FIGURE: Spectra of Lyman alpha emitting galaxies at redshifts 5.64, 4.19, 4.02, and 3.05 with the position of the redshifted 1216 Å Hydrogen Lyman alpha line marked, over a wavelength region from approximately 4800 Å to 9700 Å.
High redshift galaxies showing strong Hydrogen Lyman alpha emission may be extremely faint, or undetected, in deep optical or IR continuum images - even in deep exposures made with the 10 m Keck Telescope or with the Hubble Space Telescope. These objects may provide us with a view of galaxies in the earliest stages of the formation process, when there is massive star formation that can excite the Lyman alpha emission line, but which has not yet produced substantial amounts of dust that can suppress this line. Important consequences for our understanding of the early universe are:
The emission line searches can pick out objects which are nearly invisible in the continuum bands as can be seen when we look at the z=4.19 emitter above in a deep HST image
The 10 m Keck II telescope Narrow Band Searches for high z Lyman alpha emitting galaxies are described in more detail in this companion paper. Most of the objects found by this method are star forming galaxies. A few of the emission line objects are AGN.
See our selected bibliography for additional papers on emission-line searches and deep galaxy surveys. A separate set of catalogs for the Hubble Deep Field is also available.
Spectral Searches for these extremely faint emission lines rely on being able to accurately subtract the night sky background to extremely high precision as is described here.
GIF images of Plates 1 and 2 from the paper
The following postscript files are available: