J/A+A/581/A13 VI photometry of globular ESO 37-1 (de la Fuente Marcos+, 2015)
Ghosts of Milky Way's past: the globular cluster ESO 37-1 (E 3).
de la Fuente Marcos R., de la Fuente Marcos C., Moni Bidin C., Ortolani S.,
Carraro G.
<Astron. Astrophys. 581, A13 (2015)>
=2015A&A...581A..13D 2015A&A...581A..13D
ADC_Keywords: Clusters, globular ; Photometry, CCD ; Photometry, VRI
Keywords: globular clusters: general - globular clusters: individual: ESO 37-1 -
Galaxy: halo - Galaxy: structure - Local Group
Abstract:
In the Milky Way, most globular clusters are highly conspicuous
objects that were found centuries ago. However, a few dozen of them
are faint, sparsely populated systems that were identified largely
during the second half of the past century. One of the faintest is
ESO 37-1 (E 3) and as such it remains poorly studied, with no
spectroscopic observations published so far although it was discovered
in 1976.
We investigate the globular cluster E3 in an attempt to better
constrain its fundamental parameters. Spectroscopy of stars in the
field of E3 is shown here for the first time.
Deep, precise VI CCD photometry of E3 down to V∼26mag is
presented and analysed. Low-resolution, medium signal-to-noise ratio
spectra of nine candidate members are studied to derive radial
velocity and metallicity. Proper motions from the UCAC4 catalogue are
used to explore the kinematics of the bright members of E3.
Isochrone fitting indicates that E3 is probably very old, with an age
of about 13Gyr; its distance from the Sun is nearly 10kpc. It is
also somewhat metal rich with [Fe/H]=-0.7. Regarding its kinematics,
our tentative estimate for the proper motions is
(µ_α*cosδ, µδ=(-7.0±0.8, 3.5±0.3)mas/yr
(or a tangential velocity of 382±79km/s) and for the radial velocity
45±5km/s in the solar rest frame.
E3 is one of the most intriguing globular clusters in the Galaxy.
Having an old age and being metal rich is clearly a peculiar
combination, only seen in a handful of objects like the far more
conspicuous NGC 104 (47 Tucanae). In addition, its low luminosity and
sparse population make it a unique template for the study of the final
evolutionary phases in the life of a star cluster. Unfortunately, E3
is among the most elusive and challenging known globular clusters
because field contamination severely hampers spectroscopic studies.
Description:
Photometric data in VI for stars in the field of the globular cluster
ESO 37-1 (E3). The observations were made on the night of 13 November
2006 with the Very Large Telescope UT2 Kueyen and the FORS1 CCD
camera.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
09 20 57.07 -77 16 54.8 E 3 = ESO 37-1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 80 3372 ESO 37-1 (E 3) VI photometry
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- ID [1/3372] Sequential number
8- 15 F8.3 pix Xpos [-1/2049] X position on CCD frame
17- 24 F8.3 pix Ypos [-1/2049] Y position on CCD frame
26- 36 F11.7 deg RAdeg Right ascension (J2000)
38- 48 F11.7 deg DEdeg Declination (J2000)
50- 56 F7.3 mag Vmag [18/26]?=100 Johnson V magnitude
58- 64 F7.3 mag e_Vmag [0.003/0.55]?=100 Error in V magnitude
66- 72 F7.3 mag V-I [-0.29/4.09]?=100 V-I colour index
74- 80 F7.3 mag e_V-I [0.005/0.4]?=100 Error in V-I colour index
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Acknowledgements:
Raul de la Fuente Marcos, rauldelafuentemarcos(at)gmail.com
(End) Patricia Vannier [CDS] 27-Jul-2015