Galaxy luminosity functions in WINGS clusters ^⋆,⋆⋆

¹ INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, Padova, Italy
e-mail: alessia.moretti@oapd.inaf.it
² University of Padova, Department of Physics and Astronomy, Vicolo dell’Osservatorio 2, Padova, Italy
³ Centro de Estudios de Fisica del Cosmos de Aragon, Plaza de San Juan 1, 44001 Teruel, Spain
⁴ Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, the University of Tokyo, 113-8664 Tokyo, Japan
⁵ Observatoire de Genève, Université de Genève, Switzerland
⁶ Centro de Radioastronomia y Astrofisica, UNAM, Campus Morelia, A.P. 3-72, CP 58089, Mexico
⁷ Australian Astronomical Observatory, PO Box 915, North Ryde, NSW 1670, Australia
⁸ Niels Bohr Institute, Juliane Maries Vej 30, 2100 Copenhagen, Denmark

Received: 12 March 2015
Accepted: 26 May 2015

Abstract

Aims. Using V band photometry of the WINGS survey, we derive galaxy luminosity functions (LF) in nearby clusters. This sample is complete down to M_V = −15.15, and it is homogeneous, thus facilitating the study of an unbiased sample of clusters with different characteristics.

Methods. We constructed the photometric LF for 72 out of the original 76 WINGS clusters, excluding only those without a velocity dispersion estimate. For each cluster we obtained the LF for galaxies in a region of radius = 0.5 × r₂₀₀, and fitted them with single and double Schechter’s functions. We also derive the composite LF for the entire sample, and those pertaining to different morphological classes. Finally, we derive the spectroscopic cumulative LF for 2009 galaxies that are cluster members.

Results. The double Schechter fit parameters are correlated neither with the cluster velocity dispersion nor with the X-ray luminosity. Our median values of the Schechter’s fit slope are, on average, in agreement with measurements of nearby clusters, but are less steep that those derived from large surveys, such as the SDSS. Early-type galaxies out number late-types at all magnitudes, but both early and late types contribute equally to the faint end of the LF. Finally, the spectroscopic LF is in excellent agreement with the one derived for A2199, A85 and Virgo, and with the photometric LF at the bright magnitudes (where both are available).

Conclusions. There is a large spread in the LF of different clusters, however, this spread is not caused by correlation of the LF shape with cluster characteristics such as X-ray luminosity or velocity dispersions. The faint end is flatter than previously derived (α_f = −1.7), which is at odds with that predicted from numerical simulations.