Leo IV

Leo IV UAC: LEOIV Union Presence: Yes since 5053OTT Union Members present: Yes Traffic Connection: Gates Other designations Leo IV, PGC 4713561

General

Leo IV is a dwarf spheroidal galaxy situated in the Leo constellation, discovered in 2006 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 160 kpc from Pluribus and moves away from Pluribus with the velocity of about 130 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with the half-light radius of about 130 pc.

Leo IV is one of the smallest and faintest satellites of the Milky Way ; its integrated luminosity is about 15000 times that of the Sun (absolute visible magnitude of −5.5±0.3), which is much lower than the luminosity of a typical globular cluster. However, its mass is about 1.5 million solar masses, which means that Leo's mass to light ratio is around 150. A high mass to light ratio implies that Leo IV is dominated by the dark matter.

The stellar population of Leo IV consists mainly of old stars formed more than 12 billion years ago. The metallicity of these old stars is also very low at [Fe/H] ≈ −2.58 ± 0.75, which means that they contain 400 times less heavy elements than Pluribus. The observed stars were primarily red giants, although a number of Horizontal branch stars including three RR Lyrae variable stars were also discovered. The stars of Leo IV were probably among the first stars to form in the Universe. Nevertheless, the detailed study of the stellar population revealed the presence of a small number of much younger stars with the age of about 2 billion years or less. This discovery points to a complicated star formation history of this galaxy. Currently there is no star formation in Leo IV. The measurements have so far failed to detect any neutral hydrogen in it—the upper limit is just 600 solar masses.

In 2008, another galaxy called Leo V was discovered in the vicinity of Leo IV. The former is located 20 kpc further from the Milky Way than the latter and 3 degrees (~ 10 kpc) away from it. These two galaxies are physically associated with each other. ---

LEO IV

As a member of the local group, Leo IV was targeted for a physical survey as part of the of the Local Group Survey Project, first conceived in 4956 OTT. However the LEO IV dwarf being, being 569 Kilo Parsec (1,855,829.78 LY) distant and beyond the reach of then technology. A special seven stage ship was proposed that could make the trip but it was decided not to invest all these resources and funds. Convincing arguments were made that the Y'All would take a long time to make the trip and could be detected in advance if they came from this direction. The dwarf was first visited by Union survey ships in 5053 OTT. As part of the Gate Mapping Survey. There are no gates found that link Leo IV with the M-0 galaxy.

Observation data (J2000 epoch) Constellation    Leo Right ascension    11h 32m 57s Declination    −00° 32′ 00″ Distance    520+49 −45 kly (160+15 −14 kpc) 154±4 kpc Characteristics Type    dSph Apparent size (V)    5.7′ Other designations Leo IV, PGC 4713561 See also: Galaxy, List of galaxies