But even as the stars and quasars within these protogalaxies
began to light up, the universe as a whole remained dark.
As stars, protogalaxies
, and perhaps mini-quasars started to appear more than 100 million years later, these sources started to ionize the intergalactic gas in their vicinity.
Because intense star birth may be a signpost of the formation of galaxies, WIRE will also search for fledgling galaxies, known as protogalaxies
At this stage, each galaxy would still be a large clump of gas accompanied by a collection of uniformly blue, metal-poor globular clusters--only a few for smaller protogalaxies
, many more for massive ones.
The evidence strongly supports the notion that damped Lyman-alpha systems represent a population of protogalaxies
in the early universe, Djorgovski says.
In addition, some of the more distant of these newly identified galaxies may represent a long-sought population of protogalaxies
High on the telescope's checklist are not-quite-stellar brown dwarfs, dust-clogged infant planetary systems in star-forming regions, massive gas clouds containing wisps of sooty dust and organic molecules, and protogalaxies
dating back nearly to the dawn of time.
Thompson and Stanislav Djorgovski recently launched a search for protogalaxies
-- distant, primeval galaxies undergoing their first major burst of star formation -- by analyzing light emitted from high-redshift objects illuminated by quasars behind them.
that collapse relatively rapidly convert a large amount of gas into stars, leaving little left over to form an extended disk.
They assume protogalaxies
tend to concentrate in regions of higher-than-average density of cold dark matter, whereas low-density regions tend to harbor few protogalaxies
Wenk says Tyson and his colleagues are now looking at clouds of gas in the same area that may be protogalaxies
forming even closer to the beginning of the universe.
However, NGST will observe primarily at infrared wavelengths, as its primary task is to study high-redshift galaxies and protogalaxies