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 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:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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)
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Note (1): Radial Velocities and their errors derived from the Gaia-ESO spectra
as described in Jackson et et al. (2015A&A...580A..75J 2015A&A...580A..75J, Cat. J/A+A/580/A75)
for GIRAFFE spectra and Sacco et al. (2014A&A...565A.113S 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 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.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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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
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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)
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Acknowledgements:
Giuseppe Germano Sacco, gsacco(at)arcetri.inaf.it
INAF-Osservatorio Astrofisico di Arcetri
(End) Giuseppe Sacco [INAF], Patricia Vannier [CDS] 23-Jan-2017