J/AJ/106/493 Globular clusters in M87 (Lee+, 1993)
Metal abundances for a large sample of globular clusters in M87
LEE M.G., GEISLER D.
<Astron. J. 106, 493 (1993)>
=1993AJ....106..493L 1993AJ....106..493L (SIMBAD/NED Reference)
ADC_Keywords: Galaxies, optical; Clusters, globular; Photometry, CMT1T2V
Abstract:
We present deep integrated Washington CCD photometry of the extremely
populous globular cluster system of NGC 4486 (M87) in Virgo. The
metallicities of 407 of the best candidates with T1 < 22 have been
estimated from the (C-T1) color. These values are internally precise
to ∼0.15dex and accurate to ∼0.25dex. The mean metallicity of the
globular clusters is [Fe/H] = -0.86dex, with a formal standard error
of the mean of 0.03dex but a more realistic uncertainty of about
0.2dex. This value is higher than that of the corresponding means of
the globular clusters in the Galaxy and M31, but similar to those of
the globular clusters in NGC 1399 and NGC 5128, as expected from the
relative parent galaxy luminosities. Approximately 10% of the clusters
exceed solar abundance, similar to the case for the globular clusters
in NGC 1399 and NGC 5128. As found by Couture et al. [ApJS, 73, 671
(1990)], there is a large metallicity dispersion at any radius, with a
sigma ∼ 0.65dex. However, in contrast to their result and that of
previous small-field CCD studies, the globular clusters display a
marked gradient in both mean (M-T1) and (C-T1) color with
galactocentric distance. The mean metallicity decreases by some 0.6dex
over the radial extent of the cluster sample. This result is
consistent with the early photographic study by Strom et al. [ApJ, 245,
416 (1981)]. The metallicity distribution function is remarkably
similar to that of NGC 1399 found by Ostrov et al. [AJ, 105, 1762
(1993)] using the same technique. The two central cluster ellipticals
show significant peaks at very similar metallicities, indicating
similar formation and enrichment histories. We also find that this
structure in the metallicity distribution function persists to radii
where the halo light is dominated by the cD envelope.
File Summary:
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File Name Lrecl Records Explanations
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ReadMe 80 . This file
table3 68 144 M87 globular cluster candidates with T1 < 21
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Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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1- 2 A2 --- Field Field designator:
N1 = North, E1 = East-1, E2 = East-2,
W1 = West, and C = Center.
4- 6 I3 --- ID Running number (finding charts are given in
Plates 15-19 in the printed paper.
9- 13 F5.1 pix X X coordinate of object
16- 20 F5.1 pix Y Y coordinate of object
23- 27 F5.2 mag T1 T1 magnitude (Washington system)
29- 32 F4.2 mag e_T1 rms uncertainty on T1
35- 38 F4.2 mag M-T1 M-T1 color (Washington system)
40- 43 F4.2 mag e_M-T1 rms uncertainty on M-T1
46- 49 F4.2 mag C-T1 C-T1 color (Washington system)
51- 54 F4.2 mag e_C-T1 rms uncertainty on C-T1
57- 61 F5.2 --- [Fe/H] Derived metal abundance, [Fe/H]
64- 68 F5.1 arcsec RG Projected galactocentric distance
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Origin: AAS CD-ROM series, Volume 1, 1993
(End) Patricia Bauer [CDS] 20-Sep-1994