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Previous studies have shown significant differences in the enhancement of the star-formation rate (SFR) and the star-formation efficiency (SFE=SFR/M_mol) between spiral-spiral and spiral-elliptical mergers. In order to shed light on the physical mechanism of these differences, we present NOEMA observations of the molecular gas distribution and kinematics (linear resolutions of ~ 2kpc) in two representative close major-merger star-forming pairs: the spiral-elliptical pair Arp142 and the spiral-spiral pair Arp238. The CO in Arp142 is widely distributed over a highly distorted disk without any nuclear concentration, and an off-centric ring-like structure is discovered in channel maps. The SFE varies significantly within Arp142, with a starburst region (Region 1) near the eastern tip of the distorted disk showing an SFE ~0.3 dex above the mean of the control sample of isolated galaxies, and the SFE of the main disk (Region 4) 0.43 dex lower than the mean of the control sample. In contrast, the CO emission in Arp238 is detected only in two compact sources at the galactic centers. Compared to the control sample, Arp238-E shows an SFE enhancement of more than 1 dex whereas Arp238-W has an enhancement of ~0.7 dex. We suggest that the extended CO distribution and the large SFE variation in Arp142 are due to an expanding large-scale ring triggered by a recent high-speed head-on collision between the spiral galaxy and the elliptical galaxy, and the compact CO sources with high SFEs in Arp238 are associated with nuclear starbursts induced by gravitational tidal torques in a low-speed coplanar interaction.
We present a high spatial resolution optical and infrared study of the circumnuclear region in Arp 220, a late-stage galaxy merger. Narrowband imaging using HST/WFC3 has resolved the previously observed peak in H$alpha$+[NII] emission into a bubble-s
We present an imaging and spectral analysis of the nuclear region of the ULIRG merger Arp 220, using deep textit{Chandra}-ACIS observations summing up to (sim 300mbox{ ks}). Narrow-band imaging with sub-pixel resolution of the innermost nuclear regio
Understanding the heating and cooling mechanisms in nearby (Ultra) luminous infrared galaxies can give us insight into the driving mechanisms in their more distant counterparts. Molecular emission lines play a crucial role in cooling excited gas, and
We present the first results from the Las Cumbres Observatory Global Telescope (LCOGT) Networks Active Galactic Nuclei Key Project, a large program devoted to using the robotic resources of LCOGT to perform time domain studies of active galaxies. We
Star-forming galaxies are huge reservoirs of cosmic rays (CRs) and these CRs convert a significant fraction of their energy into $gamma$-rays by colliding with the interstellar medium (ISM). Several nearby star-forming galaxies have been detected in