Ly-α Emitting Galaxy-building Objects (LEGOs)

Since the most abundant element in the universe is hydrogen and the strongest transition in the hydrogen atom is Lyman-α (Ly-α), the Ly-α line was early on suggested as a probe of galaxy formation in the early universe (e.g. Partridge & Peebles, 1967, ApJ 147, 868, see here for more information on Ly-α). By studying the Ly-α absorption due to hydrogen clouds along the line of sight to high redshift quasars a wealth of information has been collected about the growth of structure ranging from very dilute clouds only slightly denser than the mean density of the universe and up to forming proto-galaxies - the so called Damped Ly-α Absorbers (DLAs). After many years of wandering in the darkness (Pricthet 1994, PASP 106, 1052) the search for Ly-α emission has in recent years proven to be a powerful tool for studying the galaxy population at high redshifts (z=2-7). We are involved in several projects studying the properties of high redshift Ly-α emitters (or LEGOs as we call them - short for Ly-α Emitting Galaxy-building Objects).
The term LEGO of course refers to the Danish toy building blocks. We choose this name as the Ly-α emitters seem to be the small building blocks out of which todays large galaxies formed through merging of many such small blocks.
At high redshift the Ly-α emitters can be used to map out the large scale structure. An example can be seen in the figure below where 7 LEGOs map out a filamentary structure at redshift z=3.03.

You can find more information on this discovery here:
A Glimpse of the Very Early Universal Web, A&A Letter, BBC, Scientific American, space.com.

Below you can find links with more information on some of our ongoing projects.

The NOT slice of the z=2 universe.

The "Building the Bridge" Ly-α survey.

Ly-α imaging of GRB host galaxy fields.

Here are links to searches for LEGOs at very high redshifts done by other groups: CADIS, LALA, SUBARU.

The first searches for LEGOs with 10m class telescopes were done at the Keck telescopes by Len Cowie, Esther Hu, Richard McMahon and collaborators. See more on that work here.