J/AJ/147/69 Radial velocities in Be 44, Be 81, and NGC 6802 (Hayes+, 2014)
Radial velocities of three poorly studied clusters and the kinematics of open
clusters.
Hayes C.R., Friel E.D.
<Astron. J., 147, 69 (2014)>
=2014AJ....147...69H 2014AJ....147...69H
ADC_Keywords: Clusters, open ; Radial velocities
Keywords: Galaxy: kinematics and dynamics -
open clusters and associations: individual (Be 44, Be 81, NGC 6802)
Abstract:
We present radial velocities for stars in the field of the open star
clusters Berkeley 44, Berkeley 81, and NGC 6802 from spectra obtained
using the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5m telescope. These
clusters are of intermediate age (1-3Gyr), located within the solar
Galactocentric radius, and have no previous radial velocity
measurements. We find mean radial velocities of -9.6±3.0km/s,
48.1±2.0km/s, and 12.4±2.8km/s for Be 44, Be 81, and NGC 6802,
respectively. We present an analysis of radial velocities of 134 open
clusters of a wide range of ages using data obtained in this study and
the literature. Assuming the system of clusters rotates about the
Galactic center with a constant velocity, we find older clusters
exhibit a slower rotation and larger line-of-sight (LOS) velocity
dispersion than younger clusters. The gradual decrease in rotational
velocity of the cluster system with age is accompanied by a smooth
increase in LOS velocity dispersion, which we interpret as the effect
of heating on the open cluster system over time.
Description:
For Berkeley 44, Berkeley 81, and NGC 6802, our data were obtained
using the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5m telescope, the Hydra
multi-fiber positioner, the Bench Spectrograph, and a 2600*4000 pixel
CCD (STA1) on the nights of 2012 May 7, 8, and 9. Spectra cover a
range of about 6082-6397Å.
Additionally, we perform an analysis of the radial velocities of 134
clusters with properties obtained in this paper and from the
literature (Table3).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 54 3 Properties of observed clusters
table2.dat 45 132 Individual stellar velocities and membership
table3.dat 85 134 Cluster properties and mean radial velocities
refs.dat 71 137 References
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See also:
J/MNRAS/437/1241 : Be 81, NGC 1917 and NGC 2141 BVI photometry (Donati+, 2014)
J/AJ/141/92 : BVI photometry of 10 distant open clusters (Janes+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Cluster Cluster name
13 A1 --- Ref [ab] Reference of cluster photometry (1)
15- 19 F5.2 deg GLON [34.51/55.32] Galactic longitude
21- 25 F5.2 deg GLAT [-2.07/3.35] Galactic latitude
27- 30 F4.1 mag (m-M)0 [11.3/12.6] Intrinsic distance modulus
32- 35 F4.2 mag E(B-V) [0.84/1] Reddening
37- 40 I4 pc Dist [1800/3200] Heliocentric distance
42- 44 F3.1 kpc Rgc [5.6/7.1] Galactocentric distance
46- 50 F5.2 kpc Z [-0.12/0.18] Distance from the Galactic Plane
52- 54 F3.1 Gyr Age [1/2.9] Cluster age
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Note (1): Photometric properties were obtained as follows:
a = From Janes & Hoq 2011 (cat. J/AJ/141/92);
b = From Sagar & Griffiths (1998MNRAS.299..777S 1998MNRAS.299..777S).
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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- 11 A11 --- Cluster Cluster name (Berkeley 44, Berkeley 81,
NGC 6802) (1)
13- 17 I5 --- Star [219/79900] Star number in cluster (1)
19 A1 --- f_Star [u] Star ID and photometry unpublished (2)
21- 25 F5.1 km/s RV [-73.6/93.5] Radial velocity
27- 29 F3.1 km/s e_RV Radial velocity uncertainty
31- 35 F5.2 mag Vmag [13.81/16.89] V-band magnitude
37- 40 F4.2 mag B-V The B-V color index
42- 45 A4 --- Mmb Cluster membership status (Yes or No) (3)
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Note (1): For Berkeley 44 and NGC 6802, the star numbers and the photometry
are from Janes & Hoq (2011, Cat. J/AJ/141/92). For Berkeley 81, the
star numbers dans the photometry are from Donati et al. (2014, Cat.
J/MNRAS/437/1241).
Note (2): From uncut photometry of Donati et al. (2014, cat.
J/MNRAS/437/1241) received in private communication (star number in
uncut photometry is 46455).
Note (3): To compute mean cluster velocities, the possible cluster members
must first be determined. To do so, we examined the distributions of
radial velocities in order to find a peak in the distribution of
individual stellar velocities. As the peaks in velocity are well
defined for each cluster, we considered all stars more than 10km/s
from the peak to be non-members ("No"). Any stars within about 5km/s
on either side of the peak were defined as cluster members ("Yes"),
since this range encompassed the primary distribution. Those stars
with radial velocities between 5 and 10km/s from the peak (noted with
a "?") are potential members. See additional details in Section 3.2.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Cluster Cluster name
13- 18 F6.2 deg GLON [2.88/357.94] Galactic longitude
20- 25 F6.2 deg GLAT [-79.26/32.48] Galactic latitude
27- 31 F5.1 km/s [-84/134.3] Cluster mean radial velocity
33- 35 F3.1 km/s e_ Radial velocity error
37- 43 F7.1 pc Dist [45/14500] Heliocentric distance
45- 48 F4.1 kpc Rgc [5.6/22.1] Galactocentric distance
50- 56 F7.4 kpc Z [-1.9/2.017] Distance from the Galactic Plane
58- 62 F5.2 [yr] logAge [6.2/10.1] Log of the cluster age
64- 69 F6.1 km/s RV [-234.4/230.4] Cluster radial velocity (1)
71- 77 F7.4 --- cos(psi) [-1/0.989] Cosine of the angle ψ (1)
79- 85 A7 --- Ref Reference; in refs.dat file
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Note (1): ψ is the angle between the rotational-velocity vector of the
cluster Vrot and the line passing through the cluster and the Sun;
λ is the between the apex of the Local Standard of Rest (LSR)
and the position of the cluster on the sky. With these definitions,
the radial velocity of the cluster is:
RV=Vrotcos(ψ)=VLSR+V_☉cos(λ);
V☉=220km/s(R_☉=8.0kpc).
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Ref Reference identifier
5- 23 A19 --- BibCode Bibliographic code
25- 49 A25 --- Aut Author's name
51- 71 A21 --- Cat VizeR catalog
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 09-Sep-2014