J/AJ/109/1086 VI Photometry in M54 and Sgr Dwarf Galaxy (Sarajedini+ 1995)
A Photometric Study of the Globular Cluster M54 and the Sagittarius Dwarf
Galaxy: Evidence for Three Distinct Populations
Sarajedini A., Layden A.C.
<Astron. J. 109, 1086 (1995)>
=1995AJ....109.1086S 1995AJ....109.1086S
ADC_Keywords: Photometry, CCD ; Clusters, globular
Abstract:
We present VI CCD color-magnitude diagrams for the globular cluster
M54 and the Sagittarius dwarf galaxy. These are used to derive the
following quantities:
[Fe/H] = -1.79 ± 0.08 for M54 and
[Fe/H] = -0.52 ± 0.09 for Sagittarius.
We find a metallicity dispersion of ± 0.16 dex in M54, and we
infer the possible existence of a [Fe/H] ∼ -1.3 component in
Sagittarius, which may have a metallicity dispersion as well.
The mean reddening in the direction of M54 is E(B-V) = 0.13 ± 0.02.
The distances to M54 and Sagittarius, determined using their
horizontal branch magnitudes, are identical to within the
uncertainties of existing RR Lyrae luminosity-abundance relations.
This, together with positional and radial velocity arguments, suggests
that M54 is physically associated with Sagittarius. We note that M54
is substantially brighter than the globular cluster members of the
Fornax dwarf spheroidal galaxy, and that the metal abundance of
Sagittarius is quite high for its estimated absolute magnitude.
Objects:
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RA (2000) DE Designation(s)
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18 55.1 -30 28 M 54 = NGC 6715 = C 1851-305
19 30.0 -17 41 ESO 594- 4 = Sgr Dwarf Galaxy
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 63 3214 CCD photometry for M54
table2.dat 63 1638 CCD photometry for Sgr
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See also:
J/AJ/119/1760 : M54 and Sgr dSph VI photometry (Layden+, 2000)
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Star Star number
7-15 F9.2 pix Xpos X pixel position
16-24 F9.2 pix Ypos Y pixel position
25-33 F9.2 mag Vmag V magnitude
34-42 F9.3 mag e_Vmag V magnitude error
43-51 F9.2 mag V-I V-I color
52-60 F9.3 mag e_V-I V-I color error
61-63 I3 --- Det Number of detections
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Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 17-Jul-1995
(End) [CDS] 09-Jan-1996