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J/AJ/105/1762    Globular clusters around NGC 1399                (Ostrov+ 1993)

The metallicity gradient and distribution function of globular clusters around NGC 1399 OSTROV P., GEISLER D., FORTE J.C. <Astron. J. 105, 1762 (1993)> =1993AJ....105.1762O
ADC_Keywords: Galaxies, optical; Clusters, globular; Photometry, CMT1T2V Abstract: We have obtained integrated Washington photometry (C,M,T1) of globular cluster candidates in the field of NGC 1399. This galaxy, the dominant object in the Fornax cluster, shares with NGC 4486 (M87) the property of possessing one of the largest known specific frequencies of globulars. Conflicting evidence on the presence of a B-V color gradient as a function of galactocentric distance has been reported for this cluster system. Here we investigate the existence of a gradient using the C-T1 index, which is twice as metallicity sensitive as B-V. A small gradient is detected. This color gradient, in the sense that outer clusters are bluer, amounts to approx. 0.1 mag in C-T1 over a galactocentric range from about 0.5 to 3.5 arcmin, corresponding to a difference of approx. 0.2 dex in metallicity. This confirms qualitatively the B-V gradient suggested by Bridges et al. [AJ, 101, 469 (1991)]. Photometry for 420 globular cluster candidates is presented. Metal abundances internally precise to approx. 0.25 dex and accurate to approx. 0.3 dex have been obtained for some 250 of the best candidates, after statistically subtracting a field contamination estimated at 30%. The mean abundance of -0.9 ± 0.2 confirms previous indications that the NGC 1399 globular cluster system is, on average, significantly more metal rich than that of the Galaxy, as expected from the relative parent galaxy luminosities. Approximately 10% of the clusters exceed solar abundance, similar to the case for NGC 5128. The signature of possible globular cluster formation in mergers, as suggested by Ashman and Zepf [ApJ, 384, 50 (1992)], is found in the distinct peaks in the metallicity distribution function. However, their prediction (based on a simple theory designed only for application to normal elliptical galaxies and not the more complicated cD galaxies represented by NGC 1399) that the color difference between the clusters and the background halo light monotonically increases with radius is not borne out by the observations. The difference decreases with radius from the center to approx. 2 arcmin; beyond this radius, the difference does appear to increase, however. At all radii, the mean globular cluster abundance is some 0.25-0.5 dex more metal poor than that of the background halo. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3 64 420 Washington Photometry of globular cluster candidates in NGC 1399
Byte-by-byte Description of file: table3
Bytes Format Units Label Explanations
1 I1 --- n_ID [0/3]? Field identification Central field = 0, north field = 1 south field = 2 and west field = 3 2- 5 I4 --- ID Running ID number 6- 13 F8.2 pix X X coordinate 14- 21 F8.2 pix Y Y coordinate 22- 28 F7.3 mag C-M C-M color 29- 35 F7.3 mag M-T1 M-T1 color 36- 43 F8.3 mag T1 T1 magnitude 44- 50 F7.3 mag e_C-M Error in C-M 51- 57 F7.3 mag e_M-T1 Error in M-T1 58- 64 F7.3 mag e_T1 Error in T1
Origin: AAS CD-ROM series, Volume 1, 1993
(End) Patricia Bauer [CDS] 06-Jul-1994
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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