Hidden or missing outflows in highly obscured galaxy nuclei?

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

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DOI

  • Author: Falstad, N.

    Chalmers University of Technology, Sweden

  • Author: Hallqvist, F.

    Chalmers University of Technology, Sweden

  • Author: Aalto, Sanni

    Chalmers University of Technology, Sweden

  • Author: Konig, S.

    Chalmers University of Technology, Sweden

  • Author: Müller, S.

    Chalmers University of Technology, Sweden

  • Author: Aladro, R.

    Max Planck Institute for Radio Astronomy, Germany

  • Author: Combes, F.

    Sorbonne Universités, France

  • Author: Evans, S. A.

    National Radio Astronomy Observatory, United States

  • Author: Fuller, G. A.

    University of Manchester, United Kingdom

  • Author: Gallagher, J. S.

    University of Wisconsin-Madison, United States

  • Author: Garcia-Burillo, S.

    Observatorio de Madrid, Spain

  • Author: Gonzalez-Alfonso, E.

    University of Alcalá, Spain

  • Author: Greve, T. R.

    Astrophysics and Atmospheric Physics, National Space Institute, Technical University of Denmark, Elektrovej, 2800, Kgs. Lyngby, Denmark

  • Author: Henkel, C.

    Max Planck Institute for Radio Astronomy, Germany

  • Author: Imanishi, M.

    National Astronomical Observatory of Japan, Japan

  • Author: Izumi, T.

    National Astronomical Observatory of Japan, Japan

  • Author: Mangum, J. G.

    National Radio Astronomy Observatory, United States

  • Author: Martin, S.

    European Southern Observatory, Chile

  • Author: Privon, G. C.

    University of Florida, United States

  • Author: Sakamoto, K.

    Academia Sinica Taiwan, Taiwan, Province of China

  • Author: Veilleux, S.

    University of Maryland, College Park, United States

  • Author: van der Werf, P.

    Leiden University, Netherlands

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Context. Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed.
Aims
. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs).
Methods
. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs.
Results
. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH.
Conclusions
. We conclude that the galaxy nuclei with the highest LHCN − vib/LIR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.

Original languageEnglish
Article numberA29
JournalAstronomy and Astrophysics
Volume623
ISSN0004-6361
DOIs
Publication statusPublished - 2019
CitationsWeb of Science® Times Cited: No match on DOI

    Research areas

  • Galaxies: evolution, Galaxies: nuclei, Galaxies: ISM, ISM: molecules, ISM: jets and outflows

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