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J/A+A/601/A97       Gaia-ESO Survey: Cha I members                (Sacco+, 2017)

The Gaia-ESO Survey: Structural and dynamical properties of the young cluster Chamaeleon I. Sacco G.G., Spina L., Randich S., Palla F., Parker R.J., Jeffries R. D., Jackson R., Meyer M.R., Mapelli M.,Lanzafame A.C., Bonito R., Damiani F., Franciosini E., Frasca A., Klutsch A., Prisinzano L., Tognelli E., Degl'Innocenti S., Prada Moroni P.G., Alfaro E.J., Micela G., Prusti T., Barrado D., Biazzo K., Bouy H., Bravi L., Lopez-Santiago J., Wright N.J., Bayo A., Gilmore G., Bragaglia A., Flaccomio E., Koposov S.E., Pancino E., Casey A.R. Costado M.T., Donati P., Hourihane A., Jofre P., Lardo C., Lewis J., Magrini L., Monaco L., Morbidelli L., Sousa S.G., Worley C.C., Zaggia S. <Astron. Astrophys. 601, A97 (2017)> =2017A&A...601A..97S (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Radial velocities ; Effective temperatures; Stars, masses Keywords: stars: kinematics and dynamics - stars: pre-main sequence - open clusters and associations: individual: Chamaeleon I - techniques: spectroscopic Abstract: Investigating the physical mechanisms driving the dynamical evolution of young star clusters is fundamental to our understanding of the star formation process and the properties of the Galactic field stars. The young (∼2Myr) and partially embedded cluster Chamaeleon I is one of the closest laboratories to study the early stages of star cluster dynamics in a low-density environment. The aim of this work is to study the structural and kinematical properties of this cluster combining parameters from the high-resolution spectroscopic observations of the Gaia-ESO Survey with data from the literature. Our main result is the evidence of a large discrepancy between the velocity dispersion (σstars=1.14±0.35km/s) of the stellar population and the dispersion of the pre-stellar cores (∼0.3km/s) derived from submillimeter observations. The origin of this discrepancy, which has been observed in other young star clusters is not clear. It has been suggested that it may be due to either the effect of the magnetic field on the protostars and the filaments, or to the dynamical evolution of stars driven by two-body interactions. Furthermore, the analysis of the kinematic properties of the stellar population put in evidence a significant velocity shift (∼1∼km/s) between the two sub-clusters located around the North and South main clouds of the cluster. This result further supports a scenario, where clusters form from the evolution of multiple substructures rather than from a monolithic collapse.Using three independent spectroscopic indicators (the gravity indicator γ, the equivalent width of the Li line at 6708Å, and the Hα 10% width), we performed a new membership selection. We found six new cluster members all located in the outer region of the cluster, proving that Chamaeleon I is probably more extended than previously thought. Starting from the positions and masses of the cluster members, we derived the level of substructure Q, the surface density Σ and the level of mass segregation ΛMSR of the cluster. The comparison between these structural properties and the results of N-body simulations suggests that the cluster formed in a low density environment, in virial equilibrium or supervirial, and highly substructured. Description: Table 1 lists the properties of the members of the young clusters Chamaeleon I observed by the Gaia-ESO Survey. The Table includes the common name to identify each star in the Gaia-ESO catalogue, the coordinates, the parameters used for the membership classification, the spectrograph (GIRAFFE or UVES) used in the observation, and if the star has been previously classified as member of this cluster. Table 2 lists the properties of the stars used for the structural analysis discussed in the paper. The Table includes the coordinates, the effective temperatures, the luminosities, if the parameters of the stars are retrieved from the literature or the Gaia-ESO catalogue and the masses. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 94 120 Members of Cha I observed by the Gaia-ESO Survey table2.dat 38 155 Members of Cha I used for the structural analysis
See also: J/A+A/575/A4 : Activity and accretion in γ Vel and Cha I (Frasca+, 2015) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 18 A18 --- Name Common name of Gaia-ESO targets, HHMMSSss+DDMMSSs 20- 28 F9.5 deg RAdeg Right ascension (J2000) 30- 38 F9.5 deg DEdeg Declination (J2000) 40- 46 F7.2 km/s HRV ? Heliocentric radial velocity (1) 48- 51 F4.2 km/s e_HRV ? Error on heliocentric velocity (1) 53- 56 I4 K Teff ? Effective temperature 58- 61 I4 K e_Teff ? Error on effective temperature 63- 67 F5.3 --- Gamma ? Empirical gravity index (2) 69- 73 F5.3 --- e_Gamma ? Error on empirical gravity index (2) 75- 77 I3 0.1pm EW(Li) ? Equivalent width of the Li line at 607.8nm 79- 81 I3 0.1pm e_EW(Li) ? Error on EW(Li) 83- 85 I3 km/s Ha10 ? Width of the Halpha at 10% of the peak 87- 89 I3 km/s e_Ha10 ? Error on Ha10 91 A1 --- Spec Spectrograph used for the observation (3) 93- 94 A2 --- Memb [YNS ] Membership flag (4)
Note (1): Radial Velocities and their errors derived from the Gaia-ESO spectra as described in Jackson et et al. (2015A&A...580A..75J, Cat. J/A+A/580/A75) for GIRAFFE spectra and Sacco et al. (2014A&A...565A.113S) for UVES spectra. Note (2): Empirical gravity indexes and their errors measured from GIRAFFE HR15N spectra (647-679nm) as described in Damiani et al. (2014A&A...566A..50D, Cat. J/A+A/566/A50) Note (3): Spectrograph used in the observation. U for UVES and G for GIRAFFE. Note (4): Flag as follows: Y = star is a known member from the literature N = new member discovered with this work NS = star 10563146-7618334 is likely a new member of the young stellar association epsilon Cha.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right ascension (J2000) 11- 19 F9.5 deg DEdeg Declination (J2000) 21- 25 I5 K Teff Effective temperature 27- 31 F5.2 [Lsun] logLbol Bolometric luminosity (1) 33 A1 --- Prov [GL] Origin of the parameters (2) 35- 38 F4.2 Msun Mass ? Stellar mass
Note (1): Log of the ratio between bolometric luminosity and solar luminosity, assuming a solar bolometric magnitude 4.55mag and a distance of 160pc. Note (2): Origin of the parameters as follows: G = parameters are retrieved by the Gaia-ESO catalogue L = parameters are retrieved by Luhman (2004, Cat. J/ApJ/602/816) and Luhman (2007, Cat. J/ApJS/173/104)
Acknowledgements: Giuseppe Germano Sacco, gsacco(at)arcetri.inaf.it INAF-Osservatorio Astrofisico di Arcetri
(End) Giuseppe Sacco [INAF], Patricia Vannier [CDS] 23-Jan-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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