Lyman-alpha Contours at Radio Galaxy 1138-262
April 28, 2005
False-colour picture of the ionized hydrogen gas surrounding 1138-262 (Lyman-alpha). The size of this cloud is about 5 times larger than the optical extent of the Milky Way Galaxy. A contour plot, as observed with VLT ANTU + FORS1 in a narrow-band filter around the wavelength of the redshifted Lyman-alpha line, is superposed on a false-colour representation of the same image. The contour levels are a geometric progression in steps of 21/2. The image has not been flux calibrated, so the first contour level is arbitrary. The field measures 35 x 25 arcsec2, corresponding to about 910,000 x 650,000 light-years (280 x 200 kpc). The linear scale is indicated at the lower left. North is up and East is left.
Topics: Atomic physics, Astronomical spectroscopy, Physical cosmology, Alpha, Lyman-alpha line, Lyman, Redshift, Galaxy, Milky Way, Very Large Telescope, Telescopes