Leo T dwarf galaxy

Database links to Leo T

Galaxy
Leo-T dwarf galaxy

AladinLite

Constellation

lion

Position
equinox : J2000.0 , epoch : J2000.0

Right ascension

09 ^h 34 ^m 53.4 ^s

declination

17 ° 03 ′ 05 ″

Appearance

Morphological type

dSph / dIrr

Brightness (visual)

16 likes

Angular expansion

2.8 ′

Physical data

Affiliation

Local group

distance

1,365,000 Lj /
420,000 pc

history

Catalog names

PGC 4713564 • Leo T

The Leo T , shortly also Leo T , is a dwarf galaxy in the constellation of the lion and was in the year 2006 the data for analysis survey of the Sloan Digital Sky Survey discovered.

The galaxy lies at a distance of about 420 k pc from our solar system and is moving away from it at a speed of approximately 35 km / s . In relation to the Milky Way there is a radial speed of −60 km / s, with which Leo T approaches our galaxy at low speed.

Leo T is classified as a transitional object , hence the T in the name, between a spheroidal (dSph) and irregular (dIrr) dwarf galaxy. The galaxy's half-light radius is 180 pc.

properties

General

Leo T is one of the smallest and faintest galaxies in the Local Group . The absolute brightness of M _V = −7.1 mag corresponds to about 40,000 times that of the sun (other sources also mention M _V = −8.0 mag). At 8 million M _{☉, the} total mass of the dwarf galaxy is so high that it has a high mass-luminosity ratio of around 140, an indication of the dominance by dark matter .

Star population

The star population of Leo T consists of both old and young stars . The older stars formed around 12 billion years ago. The metallicity of this population is very low at [Fe / H] ≈ −2.02 ± 0.54 (other sources also mention −1.5 here). This means that the galaxy contains about 100 times less heavy elements than our sun . The observed stars are old according to their age mostly red giants , although some stars of the horizontal branch and the Red lump (Engl. Red clump ) were observed. After a longer interruption, a star formation phase began again about 1 billion years ago. This resulted in the still visible population of young blue stars. This younger population is more concentrated towards the center of the galaxy and contains only about 10 % of the total stellar mass of the dwarf galaxy. At the moment there is no noticeable 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 is three times the mass of the stars in this galaxy. The gas contains two components, on the 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 6,000 K. However, the density is currently not high enough on average for a new star formation phase, but implies a possible star formation in the future of the galaxy.

Emergence

Leo T apparently formed when a small halo of dark matter began to accretion gas , which later led to the first generation of stars in the now older star population.

Individual evidence

↑ ^a ^b SIMBAD Astronomical Database . In: Results for Leo T Dwarf Galaxy . Retrieved March 14, 2010.
↑ ^a ^b ^c ^d ^e ^f ^g ^h V. Irwin, Belokurov, V .; Evans, NW et al. : Discovery of an Unusual Dwarf Galaxy in the Outskirts of the Milky Way . In: The Astrophysical Journal . 656, No. 1, 2007, pp. L13-L16. arxiv : astro-ph / 0701154 . bibcode : 2007ApJ ... 656L..13I . doi : 10.1086 / 512183 .
^ ^A ^b ^c Joshua D. Simon, Geha, Marla: The Kinematics of the Ultra-faint Milky Way Satellites: Solving the Missing Satellite Problem . In: The Astrophysical Journal . 670, No. 1, 2007, pp. 313-331. arxiv : 0706.0516 . bibcode : 2007ApJ ... 670..313S . doi : 10.1086 / 521816 .
↑ ^a ^b ^c ^d ^e J.TA de Jong, Harris, J .; Coleman, MG, et al. : The Structural Properties and Star Formation History of Leo T from Deep LBT Photometry . In: The Astrophysical Journal . 680, No. 2, 2008, pp. 1112-1119. arxiv : 0801.4027 . bibcode : 2008ApJ ... 680.1112D . doi : 10.1086 / 587835 .
↑ Evan N. Kirby, Simon, Joshua D .; Geha, Marla, et al. : Uncovering Extremely Metal-Poor Stars in the Milky Way's Ultrafaint Dwarf Spheroidal Satellite Galaxies . In: The Astrophysical Journal . 685, No. 1, 2008, pp. L43-L46. arxiv : 0807.1925 . bibcode : 2008ApJ ... 685L..43K . doi : 10.1086 / 592432 .
↑ ^a ^b ^c Emma V. Ryan-Weber, Begum, Ayesha; Oosterloo, Tom, et al. : The Local Group dwarf Leo T: HI on the brink of star formation . In: Mon. Not. R. Astron. Soc . 384, No. 2, 2008, pp. 535-540. arxiv : 0711.2979 . bibcode : 2008MNRAS.384..535R . doi : 10.1111 / j.1365-2966.2007.12734.x .
↑ Massimo Ricotti: Late gas accretion on to primordial minihaloes: a model for Leo T, dark galaxies and extragalactic high-velocity clouds . In: Mon. Not. R. Astron. Soc . 392, No. 1, 2009, pp. L45-L49. arxiv : 0806.2402 . bibcode : 2009MNRAS.392L..45R . doi : 10.1111 / j.1745-3933.2008.00586.x .

[simbad-1] SIMBAD Astronomical Database . In: Results for Leo T Dwarf Galaxy . Retrieved March 14, 2010.

[Irwin2007-2] ↑ ^a ^b ^c ^d ^e ^f ^g ^h V. Irwin, Belokurov, V .; Evans, NW et al. : Discovery of an Unusual Dwarf Galaxy in the Outskirts of the Milky Way . In: The Astrophysical Journal . 656, No. 1, 2007, pp. L13-L16. arxiv : astro-ph / 0701154 . bibcode : 2007ApJ ... 656L..13I . doi : 10.1086 / 512183 .

[Simon2007-3] A ^b ^c Joshua D. Simon, Geha, Marla: The Kinematics of the Ultra-faint Milky Way Satellites: Solving the Missing Satellite Problem . In: The Astrophysical Journal . 670, No. 1, 2007, pp. 313-331. arxiv : 0706.0516 . bibcode : 2007ApJ ... 670..313S . doi : 10.1086 / 521816 .

[Jong2008-4] J.TA de Jong, Harris, J .; Coleman, MG, et al. : The Structural Properties and Star Formation History of Leo T from Deep LBT Photometry . In: The Astrophysical Journal . 680, No. 2, 2008, pp. 1112-1119. arxiv : 0801.4027 . bibcode : 2008ApJ ... 680.1112D . doi : 10.1086 / 587835 .

[Kirby2008-5] Evan N. Kirby, Simon, Joshua D .; Geha, Marla, et al. : Uncovering Extremely Metal-Poor Stars in the Milky Way's Ultrafaint Dwarf Spheroidal Satellite Galaxies . In: The Astrophysical Journal . 685, No. 1, 2008, pp. L43-L46. arxiv : 0807.1925 . bibcode : 2008ApJ ... 685L..43K . doi : 10.1086 / 592432 .

[Ryan-Weber2008-6] Emma V. Ryan-Weber, Begum, Ayesha; Oosterloo, Tom, et al. : The Local Group dwarf Leo T: HI on the brink of star formation . In: Mon. Not. R. Astron. Soc . 384, No. 2, 2008, pp. 535-540. arxiv : 0711.2979 . bibcode : 2008MNRAS.384..535R . doi : 10.1111 / j.1365-2966.2007.12734.x .

[Ricotti2009-7] Massimo Ricotti: Late gas accretion on to primordial minihaloes: a model for Leo T, dark galaxies and extragalactic high-velocity clouds . In: Mon. Not. R. Astron. Soc . 392, No. 1, 2009, pp. L45-L49. arxiv : 0806.2402 . bibcode : 2009MNRAS.392L..45R . doi : 10.1111 / j.1745-3933.2008.00586.x .