J/MNRAS/399/2146 Orbits of open clusters in the Galaxy (Wu+, 2009)
The orbits of open clusters in the Galaxy.
Wu Z.-Y., Zhou X., Ma J., Du C.-H.
<Mon. Not. R. Astron. Soc., 399, 2146-2164 (2009)>
=2009MNRAS.399.2146W 2009MNRAS.399.2146W
ADC_Keywords: Clusters, open ; Radial velocities ; Proper motions ;
Space velocities
Keywords: Galaxy: disc - Galaxy: kinematics and dynamics -
open cluster and associations: general
Abstract:
We present and analyse the kinematics and orbits for a sample of 488
open clusters (OCs) in the Galaxy. The velocity ellipsoid for our
present sample is derived as (σ(U),σ(V),σ(W)) =
(28.7, 15.8, 11.0)km/s which represents a young thin-disc population.
We also confirm that the velocity dispersions increase with the age
of a cluster subsample. The orbits of OCs are calculated with three
Galactic gravitational potential models. The errors of orbital
parameters are also calculated considering the intrinsic variation of
the orbital parameters and the effects of observational uncertainties.
The observational uncertainties dominate the errors of derived orbital
parameters. The vertical motions of clusters calculated using
different Galactic disc models are rather different. The observed
radial metallicity gradient of clusters is derived with a slope of
b=-0.070±0.011dex/kpc. The radial metallicity gradient of clusters
based on their apogalactic distances is also derived with a slope
of b=-0.082±0.014dex/kpc. The distribution of derived orbital
eccentricities for OCs is very similar to that derived for the field
population of dwarfs and giants in the thin disc.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 98 488 The observed data of 488 OCs in our sample
table2.dat 89 488 The present positions and velocities of 488 OCs
in our sample
table4.dat 98 488 *The orbital parameters and their errors of
488 OCs in our sample
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Note on table4.dat: calculated with the Allen and Santillan
(1991RMxAA..22..255A 1991RMxAA..22..255A) model.
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See also:
B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Cluster name
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 26 I2 s RAs Right ascension (J2000)
28 A1 --- DE- Declination sign (J2000)
29- 30 I2 deg DEd Declination (J2000)
32- 33 I2 arcmin DEm Declination (J2000)
35- 36 I2 arcsec DEs Declination (J2000)
38- 43 F6.3 kpc Dist Heliocentric distance
45- 49 F5.3 kpc e_Dist rms uncertainty on Dist
51- 56 F6.1 km/s RV Radial velocity
58- 61 F4.1 km/s e_RV rms uncertainty on RV
63- 68 F6.2 mas/yr pmRA Absolute proper motion along RA (pmRA*cosDE)
70- 73 F4.2 mas/yr e_pmRA rms uncertainty on pmRA
75- 80 F6.2 mas/yr pmDE Absolute proper motion along DE
82- 85 F4.2 mas/yr e_pmDE rms uncertainty on pmDE
87- 92 F6.1 Myr Age ? Cluster age
94- 98 F5.2 [Sun] [Fe/H] ? Cluster metallicity
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Cluster name
19- 25 F7.3 kpc Xpos X coordinate in Galactic Plane
27- 31 F5.3 kpc e_Xpos rms uncertainty on Xpos
33- 38 F6.3 kpc Ypos Y coordinate in Galactic Plane
40- 44 F5.3 kpc e_Ypos rms uncertainty on Ypos
46- 51 F6.3 kpc Zpos Z coordinate above Galactic Plane
53- 57 F5.3 kpc e_Zpos rms uncertainty on Zpos
59- 64 F6.1 km/s Uvel U velocity
66- 69 F4.1 km/s e_Uvel rms uncertainty on Uvel
71- 75 F5.1 km/s Vvel V velocity
77- 79 F3.1 km/s e_Vvel rms uncertainty on Vvel
81- 85 F5.1 km/s Wvel W velocity
87- 89 F3.1 km/s e_Wvel rms uncertainty on Wvel
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Cluster name
19- 22 F4.1 kpc Ra Apogalactic distance
24- 27 F4.1 kpc e_Ra rms uncertainty on Ra
29- 32 F4.1 kpc Rp Perigalactic distance
34- 36 F3.1 kpc e_Rp rms uncertainty on Rp
38- 41 F4.2 --- e Orbital eccentricity
43- 46 F4.2 --- e_e rms uncertainty on e
48- 52 F5.2 kpc zmax Maximum distance above the Galactic plane
54- 58 F5.2 kpc e_zmax rms uncertainty on zmax
60- 65 F6.1 Myr Tp Orbital period
67- 71 F5.1 Myr e_Tp rms uncertainty on Tp Tp
73- 77 F5.1 Myr Tz Mean time interval of the cluster to cross
the Galactic plane from one zmax to the
other in the opposite direction
79- 83 F5.1 Myr e_Tz rms uncertainty on Tz
85- 91 F7.1 kpc.km/s Jz z-component of the angular momentum vector (1)
93- 98 F6.1 kpc.km/s e_Jz rms uncertainty on Jz
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Note (1): Because of the right-handed orientation of the coordinate system
adopted here, the negative Jz of the z-component of the angular
momentum vector corresponds to prograde rotation in the Galaxy
and vice versa.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 12-Aug-2011