Modelling of the free-free absorption in the starburst galaxy M82 and
  the Sgr A Complex
  The radio emission of normal galaxies may become opaque at low radio
frequencies due to thermal ionized gas. We performed modelling of the free-free
absorption to reproduce the ocal spectrum of SgrA Complex and the global
spectrum of the starburst galaxy M82. We show the importance of resolution of
radio observations and the value of filling factor of the absorbing gas for
correct modelling of the absorption.
