Astronomy:Pisces II

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Pisces II
Observation data (J2000 epoch)
ConstellationPisces
Right ascension 22h 58m 31s[1]
Declination+05° 57′ 09″[1]
Distance585 kly (180 kpc)[1]
Apparent magnitude (V)17.03[2]
Absolute magnitude (V)−4.28[2]
Characteristics
TypedSph
Apparent size (V)2.2+0.2−0.2′[1]
Other designations
Pisces II,[3] Psc II[4][upper-alpha 1]

Pisces II (Psc II)[6][upper-alpha 1] is an ultra-faint dwarf-spheroidal galaxy and satellite of the Milky Way, located in the Pisces constellation 180 kpc (587,081 light years) from Earth.[1] Discovered in 2009 by public analysis of Data Release 7 (DR7) of the Sloan Digital Sky Survey,[1] it is classified as a dwarf spheroidal galaxy (dSph) and is one of the smallest and faintest satellite galaxies of the Milky Way.[2][7]

Structure

Pisces is a small irregular galaxy, with a moderately-aged and older stellar population of metal-poor stars, consisting primarily of stars formed about 10 billion years ago.[1][8] The metallicity of these old stars is low, at −2.3 < [Fe/H] < −1.7, which means that the ratio of their mass that consists of heavy metals[upper-alpha 2] is less than that of the Sun.[1] Its luminosity is about 10,000 times that of the Sun (absolute magnitude of about −5), which corresponds to the luminosity of an average globular cluster.[6][8]

Potential past interactions

In 2016, follow-up work on Pisces II and Pegasus III[8] highlighted that both lie relatively close to each other (within approximately 43 kiloparsecs), and share similar radial velocities in the Milky Way's rest frame.[2][8] This suggests that these two satellite galaxies may actually be associated with one another, potentially having interacted in the past; however, further spectroscopic measurements are needed to confirm this.[2][7]

See Also

Notes

  1. ↑ 1.0 1.1 Andromeda II was also given the alias Pisces II by Martin et al. (2009), who also proposed aliases for several other satellite galaxies of the Andromeda Galaxy[5] However, that name was later used by a different group unaware of these names, for this object.
  2. ↑ In astronomy and physical cosmology, unlike other physical sciences, "heavy metals" refers to all elements except hydrogen and helium.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Belokurov, V.; Walker, M. G.; Evans, N. W.; Gilmore, G.; Irwin, M. J.; Just, D.; Koposov, S.; Mateo, M. et al. (2010). "Big Fish, Little Fish: Two New Ultra-Faint Satellites of the Milky Way". The Astrophysical Journal 712 (1): L103–L106. doi:10.1088/2041-8205/712/1/L103. Bibcode: 2010ApJ...712L.103B. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Richstein, Hannah; Patel, Ekta; Kallivayalil, Nitya; Simon, Joshua D.; Zivick, Paul; Tollerud, Erik; Fritz, Tobias; Warfield, Jack T. et al. (2022). "Structural Parameters and Possible Association of the Ultra-faint Dwarfs Pegasus III and Pisces II from Deep Hubble Space Telescope Photometry". The Astrophysical Journal 933 (2): 217. doi:10.3847/1538-4357/ac7226. Bibcode: 2022ApJ...933..217R. 
  3. ↑ "Object No. 1 - PISCES II". NASA/IPAC Extragalactic Database. https://ned.ipac.caltech.edu/cgi-bin/objsearch?objname=pisces+II&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES. 
  4. ↑ "NAME Pisces II -- Galaxy". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NAME+Pisces+II+--+Galaxy. 
  5. ↑ Martin, Nicolas F.; McConnachie, Alan W.; Irwin, Mike; Widrow, Lawrence M.; Ferguson, Annette M. N.; Ibata, Rodrigo A.; Dubinski, John; Babul, Arif et al. (1 November 2009). "PAndAS' CUBS: Discovery of Two New Dwarf Galaxies in the Surroundings of the Andromeda and Triangulum Galaxies". The Astrophysical Journal 705 (1): 758–765. doi:10.1088/0004-637X/705/1/758. Bibcode: 2009ApJ...705..758M. 
  6. ↑ 6.0 6.1 "Dwarf Galaxies in Pisces - NASA Science" (in en-US). 2016-08-11. https://science.nasa.gov/asset/hubble/dwarf-galaxies-in-pisces/. 
  7. ↑ 7.0 7.1 Kim, Dongwon; Jerjen, Helmut; Geha, Marla; Chiti, Anirudh; Milone, Antonino P.; Mackey, Dougal; da Costa, Gary; Frebel, Anna et al. (2016). "Portrait of a Dark Horse: A Photometric and Spectroscopic Study of the Ultra-Faint Milky Way Satellite Pegasus III". The Astrophysical Journal 833 (1): 16. doi:10.3847/0004-637X/833/1/16. Bibcode: 2016ApJ...833...16K. 
  8. ↑ 8.0 8.1 8.2 8.3 Garofalo, Alessia; Tantalo, Maria; Cusano, Felice; Clementini, Gisella; Calura, Francesco; Muraveva, Tatiana; Paris, Diego; Speziali, Roberto (2021-07-01). "Born in a Pair (?): Pisces II and Pegasus III*". The Astrophysical Journal 916 (1): 10. doi:10.3847/1538-4357/ac0253. ISSN 0004-637X. Bibcode: 2021ApJ...916...10G. 

Further reading

  • Sand, David J; Strader, Jay; Willman, Beth; Zaritsky, Dennis; McLeod, Brian; Caldwell, Nelson; Seth, Anil; Olszewski, Edward (2012). "Tidal Signatures in the Faintest Milky Way Satellites: The Detailed Properties of Leo V, Pisces Ii, and Canes Venatici Ii". The Astrophysical Journal 756 (1): 79. doi:10.1088/0004-637X/756/1/79. Bibcode: 2012ApJ...756...79S. 



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