Free Astronomy Magazine March-April 2018

36 MARCH-APRIL 2018 SPACE CHRONICLES Outflow in ultraluminous infrared galaxy observed by ALMA Observatory A stronomers using the Atacama Large Millime- ter/ submillimeter Array (ALMA) observed for the first time an outflow emerging from one of the nuclei in Arp 220, the closest Ultraluminous Infrared Galaxy to Earth resulting from the collision of two galaxies which are now in the process of merging. Although this object has been extensively studied, its compactness and obscuration have been a challenge for as- tronomers until now: ALMA ob- served the outflow from one of its nuclei in three dimensions (velocity and 2D spatial infor- mation). The results of this re- search appeared in The Astro- physical Journal Letters. The presence of an outflow has been previously detected in Arp 220. However, this is the first time it has been imaged and its kinematics and morphological characteristics determined. The flow is collimated, instead of the wide-angle morphology that is usually observed. With this discovery, it is possible now to start studying extragalactic outflows at 100 pc scales, giv- ing the opportunity to research A rp 220 appears to be a single, odd-looking galaxy, but is in fact a nearby example of the aftermath of a collision between two spiral galaxies. It is the brightest of the three galac- tic mergers closest to Earth, about 250 million light-years away in the constellation of Ser- pens, the Serpent. [NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collab- oration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)]