Feedback in W49A diagnosed with radio recombination lines and models

¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: rugel@mpia.de
² Zentrum für Astronomie, Institut für Theoretische Astrophysik, Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
³ National Radio Astronomy Observatory, PO Box O, 1003 Lopezville Road, Socorro, NM 87801, USA
⁴ Max Planck Institute for Radioastronomy, Auf dem Hügel 69, 53121 Bonn, Germany
⁵ Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506, USA
⁶ Adjunct Astronomer at the Green Bank Observatory, PO Box 2, Green Bank, WV 24944, USA
⁷ Center for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USA
⁸ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁹ Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
¹⁰ Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, INF 205, Universität Heidelberg, 69120 Heidelberg, Germany
¹¹ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
¹² School of Physical Sciences, University of Kent, Ingram Building, Canterbury, Kent CT2 7NH, UK
¹³ School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff, CF24 3AA, UK
¹⁴ Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT, Australia
¹⁵ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁶ Department of Physics, Indian Institute of Science, Bangalore 560012, India

Received: 10 August 2018
Accepted: 28 November 2018

Abstract

We present images of radio recombination lines (RRLs) at wavelengths around 17 cm from the star-forming region W49A to determine the kinematics of ionized gas in the THOR survey (The H I/OH/Recombination line survey of the inner Milky Way) at an angular resolution of 16.′′8 × 13.′′8. The distribution of ionized gas appears to be affected by feedback processes from the star clusters in W49A. The velocity structure of the RRLs shows a complex behavior with respect to the molecular gas. We find a shell-like distribution of ionized gas as traced by RRL emission surrounding the central cluster of OB stars in W49A. We describe the evolution of the shell with the recent feedback model code WARPFIELD that includes the important physical processes and has previously been applied to the 30 Doradus region in the Large Magellanic Cloud. The cloud structure and dynamics of W49A are in agreement with a feedback-driven shell that is re-collapsing. The shell may have triggered star formation in other parts of W49A. We suggest that W49A is a potential candidate for star formation regulated by feedback-driven and re-collapsing shells.