1999A&A...349...97N

We present a morphological and structural analysis of the Richness zero cluster ABCG 194, known as a ``linear cluster''. This study is based on a catalogue of 97 galaxies with B magnitudes and redshifts belonging to the cluster, a ROSAT PSPC image and radio data. We show that the overall large scale structure is rather smooth and comparable at optical and X-ray wavelengths. The cluster is elongated along PA≃50; however it appears as ``linear'' when taking into account only galaxies in the very central part (the axial ratio varies from 0.2 in the central region to 0.8 for a larger region). We have obtained the galaxy density profile and despite the very low X-ray emission the X-ray emitting gas density profile. We have estimated the X-ray gas and dynamical masses up to the limiting radius R_L of the PSPC image (respectively 9x10¹² and 8x10¹³M_☉) and the stellar mass up to R_L and to 3 Mpc (3x10¹² and 7.5x10¹²M_☉). At smaller scales, the analysis of both positions and velocities reveals the existence of several groups but which are not strongly linked dynamically; however a main structure with a nearly gaussian velocity distribution is exhibited. The velocity dispersion is small (σ_los=360km/s). A wavelet analysis of the X-ray image reveals no large scale substructures. Small scale X-ray sources are detected, mainly corresponding to individual galaxies; we give an estimate of their luminosities. The lack of strong substructuring suggests that ABCG 194 is overall a relaxed cluster. ABCG 194 is a poor and cold cluster; we compare how its characteristics fit into various correlations found in the literature, but generally for richer/hotter clusters, such as the σ-T_X, L_X-T_X, L_X-σ relations or the ratios of various kinds of masses.