Exploring the making of a galactic wind in the starbursting dwarf irregular galaxy IC 10 with LOFAR
Journal article, 2018
Low-mass galaxies are subject to strong galactic outflows, in which cosmic rays may play an important role; they can be best traced with low-frequency radio continuum observations, which are less affected by spectral ageing. We present a study of the nearby starburst dwarf irregular galaxy IC 10 using observations at 140MHz with the Low-Frequency Array (LOFAR), at 1580MHz with the Very Large Array (VLA), and at 6200MHz with the VLA and the 100-m Effelsberg telescope.We find that IC 10 has a low-frequency radio halo, which manifests itself as a second component (thick disc) in the minor axis profiles of the non-thermal radio continuum emission at 140 and 1580 MHz. These profiles are then fitted with 1D cosmic ray transport models for pure diffusion and advection.We find that a diffusion model fits best, with a diffusion coefficient of D = (0.4-0.8) × 10 26 (E/GeV) 0.5 cm 2 s -1 , which is at least an order of magnitude smaller than estimates both from anisotropic diffusion and the diffusion length. In contrast, advection models, which cannot be ruled out due to the mild inclination, while providing poorer fits, result in advection speeds close to the escape velocity of ≈50 km s -1 , as expected for a cosmic ray-driven wind. Our favoured model with an accelerating wind provides a self-consistent solution, where the magnetic field is in energy equipartition with both the warm neutral and warm ionized medium with an important contribution from cosmic rays. Consequently, cosmic rays can play a vital role for the launching of galactic winds in the disc-halo interface.
Galaxies: magnetic fields
Radio continuum: galaxies
Cosmic rays
Author
V. Heesen
University of Hamburg
D. Rafferty
University of Hamburg
A. Horneffer
Max Planck Society
R. Beck
Max Planck Society
A. Basu
Bielefeld University
Max Planck Society
J. Westcott
University of Hertfordshire
L. Hindson
University of Hertfordshire
E. Brinks
University of Hertfordshire
K. T. Chyy
Jagiellonian University in Kraków
A. M. M. Scaife
Jodrell Bank Centre for Astrophysics
M. Brueggen
University of Hamburg
G. Heald
University of Groningen
CSIRO Astronomy and Space Science
A. Fletcher
Newcastle University
Cathy Horellou
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
F. Tabatabaei
University of La Laguna
Instituto de Astrofísica de Canarias
R. Paladino
Istituto di Radioastronomia
B. Nikiel-Wroczýnski
University of Hertfordshire
Jagiellonian University in Kraków
M. Hoeft
Thüringer Landessternwarte Tautenburg
R. J. Dettmar
Ruhr-Universität Bochum
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 476 2 1756-1764Subject Categories
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Ocean and River Engineering
DOI
10.1093/mnras/sty325