Red nugget

Short description: Unusually small galaxies with large red stars

Red nuggets is the nickname given to rare, unusually small galaxies packed with large amounts of red stars that were originally observed by Hubble Space Telescope in 2005 in the young universe.[1] They are ancient remnants of the first massive galaxies.[2] The environments of red nuggets are usually consistent with the general elliptical galaxy population.[3] Most red nuggets have merged with other galaxies, but some managed to stay unscathed.[4]

## Contents

* 1 Naming
* 2 Formation of red nuggets
* 3 Star formation
* 4 Sloan Digital Sky Survey
* 5 See also
* 6 References

## Naming

Red nuggets are not only nicknamed for their size and color, but also for how precious the discovery is to curious astronomers since it challenged current theories at the time the term was coined on galaxy formation.[1]

## Formation of red nuggets

Red nuggets are formed from blue nuggets. Blue nuggets are early, stream-fed, star-forming systems that are quenched inside-out within the inner kiloparsec (kpc) and dissipatively compacted into red nuggets at their peak of gas compaction. The compaction of the blue nugget happens at an approximately constant specific star formation rate (or SFR). The quenching of the blue nugget happens at a completely constant stellar surface density. Galaxies with more mass quench earlier than galaxies with low amounts of mass because galaxies with low amounts of mass try to quench several times. The compaction happens due to a fierce period of inflow involving (mostly small) mergers and counter-rotating streams or recycled gas. It is also frequently associated with extreme disc instability. The quenching happens because of the extremely high SFR, stellar and supernova feedback, and possibly also active galactic nuclei feedback due to the high gas density in the center of the red nugget.[5][6]

## Star formation

Data from NASA's Chandra X-Ray Observatory observing the red nuggets Mrk 1216 and PGC 032673 has shown that the central black holes suppress star formation in red nuggets with their heat and feed on the gas surrounding them.[7][8][9] This brings up the intriguing question on how they could possibly be packed so densely with stars. Results show that red nuggets may have untapped stellar "fuel" to produce their unusually large number of stars.[10] Another theory says that red nuggets are young elliptical galaxies, therefore forming the same way those do.[11]

## Sloan Digital Sky Survey

A team led by Ivana Damjanov found over 600 red nugget candidates in the Sloan Digital Sky Survey (SDSS) database, of which 9 were confirmed as red nuggets.[12] These red nuggets have been missed so long because, due to their extremely small size, they look like stars in pictures. But their spectra shows what they really are.[13] Damjanov expressed how truly amazing the discovery was when she said, "Looking for 'red nuggets' in the Sloan Digital Sky Survey was like panning a riverbed, washing away silt and mud to uncover bits of gold".[14]

Before Damjanov and her team had thought to look through the immense database of the SDSS, no one could find the elusive galaxies after their original discovery in 2005.[15][16]

## See also

* List of galaxies
* List of nearest galaxies
* List of spiral galaxies

## References

1. ↑ 1.0 1.1 ""Red Nugget" galaxies were hiding in plain sight". Astronomy.com. http://www.astronomy.com/news/2013/09/red-nugget-galaxies-were-hiding-in-plain-sight.
2. ↑ "Ancient "Red Nuggets" Detected --Relics of the 1st Massive Galaxies in the Universe with Gigantic Supermassive Black Holes". http://www.dailygalaxy.com/my_weblog/2018/06/ancient-red-nuggets-detected-relics-of-the-1st-massive-galaxies-in-the-universe-with-gigantic-superm.html.
3. ↑ Oldham, Lindsay; Auger, Matthew W.; Fassnacht, Christopher D.; Treu, Tommaso; Brewer, Brendon J.; Koopmans, L. V. E.; Lagattuta, David; Marshall, Philip et al. (2016-11-03). "Red nuggets grow inside-out: evidence from gravitational lensing" (in en). Monthly Notices of the Royal Astronomical Society 465 (3): 3185–3202. doi:10.1093/mnras/stw2832. ISSN 0035-8711. https://academic.oup.com/mnras/article-abstract/465/3/3185/2417057.
4. ↑ "'Red nuggets' are galactic gold for astronomers". https://phys.org/news/2018-06-red-nuggets-galactic-gold-astronomers.html.
5. ↑ Zolotov, Adi; Dekel, Avishai; Mandelker, Nir; Tweed, Dylan; Inoue, Shigeki; DeGraf, Colin; Ceverino, Daniel; Primack, Joel R. et al. (2015-05-06). "Compaction and quenching of high-z galaxies in cosmological simulations: blue and red nuggets" (in en). Monthly Notices of the Royal Astronomical Society 450 (3): 2327–2353. doi:10.1093/mnras/stv740. ISSN 0035-8711. Bibcode: 2015MNRAS.450.2327Z. https://academic.oup.com/mnras/article-abstract/450/3/2327/1057925.
6. ↑ Dekel, A.; Burkert, A. (2013-12-21). "Wet disc contraction to galactic blue nuggets and quenching to red nuggets" (in en). Monthly Notices of the Royal Astronomical Society 438 (2): 1870–1879. doi:10.1093/mnras/stt2331. ISSN 0035-8711.
7. ↑ Werner, N.; Lakhchaura, K.; Canning, R. E. A.; Gaspari, M.; Simionescu, A. (2018-07-01). "Digging for red nuggets: discovery of hot halos surrounding massive, compact, relic galaxies". Monthly Notices of the Royal Astronomical Society 477 (3): 3886–3891. doi:10.1093/mnras/sty862. ISSN 0035-8711. Bibcode: 2018MNRAS.477.3886W.
8. ↑ "Supermassive Black Holes In Unusual 'Red Nugget' Galaxies Kill Star Formation". International Business Times. 2018-06-22. http://www.ibtimes.com/supermassive-black-holes-unusual-red-nugget-galaxies-kill-star-formation-2693601.
9. ↑ Arce, Nicole (2018-06-22). "Red Nuggets Show Glimpse Into How Supermassive Black Holes Grow So Big" (in en). Tech Times. https://www.techtimes.com/articles/230876/20180622/red-nuggets-show-glimpse-into-how-supermassive-black-holes-grow-so-big.htm.
10. ↑ "Chandra :: Photo Album :: Mrk 1216 :: June 21, 2018". http://chandra.harvard.edu/photo/2018/mrk1216/.
11. ↑ "Digging up "red nuggets" in local elliptical galaxies" (in en-US). Astrobites. 2013-04-14. https://astrobites.org/2013/04/14/digging-up-red-nuggets-in-local-elliptical-galaxies/.
12. ↑ Damjanov, Ivana; Chilingarian, Igor; Hwang, Ho Seong; Geller, Margaret J. (2013). "Discovery of Nine Intermediate-Redshift Compact Quiescent Galaxies in the Sloan Digital Sky Survey". The Astrophysical Journal 775 (2): L48. doi:10.1088/2041-8205/775/2/L48. Bibcode: 2013ApJ...775L..48D.
13. ↑ "Researchers Discover Over 600 "Red Nugget" Galaxy Candidates" (in en-US). SciTechDaily. 2013-09-13. https://scitechdaily.com/researchers-discover-600-red-nugget-galaxy-candidates/.
14. ↑ ""Red Nugget" Galaxies Were Hiding in Plain Sight" (in en). www.cfa.harvard.edu/. 2013-09-30. https://www.cfa.harvard.edu/news/2013-24.
15. ↑ "The Eighth SDSS Data Release (DR8) - SDSS-III". http://www.sdss3.org/dr8/.
16. ↑ "Archival research reveals a missing link." (in en). http://cfht.hawaii.edu/en/news/RedNuggets/.

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