The globular cluster system of the edge-on spiral galaxy NGC 5170
Date
1989
Authors
Fischer, Philippe
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Abstract
A CCD study of the edge-on spiral galaxy, NGC 5170, was carried out with the CTIO 4m telescope to search for its globular cluster system. Three V frames near the galaxy and two removed from it (for background estimation) were analysed. Following median filtering to remove as much of the galaxy light as possible and DAOPHOT analyses, a total of about 130 ± 20 presumed clusters were detected within 2 arcmin of the galaxy's centre above a foreground of Galactic stars and a background of distant galaxies. The photometry does not appear to reach the peak of the globular cluster luminosity function . After incompleteness corrections are made, a total cluster population of~ 815 ± 320 is inferred. This leads to a specific frequency of S = 1.3 ± 0.5 or Sapheroidal = 3.9 ± 1.5, values consistent with what is seen for other isolated disk galaxies. A power law fit to the radial density distribution yields an index of -1.69 ± 0.26, which is again consistent with the globular cluster systems of other galaxies .of NGC 5170's total luminosity. The visual distance modulus estimated from the globular cluster luminosity function, 32.3 ± 0.3, agrees well with the Fisher-Tully distance, 32.5, but the agreement may be somewhat fortuitous, inasmuch as the cluster data do not reach the luminosity function peak.