| SagDIG | |
| Type: | IB(s)m[1] V (Dwarf irregular galaxy) |
| Epoch: | J2000 |
| Dist Ly: | 3.39±0.23 Mly (1.04±0.07 Mpc)[2] [3] |
| Appmag V: | 15.5 |
| Size V: | 2.9 × 2.1 |
| Constellation Name: | Sagittarius |
| Z: | -79±1 km/s |
| Names: | Sagittarius Dwarf Irregular, SGR Dwarf, ESO594-G004, PGC 63287, Kowal's Object |
The Sagittarius Dwarf Irregular Galaxy (SagDIG) is a dwarf galaxy in the constellation of Sagittarius. (SagDIG should not be confused with the Sagittarius Dwarf Spheroidal Galaxy, SagDEG, a satellite galaxy of the Milky Way discovered decades later in the same constellation.) It lies about 3.4 million light-years away. It was discovered by Cesarsky et al. on a photographic plate taken for the ESO (B) Atlas on 13 June 1977 using the ESO 1 meter Schmidt telescope.
The SagDIG is thought to be the member of the Local Group most remote from the Local Group's barycenter. It is only slightly outside the zero-velocity surface of the Local Group.[4]
SagDIG is a much more luminous galaxy than the Aquarius Dwarf and it has been through a prolonged period of star formation.[5] This has resulted in it containing a rich intermediate-age population of stars. Twenty-seven candidate carbon stars have been identified inside SagDIG. Analysis shows that the underlying stellar population of SagDIG is metal-poor (at least [Fe/H] ≤ -1.3). Further, the population is young, with the most likely average age between 4 and 8 billion years for the dominant population.[6]