A multi-wavelength analysis of the cluster of galaxies ABCG 194

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 "lin- ear" 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 RL of the PSPC image (respec- tively 91 0 12 and 81 0 13 M) and the stellar mass up to RL and to 3 Mpc (3 10 12 and 7.5 10 12 M). At smaller scales, the analysis of both positions and veloc- ities 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 (los = 360 km s 1 ). A wavelet analysis of the X-ray image reveals no large scale substructures. Small scale X-ray sources are detected, mainly corresponding to indi- vidual 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 litera- ture, but generally for richer/hotter clusters, such as the -TX, LX-TX ,L X- relations or the ratios of various kinds of masses.