1 Introduction

Field galaxies should experience interactions with the hostile cluster environment during infall in the cluster because of harassment (Moore et al. 1996), tidal tails and eventually mergers (Toomre & Toomre 1972) and possibly other cluster-specific phenomena. These effects influence infalling galaxies well before they reach the cluster core. Therefore, it is important to observe galaxies when interactions are occurring, i.e. at large clustercentric distances. The dependence of the galaxy properties on clustercentric distance is therefore informative of cluster-related phenomena.

Figure 1: Detected galaxies (ellipses), brighter than $K_{\rm s}=20$ mag. The area of ellipses is twice the galaxy isophotal area computed at $1.5\sigma$ above the background (20.8-21.8 mag arcsec-2). North is up and East is to the left. The origin is at ( $\alpha , \delta ) = (00 \ 14 \ 20, \ -30 \ 24 \ 00)$ (J2000).

Studies of galaxy evolution in clusters often sample only the cluster core because the cluster outskirts have a low contrast with respect to the background galaxies, making the measure of cluster galaxy properties subjected to large errors. Furthermore, the small field of view of the available imagers, in particular in the near-infrared, makes the sampling of the cluster outskirts expensive in telescope time. For these reasons, cluster outskirts are less frequently studied, in particular in the near-infrared, even if the near-infrared is very informative: for example it is a good tracer of the stellar mass (Bruzual & Charlot 1993; Pierini et al. 1996) and it is not too affected by short star bursts (Bruzual & Charlot 1993). Figure 10 in Andreon (2001) shows that there are only three investigations (de Propris et al. 1998; Andreon & Pelló 2000; Andreon 2001) sampling galaxies fainter than M^*+1 and exploring radii larger than 0.4 Mpc. Since then, another work has appeared (Tustin et al. 2001). The situation is now rapidly changing thanks to 2MASS (Skrutskie et al. 1997) and large panoramic infrared receivers, such as CIRSI (Mackay et al. 2000).

In this paper we make use of a large panoramic near-infrared receiver, an Hawaii chip, by imaging the intermediate redshift cluster AC118. AC118 has been observed with three pointings, two of which image the cluster outskirts and are presented in Sect. 2. The central pointing was, instead, presented in Andreon (2001, hereafter Paper I). In Sect. 3 the spatial distribution of galaxies of various luminosities, the dwarf to giant radial profile and the luminosity function at various cluster locations are presented. In Sect. 4 we present a summary and discuss the results.

In this paper we assume H₀=50 km s^-1 Mpc^-1 and q₀=0.5. The choice of the cosmology has a small or null impact on the results because all the compared galaxies are at the same redshift (see Sect. 4).