J/A+A/612/A99 Gaia-ESO Survey in 7 open star cluster fields (Randich+, 2018)
The Gaia-ESO Survey: open clusters in Gaia-DR1.
A way forward to stellar age calibration.
Randich S., Tognelli E., Jackson R., Jeffries R.D., Degl'Innocenti S.,
Pancino E., Re Fiorentin P., Spagna A., Sacco G., Bragaglia A.,
Magrini L., Prada Moroni P.G., Alfaro E., Franciosini E., Morbidelli L.,
Roccatagliata V., Bouy H., Bravi L., Jimenez-Esteban F.M., Jordi C.,
Zari E., Tautvaisiene G., Drazdauskas A., Mikolaitis S., Gilmore G.,
Feltzing S., Vallenari A., Bensby T., Koposov S., Korn A., Lanzafame A.,
Smiljanic R., Bayo A., Carraro G., Costado M.T., Heiter U., Hourihane A.,
Jofre P., Lewis J., Monaco L., Prisinzano L., Sbordone L., Sousa S.G.,
Worley C.C., Zaggia S. (Gaia-ESO collaboration)
<Astron. Astrophys. 612, A99 (2018)>
=2018A&A...612A..99R 2018A&A...612A..99R (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Abundances, [Fe/H] ; Effective temperatures ;
Equivalent widths ; Radial velocities ; Rotational velocities ;
Spectroscopy
Keywords: parallaxes - surveys - stars: evolution -
open clusters and associations: general -
Abstract:
Determination and calibration of the ages of stars, which heavily rely
on stellar evolutionary models, are very challenging, while
representing a crucial aspect in many astrophysical areas.
We describe the methodologies that, taking advantage of Gaia-DR1 and
the Gaia-ESO Survey data, enable the comparison of observed open star
cluster sequences with stellar evolutionary models. The final,
long-term goal is the exploitation of open clusters as age
calibrators.
We perform a homogeneous analysis of eight open clusters using the
Gaia-DR1 TGAS catalogue for bright members and information from the
Gaia-ESO Survey for fainter stars. Cluster membership probabilities
for the Gaia-ESO Survey targets are derived based on several
spectroscopic tracers. The Gaia-ESO Survey also provides the cluster
chemical composition. We obtain cluster parallaxes using two methods.
The first one relies on the astrometric selection of a sample of bona
fide members, while the other one fits the parallax distribution of a
larger sample of TGAS sources. Ages and reddening values are recovered
through a Bayesian analysis using the 2MASS magnitudes and three sets
of standard models. Lithium depletion boundary (LDB) ages are also
determined using literature observations and the same models employed
for the Bayesian analysis.
For all but one cluster, parallaxes derived by us agree with those
presented in Gaia Collaboration (2017A&A...601A..19G 2017A&A...601A..19G, Cat.
J/A+A/601/A19), while a discrepancy is found for NGC 2516; we provide
evidence supporting our own determination. Inferred cluster ages are
robust against models and are generally consistent with literature
values.
The systematic parallax errors inherent in the Gaia DR1 data presently
limit the precision of our results. Nevertheless, we have been able to
place these eight clusters onto the same age scale for the first time,
with good agreement between isochronal and LDB ages where there is
overlap. Our approach appears promising and demonstrates the potential
of combining Gaia and ground-based spectroscopic datasets.
Description:
We present spectroscopic parameters of the targets observed by the
Gaia-ESO Survey in seven open star cluster fields. The spectra have
been obtained with FLAMES on the VLT and the UVES or Giraffe
spectrographs. The parameters have been derived by the Gaia-ESO
consortium during the fourth analysis cycle (iDR4). The tables list,
for each cluster, the parameters used for the membership analysis.
Specifically, we include: the star ID; cluster name; instrument (UVES
or Giraffe); stellar parameters (effective temperature, surface
gravity, metallicity) and their errors; equivalent width of the
Li 6707.8Å line and error; a flag indicating if the Li EW is a
detection (flag=0) or an upper limit (flag=1); gamma index and error;
radial and rotational velocities and errors; upper limits in
rotational velocities; membership probabilities. For all clusters but
NGC 2451, Memb(PA) should be considered. For NGC 2451 Memb(PA) and
Memb(PB) should be considered for clusters A and B, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ic2391.dat 158 447 Parameters for IC2391
ic2602.dat 158 1505 Parameters for IC2602
ic4665.dat 158 579 Parameters for IC4665
ngc2451.dat 158 1696 Parameters for NGC2451
ngc2516.dat 158 796 Parameters for NGC2516
ngc2547.dat 158 510 Parameters for NGC2547
ngc6633.dat 158 564 Parameters for NGC6633
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
Byte-by-byte Description of file: ic*.dat ngc*.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- CName Star ID (HHMMSSss+DDMMSSs)
18- 24 A7 --- Cluster Cluster name
26- 32 A7 --- Inst Intrument XX
34- 38 I5 K Teff Effective temperature
40- 43 I4 K e_Teff ?=-999 Effective temperature error
45- 52 F8.3 [cm/s2] logg ?=-999 10-logarithm surface gravity
54- 61 F8.3 [cm/s2] e_logg ?=-999 10-logarithm surface gravity error
63- 70 F8.3 [-] [Fe/H] ?=-999 Metallicity
72- 79 F8.3 [-] e_[Fe/H] ?=-999 Metallicity error
81 A1 --- l_EWLi [<] Upper limit flag on EWLi
82- 89 F8.3 [0.1pm] EWLi ?=-999 Lithium line equivalent width
91- 98 F8.3 [0.1pm] e_EWLi ?=-999 Lithium line equivalent width error
100-103 I4 --- f_EWLi [0/3]?=-999 Flag for lithium line
equivalent width (1)
105-112 F8.3 --- Gamma ?=-999 Gamma index
114-121 F8.3 --- e_Gamma ?=-999 Gamma index error
123-130 F8.3 km/s RV ?=-999 Radial velocity
132-139 F8.3 km/s e_RV ?=-999 Radial velocity error
141-146 F6.3 --- MembPA ?=-1 Membership probability: population A
148-153 F6.3 --- MembPB ?=-1 Membership probability: population B
155-158 I4 --- ID Sequential ID number
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Note (1): Upper limit flag as follows:
0 = not an upper limit
3 = upper limit
-999 = data not available
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Acknowledgements:
Sofia Randich, randich(at)arcetri.astro.it
(End) Patricia Vannier [CDS] 23-Nov-2017