J/A+A/567/A69 Radial velocity and photometry in NGC 4372 (Kacharov+, 2014)
A study of rotating globular clusters.
The case of the old, metal-poor globular cluster NGC 4372.
Kacharov N., Bianchini P., Koch A., Frank M.J., Martin N.F., van de Ven G.,
Puzia T.H., McDonald I., Johnson C.I., Zijlstra A.A.
<Astron. Astrophys. 567, A69 (2014)>
=2014A&A...567A..69K 2014A&A...567A..69K
ADC_Keywords: Clusters, globular ; Photometry, UBVRI ; Reddening ;
Radial velocities
Keywords: Globular clusters: general - Globular clusters: individual: NGC4372 -
Galaxy: halo - Galaxy: kinematics and dynamics
Abstract:
We present the first in-depth study of the kinematic properties and
derive the structural parameters of NGC 4372 based on the fit of a
Plummer profile and a rotating, physical model. We explore the link
between internal rotation to different cluster properties and together
with similar studies of more GCs, we put these in the context of
globular cluster formation and evolution. We present radial velocities
for 131 cluster member stars measured from high-resolution
FLAMES/GIRAFFE observations. Their membership to the GC is
additionally confirmed from precise metallicity estimates. Using this
kinematic data set we build a velocity dispersion profile and a
systemic rotation curve. Additionally, we obtain an elliptical number
density profile of NGC 4372 based on optical images using a MCMC
fitting algorithm. From this we derive the cluster's half-light radius
and ellipticity as rh=3.4'±0.04' and e=0.08±0.01. Finally, we
give a physical interpretation of the observed morphological and
kinematic properties of this GC by fitting an axisymmetric,
differentially rotating, dynamical model. Our results show that NGC
4372 has an unusually high ratio of rotation amplitude to velocity
dispersion (1.2 vs. 4.5km/s) for its metallicity. This, however, puts
it in line with two other exceptional, very metal-poor GCs - M 15 and
NGC 4590. We also find a mild flattening of NGC 4372 in the direction
of its rotation. Given its old age, this suggests that the flattening
is indeed caused by the systemic rotation rather than tidal
interactions with the Galaxy. Additionally, we estimate the dynamical
mass of the GC M_dyn=2.0±0.5 x 10^5 M_Sun based on the dynamical
model, which constrains the mass-to-light ratio of NGC 4372 between
1.4 and 2.3 MSun/LSun, representative of an old, purely stellar
population.
Description:
We present the radial velocities of 220 stars in the field of the
globular cluster NGC 4372 measured from high resolution FLAMES/GIRAFFE
spectra. We have confirm 131 cluster member stars from radial velocity
and metallicity constraints. The rest are foreground contaminants. We
also present a BVI photometric catalogue in a field of view covering
30x30arcmin, centred on NGC 4372. We used archival imaging obtained
with the Wide Field Imager (WFI) at the 2.2m MPG/ESO telescope at La
Silla. We used the 2MASS point source catalog as astrometric
reference. Photometric zero points were fixed to standard stars in the
same field from the standard star database of Stetson
(2000PASP..112..925S 2000PASP..112..925S, 2005PASP..117..563S 2005PASP..117..563S). We have estimated
individual reddening for each star in the catalogue.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
kinemat.dat 60 220 Star positions and radial velocities
photom.dat 72 64410 Photometric catalog
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See also:
J/ApJ/420/612 : Proper motions + radial velocities in M22 (Peterson+ 1994)
J/ApJ/602/264 : Proper motions + radial velocities in M15 (Mcnamara+, 2004)
J/A+A/417/597 : Radial velocities in 4 globulars (Recio-Blanco+, 2004)
J/AJ/130/2140 : Abundances + velocities in globular clusters (Pritzl+, 2005)
J/A+A/462/L9 : Radial velocities in NGC 7099 (Scarpa+, 2007)
J/AJ/140/1119 : Radial velocities of NGC 5466 members (Shetrone+, 2010)
J/A+A/525/A148 : Radial velocities in two globular clusters (Scarpa+, 2011)
J/A+A/528/A127 : Radial velocities in NGC 2808 (Moni Bidin+, 2011)
J/A+A/566/A58 : Radial velocities in M3, M13, and M92 (Kamann+, 2014)
J/MNRAS/423/2917 : Radial velocities in Pal 4 (Frank+, 2012)
J/MNRAS/426/1137 : Radial velocities in NGC 1851 (Sollima+, 2012)
J/ApJ/754/91 : Abundances and velocities of NGC 6397 stars (Lovisi+, 2012)
Byte-by-byte Description of file: kinemat.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- ID Star identification
8- 9 I2 h RAh Right ascension (J2000.0)
11- 12 I2 min RAm Right ascension (J2000.0)
14- 18 F5.2 s RAs Right ascension (J2000.0)
20 A1 --- DE- Declination sign (J2000.0)
21- 22 I2 deg DEd Declination (J2000.0)
24- 25 I2 arcmin DEm Declination (J2000.0)
27- 31 F5.2 arcsec DEs Declination (J2000.0)
33- 43 F11.9 deg Dist Radial distance from the cluster centre
45- 50 F6.2 km/s RV Radial velocity
52- 56 F5.2 km/s e_RV Uncertainty of the radial velocity
58- 60 A3 --- Mmb [yes/no ] Is the star a cluster member?
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Byte-by-byte Description of file: photom.dat
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Bytes Format Units Label Explanations
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1- 13 F13.9 deg RAdeg Right ascension (J2000.0)
15- 27 F13.9 deg DEdeg Declination (J2000.0)
29- 34 F6.2 mag Bmag ?=105.50 B-band magnitude
36- 40 F5.2 mag e_Bmag ?=10.00 B-band magnitude uncertainty
42- 46 F5.2 mag Vmag V-band magnitude
48- 51 F4.2 mag e_Vmag V-band magnitude uncertainty
53- 57 F5.2 mag Imag I-band magnitude
59- 62 F4.2 mag e_Imag I-band magnitude uncertainty
64- 67 F4.2 mag E(V-I) Individual reddening E(V-I) (1)
69- 72 F4.2 mag E(B-V) Individual reddening E(B-V) (1)
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Note (1): Av=2.2E(V-I)=3.1E(B-V).
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Acknowledgements:
Nikolay Kacharov, nkacharo(at)lsw.uni-heidelberg.de
(End) N. Kacharov [LSW Heidelberg, Germany], P. Vannier [CDS] 20-Jun-2014