2007AJ....133..220G

We present a comprehensive study of the local environments of four elliptical+spiral (E+S) galaxy pairs with the main goal of investigating their formation/evolution histories. We obtained new XMM-Newton data for two pairs (RR 143 and RR 242) that complement existing ROSAT data for the other two (RR 210 and RR 216). The new observations reveal diffuse X-ray emission in both pairs with luminosities of L_X∼3x10⁴¹ ergs/s (0.5-2.0 keV). The emission is asymmetric in both cases and extends out to ∼500" (120 kpc) and 700" (160 kpc) in RR 143 and RR 242, respectively. The nucleus of RR 242 hosts a low-luminosity (L_X∼10⁴¹ ergs/s [2.0-10 keV]) mildly absorbed (N_H∼10²²/cm2) active galactic nucleus. We find that the early-type components of pairs with diffuse hot gas appear to be relaxed objects, while those in RR 210 and RR 216, where no diffuse emission has been found, display unambiguous signatures of ongoing interaction. New wide-field V- and R-band observations are used to study the photometric properties of the early-type components and to search for candidate faint galaxy populations around each of the pairs. While no diffuse optical light is found for any of the pairs, all of the early-type members show very extended and concentric luminous envelopes. We identify a faint galaxy sample in each field, and we consider whether they could be physically associated with the luminous pairs based on (V-R) colors and photometric properties. We find that the distribution of r_eand M_Rfor the candidates are similar in three of the fields (RR 143, 216, and 242). The same selection criteria applied to the field of RR 210 suggest a fainter and more compact population, possibly suggesting a larger background fraction than in the other fields.