J/MNRAS/434/194 UBVI photometry in NGC 1252 (de la Fuente Marcos+, 2013)
NGC 1252: a high altitude, metal poor open cluster remnant.
de la Fuente Marcos R., de la Fuente Marcos C., Moni Bidin C., Carraro G.,
Costa E.
<Mon. Not. R. Astron. Soc., 434, 194-208 (2013)>
=2013MNRAS.434..194D 2013MNRAS.434..194D
ADC_Keywords: Clusters, open ; Photometry, UBVRI
Keywords: stars: individual: HD 20286 - stars: individual: NGC 1252 17 -
stars: individual: NGC 1252 21 - stars: individual: TW Hor -
open clusters and associations: general -
open clusters and associations: individual: NGC 1252
Abstract:
If stars form in clusters but most stars belong to the field,
understanding the details of the transition from the former to the
latter is imperative to explain the observational properties of the
field. Aging open clusters are one of the sources of field stars. The
disruption rate of open clusters slows down with age but, as an object
gets older, the distinction between the remaining cluster or open
cluster remnant (OCR) and the surrounding field becomes less and less
obvious. As a result, finding good OCR candidates or confirming the
OCR nature of some of the best candidates still remain elusive. One of
these objects is NGC 1252, a scattered group of about 20 stars in
Horologium. Here we use new wide-field photometry in the UBVI
passbands, proper motions from the Yale/San Juan SPM 4.0 catalogue and
high-resolution spectroscopy concurrently with results from N-body
simulations to decipher NGC 1252's enigmatic character. Spectroscopy
shows that most of the brightest stars in the studied area are
chemically, kinematically and spatially unrelated to each other.
However, after analysing proper motions, we find one relevant
kinematic group. This sparse object is relatively close (∼1kpc), metal
poor and is probably not only one of the oldest clusters (3Gyr) within
1.5kpc from the Sun but also one of the clusters located farthest from
the disc, at an altitude of nearly -900pc. That makes NGC 1252 the
first open cluster that can be truly considered a high Galactic
altitude OCR: an unusual object that may hint at a star formation
event induced on a high Galactic altitude gas cloud. We also conclude
that the variable TW Horologii and the blue straggler candidate
HD 20286 are unlikely to be part of NGC 1252. NGC 1252 17 is
identified as an unrelated, Population II cannonball star moving at
about 400km/s.
Description:
The region of interest (20x20arcmin2 area enclosed by the square
in Fig. 1) was observed with the Y4KCAM camera attached to the Cerro
Tololo Inter-American Observatory (CTIO) 1-m telescope, operated by
the Small and Moderate Aperture Research Telescope System (SMARTS)
consortium.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ngc1252.dat 102 356 NGC 1252 photometry
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Byte-by-byte Description of file: ngc1252.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Sequential number
5- 14 F10.7 deg RAdeg Right ascension (J2000)
16- 26 F11.7 deg DEdeg Declination (J2000)
28- 34 F7.4 mag Vmag Johnson V magnitude
36- 41 F6.4 mag e_Vmag rms uncertainty on Vmag
43- 49 F7.4 mag U-B Johnson U-B colour index
51- 56 F6.4 mag e_U-B rms uncertainty on U-B
58- 64 F7.4 mag B-V Johnson B-V colour index
66- 71 F6.4 mag e_B-V rms uncertainty on B-V
73- 79 F7.4 mag V-I Johnson-Cousins V-I colour index
81- 86 F6.4 mag e_V-I rms uncertainty on V-I
88- 94 F7.4 --- chi DAOPHOT chi parameter
96-102 F7.4 --- sha DAOPHOT sharpness parameter (0=isolated star)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 29-Jul-2014