SIMBAD references

Based on Chandra and ROSAT observations, we investigated the nearby poor cluster A194, which hosts two luminous radio galaxies, NGC 547 (3C 40B) and NGC 541 (3C 40A). We demonstrated the presence of a large X-ray cavity (r ∼ 34 kpc) formed by the giant southern radio lobe arising from 3C 40B in NGC 547. The estimated age of the cavity is t = 7.9x10⁷ years and the total work of the active galactic nucleus is 3.3x10⁵⁹ erg, hence the cavity power is P_cav= 1.3x10⁴⁴ erg/s. Furthermore, in the Chandra images of NGC 545 and NGC 541 we detected sharp surface brightness edges, identified as merger cold fronts, and extended tails. Using the pressure ratios between inside and outside the cold fronts we estimated that the velocities of NGC 545 and NGC 541 correspond to Mach numbers of M = 1.0^+0.3_–0.5 and M = 0.9^+0.2_–0.5, respectively. The low radial velocities of these galaxies relative to the mean radial velocity of A194 imply that their motion is oriented approximately in the plane of the sky. Based on these and earlier observations, we concluded that NGC 545 and NGC 541 are falling through the cluster, whose center is NGC 547, suggesting that A194 is undergoing a significant cluster merger event. Additionally, we detected 20 bright X-ray sources around NGC 547 and NGC 541, a surprisingly large number, since the predicted number of resolved low-mass X-ray binaries and cosmic X-ray background sources is 2.2 and 4.1, respectively. To explain the nature of additional sources, different possibilities were considered, none of which are satisfactory. We also studied the origin of X-ray emission in Minkowski's object (MO) and concluded that it is most likely dominated by the population of high-mass X-ray binaries rather than by hot diffuse interstellar medium. Moreover, in view of the galaxy dynamics in A194, we explored the possibility that the starburst in MO was triggered by its past interaction with NGC 541, and concluded that it may be a viable path.