J/A+A/671/A106 Galactic globular cluster stars RVs (Martens+, 2023)
Kinematic differences between multiple populations in Galactic globular
clusters.
Martens S., Kamann S., Dreizler S., Goettgens F., Husser T.-O., Latour M.,
Balakina E., Krajnovic D., Pechetti R., Weilbacher P.M.
<Astron. Astrophys. 671, A106 (2023)>
=2023A&A...671A.106M 2023A&A...671A.106M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Populations, stellar ; Radial velocities ;
Optical
Keywords: globular clusters: general - stars: kinematics and dynamics -
techniques: imaging spectroscopy
Abstract:
The formation process of multiple populations in globular clusters is
still up for debate. Kinematic differences between the populations are
particularly interesting in this respect, because they allow us to
distinguish between single-epoch formation scenarios and multi-epoch
formation scenarios. We analyze the kinematics of 25 globular clusters
and aim to find kinematic differences between multiple populations to
constrain their formation process. We split red-giant branch (RGB)
stars in each cluster into three populations (P1, P2, P3) for the
type-II clusters and two populations (P1 and P2) otherwise using
Hubble photometry. We derive the rotation and dispersion profiles for
each cluster and its populations by using all stars with radial
velocity measurements obtained from MUSE spectroscopy. Based on these
profiles, we calculate the rotation strength in terms of
ordered-over-random motion (v/σ)HL evaluated at the half-light
radius of the cluster. We detect rotation in all but four clusters.
For NGC 104, NGC1851, NGC 2808, NGC 5286, NGC 5904, NGC 6093,
NGC 6388, NGC 6541, NGC 7078 and NGC 7089 we also detect rotation for
P1 and/or P2 stars. For NGC 2808, NGC 6093 and NGC 7078 we find
differences in (v/σ)HL between P1 and P2 that are larger than
1σ. Whereas we find that P2 rotates faster than P1 for NGC 6093
and NGC 7078, the opposite is true for NGC 2808. However, even for
these three clusters, the differences are still of low significance.
We find that the strength of rotation of a cluster generally scales
with its median relaxation time. For P1 and P2, the corresponding
relation is very weak at best. We observe no correlation between the
difference in rotation strength between P1 and P2 and cluster
relaxation time.
Description:
We derived the line-of-sight velocities for stars in 25 globular
clusters from MUSE observations. We exclude spectra of stars that have
a reliability R<0.8 (Giesers et al., 2019A&A...632A...3G 2019A&A...632A...3G, Cat.
J/A+A/632/A3). If a star has been observed multiple times we average
the velocity measurements and exclude stars that show temporal
variation in their line-of-sight velocities. The populations of each
globular cluster are determined from their chromosome maps based on
HUGS photometry. We note that only RGB stars were included in the
population analysis because the chromosome maps are tailored to
distinguish populations at this evolutionary phase. We derived the
membership probability of all stars based their velocities and the
stellar surface density of each cluster. We used Limepy models (Gieles
et al., 2015MNRAS.454..576G 2015MNRAS.454..576G) with parameters for each cluster
determined by de Boer et al., 2019MNRAS.485.4906D 2019MNRAS.485.4906D, Cat.
J/MNRAS/485/4906, but for NGC 6441 and NGC 6522 these parameters were
not available. The membership probabilities for NGC 6441 and NGC 6522
are based on King profiles (King, 1966AJ.....71...64K 1966AJ.....71...64K), which show a
very steep decline in density beyond the halflight radius. Some stars
may be present more than once.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 65 261195 Stellar coordinates and averaged radial
velocities used for this analysis
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See also:
J/AJ/133/1658 : ACS survey of galactic globular clusters (Sarajedini+, 2007)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Cluster name
9- 16 I8 --- ACS Star ID from (Sarajedini+, 2007AJ....133.1658S 2007AJ....133.1658S,
Cat. J/AJ/133/1658)
18- 28 F11.7 deg RAdeg Right ascension (J2000)
30- 40 F11.7 deg DEdeg Declination (J2000)
42- 49 F8.3 km/s RV Averaged line-of-sight stellar velocity
51- 56 F6.3 km/s e_RV Uncertainty of the stellar velocity
58- 62 F5.3 --- PMember Membership probability
64- 65 A2 --- Pop [P1 P2 P3] Population tag
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Acknowledgements:
Sven Martens, sven.martens(at)uni-goettingen.de
(End) Patricia Vannier [CDS] 01-Feb-2023