Yes, I believe it was a copy of a statue erected in Perganom to commemorate a victory over the various Galation tribes. The original, as I was told, was part of a tri-podia statue: on the left podium was the beautiful, yet pathetic depiction of the 'Dying Gaul'; the centre one showed a more noble Galation holding his dead wife in one arm, while he gloriously fell on his sword; and on the right, if my memory serves, was a fallen warrior. Below is an artists impression:
In regards to contemporary sources on the Galations themselves, I vaguely remember Strabo writing about them. Does anybody have a quote handy?