Theo Oberon
From Battlestar Wiki, the free, open content Battlestar Galactica encyclopedia and episode guide
Dash is the callsign of a pilot who was part of Galactica's Viper group.
Dash was killed sometime prior to the destruction of Scar and mentioned by Captain Thrace during a speech about dead Galactica pilots. (Scar)
Notes
It is possible that Dash's callsign was taken from the name of Galactica's first captain Peter Dash.