Ida is the name of a galaxy that was home to the Asgard. At one point, the Ancients also inhabited space in the Ida galaxy or may have been made aware of the Asgard by way of the Destiny. The galaxy is approximately 4 million light years from the Milky Way. (SG1: "The Fifth Race", "Enemies")
The galaxy of Ida was the home of the Asgard race. A millennia ago, it was explored by them once they had attained interstellar travel. It possesses its own Stargate network (which is evidence that the Ancients once explored that part of space). Even though it is not as large as the Milky Way galaxy, it was known to encompass hundreds of worlds. The Stargates within the Ida galaxy can be reached from other galaxies such as the Milky Way or Pegasus by dialing an 8-glyph Stargate address. As the distances between galaxies is so vast, the dialing gate must have a large power source, such as a Zero Point Module to maintain a wormhole. (RPG: "Friends and Foes: Stargate Season Two")
The galaxy of Ida has never been identified with any known galaxy. The possible candidates (i.e. lying approximately 4 million light years (Mly) from the Milky Way) are: Sextans B (4.44 ± 0.23 Mly), NGC 3109 (4.3 ± 0.3 Mly), Sextans A (4.31 ± 0.13 Mly), and Antlia Dwarf (4.31 ± 0.20 Mly). All these 4 galaxies are on the other side of the local cluster compared to the Pegasus galaxy.