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HCG 2

HCG 2
HCG 2 by Legacy Surveys DR10
Observation data (Epoch J2000)
ConstellationPisces
Right ascension00h 31m 30.0s
Declination+08° 25′ 52.0″
Number of galaxies4
Velocity dispersion55 km/s
Redshift0.014479
Distance192 Mly (58.9 Mpc)
Other designations
HCG 002; WBL 012; PPS2 069; HIPASS J0031+08

HCG 2 is one of the compact groups of galaxies in the Hickson Compact Group of galaxies. It is located in Pisces east of HD 2679 and is 192 million light-years away. HCG 2 is one of a hundred such groups identified by a systematic search of the Palomar Observatory Sky Survey red prints in 1982 by Paul Hickson.[1] Hickson Compact Group 2 has a velocity dispersion of 55 km/s and the crossing time (H0tc) of HCG 2 is 0.087.[2] HCG 2 is classified as a Gas Rich Group, which studies show that UGC 00312 has many bright star forming regions, whereas MCG +01-02-018 (Mrk 552[3]) is a compact and luminous galaxy[4].

Properties

HCG 2A is the brightest member of this group, which has a Blue Minus Red (B-R) of 0.88, and a Corrected Total Blue Magnitude (B_TC) of 13.35, suggesting that it is a galaxy high in Star Birth and Interstellar Gas Reservoirs. While HCG 2A is the brightest, HCG 2D is dimmest and furthest galaxy, which has a B-R of 1.54, B_TC of 15.74, a distance and a velocity of 1,009.8 Million Light Years, 21340 km/s respectively, revealing it is a galaxy in the deep universe and is likelihood dominated by ageing and cooling stars.[5]

A study suggests that the Spiral fraction is 100%, indicating all 4 galaxies in this group are spirals.[5] In another study, HCG 2A, 2B and 2C have a disturbed morphology, hinting to astronomers that it is gravitationally interacting with other galaxies and possibly merging. For HCG 2A, it has a tail, and is a possible strong Infrared source, while HCG 2B, is a strong Infrared source, indicating a high amount star formation and stellar nurseries. [6]

Another study shows that in the background field of HCG 2, there are 18 foreground stars and 27 foreground galaxies that are in a significant distance away from the group.[5]

Members

HCG 2 consists of four member galaxies.[1] Their names and basic properties are listed below.[7]

Galaxy Type Right ascension Declination Diameter (Arcsec") Distance B_TC B-R Redshift Velocity (km/s)[8] Minor Axis Diameter(")[9] Major Axis Diameter(")[9]
UGC 00312[10] SB? 00h 31m 23.9041s +08° 28′ 01.287″ 102.00 193.3 Mly (59.27 Mpc) 13.35 0.88 0.014570 4326 40.50 19.70
MCG +01-02-018[11] S? 00h 31m 18.8591s +08° 28′ 30.229″ 66.00 192.5 Mly (59.02 Mpc) 14.39 1.14 0.014513 4366 21.20 18.40
UGC 00314[12] S? 00h 31m 29.3520s +08° 28′ 02.232″ 72.00 188.6 Mly (57.83 Mpc) 14.15 1.10 0.014243 4235 32.90 18.10
UGC 00315[13] SBc 00h 31m 38.3062s +08° 28′ 26.423″ 60.00 1,009.8 Mly (309.60 Mpc) 15.72 1.54 0.071183 21340 13.20 12.00

References

  1. ^ a b Hickson, P. (1982). "Systematic properties of compact groups of galaxies". Astrophysical Journal. 255: 382. Bibcode:1982ApJ...255..382H. doi:10.1086/159838.
  2. ^ Hickson, P. (1992). "Dynamical Properties of Compact Groups of Galaxies". Astrophysical Journal. 399: 353. Bibcode:1992ApJ...399..353H. doi:10.1086/171932.
  3. ^ "NED results for Mrk 552". NASA/IPAC Extragalactic Database. Retrieved 2026-05-16.
  4. ^ Johnson, K. E. (2007). "The Infrared Properties of Hickson Compact Groups". The Astronomical Journal. 134: 1522. arXiv:0706.4461. Bibcode:2007AJ....134.1522J. doi:10.1086/520921.
  5. ^ a b c Kindl, Enrico (1991). A photometric and morphological study of compact groups of galaxies and their environments (Ph.D. thesis). University of British Columbia.
  6. ^ Mendes de Oliveira, C.; Hickson, P. (1994). "Morphology of Galaxies in Compact Groups". The Astrophysical Journal. 427: 684. arXiv:astro-ph/9311065. Bibcode:1994ApJ...427..684M. doi:10.1086/174176.
  7. ^ "NED results for HCG 2". NASA/IPAC Extragalactic Database. Retrieved 2026-05-16.
  8. ^ Hickson, P. (1993). "Atlas of Compact Groups of Galaxies". Astrophysical Letters and Communications. 29: 10. Bibcode:1993ApL&C..29....1H.
  9. ^ a b Hickson, P.; Kindl, E.; Auman, J. R. (1989). "A photometric catalog of compact groups of galaxies". The Astrophysical Journal Supplement Series. 70: 687. Bibcode:1989ApJS...70..687H. doi:10.1086/191354.
  10. ^ "NED results for UGC 312". NASA/IPAC Extragalactic Database. Retrieved 2026-05-16.
  11. ^ "NED results for MCG +01-02-018". NASA/IPAC Extragalactic Database. Retrieved 2026-05-16.
  12. ^ "NED results for UGC 314". NASA/IPAC Extragalactic Database. Retrieved 2026-05-16.
  13. ^ "NED results for UGC 315". NASA/IPAC Extragalactic Database. Retrieved 2026-05-16.

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