Fossil group origins V. The dependence of the luminosity function on the magnitude gap

S. Zarattini; J. A. L Aguerri; R. Sanchez-Janssen; R. Barrena; W. Boschin; C. del Burgo; N. Castro-Rodriguez; E. M. Corsini; E. D'Onghia; M. Girardi; J. Iglesias-Paramo; A. Kundert; J. Mendez-Abreu; J. M. Vilchez

doi:10.1051/0004-6361/201425506

paper

Fossil group origins V. The dependence of the luminosity function on the magnitude gap

arXiv:1506.03076 · doi:10.1051/0004-6361/201425506

Abstract

In nature we observe galaxy aggregations that span a wide range of magnitude gaps between the two first-ranked galaxies of a system ( $Δ m_{12}$ ). There are systems with gaps close to zero (e.g., the Coma cluster), and at the other extreme of the distribution, the largest gaps are found among the so-called fossil systems. Fossil and non-fossil systems could have different galaxy populations that should be reflected in their luminosity functions. In this work we study, for the first time, the dependence of the luminosity function parameters on $Δ m_{12}$ using data obtained by the fossil group origins (FOGO) project. We constructed a hybrid luminosity function for 102 groups and clusters at $z \leq 0.25$ . We stacked all the individual luminosity functions, dividing them into bins of $Δ m_{12}$ , and studied their best-fit Schechter parameters. We additionally computed a relative luminosity function, expressed as a function of the central galaxy luminosity, which boosts our capacity to detect differences, especially at the bright end. We find trends as a function of $Δ m_{12}$ at both the bright and faint ends of the luminosity function. In particular, at the bright end, the larger the magnitude gap, the fainter the characteristic magnitude $M^{*}$ . We also find differences at the faint end. In this region, the larger the gap, the flatter the faint-end slope $α$ . The differences found at the bright end support a dissipationless, dynamical friction-driven merging model for the growth of the central galaxy in group- and cluster-sized halos. The differences in the faint end cannot be explained by this mechanism. Other processes, such as enhanced tidal disruption due to early infall and/or prevalence of eccentric orbits, may play a role. However, a larger sample of systems with $Δ m_{12} > 1.5$ is needed to establish the differences at the faint end.

11 pages, 10 figures, accepted for publication in A&A

Fossil group origins V. The dependence of the luminosity function on the magnitude gap

Abstract

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