J/A+A/583/A76 Omega Cen candidates RAVE-selected (Fernandez-Trincado+, 2015)
RAVE stars tidally stripped or ejected from the Omega Centauri globular cluster.
Fernandez-Trincado J.G., Robin A.C., Vieira K., Moreno E., Bienayme O.,
Reyle C., Valenzuela O., Pichardo B., Robles-Valdez F., Martins A.M.M.
<Astron. Astrophys. 583, A76 (2015)>
=2015A&A...583A..76F 2015A&A...583A..76F (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Space velocities ; Radial velocities ;
Abundances
Keywords: stars: abundances - stars: kinematics and dynamics -
Galaxy: structure - globular clusters: individual: omega Centauri
Abstract:
Using six-dimensional phase-space information from the Fourth Data
release of the RAdial Velocity Experiment (RAVE) over the range of
Galactic longitude 240°<l<360° and VLSR←239km/s, we computed
orbits for 329 RAVE stars that were originally selected as chemically
and kinematically related to Omega Centauri. The orbits were
integrated in a Milky-Way-like axisymmetric Galactic potential,
ignoring the effects of the dynamical evolution of Omega Centauri due
to the tidal effects of the Galaxy disk on the cluster along time. We
also ignored secular changes in the Milky Way potential over time. In
a Monte Carlo scheme, and under the assumption that the stars may have
been ejected with velocities greater than the escape velocity
(Vrel>Vesc,0) from the cluster, we identified 15 stars as having
close encounters with Omega Centauri: (i) 8 stars with relative
velocities Vrel<200km/s may have been ejected ∼200Myr ago from
Centauri; (ii) another group of 7 stars were identified with high
relative velocity Vrel>200km/s during close encounters, and it seems
unlikely that they were ejected from Omega Centauri. We also confirm
the link between J131340.4-484714 as a potential member of Omega
Centauri, and probably ejected ∼2.0Myr ago, with a relative velocity
Vrel∼80km/s.
Description:
The sample was selected from the RAVE DR4 catalog (Kordopatis et al.,
2013, Cat. III/272), which provides accurate radial velocities with
typical errors of σRV∼2km/s, and distances and individual
abundances with errors of about 10-20%, determined for approximately
390000 relatively bright stars (9mag<IDENIS<13mag). The proper
motions on RAVE DR4 were compiled from several catalogs, however, in
this work we use UCAC4 (Zacharias et al., 2013, Cat. I/322). We used
these data to make a kinematical selection of RAVE stars possibly
related to omega Centauri, also taking spatial distribution and
metallicity into account, as well as some additional quality control
cuts to select robust data.
In this work we restricted our study to RAVE stars with Galactic
longitudes 240°<l<360°, where Omega Centauri's remnant
candidates have been found (e.g., Majewski et al.,
2012ApJ...747L..37M 2012ApJ...747L..37M). We restricted our sample to giant stars, with
effective temperature between 4000-5500K, and surface gravity
0.5dex<log(g)<3.5dex, following Boeche et al. (2011, Cat.
J/AJ/142/193). Additionally, we required the stars to have high
quality spectra (χ2<2000) with a signal-to-noise ratio S/N>20
(algo_conv=0 was required, indicating that the pipeline converges, see
Kordopatis et al., 2013, Cat. III/272). This cut allowed us to obtain
precise radial velocity measurements, typically σRV<2km/s, in
order to constraint the full space motion. The metallicity [Fe/H]
distribution for giant stars within Omega Centauri spans more than a
magnitude order, from -2.2dex<[Fe/H]←0.7dex (Johnson & Pilachowski,
2010, Cat. J/ApJ/722/1373), therefore we allowed stars in our sample
to be in this range of metallicity.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 153 329 Omega Centauri candidates selected from RAVE catalog,
their abundance ratios, and space velocities
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See also:
III/272 : RAVE 4th data release (Kordopatis+, 2013)
J/AJ/142/193 : RAVE stellar elemental abundances (DR1) (Boeche+, 2011)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name RAVE ID, JHHMMSS.s+DDMMSS
18- 19 I2 h RAh Right ascension (J2000)
21- 22 I2 min RAm Right ascension (J2000)
24- 28 F5.2 s RAs Right ascension (J2000)
30 A1 --- DE- Declination sign (J2000)
31- 32 I2 deg DEd Declination (J2000)
34- 35 I2 arcmin DEm Declination (J2000)
37- 40 F4.1 arcsec DEs Declination (J2000)
42- 47 F6.1 K Teff Effective temperature Teff_K
49- 52 F4.2 [cm/s2] logg Surface gravity logg_K
54- 58 F5.2 [-] [Al/H] ?=- Al abundance
60- 64 F5.2 [-] [Si/H] ?=- Si abundance
66- 70 F5.2 [-] [Fe/H] ?=- Fe abundance
72- 76 F5.2 [-] [Ti/H] ?=- Ti abundance
78- 82 F5.2 [-] [Ni/H] ?=- Ni abundance
84- 88 F5.2 [-] [Mg/H] ?=- Mg abundance
90- 95 F6.1 km/s Uvel LSR U velocity
97-101 F5.1 km/s e_Uvel rms uncertainty on Uvel
103-108 F6.1 km/s Vvel LSR V velocity
110-114 F5.1 km/s e_Vvel rms uncertainty on Vvel
116-122 F7.1 km/s Wvel LSR W velocity
124-128 F5.1 km/s e_Wvel rms uncertainty on Uvel
130-133 F4.1 kpc Dist Distance
135-137 F3.1 kpc e_Dist rms uncertainty on Dist
139-144 F6.1 km/s HRV Heliocentric radial velocity
146-148 F3.1 km/s e_HRV rms uncertainty on HRV
150-153 I4 --- Flag Number of Monte Carlo samples with close
encounters within 0.2Gyr at less than
100pc with a relative velocity less than
200km/s at an axisymmetric Galactic potential
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Acknowledgements:
Jose Fernandez-Trincado, jfernandez(at)obs-besancon.fr
(End) Patricia Vannier [CDS] 03-Nov-2015