EDP Sciences
Free access
Volume 410, Number 2, November I 2003
Page(s) 445 - 459
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20031296

A&A 410, 445-459 (2003)
DOI: 10.1051/0004-6361:20031296

Distance to the Centaurus cluster and its subcomponents from surface brightness fluctuations

S. Mieske1, 2 and M. Hilker1

1  Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
2  Departamento de Astronomía y Astrofísica, P. Universidad Católica, Casilla 104, Santiago 22, Chile

(Received 19 May 2003 / Accepted 28 July 2003 )

We present I-band Surface Brightness Fluctuations (SBF) measurements for 15 early type galaxies (3 giants, 12 dwarfs) in the central region of the Centaurus cluster, based on deep photometric data in 7 fields obtained with VLT FORS1 and with very good seeing. From the SBF-distances to our sample galaxies we determine the distance of the Centaurus cluster to be 41.3  $\pm$ 2.1 Mpc (33.08  $\pm$ 0.11 mag). This places the Centaurus cluster at about the same distance as the "Great Attractor". We find a distance difference of 0.27  $\pm$ 0.34 mag between the two subcomponents Cen 30 and Cen 45, ruling out that both components are separated by their Hubble flow distance. A distance difference of 0.48  $\pm$ 0.21 mag is found between the central galaxies NGC 4696 (Cen 30) and NGC 4709 (Cen 45) of both components, supported by the different turn-over magnitudes of their respective globular cluster systems. This suggests that Cen 45 is falling into but has not yet reached Cen 30, supporting the idea of a large scale filament along the line of sight towards Centaurus (Churazov et al. 1999). $H_{\rm0}=$ 83.0  $\pm$ 8.3 km s -1 Mpc -1 is obtained for our Cen 30 sample taking into account the peculiar motion of the Local Group into the direction of the Centaurus cluster. This value of $H_{\rm0}$ corresponds to a much smaller Hubble flow distortion in the direction of Centaurus than determined by Tonry et al. (2000), implying that the GA mass estimate by Tonry et al. may be too high and/or that the Centaurus cluster falls into the GA almost perpendicularly to the line of sight. As our mean single measurement error is very close to the measured distance scatter of the investigated galaxies, we can only derive an upper limit of $\pm$10 Mpc radial extension for the Centaurus cluster, corresponding to a five times larger radial than tangential extension. No evidence for an infall pattern into the Great Attractor is found within the uncertainties for the 11 galaxies with measured redshifts.

Key words: galaxies: clusters: individual: Centaurus cluster -- galaxies: distances and redshift -- techniques: photometric

Offprint request: S. Mieske, smieske@astro.puc.cl

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