High-velocity extended molecular outflow in the star-formation dominated luminous infrared galaxy ESO 320-G030

M. Pereira-Santaella, L. Colina, S. García-Burillo, A. Alonso-Herrero, S. Arribas, S. Cazzoli, B. Emonts, J. Piqueras López, P. Planesas, T. Storchi Bergmann, A. Usero, M. Villar-Martín. 2016. High-velocity extended molecular outflow in the star-formation dominated luminous infrared galaxy ESO 320-G030. Astronomy and Astrophysics 594, DOI: 10.1051/0004-6361/201628875

We analyze new high spatial resolution (similar to 60 pc) ALMA CO(2-1) observations of the isolated luminous infrared galaxy ESO 320-G030 (d = 48 Mpc) in combination with ancillary Hubble Space Telescope optical and near infrared (IR) imaging, as well as VLT/SINFONI near-IR integral field spectroscopy. We detect a high-velocity (similar to 450 km s(-1)) spatially resolved (size similar to 2.5 kpc; dynamical time similar to 3 Myr) massive (similar to 10(7) M-circle dot; (M) over dot similar to 2-8 M-circle dot yr(-1)) molecular outflow that has originated in the central similar to 250 pc. We observe a clumpy structure in the outflowing cold molecular gas with clump sizes between 60 and 150 pc and masses between 10(5.5) and 1064 M.. The mass of the clumps decreases with increasing distance, while the velocity is approximately constant. Therefore, both the momentum and kinetic energy of the clumps decrease outwards. In the innermost (similar to 100 pc) part of the outflow, we measure a hot-to-cold molecular gas ratio of 7 x 10(-5), which is similar to that measured in other resolved molecular outflows. We do not find evidence of an ionized phase in this outflow. The nuclear IR and radio properties are compatible with strong and highly obscured star-formation (A(k) similar to 4.6 mag; star formation rate similar to 15 M-circle dot yr(-1)). We do not find any evidence for the presence of an active galactic nucleus. We estimate that supernova explosions in the nuclear starburst (nu(SN) similar to 0.2 yr(-1)) can power the observed molecular outflow. The kinetic energy and radial momentum of the cold molecular phase of the outflow correspond to about 2% and 20%, respectively, of the supernovae output. The cold molecular outflow velocity is lower than the escape velocity, so the gas will likely return to the galaxy disk. The mass loading factor is similar to 0.1-0.5, so the negative feedback owing to this star-formation-powered molecular outflow is probably limited.

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