MacroCosmos mars-avril 2018

37 MARS-AVRIL 2018 CHRONIQUES DE L'ESPACE A LMA 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 de- tected a bipolar out- flow 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. [L. Barcos-Muñoz, N. Lira, J. Pinto – ALMA (NRAO/NAOJ/ESO) / Hubble Space Teles- cope – (NASA/ESA)] ral Fellow at ALMA observatory, and Principal Investigator of this re- search. “We confirmed the presence of an outflow and obtained a detai- led image of its morphology and its velocity at the same time.” 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 out- flow could be energy from superno- vae and momentum transfers, radiation pressure feedback, and a central AGN. Another finding that surprised the team of astron-omers 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 deter- mine the origin of this behavior, but this discovery challenges the current knowledge about extraga-lactic outflow gas properties. feedback processes in these deeply embedded galaxy nuclei. “ALMA’s observation wavelength, combined with its high sensitivity and resolu- tion, allowed us to observe inside this very compact and dust obscured galaxy nucleus,” explained Loreto Barcos-Muñoz, an NRAO Postdocto- ! A n enlargement of the two nuclei in Arp 220 observed with ALMA. [L. Barcos-Muñoz, N. Lira, J. Pinto – ALMA (NRAO/NAOJ/ESO)]