J/MNRAS/465/3515 M13 stars radial velocities (Cordero+, 2017)
Differences in the rotational properties of multiple stellar populations in M13:
a faster rotation for the 'extreme' chemical subpopulation.
Cordero M.J., Henault-Brunet V., Pilachowski C.A., Balbinot E.,
Johnson C.I., Varri A.L.
<Mon. Not. R. Astron. Soc., 465, 3515-3535 (2017)>
=2017MNRAS.465.3515C 2017MNRAS.465.3515C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Radial velocities ; Abundances
Keywords: stars: abundances - stars: kinematics and dynamics -
globular clusters: general - globular clusters: individual: M13 -
globular clusters: individual: NGC 6205 -
galaxies: star clusters: general
Abstract:
We use radial velocities from spectra of giants obtained with the WIYN
telescope, coupled with existing chemical abundance measurements of Na
and O for the same stars, to probe the presence of kinematic
differences among the multiple populations of the globular cluster
(GC) M13. To characterize the kinematics of various chemical
subsamples, we introduce a method using Bayesian inference along with
a Markov chain Monte Carlo algorithm to fit a six-parameter kinematic
model (including rotation) to these subsamples. We find that the
so-called extreme population (Na-enhanced and extremely O-depleted)
exhibits faster rotation around the centre of the cluster than the
other cluster stars, in particular, when compared with the dominant
`intermediate' population (moderately Na-enhanced and O-depleted). The
most likely difference between the rotational amplitude of this
extreme population and that of the intermediate population is found to
be 4km/s , with a 98.4 per cent probability that the rotational
amplitude of the extreme population is larger than that of the
intermediate population. We argue that the observed difference in
rotational amplitudes, obtained when splitting subsamples according to
their chemistry, is not a product of the long-term dynamical evolution
of the cluster, but more likely a surviving feature imprinted early in
the formation history of this GC and its multiple populations. We also
find an agreement (within uncertainties) in the inferred position
angle of the rotation axis of the different subpopulations considered.
We discuss the constraints that these results may place on various
formation scenarios.
Description:
The spectra were acquired using the WIYN-Hydra fibre positioner
(R~=18000) on 2011 May 19-20 (Johnson & Pilachowski,
2012ApJ...754...38C 2012ApJ...754...38C, Cat. J/ApJ/754/38) and have a wavelength coverage
ranging from 6050 to 6350Å.
Table 1 presents the identifications from Ludendorf
(1905POPot..50....1L 1905POPot..50....1L, Cat. IV/26) and Kadla (1966IzPul.181...93K 1966IzPul.181...93K, Cat.
II/248), coordinates, V magnitudes, error-weighted average
heliocentric radial velocities, radial velocity errors, chemical
abundance ratios for Na and O from Johnson & Pilachowski
(2012ApJ...754L..38J 2012ApJ...754L..38J, Cat. J/ApJ/754/L38), and a chemical population
classification (see the next section) for a sample of 113 giant stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 63 113 Basic data and derived radial velocities for M13
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See also:
IV/26 : Hercules Messier 13 (M13) photometry (Ludendorff, 1905)
II/248 : UBV photometry and proper motions in M13 (Kadla, 1966)
J/ApJ/754/L38 : Abundances and radial velocities of M13 giants (Johnson+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Star name
9- 18 F10.6 deg RAdeg Right ascension (J2000)
20- 28 F9.6 deg DEdeg Declination (J2000)
30- 34 F5.2 mag Vmag V magnitude
36- 41 F6.1 km/s Mean radial velocity
43- 45 F3.1 km/s e_ rms uncertainty on
47- 51 F5.2 [-] [O/Fe] ?=- Abundance [O/Fe]
53- 57 F5.2 [-] [Na/Fe]LTE ?=- LTE abundance [Na/Fe]
59- 63 A5 --- Pop Population
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Nov-2018