A group of objects at redshift 3.04

This is a "true-colour" image of part of the sky field near the quasar Q 1205-30. Red, blue and yellow objects are displayed with their true colours, while objects at a redshift of about 3 and with strong Lyman-alpha emission lines have a bright green colour (see the text). Six Lyman-alpha Emitting Galaxy-building Objects (LEGOs for short) are marked by hexagons. The quasar (at the lower left) is marked by a larger hexagon and is seen to have an extended Lyman-alpha cloud in front of it, here visible as extended green light.

Technical information: this image is a colour composite, based on three images. The green channel is based on images with a total exposure time of 17.8 hours, obtained through a 2 nm wide, optical filter, centred at wavelength 490.6 nm and obtained in 1998 with the SuSI2 instrument at the ESO 3.58-m New Technology Telescope (NTT) on La Silla. The blue and red channels are based on 13 400-sec exposures in a B-filter and 15 250-sec exposures in an I-filter, respectively, both obtained with 8.2-m VLT ANTU telescope and the multi-mode FORS1 instrument. The field measures 3.0 x 1.8 arcmin 2. North is up and East is left.