J/ApJ/521/577 HST studies of the WLM globular cluster (Hodge+, 1999)
Hubble space Telescope Studies of the WLM galaxy. I. The age and metallicity
of the globular cluster
Hodge P.W., Dolphin A.E., Smith T.R. Mateo M.
<Astrophys. J. 521, 577 (1999)>
=1999ApJ...521..577H 1999ApJ...521..577H
ADC_Keywords: Abundances, [Fe/H]; Clusters, globular; Colors; Galaxies, nearby
Mission_Name: HST
Keywords: galaxies: individual (WLM) - galaxies: star clusters - Local Group
Abstract:
We have obtained V and I images of the lone globular cluster that
belongs to the dwarf Local Group irregular galaxy known as WLM. The
color-magnitude diagram of the cluster shows that it is a normal old
globular cluster with a well-defined giant branch reaching to
MV=-2.5, a horizontal branch at MV=+0.5, and a subgiant branch
extending to our photometry limit of MV=+2.0. A best fit to
theoretical isochrones indicates that this cluster has a metallicity
of [Fe/H]=-1.52±0.08 and an age of 14.8±0.6 Gyr, thus
indicating that it is similar to normal old halo globulars in our
Galaxy. From the fit we also find that the distance modulus of the
cluster is 24.73±0.07 and the extinction is AV=0.07±0.06,
both values that agree within the errors with data obtained for the
galaxy itself by others.
Description:
As part of a Cycle 6 HST GO program, we obtained four images of the
WLM globular cluster on 1998 September 26. There were two exposures
taken with the F814W filter of 2700 s and two with the F555W filter,
one each of 2700 and 2600 s. The globular cluster was centered on the
PC chip and the orientation of the camera was such that the WF chips
lay approximately along the galaxy's minor axis. Photometry was then
carried out using a program specifically designed to reduce
undersampled WFPC2 data.
Objects:
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RA (2000) DE Designation(s)
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00 01 49.9 -15 28 01 Wolf-Lundmark-Melotte (WLM) Globular Cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 796 V and I photometry of the WLM globular cluster
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 pix Xpos X coordinate on the chip
8- 12 F5.1 pix Ypos Y coordinate on the chip
14- 19 F6.3 mag Vmag V band magnitude
23- 27 F5.3 mag e_Vmag uncertainty in Vmag
29- 34 F6.3 mag Imag I band magnitude
38- 42 F5.3 mag e_Imag uncertainty in Imag
44- 49 F6.3 mag V-I V-I color
53- 57 F5.3 mag e_V-I uncertainty in the V-I color
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History:
From ApJ electronic edition.
(End) Greg Schwarz [AAS] 28-Feb-2000