DO NOT USE THIS MAP
It was made in 2005 as a first draft and doesn't remotely satisfy inclusion criteria for Wikipedia.
Original caption:[1]

"The green area suggests a possible extent of (proto-)Celtic influence around 1000 BC. The orange area shows the region of birth of the La Tene style. The red area indicates an idea of the possible region of Celtic influence around 400 BC."  core Hallstatt territory  "birth of the La Tene style"  sphere of possible Celtic influence in 400 BC 275 BC [includes Galatia]
Dubious accuracy / no sources. Compare the maps at  Atlas of the Celtic World, by John Haywood; London Thames &amp; Hudson Ltd., 2001, pp.30-37..
Celts 800-400BC.PNG by Dbachmann
Original:  Dbachmann Vector:  Karl Udo Gerth