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RGS spectrum of NGC 253
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RGS spectrum of NGC 253

January 24, 2013
The spectrum is dominated by Ly emission lines of silicon, magnesium, neon, oxygen, nitrogen and carbon together with their helium-state emission lines. Additionally we see emission lines from iron. The line strength changes with distance from the galactic centre as the outflowing gas cools. Temperatures in the outflow are between 0.79 keV in the centre of the galaxy down to 0.21 keV furthest away from the starburst nucleus. The iron lines point at a primarily collisional ionized plasma. They also show features of a non-equilibrium plasma especially in region SE 1, where we see additional emission from delayed recombining Fe XVIII.