In an attempt to use Cepheid variables to determine the distance to the Centaurus cluster, we have obtained images of NGC 4603 with the Hubble Space Telescope on 9 epochs (totalling 24 orbits) over 14 months in the F555W filter and 2 epochs (6 orbits) in the F814W filter. This galaxy lies within the "Cen30" portion of the Centaurus cluster, which is concentrated around a redshift of ~ 3000 km/sec. Previous distance estimates for this cluster have varied significantly and presented disagreements with studies of large-scale structure, motivating our investigation. NGC 4603 is the most distant galaxy in which a search for Cepheids has been conducted. Using our WFPC2 observations, we have found a number of candidate Cepheid variable stars; however, at such faint magnitudes, magnitude measurement errors may lead to apparent variability of significant amplitude in intrinsically nonvarying stars. We have examined this effect through detailed simulations, and by means of a maximum likelihood analysis obtain limits on the distance of NGC 4603.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1998