Leo T (dwarf galaxy)
The Leo T dwarf galaxy shortly Leo T is a dwarf galaxy in the constellation of the Lion, and was discovered in 2006 after analysis of the data of the survey of the Sloan Digital Sky Survey.
The galaxy is at a distance of about 420 kpc away from our solar system and moves away from this with a speed of approximately 35 km / s In relation to the Milky Way gives a radial velocity of -60 km / s, making Leo T our galaxy is approaching at a low speed.
Leo T is a transition type ( engl. transitional object, and the T in the name of therefore ) between a spheroidal ( dSph ) and irregular ( dIrr ) classified dwarf galaxy. The half- light radius of the galaxy is located at 180 pc.
Properties
Generally
Leo T is among the smallest and faintest galaxies of the Local Group. The absolute magnitude of MV = -7.1 likes equivalent to about 40,000 times the sun (other sources mention MV = -8.0 mag). The total mass of the dwarf galaxy is so high that it comes to a high mass-luminosity ratio of about 140, an indication of the dominance of dark matter with 8 million M ☉.
Stellar population
The stellar population of Leo T consists of both old as well as from young stars. The older stars formed already about 12 billion years ago. The metallicity of this population falls to be [Fe / H] ≈ -2.02 ± 00:54 very low ( other sources mention here also -1.5 ). This means the galaxy contains about 100 times less in heavy elements than our Sun. The observed old stars are matched for age, mainly red giants, although some stars of the horizontal branch and the red clump (german red clump ) were observed. After a break sat billion years ago, about 1 again a star formation phase. This resulted in the even now visible population of young blue stars. This younger population is more focused to the center of the galaxy and contains only about 10 % of the stellar mass of the dwarf galaxy. At present, it should be noted no significant star formation in Leo T.
Composition
Leo T has a significant amount of neutral hydrogen gas ( HI) with a mass of about 280,000 M ☉, which corresponds to three times the mass of stars in this galaxy. The gas contains two components, one hand cool gas in the center of the dwarf galaxy with a temperature of approximately 500 K, on the other hand warm gas evenly distributed over the entire galaxy with a temperature of about 6000 K. However, the density is in the middle currently not large enough for a new star formation phase, but implies a possible star formation in the future of the galaxy.
Formation
Leo T formed probably as a small halo of dark matter began to accrete gas, which then led to the first generation of stars of the now older stellar population later.