The Peculiar System ESO 244−G012
E. L. Agüero, S. Paolantonio, G. Günthardt
We present spectroscopic and photometric observations of the peculiar galaxy ESO 244[G012, the most prominent features of which are two distinct nuclei and a long asymmetric tail visible up to about 40 kpc from the center of the main body. The spectral characteristics of all the observed zones are typical of H II regions of low excitation ; their N(N)/N(O) ratios indicate a comparative overabundance of nitrogen with respect to the oxygen. Around the northern nucleus, the internal reddenings,
... excitations, the equivalent widths, and the derived abundances are systematically di †erent from those of the southern one, suggesting they have had di †erent evolutions. The equivalent width of the Ha ] [N II] lines of the northern nucleus indicates it is a starburst ; that of the southern one is compatible with a Sb galaxy. The Ha ] [N II] equivalent width of the integrated spectrum is comparable with those observed in mergers of two disk galaxies. The starburst nature of the northern nucleus, observed in the optical range, is in agreement with the properties of ESO 244[G012 detected in the far IR and with the CO and radio observations. In this object, one of the nuclei dominates the IR emission, and the enhancement of the star formation activity is observed in only one of them. The integrated total color B[V corresponds to an Sa-Sab galaxy. The integrated colors B[V , V [R, R[I, and B[I do not show big radial variations reÑecting a rather uniform population, on average, which would be between G8 and K0 types. Indicative B[V colors of the nuclei, corrected for internal absorption, give very di †erent results, and that of the northern nucleus suggests it is an active star-forming region as found from the spectroscopic data. The velocity distribution of ESO 244[G012 has two branches, being similar to that of other system which also has two nuclei. The derived data would indicate that ESO 244[G012 is a merger system ; the two distinct visible nuclei suggest that the components are still interacting.