The Antlia Dwarf is a dwarf spheroidal/irregular galaxy. It lies about 1.3 Mpc (4.3 million light-years) from Earth in the constellation Antlia. It is the fourth and faintest member of the nearby Antlia Group of galaxies. The galaxy contains stars of all ages, contains significant amounts of gas, and has experienced recent star formation. The Antlia Dwarf is believed to be tidally interacting with the small barred spiral galaxy NGC 3109.
The Antlia Dwarf is classified alternatively as a dwarf elliptical galaxy of type dE3.5, or either as a dwarf spheroidal galaxy (dSph) or as a transitional galaxy from spheroidal to irregular types (dSph/Irr). The last classification is due to a substantial star formation in this galaxy in the last 0.1 billion years.
Antlia Dwarf comprises two components: a core and an old halo. Its half-light radius is about 0.25 kpc. The metallicity is very low, at about [Fe/H]=−1.6 to −1.9 meaning that Antlia Dwarf contains 40–80 times less heavy elements than the Sun. The galaxy has a well-defined and easily observed red giant branch, which makes measuring its distance relatively easy. The total luminosity of Antlia Dwarf is approximately 1 million times that of the Sun (the visible absolute magnitude is MV=−10.3).
The stellar mass of Antlia Dwarf is estimated to be about 2–4×106 solar masses, while its total mass (within the visible radius) is approximately 4 × 107 solar masses.w The galaxy contains stars of all ages but is dominated by old stars with the age of more than 10 billion year. There seems to have been a major episode of star formation in the Antlia Dwarf around 100 million years ago. However, the young stars are confined to the central core of the galaxy.
Antlia Dwarf is unusual among dwarf spheroidal galaxies in that it contains large amounts (as much as 7 ×105 solar masses) of neutral atomic hydrogen. However it does not have significant H II regions and does not actively form stars at the present moment.
Distance: 4076954 ly
Mass: 6 x 1037 kg