Measuring size evolution of distant, faint galaxies in the radio regime
Journal article, 2018

We measure the evolution of sizes for star-forming galaxies as seen in 1.4 GHz continuum radio for z = 0-3. The measurements are based on combined VLA+MERLIN data of the Hubble Deep Field, and using a uv-stacking algorithm combined with model fitting to estimate the average sizes of galaxies. A sample of similar to 1000 star-forming galaxies is selected from optical and near-infrared catalogues, with stellar masses Me-circle dot approximate to 10(10)-10(11) M-circle dot and photometric redshifts 0-3. The median sizes are parametrized for stellar mass M-* = 5 x 10(10) M-circle dot as R-e = A x (H(z)/H(1.5))(alpha z). We find that the median radio sizes evolve towards larger sizes at later times with alpha(z) = 1.1 +/- 0.6, and A (the median size at z approximate to 1.5) is found to be 0 ''.26 +/- 0 ''.07 or 2.3 +/- 0.6 kpc. The measured radio sizes are typically a factor of 2 smaller than those measure in the optical, and are also smaller than the typical H alpha sizes in the literature. This indicates that star formation, as traced by the radio continuum, is typically concentrated towards the centre of galaxies, for the sampled redshift range. Furthermore, the discrepancy of measured sizes from different tracers of star formation, indicates the need for models of size evolution to adopt a multiwavelength approach in the measurement of the sizes star-forming regions.

galaxies: structure

techniques: interferometric

galaxies: statistics

radio continuum: galaxies


Lukas Lindroos

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Kirsten Kraiberg Knudsen

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Flora Stanley

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

T. W. B. Muxlow

University of Manchester

R. J. Beswick

University of Manchester

John Conway

Chalmers, Space, Earth and Environment, Onsala Space Observatory

J. F. Radcliffe

Netherlands Institute for Radio Astronomy (ASTRON)

University of Groningen

University of Manchester

N. Wrigley

University of Manchester

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 476 3 3544-3554

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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6/7/2018 1