The active merging system ESO 202-G23 (Carafe Nebula)

We present the results of observations both in imaging and spectroscopy of the nearby active galaxy ESO 202-G23 (Carafe Nebula). The main result of th is investigation is that the peculiar morphology of the galaxy, formerly at tributed to the presence of an asymmetric bar, is produced by the merging o f two galaxies both hosting an active nucleus. Our deep R image reveals une xpectedly the presence of a knot (G2), not visible in the B image, at 3.5 k pc on the northern of the nucleus (G1), classified in the literature as a S eyfert 2. A long-slit spectrum provides evidence that G1 is a Seyfert 1.5 n ucleus and that G2 is also a nucleus, showing features typical of a LINER h eavily reddened by dust. The presence of tails and plumes in the outermost parts of the galaxy and the double U shape of the rotation curve of the gas around G1 and G2 strongly support the hypothesis of a merger that occurred 10(6)-10(9) years ago, as suggested by the comparison of the current (14 M . yr(-1)) and the recent (24 M. yr(-1)) star formation rates. The system ES O 202-G23 is an infrared bright source (L-FIR/L. = 2.18 x 10(10)) and the I RAS flux ratios suggest a predominantly thermal origin of the infrared emis sion. The analysis of the IRAS data allows us to obtain some important prop erties concerning both the gas and the dust : T-d(warm) similar to 36 K; M- d(warm) = 4.1 x 10(6) M.; T-d(cold) similar to 21 K; M-d(cold) = (6.9-8.3) x 10(7) M.; M-H I = 8.6 x 10(9) M.; M-H II = (2.3-4.3) x 10(9) M.; M-gas = (1.1-1.3) x 10(10) M.. The derived mass-to-light ratio M-H I/L-B = 2.23 and the value of the parameter K = v(max)/r(max), K(G1) = 201, K(G2) = 179, in dicate that the precursor is not later than Sbc.