Molecular outflows in local galaxies: Method comparison and a role of intermittent AGN driving
Year: 2019
Type: article
Abstract: We report new detections and limits from a NOEMA and ALMA CO(1-0) search for molecular outflows in 13 local galaxies with high far-infrared surface brightness, and combine these with local universe CO outflow results from the literature. The CO line ratios and spatial outflow structure of our targets provide some constraints on the conversion steps from observables to physical quantities such as molecular mass outflow rates. Where available, ratios between outflow emission in higher J CO transitions and in CO(1-0) are typically consistent with excitationRi1 ≲ 1. However, for IRAS 13120−5453,R31 = 2.10 ± 0.29 indicates optically thin CO in the outflow. Like much of the outflow literature, we useαCO(1 − 0)= 0.8, and we present arguments for usingC = 1 in deriving molecular mass outflow ratesṀout=CMoutvout/Rout. We compare the two main methods for molecular outflow detection: CO millimeter interferometry andHerschelOH-based spectroscopic outflow searches. For 26 sources studied with both methods, we find an 80% agreement in detectingvout≳ 150 km s−1outflows, and non-matches can be plausibly ascribed to outflow geometry and signal-to-noise ratio. For a published sample of 12 bright ultraluminous infrared galaxies with detailed OH-based outflow modeling, CO outflows are detected in all but one. Outflow masses, velocities, and sizes for these 11 sources agree well between the two methods, and modest remaining differences may relate to the different but overlapping regions sampled by CO emission and OH absorption. Outflow properties correlate better with active galactic nucleus (AGN) luminosity and with bolometric luminosity than with far-infrared surface brightness. The most massive outflows are found for systems with current AGN activity, but significant outflows in nonAGN systems must relate to star formation or to AGN activity in the recent past. We report scaling relations for the increase of outflow mass, rate, momentum rate, and kinetic power with bolometric luminosity. Short flow times of ∼106yr and some sources with resolved multiple outflow episodes support a role of intermittent driving, likely by AGNs.
Source: Astronomy and Astrophysics
Authors: D. Lutz, E. Sturm, A. Janssen, S. Veilleux, S. Aalto, C. Cicone, A. Contursi, R. I. Davies, C. Feruglio, J. Fischer, A. Fluetsch, S. Garcia-Burillo, R. Genzel, E. González-Alfonso, J. Graciá-Carpio, R. Herrera-Camus, R. Maiolino, A. Schruba, T. Shimizu, A. Sternberg, L. J. Tacconi, A. Weiß
Institutions: Max Planck Institute for Extraterrestrial Physics, Netherlands Institute for Radio Astronomy, Space Telescope Science Institute, University of Cambridge, Joint Space Science Institute, University of Maryland, College Park, Chalmers University of Technology, University of Oslo, Brera Astronomical Observatory, Institut de Radioastronomie Millimétrique, Trieste Astronomical Observatory, George Mason University, Spanish National Observatory, Universidad de Alcalá, University of Concepción, Tel Aviv University, Max Planck Institute for Radio Astronomy
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $1,680
Funders: National Science Foundation, National Radio Astronomy Observatory, Korea Astronomy and Space Science Institute, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, National Astronomical Observatory of Japan, Science and Technology Facilities Council, National Institutes of Natural Sciences
Awards: G1461837398, G8931419319
OpenAlex ID: W2986387576