Pisces Overdensity

Not to be confused with Pisces Dwarf.

Pisces Overdensity
Observation data (J2000 epoch)
Constellation	Pisces
Right ascension	23^h 19^m 00^s[1]
Declination	+00° 00′ 00″[1]
Distance	260 kly (80 kpc)[2]
Absolute magnitude (V)	−10.35[3]
Characteristics
Type	dIrr/dSph[3]
Apparent size (V)	~1°[4]
Other designations
Pisces Plume[1]

The Pisces Overdensity is a clump of stars in the Milky Way's halo, which may be a disrupted dwarf spheroidal galaxy.^[5] It is situated in the Pisces constellation and was discovered in 2009 by analysis of distribution of RR Lyrae stars in the data obtained by the Sloan Digital Sky Survey's data.^[2] The galaxy is located at the distance of about 80 kpc from the Sun and moves towards it with a speed of about 75 km/s.^[4]

The Pisces Overdensity is one of the faintest satellites of the Milky Way.^[5] Its mass is estimated to be at least 10⁵ Solar masses.^[2] However it has a large size of about several degrees (around 1 kpc) and may be in a transitional phase between a gravitationally bound galaxy and completely unbound system.^[4] The Pisces Overdensity is located near the plane, where the Magellanic Clouds lie. There may exist a connection between the Magellanic Stream and this galaxy.^[2]

References

1. "NAME Pisces Overdensity". SIMBAD. Centre de données astronomiques de Strasbourg.
2. Watkins, L. L.; et al. (2009), "Substructure revealed by RR Lyraes in SDSS Stripe 82", Monthly Notices of the Royal Astronomical Society, 398 (4): 1757–70, arXiv:0906.0498, Bibcode:2009MNRAS.398.1757W, doi:10.1111/j.1365-2966.2009.15242.x, S2CID 14409027.
3. Boyer, Martha L; Skillman, Evan D; Van Loon, Jacco Th; Gehrz, Robert D; Woodward, Charles E (2009). "Aspitzerstudy of Asymptotic Giant Branch Stars. Iii. Dust Production and Gas Return in Local Group Dwarf Irregular Galaxies". The Astrophysical Journal. 697 (2): 1993. arXiv:0903.3871. Bibcode:2009ApJ...697.1993B. doi:10.1088/0004-637X/697/2/1993. S2CID 12162514.
4. Kollmeier, Juna A.; et al. (2009), "Spectroscopic Confirmation of the Pisces Overdensity", The Astrophysical Journal Letters, 705 (2): L158 – L162, arXiv:0908.1381, Bibcode:2009ApJ...705L.158K, doi:10.1088/0004-637X/705/2/L158, S2CID 9825846.
5. Belokurov, V.; et al. (2010), "Big fish, small fish: Two New Ultra-Faint Satellites of the Milky Way", The Astrophysical Journal Letters, 712 (1): L103–106, arXiv:1002.0504, Bibcode:2010ApJ...712L.103B, doi:10.1088/2041-8205/712/1/L103, S2CID 29195107.