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  • Review Article
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Ionized outflows from active galactic nuclei as the essential elements of feedback

Nature Astronomy volume 5, pages 13–24 (2021)Cite this article

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Abstract

Outflows from active galactic nuclei (AGNs) are one of the fundamental mechanisms by which the central supermassive black hole interacts with its host galaxy. Detected in ≥50% of nearby AGNs, these outflows have been found to carry kinetic energy that is a large fraction of the AGN power, and thereby give ‘negative’ feedback to their host galaxies. To understand the physical processes that regulate them, it is important to have a robust estimate of their physical and dynamical parameters. In this Review Article, we summarize our current understanding of the physics of the ionized outflows detected via absorption in the ultraviolet and X-ray wavelength bands. We discuss the most relevant observations and our current knowledge and uncertainties in the measurements of the outflow parameters, as well as their origin and acceleration mechanisms. The commissioning and concept studies of large telescope missions with high-resolution spectrographs in ultraviolet/optical and X-rays along with rapid advancements in simulations offer great promise for discoveries in this field over the next decade.

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Fig. 1: Cartoon depicting the different ionized outflows detected in AGNs and their average physical parameters.
Fig. 2: The deep absorption features in the soft X-ray and UV spectra by ionized absorbers along the line of sight to the AGN.
Fig. 3: Some of the important discoveries in X-ray ionized absorbers made in the last decade.
Fig. 4: The high spectral resolution observations that will be made possible in the soft and hard X-ray energy bands by future telescopes, improving our understanding of the ionized outflows.

The Arcus Collaboration (a); DB/X-IFU (b).

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Authors and Affiliations

  1. Astroparticle Physics Laboratory, NASA Goddard Spaceflight Center, Greenbelt, MD, USA

    Sibasish Laha

  2. Center for Space Science and Technology, University of Maryland Baltimore County, Baltimore, MD, USA

    Sibasish Laha

  3. Institute of Astronomy, University of Cambridge, Cambridge, UK

    Christopher S. Reynolds

  4. Department of Physics, Institute for Astrophysics and Computational Sciences, The Catholic University of America, Washington, DC, USA

    James Reeves

  5. INAF, Osservatorio Astronomico di Brera, Merate, Lecco, Italy

    James Reeves

  6. Space Telescope Science Institute, Baltimore, MD, USA

    Gerard Kriss

  7. ESTEC/ESA, Keplerlaan 1, Noordwijk, The Netherlands

    Matteo Guainazzi

  8. High Energy Astrophysics, Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA

    Randall Smith

  9. Department of Astronomy, University of Maryland, College Park, MD, USA

    Sylvain Veilleux

  10. Joint Space-Science Institute, University of Maryland, College Park, MD, USA

    Sylvain Veilleux

  11. Department of Physics & Astronomy, University of Nevada, Las Vegas, NV, USA

    Daniel Proga

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Laha, S., Reynolds, C.S., Reeves, J. et al. Ionized outflows from active galactic nuclei as the essential elements of feedback. Nat Astron 5, 13–24 (2021). https://doi.org/10.1038/s41550-020-01255-2

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