NGC 520

NGC 520 is a pair of colliding spiral galaxies about 105 million light-years away in the constellation Pisces.[6] They were discovered by astronomer William Herschel on 13 December 1784.[7]

NGC 520
NGC 520 by HST
Observation data (J2000 epoch)
ConstellationPisces
Right ascension01h 24m 35.071s[1]
Declination+03° 47′ 32.68″[1]
Redshift0.007609±0.000010[2]
Heliocentric radial velocity2,281±3 km/s[2]
Distance105 Mly (32.2 Mpc)[3]
Apparent magnitude (V)12.2[4]
Characteristics
TypePec[4]
Apparent size (V)4.5′[4]
Notable featuresInteracting galaxies
Other designations
UGC 966, Arp 157,[5] PGC 5193[4]

Halton Arp called this the second-brightest very disturbed galaxy in the sky, and it is as bright in the infrared and radio bands as the Antennae Galaxies. Simulations indicate this object consists of two galactic disks that began interacting about 300 million years ago. The system is still in an early stage of its merger, showing two separate velocity systems in the spectra, and two small tails. Two galactic nuclei have been detected,[8] and one is an H II nucleus.[9]

The main galactic component is being viewed edge-on, making it fainter in the optical band. The secondary component is brighter but less massive than the main, and is located to the northwest. They are separated by a dark lane of dust. The region of the galaxies outside their nuclei experienced a period of increased star formation roughly around the time they began to interact.[8] Two dwarf objects are located in the vicinity of this merging pair, and one of them, designated UGC957, is located in the northern tidal tail – it may be the result of the interaction.[10]

When viewed in the X-ray band, the interacting galaxies appear around half as luminous as expected given their merger state. Analysis of the gas and molecular features suggests the secondary merger component is gas poor. Most of the star formation, therefore, took place in the gas-rich main component to the southeast. 15 X-ray sources are detected within the merger, with many of them displaying long-term variability. A large galactic wind is evident, being driven by the starburst activity.[8]

References
  1. Skrutskie, Michael F.; et al. (1 February 2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708. ISSN 0004-6256. S2CID 18913331.
  2. Crook, Aidan C.; Huchra, John P.; Martimbeau, Nathalie; Masters, Karen L.; Jarrett, Tom; Macri, Lucas M. (February 2007). "Groups of Galaxies in the Two Micron All Sky Redshift Survey". The Astrophysical Journal. 655 (2): 790–813. arXiv:astro-ph/0610732. Bibcode:2007ApJ...655..790C. doi:10.1086/510201. S2CID 11672751.
  3. Cappellari, Michele; et al. (May 2011). "The ATLAS3D project - I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria". Monthly Notices of the Royal Astronomical Society. 413 (2): 813–836. arXiv:1012.1551. Bibcode:2011MNRAS.413..813C. doi:10.1111/j.1365-2966.2010.18174.x. S2CID 15391206.
  4. "NASA/IPAC Extragalactic Database". Results for NGC 520. Retrieved 2006-12-22.
  5. "NGC 520". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-04-02.
  6. "Distance Results for NGC 0520". NASA/IPAC Extragalactic Database. Retrieved 2010-05-05.
  7. "New General Catalog Objects: NGC 500 - 549". cseligman.com. Retrieved 2017-12-10.
  8. Read, Andrew M. (May 2005). "A Chandra view of the anomalous half-merger NGC 520". Monthly Notices of the Royal Astronomical Society. 359 (2): 455–463. arXiv:astro-ph/0502483. Bibcode:2005MNRAS.359..455R. doi:10.1111/j.1365-2966.2005.08958.x. S2CID 15244648.
  9. Ho, Luis C.; et al. (October 1997). "A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". Astrophysical Journal Supplement. 112 (2): 315–390. arXiv:astro-ph/9704107. Bibcode:1997ApJS..112..315H. doi:10.1086/313041. S2CID 17086638.
  10. Delgado-Donate, E. J.; et al. (May 2003). "Dwarfs after mergers? The case of NGC 520, NGC 772, Arp 141, NGC 3226/7, NGC 3656 and Arp 299". Astronomy and Astrophysics. 402 (3): 921–928. arXiv:astro-ph/0302492. Bibcode:2003A&A...402..921D. doi:10.1051/0004-6361:20030211-1. S2CID 5932040.
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