Credit: ESO

A spectrum, covering the 1.6 - 2.45 micron infrared wavelength region was obtained with SOFI''s 'red grism' of the radio galaxy MRC 0406-244 showing the redshifted 'visible' [OIII] doublet (emission from double-ionized oxygen atoms at rest wavelength 4959A and 5007A) and H-alpha (6563 A) emission lines. The oxygen lines are seen to the left and the hydrogen line is in the right half of the diagramme. The 1.8 - 2.0 micron spectral region suffers from absorption in the terrestrial atmosphere and has been removed. After identifying the galaxy in a 1-min imaging exposure and centering it in the 2 arcsec wide entrance slit, four spectral exposures were obtained, each lasting 15 minutes, on two positions along the slit, to permit cancellation of sky emission lines and produce the 'clean' spectrum shown here.

Provider: European Southern Observatory

Image Source: https://www.eso.org/public/images/eso9805f/

Curator: European Southern Observatory, Garching bei München, Germany

Image Use Policy: Creative Commons Attribution 4.0 International License