Editing Protogalaxy (section)

{{Short description|Gas cloud forming into a galaxy}}
{{for|the 2010 action-adventure video game|ProtoGalaxy}}

In [[physical cosmology]], a '''protogalaxy''', which could also be called a "'''primeval galaxy'''", is a cloud of [[gas]] which is forming into a [[galaxy]]. It is believed that the rate of [[star formation]] during this period of [[galaxy formation and evolution|galactic evolution]] will determine whether a galaxy is a [[spiral galaxy|spiral]] or [[elliptical galaxy]]; a slower star formation tends to produce a spiral galaxy. The smaller clumps of gas in a protogalaxy form into [[star]]s.

The term "protogalaxy" itself is generally accepted to mean "Progenitors of the present day (normal) galaxies, in the early stages of formation." However, the "early stages of formation" is not a clearly defined phrase. It could be defined as: "The first major burst of [[star formation]] in a progenitor of a present day elliptical galaxy"; "The peak merging [[Epoch (astronomy)|epoch]] of [[dark halo]]s of the fragments which assemble to produce an average galaxy today"; "A still gaseous body before any star formation has taken place."; or " an over-dense region of [[dark matter]] in the very [[early universe]], destined to become [[gravitationally bound]] and to collapse."<ref name=EAAV3>{{cite book|last1=Djorgovski|first1=S.G.|title=Encyclopedia of Astronomy and Astrophysics|volume=3|date=2001|publisher=Institute of Physics Publishing, Nature Publishing Group|location=Dirac House, Temple Back, Bristol|isbn=978-0-333-75088-9|pages=2159–2165|edition=1st}}</ref>