| Reticulum II | |
|---|---|
| Observation data ( J2000 epoch) | |
| Constellation | Reticulum |
| Right ascension | 03h 35m 42.14s [1] |
| Declination | −54° 2′ 57.1″ [1] |
| Distance | 103 kly (31.6 kpc) [2] |
| Apparent magnitude (V) | 17.4 [1] |
| Characteristics | |
| Apparent size (V) | 3.37′ × 3.64′ [1] |
| Notable features | Enriched in r-process elements |
| Other designations | |
| Reticulum II, Reticulum 2 [1] | |
Reticulum II (or Reticulum 2) is a dwarf galaxy in the Local Group. Reticulum II was discovered in 2015 by analysing images from the Dark Energy Survey. It is a satellite of the Magellanic Clouds and was probably captured relatively recently. [3] Like other dwarf spheroidal galaxies, its stellar population is old: the galaxy was quenched before 11.5 billion years ago. [3]
Reticulum II is elongated, having an major/minor axis ratio of 0.6. The size is given by a half-light radius of 15 parsecs (pc). This is too large for it to be a globular cluster. The absolute magnitude (MV) of the galaxy is −2.7. The distance from Earth is about 30 kpc. [2] The galaxy contains some blue horizontal branch stars. Other features visible are a main sequence, and a main sequence turn off, and a red giant branch. [1] [4] It has an unusual enhancement of r-process elements, meaning that gold and europium are enriched in the brightest stars in the galaxy. [5] About 72% of its stars are enriched in r-process elements. [2] The implication of the unusual enrichment in elements heavier than zinc, is that the r-process is very rare, and only happened once in this galaxy, possibly by the collision of two neutron stars. [6]
Gamma rays mostly with energies between 2 and 10 GeV have been detected by the Fermi satellite. [7] The radiation from Reticulum II is more significant than that of other dwarf galaxy emissions. [8] However this finding has been contested. [9]
- ^ a b c d e f Sergey E. Koposov; Vasily Belokurov; Gabriel Torrealba; N. Wyn Evans (10 March 2015). "Beasts of the Southern Wild. Discovery of a large number of Ultra Faint satellites in the vicinity of the Magellanic Clouds". The Astrophysical Journal. 805 (2): 130. arXiv: 1503.02079. Bibcode: 2015ApJ...805..130K. doi: 10.1088/0004-637X/805/2/130. S2CID 118267222.
- ^ a b c Simon, Joshua D.; et al. (2023). "Timing the r-process Enrichment of the Ultra-faint Dwarf Galaxy Reticulum II". The Astrophysical Journal. 944 (1): 43. arXiv: 2212.00810. Bibcode: 2023ApJ...944...43S. doi: 10.3847/1538-4357/aca9d1. S2CID 254221028.
- ^ a b Sacchi, Elena; Richstein, Hannah; Kallivayalil, Nitya; Van Der Marel, Roeland; Libralato, Mattia; Zivick, Paul; Besla, Gurtina; Brown, Thomas M.; Choi, Yumi; Deason, Alis; Fritz, Tobias; Geha, Marla; Guhathakurta, Puragra; Jeon, Myoungwon; Kirby, Evan; Majewski, Steven R.; Patel, Ekta; Simon, Joshua D.; Tony Sohn, Sangmo; Tollerud, Erik; Wetzel, Andrew (2021). "Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites?". The Astrophysical Journal Letters. 920 (1): L19. arXiv: 2108.04271. Bibcode: 2021ApJ...920L..19S. doi: 10.3847/2041-8213/ac2aa3. S2CID 236965965.
- ^ DES Collaboration (10 March 2015). "Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data". The Astrophysical Journal. 807 (1): 50. arXiv: 1503.02584. Bibcode: 2015ApJ...807...50B. doi: 10.1088/0004-637X/807/1/50. S2CID 12011753.
- ^ Ji, Alex (22 March 2016). "The Origin of the Cosmos' Heaviest Elements". Phys.org. Retrieved 24 March 2016.
- ^ Ji, Alexander P.; Frebel, Anna; Chiti, Anirudh; Simon, Joshua D. (21 March 2016). "R-process enrichment from a single event in an ancient dwarf galaxy". Nature. 531 (7596): 610–613. arXiv: 1512.01558. Bibcode: 2016Natur.531..610J. doi: 10.1038/nature17425. PMID 27001693. S2CID 205248401.
- ^ Hooper, Dan; Linden, Tim (3 September 2015). "On The gamma-ray emission from Reticulum II and other dwarf galaxies". Journal of Cosmology and Astroparticle Physics. 2015 (9): 016. arXiv: 1503.06209. Bibcode: 2015JCAP...09..016H. doi: 10.1088/1475-7516/2015/09/016. S2CID 118482641.
- ^ Geringer-Sameth, Alex; Walker, Matthew G.; Koushiappas, Savvas M.; Koposov, Sergey E.; Belokurov, Vasily; Torrealba, Gabriel; Evans, N. Wyn (17 August 2015). "Indication of Gamma-Ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II". Physical Review Letters. 115 (8): 081101. arXiv: 1503.02320. Bibcode: 2015PhRvL.115h1101G. doi: 10.1103/PhysRevLett.115.081101. PMID 26340176. S2CID 16494335.
- ^ Overbye, Dennis (10 March 2015). "Gamma Rays May Be Clue on Dark Matter". The New York Times. Retrieved 20 October 2016.
| Location |
Milky Way →
Milky Way subgroup →
Local Group →
Local Sheet →
Virgo Supercluster →
Laniakea Supercluster →
Local Hole →
Observable universe →
Universe Each arrow (→) may be read as "within" or "part of". |  | |||||
|---|---|---|---|---|---|---|---|
| Structure |
| ||||||
|
Satellite galaxies | |||||||
| Related | |||||||
| Reticulum II | |
|---|---|
| Observation data ( J2000 epoch) | |
| Constellation | Reticulum |
| Right ascension | 03h 35m 42.14s [1] |
| Declination | −54° 2′ 57.1″ [1] |
| Distance | 103 kly (31.6 kpc) [2] |
| Apparent magnitude (V) | 17.4 [1] |
| Characteristics | |
| Apparent size (V) | 3.37′ × 3.64′ [1] |
| Notable features | Enriched in r-process elements |
| Other designations | |
| Reticulum II, Reticulum 2 [1] | |
Reticulum II (or Reticulum 2) is a dwarf galaxy in the Local Group. Reticulum II was discovered in 2015 by analysing images from the Dark Energy Survey. It is a satellite of the Magellanic Clouds and was probably captured relatively recently. [3] Like other dwarf spheroidal galaxies, its stellar population is old: the galaxy was quenched before 11.5 billion years ago. [3]
Reticulum II is elongated, having an major/minor axis ratio of 0.6. The size is given by a half-light radius of 15 parsecs (pc). This is too large for it to be a globular cluster. The absolute magnitude (MV) of the galaxy is −2.7. The distance from Earth is about 30 kpc. [2] The galaxy contains some blue horizontal branch stars. Other features visible are a main sequence, and a main sequence turn off, and a red giant branch. [1] [4] It has an unusual enhancement of r-process elements, meaning that gold and europium are enriched in the brightest stars in the galaxy. [5] About 72% of its stars are enriched in r-process elements. [2] The implication of the unusual enrichment in elements heavier than zinc, is that the r-process is very rare, and only happened once in this galaxy, possibly by the collision of two neutron stars. [6]
Gamma rays mostly with energies between 2 and 10 GeV have been detected by the Fermi satellite. [7] The radiation from Reticulum II is more significant than that of other dwarf galaxy emissions. [8] However this finding has been contested. [9]
- ^ a b c d e f Sergey E. Koposov; Vasily Belokurov; Gabriel Torrealba; N. Wyn Evans (10 March 2015). "Beasts of the Southern Wild. Discovery of a large number of Ultra Faint satellites in the vicinity of the Magellanic Clouds". The Astrophysical Journal. 805 (2): 130. arXiv: 1503.02079. Bibcode: 2015ApJ...805..130K. doi: 10.1088/0004-637X/805/2/130. S2CID 118267222.
- ^ a b c Simon, Joshua D.; et al. (2023). "Timing the r-process Enrichment of the Ultra-faint Dwarf Galaxy Reticulum II". The Astrophysical Journal. 944 (1): 43. arXiv: 2212.00810. Bibcode: 2023ApJ...944...43S. doi: 10.3847/1538-4357/aca9d1. S2CID 254221028.
- ^ a b Sacchi, Elena; Richstein, Hannah; Kallivayalil, Nitya; Van Der Marel, Roeland; Libralato, Mattia; Zivick, Paul; Besla, Gurtina; Brown, Thomas M.; Choi, Yumi; Deason, Alis; Fritz, Tobias; Geha, Marla; Guhathakurta, Puragra; Jeon, Myoungwon; Kirby, Evan; Majewski, Steven R.; Patel, Ekta; Simon, Joshua D.; Tony Sohn, Sangmo; Tollerud, Erik; Wetzel, Andrew (2021). "Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites?". The Astrophysical Journal Letters. 920 (1): L19. arXiv: 2108.04271. Bibcode: 2021ApJ...920L..19S. doi: 10.3847/2041-8213/ac2aa3. S2CID 236965965.
- ^ DES Collaboration (10 March 2015). "Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data". The Astrophysical Journal. 807 (1): 50. arXiv: 1503.02584. Bibcode: 2015ApJ...807...50B. doi: 10.1088/0004-637X/807/1/50. S2CID 12011753.
- ^ Ji, Alex (22 March 2016). "The Origin of the Cosmos' Heaviest Elements". Phys.org. Retrieved 24 March 2016.
- ^ Ji, Alexander P.; Frebel, Anna; Chiti, Anirudh; Simon, Joshua D. (21 March 2016). "R-process enrichment from a single event in an ancient dwarf galaxy". Nature. 531 (7596): 610–613. arXiv: 1512.01558. Bibcode: 2016Natur.531..610J. doi: 10.1038/nature17425. PMID 27001693. S2CID 205248401.
- ^ Hooper, Dan; Linden, Tim (3 September 2015). "On The gamma-ray emission from Reticulum II and other dwarf galaxies". Journal of Cosmology and Astroparticle Physics. 2015 (9): 016. arXiv: 1503.06209. Bibcode: 2015JCAP...09..016H. doi: 10.1088/1475-7516/2015/09/016. S2CID 118482641.
- ^ Geringer-Sameth, Alex; Walker, Matthew G.; Koushiappas, Savvas M.; Koposov, Sergey E.; Belokurov, Vasily; Torrealba, Gabriel; Evans, N. Wyn (17 August 2015). "Indication of Gamma-Ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II". Physical Review Letters. 115 (8): 081101. arXiv: 1503.02320. Bibcode: 2015PhRvL.115h1101G. doi: 10.1103/PhysRevLett.115.081101. PMID 26340176. S2CID 16494335.
- ^ Overbye, Dennis (10 March 2015). "Gamma Rays May Be Clue on Dark Matter". The New York Times. Retrieved 20 October 2016.
| Location |
Milky Way →
Milky Way subgroup →
Local Group →
Local Sheet →
Virgo Supercluster →
Laniakea Supercluster →
Local Hole →
Observable universe →
Universe Each arrow (→) may be read as "within" or "part of". | | |||||
|---|---|---|---|---|---|---|---|
| Structure |
| ||||||
|
Satellite galaxies | |||||||
| Related | |||||||