ALMA | NRAO | NAOJ | ESO | 2018 Feb 02
Astronomers using the Atacama Large Millimeter/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 astronomers until now: ALMA observed the outflow from one of its nuclei in three dimensions (velocity and 2D spatial information). ...
- ALMA image of Arp 220 cores over HST image of Arp 220. The two cores (yellow), obscured by dust on visible wavelengths, are observed by ALMA. The research team detected a bipolar outflow from the western nucleus and measured its velocity. In red, the North section of the outflow, particles are moving away from Earth. In blue, the South section of the outflow, particles are moving towards Earth. Credit: L. Barcos-Muñoz et al / ALMA (NRAO/NAOJ/ESO) / HST (NASA/ESA)
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, giving the opportunity to research feedback processes in these deeply embedded galaxy nuclei. ...
The new ALMA observations reveal a bipolar, fast, collimated outflow emerging from the western nucleus of Arp 220. The material transported from the core through the flows has a maximum speed of 840 km/s. According to Loreto Barcos-Muñoz, possible explanations for this outflow could be energy from supernovae and momentum transfers, radiation pressure feedback, and a central AGN.
Another finding that surprised the team of astronomers is that the outflow is brighter in HCN than in CO, while the opposite is the norm for most extragalactic outflows detected to date. Further observations are needed to determine the origin of this behavior, but this discovery challenges the current knowledge about extragalactic outflow gas properties.
Fast, Collimated Outflow in the Western Nucleus of Arp 220 - Loreto Barcos-Muñoz et al