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Astron. Astrophys. 353, 930-936 (2000)

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A turn-over in the galaxy luminosity function of the Coma cluster core?

C. Adami 1,2, M.P. Ulmer 2, F. Durret 3,4, R.C. Nichol 5, A. Mazure 1, B.P. Holden 6, A.K. Romer 5 and C. Savine 1

1 IGRAP, Laboratoire d'Astronomie Spatiale, Traverse du Siphon, 13012 Marseille, France
2 Department of Physics and Astronomy, Northwestern University, Dearborn Observatory, 2131 Sheridan, 60208-2900 Evanston, USA
3 Institut d'Astrophysique de Paris, CNRS, 98 bis Bd Arago, 75014 Paris, France
4 DAEC, Observatoire de Paris, Universite Paris VII, CNRS, 92195 Meudon Cedex, France
5 Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
6 Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637, USA

Received 15 September 1999 / Accepted 20 October 1999

Abstract

Our previous study of the faint end (R[FORMULA]21.5) of the galaxy luminosity function (GLF) was based on spectroscopic data in a small region near the Coma cluster center. In this previous study Adami et al. (1998) suggested, with moderate statistical significance, that the number of galaxies actually belonging to the cluster was much smaller than expected. This led us to increase our spectroscopic sample. Here, we have improved the statistical significance of the results of the Coma GLF faint end study (R[FORMULA]22.5) by using a sample of 88 redshifts. This includes both new spectroscopic data and a literature compilation.

The relatively small number of faint galaxies belonging to Coma that was suggested by Adami et al. (1998) and Secker et al. (1998) has been confirmed with these new observations. We also confirm that the color-magnitude relation is not well suited for finding the galaxies inside the Coma cluster core, close to the center at magnitudes fainter than R[FORMULA]19. We show that there is an enhancement in the Coma line of sight of field galaxies compared to classical field counts. This can be explained by the contribution of groups and of a distant [FORMULA] cluster along the line of sight.

The result is that the Coma GLF appears to turn-over or at least to become flat for the faint galaxies. We suggest that this is due to environmental effects.

Key words: galaxies: clusters: individual: – galaxies: distances and redshifts – galaxies: luminosity function, mass function – cosmology: observations

Send offprint requests to: C. Adami

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© European Southern Observatory (ESO) 2000

Online publication: January 18, 2000
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