C A C µ α c o s δ µ δ V r R I J HKN o t e s ( m a s / y r)( m a s / y r)( k m / s )( m a g )( m a g )( m a g )( m a g )( m a g ) - - . ± . . ± . . . . ± . . ± . . ± . ( ) N o t e s . ( ) D ub i ou s p r op e r m o ti on . ( ) D i s c r e p a n t p r op e r m o ti on f o r m H i pp a r c o s . ( ) R O S A T s ou r ce s t ud i e dby C ov i no e t a l . ( ) . ( ) S p ec t r o s c op i c b i n a r y . ( ) S o m e ti m e s c l a ss i fi e d i n t h e lit e r a t u r ea s a m e m b e r o f t h e (cid:15) C h ac l u s t e r( s ee t e x t f o r d i s c u ss i on ) . ( ) P o ss i b l e i n t e r l op e rfr o m t h e (cid:15) C h ac l u s t e r( s ee t e x t f o r d i s c u ss i on ) . T a b l e . K i n e m a ti c m e m b e r s o f t h e f o r e g r ound (cid:15) a nd η C h a m ae l e on ti s c l u s t e r s ( e x c l ud i ng w r ong m ea s u r e m e n t s a nd i n t e r l op e r s ) M A SS J O t h e r n a m e s U C A C µ α c o s δ µ δ R v R I J HKN o t e s ( m a s / y r)( m a s / y r)( k m / s )( m a g )( m a g )( m a g )( m a g )( m a g ) (cid:15) C h a m ae l e on ti s c l u s t e r - C P - - - . ± . . ± . . . . . ± . . ± . . ± . ( ) - V W C h a , R X J . - - - . ± . - . ± . . . . ± . . ± . . ± . ( ) - (cid:15) C h a - - . ± . . ± . . . . ± . . ± . . ± . ( ) - D Z C h a - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( ) - T C h a , R X J . - - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( ) - G S C - - - . ± . - . ± . . ± . . ± . . ± . . ± . - D W C h a , R X J . - - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( ) - R X J . - - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( ) - HD D - - . ± . . ± . . ± . . ± . . ± . ( ) - HD E - . ± . . ± . . ± . . ± . . ± . ( ) - HD , R X J . - - - . ± . - . ± . . ± . . ± . . ± . . ± . ( ) - G S C - , R X J . - - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( , ) - G S C - , R X J . - - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( ) - M A SS J - - - . ± . - ± . . . . ± . . ± . . ± . - HD , H I P - - . ± . - . ± . . . . . ± . . ± . . ± . - R X J . - , G S C - - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( ) - G S C - , R X J . - - - . ± . - . ± . . ± . . . . ± . . ± . . ± . ( ) - R X J . - , C D - - - . ± . - ± . . ± . . . . ± . . ± . . ± . ( ) - C D - - - . ± . - ± . . . . . ± . . ± . . ± . - C M C h a , I R A S - - - . ± . . ± . . . . ± . . ± . . ± . ( ) - M P M u s - - . ± . - ± . . ± . . ± . . ± . . ± . η C h a m ae l e on ti s c l u s t e r - E G C h a , R E C X - − . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - E H C h a , R E C X - − . ± . . ± . . . . ± . . ± . . ± . - HD - − . ± . . ± . . . . ± . . ± . . ± . - E I C h a , R E C X - − . ± . . ± . . . . ± . . ± . . ± . - E K C h a , R E C X - − . ± . . ± . . . . ± . . ± . . ± . - EL C h a , R E C X - − . ± . . ± . . . . ± . . ± . . ± . - E M C h a , R E C X - − . ± . . ± . . ± . . ± . . ± . . ± . ( , ) - ET C h a , R E C X - − . ± . . ± . . . . ± . . ± . . ± . - E N C h a , R E C X - − . ± . . ± . . . . ± . . ± . . ± . - E O C h a , R E C X - − . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) - E P C h a , R E C X - − . ± . . ± . . . . ± . . ± . . ± . - E Q C h a , R E C X - − . ± . . ± . . ± . . . . ± . . ± . . ± . ( ) N o t e s . ( ) P o ss i b l e i n t e r l op e r( s ee t e x t f o r d i s c u ss i on ) . ( ) R O S A T s ou r ce s t ud i e dby C ov i no e t a l . ( ) . ( ) C l a ss i fi e d i n t h e lit e r a t u r ea s a C h a m e l e on I o rII m e m b e r . ( ) D ub i ou s p r op e r m o ti on . ( ) D i s c r e p a n t r a d i a l v e l o c it y r e s p ec tt h e m ea ng r oupv a l u e . Table 3.
Background objects. µ α cos δ µ δ (mas / yr) (mas / yr)10452780-7715335 026-023750 1.2 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Table 7.
Kinematic properties of ROSAT stars not included in our initial member lists
RXJ 2MASS J Other names UCAC3 µ α cos δ µ δ V r Evolutionary Group b (mas / yr) (mas / yr) (km / s) status a − ± − ± ± − ± − ± ± (cid:15) Cha 14 022-022912 − ± − ± ± (cid:15) Cha?1150.4-7704 11502829-7704380 (cid:15)
Cha 19 026-027460 − ± − ± (cid:15) Cha1216.8-7753 12164593-7753333 025-028496 − ± − ± ± (cid:15) Cha0850.1-7554 08500540-7554380 029-020107 − ± ± ± η Cha0902.9-7759 025-017479 − ± ± ± η Cha0915.5-7608 09152912-7608471 028-021037 − ± ± ± η Cha0928.5-7815 09282116-7815352 HD 82879 024-017885 − ± ± ± η Cha0935.0-7804 09345604-7804193 024-018258 − ± ± ± η Cha0951.9-7901 09515069-7901377 HD 86356 022-017379 − ± ± ± η Cha1001.1-7913 10010873-7913074 022-017956 − ± ± ± η Cha1140.3-8321 11401658-8321003 014-014885 − ± ± ± η Cha1017.9-7431 10175369-7431172 031-030277 − ± ± ± − ± ± ± − ± ± − ± − ± ± − ± − ± ± − ± ± − ± ± − ± ± ± − ± − ± ± − ± ± ± − ± ± − ± − ± ± ± − ± ± ± − ± ± ± − ± ± − ± − ± − ± − ± − ± − ± ± − ± − ± − ± − ± ± ± − ± ± ± − ± − ± − ± − ± ± ± − ± ± − ± − ± − ± ± Notes. a Covino et al. (1997) b This work (a question mark if dubious, see text) 21el´en L´opez Mart´ı et al.: Proper motions of young stars in Chamaeleon T a b l e . U C A C r op e r m o ti on s f o r ca nd i d a t e m e m b e r s o f t h e C h a m ae l e ond a r k c l oud s fr o m t h e lit e r a t u r e M A SS J O t h e r n a m e s U C A C µ α c o s δ µ δ R pho t I pho t J HK R e f . ( a ) N o t e s ( b ) ( m a s / y r)( m a s / y r) m a g m a g m a g m a g m a g C h a m ae l e on I C l oud11094646 - C - - - . ± . . ± . . . . ± . . ± . . ± . C C h a m ae l e on II C l oud12482571 - I R A S - - - . ± . . ± . . . . ± . . ± . . ± . R - [ V C E ] C - - . ± . . ± . . . . ± . . ± . . ± . R - [ V C E ] C - - . ± . . ± . . . . ± . . ± . . ± . R - I R A S - , I s o - C h a II - . ± . . ± . . . . ± . . ± . . ± . R - [ V C E ] X - - . ± . . ± . . . . ± . . ± . . ± . R - [ V C E ] X - - . ± . - . ± . . . . ± . . ± . . ± . R - [ V C E ] C - - . ± . . ± . . . . ± . . ± . . ± . R N o t e s . a R e f e r e n ce s : ) L uh m a n e t a l . ( ) ; S p ezz i e t a l . ( ) ; V uong e t a l . ( ) b N o t e s : C = c on fi r m e d a s p r ob a b l e k i n e m a ti ca l m e m b e r ; R = r e j ec t e d ca nd i d a t e ( p r op e r m o ti onno t c on s i s t e n t w it h m e m b e r s h i p ) . Table 9.
Space velocities for members and candidate members of the Chamaeleon associations.
Name
U V W U
LSR V LSR W LSR
Notes(km / s) (km / s) (km / s) (km / s) (km / s) (km / s)Chamaeleon I cloudT3A − ± − ± − ± − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − ± − ± − ± − − − ± − ± − ± − − ± − ± − ± − − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − − ± − ± − ± − − ± − ± − ± − − − σ ) 7.0 (3.8) − − − − − ± − ± ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − − ± − ± ± − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − σ ) 10.7 (11.4) − − − (cid:15) Chamaeleontis clusterCM Cha 9.6 ± − ± ± − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − − σ ) 12.1 (2.4) − − − − η Chamaeleontis clusterEG Cha 9.5 ± − ± − ± − − ± − ± − ± − ± − ± − ± − − ± − ± − ± − − ± − ± − ± − ± − ± − ± − − ± − ± − ± − − − ± − ± − ± − − − ± − ± − ± − − ± − ± ± − ± − ± ± − ± − ± ± − σ ) 11.2 (2.3) − − − Notes. (1) The distance inferred from the Hipparcos parallax (Table 5) was used in the calculation.(2) Assuming the distance to (cid:15)
Cha for this star, the following space velocities are obtained ( U , V , W ) = (2 . ± . , − . ± . , − . ± .
2) km / s(3) If the distance to Cha II is assumed for this object, the resulting space velocities are ( U , V , W ) = (20 . ± . , − . ± . , . ± .
7) km / s(4) With a parallax π = . ± .
31, we obtain for this star ( U , V , W ) = (1 . ± . , − . ± . , − . ± .
7) km / s(5) Assuming the distance to Cha II for this star, we obtain ( U , V , W ) = (14 . ± . , − . ± . , − . ± .
6) km / s 23el´en L´opez Mart´ı et al.: Proper motions of young stars in Chamaeleon Table 10.
Table 10: Physical parameters for kinematic members of the Chamaeleon clouds a ef f L bol K LsunChamaeleon I Cloud11022491-7733357 II 4205 1.211023265-7729129 II 3415 0.1711025504-7721508 II 3198 0.08111035682-7721329 III 3342 0.2111040909-7627193 II 4350 0.9511045100-7625240 III 3955 0.3511045285-7625514 III 3596 0.2611051467-7711290 III 3379 0.3111055261-7618255 III 3632 0.3511061540-7721567 III 5770 16.011064346-7726343 III 3415 0.4211064510-7727023 II 4205 1.111065906-7718535 II 3234 0.1111071148-7746394 III 3415 0.3411071915-7603048 III 3488 0.2411072074-7738073 II 5860 12.011074366-7739411 II 3850 1.411075588-7727257 III 4205 4.011075792-7738449 Flat 4205 2.411080148-7742288 II 3955 3.011080329-7739174 II 10010 70.011081648-7744371 III 3306 0.1511083905-7716042 II 3955 0.5311084069-7636078 III 3488 0.7411085464-7702129 II 3778 0.3411091769-7627578 III 4060 1.111092379-7623207 II 4205 0.5311094006-7628391 III 3669 0.6811095407-7629253 II 3560 0.4811095873-7737088 II 3669 0.8411100469-7635452 II 3705 0.4311100704-7629376 II 3850 1.411101141-7635292 II 4278 1.211103801-7732399 II 4730 2.611105333-7634319 II 3306 0.1311113474-7636211 III 3488 0.2111114632-7620092 II 4205 1.311115400-7619311 III 3488 0.3611122441-7637064 II 4660 1.011122772-7644223 II 5410 5.011124268-7722230 II 5520 4.211124299-7637049 III 4470 0.6111132446-7629227 II 3342 0.07311132737-7634165 III 3451 0.2411132970-7629012 III 3234 0.08911141565-7627364 III 3306 0.1511145031-7733390 III 3451 0.24Chamaeleon II Cloud12571172-7640111 II 3850 1.3813005323-7654151 II 3777 0.2013005532-7710222 II 3415 1.1513005534-7708296 III 3687 0.35513015891-7751218 II 3955 0.4413030444-7707027 III 3850 1.2613045571-7739495 II 3850 1.04713052072-7739015 II 4350 1.9513063053-7734001 II 3560 0.12513070922-7730304 II 4060 0.8913072241-7737225 III 3705 0.2913080628-7755051 II 4350 1.17513095036-7757240 II 3487 0.3313100415-7710447 II 3415 0.23
Notes. a References: Luhman et al. (2008); Alcal´a et al. (2008); Spezzi et al. (2008)24el´en L´opez Mart´ı et al.: Proper motions of young stars in Chamaeleon , Online Material p 1
Table 4.
Compiled photometry for Chamaeleon I and II members.Cloud 2MASS J Filter λ ef f Flux Flux error(Å) (erg / cm / s / Å) (erg / cm / s / Å)ChaI 10463795-7736035 GALEX / GALEX.FUV 1542.3 2.409492947054E-16 1.3892712556971E-17ChaI 10463795-7736035 GALEX / GALEX.NUV 2274.4 7.1026990635684E-15 3.8503326252756E-17ChaI 10463795-7736035 TYCHO / TYCHO.B 4280.0 5.7787397363199E-13 1.4370523170994E-14ChaI 10463795-7736035 TYCHO / TYCHO.V 5340.0 6.7712367865798E-13 1.2473079108729E-14ChaI 10463795-7736035 DENIS / DENIS.I 7862.1 2.8492382854225E-13 2.0993963527685E-14ChaI 10463795-7736035 2MASS / / / / WISE.W1 33156.6 8.674311371174E-15 2.1571207259674E-16ChaI 10463795-7736035 WISE / WISE.W2 45645.0 2.5436716474833E-15 4.6856163335733E-17ChaI 10463795-7736035 AKARI / IRC.S9W 82283.6 3.304074731026E-16 3.9850807530467E-17ChaI 10463795-7736035 WISE / WISE.W3 107868.4 6.8415691439533E-17 1.0082108879075E-18ChaI 10463795-7736035 WISE / WISE.W4 219149.6 5.4364535147677E-18 4.0557985702824E-19ChaI 10555973-7724399 GALEX / GALEX.FUV 1542.3 3.4666792373282E-17 6.336030288325E-18ChaI 10555973-7724399 GALEX / GALEX.NUV 2274.4 2.5294576603161E-17 3.2778926195947E-18...