Antlia Dwarf
| Antlia Dwarf | |
|---|---|
Antlia Dwarf by Hubble space telescope
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| Observation data (J2000 epoch) | |
| Constellation | Antlia |
| Right ascension | 10h 04m 03.9s |
| Declination | −27° 19′ 55″ |
| Redshift | 362 ± 0 km/s |
| Distance | 1.32 ± 0.06Mpc 1.33 ± 0.10 Mpc 1.31 ± 0.03 Mpc 1.29 ± 0.02 Mpc 1.25 Mpc |
| Group or cluster | Antlia Group |
| Apparent magnitude (V) | 15.67 ± 0.02 |
| Characteristics | |
| Type | dE3.5 dSph, dSph/Irr |
| Mass | 3 × 107M☉ |
| Apparent size (V) | 2′.0 × 1′.5 |
| Other designations | |
| Antlia Dwarf Galaxy,PGC 29194 | |
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.
Antlia Dwarf was first cataloged in 1985 by H. Corwin, Gérard de Vaucouleurs, and A. de Vaucouleurs. Later in 1985 and 1987 it was noted as a possible nearby dwarf galaxy by two groups of astronomers. It was finally confirmed as a dwarf galaxy in 1997 by Alan Whiting, Mike Irwin and George Hau during a survey of the northern sky. They for the first time resolved it into stars and determined the distance to it—1.15 Mpc (the modern distance estimate is slightly larger).
In 1999 Antlia Dwarf was identified by Sidney van den Bergh as the fourth member of the Antlia Group—the group of galaxies closest to the Local Group.
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 that of the Sun (the visible absolute magnitude is MV=−10.3).
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