J/A+AS/93/311 Relative proper motions in NGC 362 (Tucholke 1992)
Astrometry of globular clusters.
II. Relative proper motions and the space motion of NGC 362.
TUCHOLKE H.J.
<Astron. Astrophys. Suppl. Ser. 93, 311 (1992)>
=1992A&AS...93..311T 1992A&AS...93..311T
ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Positional data
Keywords: clusters: globular: NGC 362 - astrometry - galaxies: Magellanic Clouds
Abstract:
Relative proper motions are determined for stars brighter than
B~=17mag in a 1.5°x1.5° field centered on the globular cluster
NGC 362. Proper motions and membership probabilities are tabulated for
488 stars within 10.2' of the cluster center. 14 astrographic plates
with epoch differences up to 92 years were completely scanned, and
each detectable object was stored. Proper motions were computed with
an iterative central-overlap technique. A modal proper motion accuracy
of 0.9 milliarcsec/year (mas/a) was achieved. NGC 362 appears
projected onto the Small Magellanic Cloud (SMC), allowing to measure
the proper motion of the cluster relative to extragalactic background
stars. SMC stars were identified by position, proper motion and
colour; the mean proper motion of these SMC candidates agrees well
with the proper motions of SMC members known from the literature. The
proper motion of NGC 362 relative to the SMC is +3.5±0.8mas/a in
right ascension and -2.6±0.8mas/a in declination. For reasonable
assumptions on the absolute proper motion of the SMC, the absolute
proper motion and space motion of NGC 362 are computed. NGC 362
exhibits a highly eccentric orbit, typical for a member of the halo
subgroup of the galactic globular cluster system. The perigalactic
distance of NGC 362 is very small (≲1kpc), which raises the
interesting question of how the cluster can survive the many passages
near the galactic bulge over its lifetime.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 98 488 NGC 362 stars
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- N Running number
6- 13 A8 --- Id Identifier:
Prefix A: Alcaino, 1976A&AS...26..359A 1976A&AS...26..359A
No prefix: Harris, 1982ApJS...50..573H 1982ApJS...50..573H
15- 19 F5.2 mag Bmag ? Magnitude in B (± 0.25 mag)
20 A1 --- u_Bmag Uncertainty flag on Bmag
22- 26 F5.2 mag B-R ? Color index (± 0.40 mag)
27 A1 --- u_B-R Uncertainty flag on B-R
29- 35 F7.1 pix x Relative position to adopted cluster centre
(1 pixel = 0.7695 arcsec)
37- 43 F7.1 pix y Relative position to adopted cluster centre
(1 pixel = 0.7695 arcsec)
45- 50 F6.1 mas/a pmRA Proper motion in RA (mu_alpha.cos(delta))
52- 54 F3.1 mas/a e_pmRA Error on pmRA
56- 61 F6.1 mas/a pmDE Proper motion in Dec
63- 65 F3.1 mas/a e_pmDE Error on pmDE
67 I1 --- N1 Number of first-epoch plates
68 I1 --- N2 Number of second-epoch plates
70- 73 F4.1 % Pr Membership probability
75 I1 h RAh Right Ascension 1950 (hours)
(Epoch 1985.5, Perth-70-System, ± 0.4")
77- 78 I2 min RAm Right Ascension 1950 (minutes)
80- 85 F6.3 s RAs Right Ascension 1950 (seconds)
87 A1 --- DE- Declination 1950 (sign)
(Epoch 1985.5, Perth-70-System, ± 0.4")
88- 89 I2 deg DEd Declination 1950 (degrees)
91- 92 I2 arcmin DEm Declination 1950 (minutes)
94- 98 F5.2 arcsec DEs Declination 1950 (seconds)
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(End) Francois Ochsenbein [CDS] 09-Apr-1993