Multi-wavelength structure analysis of local cluster galaxies

A Psychogyios,M Vika,S Bamford,A Moretti,V Charmandaris,B Vulcani,B Häußler,B Poggianti,G Fasano

doi:10.1051/0004-6361/201833522

Abstract

We present a multi-wavelength analysis of the galaxies in nine clusters selected from the WINGS dataset, examining how galaxy structure varies as a function of wavelength and environment using the state of the art software GALAPAGOS-2. We simultaneously fit single-Sérsic functions on three optical (u, B and V) and two near-infrared (J and K) bands thus creating a wavelength-dependent model of each galaxy. We measure the magnitudes, effective radius (Re), the Sérsic index (n), axis ratio, and position angle in each band. The sample contains 790 cluster members (located close to the cluster centre < 0.64 × R200) and 254 non-member galaxies that we further separate based on their morphology into ellipticals, lenticulars, and spirals. We find that the Sérsic index of all galaxies inside clusters remains nearly constant with wavelength while Re decreases as wavelength increases for all morphological types. We do not observe a significant variation on n and Re as a function of projected local density and distance from the clusters centre. Comparing the n and Re of bright cluster galaxies with a subsample of non-member galaxies we find that bright cluster galaxies are more concentrated (display high n values) and are more compact (low Re). Moreover, the light profile (𝒩) and size (ℛ) of bright cluster galaxies does not change as a function of wavelength in the same manner as non-member galaxies.

Highlights

A large fraction of the galaxies in the local Universe have been observed and statistically analysed and it is widely accepted that only a few galaxies are found isolated in the field, while the majority of them are preferentially located in denser environments such as groups or clusters (Schmidt et al 1997; Robotham et al 2011)
Since the stellar mass distribution is not the same for different morphological galaxy types (Vulcani et al 2012), we examined the dependence of the structural parameters (Sérsic index and Re) of the cluster galaxies on the stellar mass
In this paper we study the structural parameters of cluster galaxies across optical and NIR wavelengths

Summary

Introduction

A large fraction of the galaxies in the local Universe have been observed and statistically analysed and it is widely accepted that only a few galaxies are found isolated in the field, while the majority of them are preferentially located in denser environments such as groups or clusters (Schmidt et al 1997; Robotham et al 2011). The study of local galaxy clusters is of paramount importance as they can be used to quantify changes in the properties of their members as a function of the baryonic density in the environment, and to place constraints as a reference “zero-point” for comparison with similar studies at higher redshifts. Even though it was Hubble & Humason (1931) who found that “the predominance of early-types is a conspicuous feature of clusters in general”, the systematic study of the properties of galaxy clusters began some decades later when improvements to observing facilities enabled these studies to be done in more detail. This result was interpreted as the ageing of spiral galaxies after consuming their gas supply and diminishing their star formation rates

Results

Discussion

Conclusion