NOEMA Observations of CO Emission in Arp 142 and Arp 238

Previous studies have shown significant differences in the enhancement of star-formation rate (SFR) and efficiency (SFE=SFR/M_mol) between spiral-spiral spiral-elliptical mergers. In order to shed light on physical mechanism these differences, we present NOEMA observations molecular gas distribution kinematics (linear resolutions ~ 2kpc) two representative close major-merger star-forming pairs: pair Arp142 Arp238. The CO is widely distributed over a highly distorted disk without any nuclear concentration, an off-centric ring-like structure discovered channel maps. SFE varies significantly within Arp142, with starburst region (Region 1) near eastern tip showing ~0.3 dex above mean control sample isolated galaxies, main 4) 0.43 lower than sample. contrast, emission Arp238 detected only compact sources at galactic centers. Compared sample, Arp238-E shows more 1 whereas Arp238-W has ~0.7 dex. We suggest that extended large variation are due expanding large-scale ring triggered by recent high-speed head-on collision spiral galaxy elliptical galaxy, high SFEs associated starbursts induced gravitational tidal torques low-speed coplanar interaction.