Astronomy:Goldfish galaxy

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Goldfish galaxy
SDSS image of the Goldfish galaxy
Observation data (J2000.0 epoch)
ConstellationDraco
Right ascension 17h 13m 03.78s[1]
Declination+64° 07′ 01.71″[1]
Redshift0.080923[1]
Helio radial velocity24,260 km/s ± 4[1]
Distance1,176.3 ± 82.4 Mly (360.67 ± 25.25 Mpc)
Group or clusterAbell 2255
Characteristics
TypeRadio galaxy[1]
Size~192,000 ly (58.9 kpc) (estimated)[1]
Other designations
14W 118, 7C 1713+6407a, ABELL 2255:[DMM2003] 2, PGC 59858, SDSS J171303.78+640701.6, 2MASX J17130384+6407014[1]

The Goldfish galaxy, also known as 7C 1713+6407a, is a radio galaxy located in the constellation of Draco. The redshift of the galaxy is z=0.080[1] and it was first discovered by astronomers in 1974 as an astronomical radio source whom they described it having a steep radio spectrum.[2] It is considered to be a member of the rich galaxy cluster Abell 2255, alongside the Beaver galaxy, the Embryo galaxy, the Original TRG, and the Bean Galaxy.[3][4][5]

Description

The Goldfish galaxy is classified as an elliptical galaxy with an active galactic nucleus (AGN).[3] It is a head-tail radio galaxy[4] or alternatively a Fanaroff-Riley class type I narrow-tailed radio galaxy.[6][7] When observed, it is found to have a weak tail feature. The head feature on the other hand, is shown little polarized by around 4%.[4]

Radio imaging made at 1.4 GHz frequencies has found the head of the Goldfish galaxy as clearly resolved with two radio jets on opposite sides, one of them displaying a bend degree towards the east. A compact radio core is detected at 5 GHz frequencies. When imaged at 15 GHz, the nucleus and only the part of the northern jet is found.[7] The tail feature of the Goldfish galaxy is shown to have an total extension of 261 kiloparsecs and further extended by around 180 kiloparsecs towards the direction of southeast.[8] Earlier observations depicted the nucleus as unresolved.[9]

Further observations at sub-arcsecond resolutions have detected traces of radio emission emitting out from the tail region of the Goldfish galaxy. Evidence also found the tail exhibits a helical morphology with jets appearing to spiral around each other before merging back into a single tail feature. A region of increased surface brightness is detected about 170 kiloparsecs away from the core region.[6]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 "NED Search results for Goldfish galaxy". https://ned.ipac.caltech.edu/byname?objname=LEDA+59858&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1. 
  2. ↑ Slingo, A.; Baldwin, J. E. (1974-08-01). "The Structure and Origin of Radio Sources with Very Steep Spectra". Monthly Notices of the Royal Astronomical Society 168 (2): 307–330. doi:10.1093/mnras/168.2.307. ISSN 0035-8711. 
  3. ↑ 3.0 3.1 Davis, David S.; Miller, Neal A.; Mushotzky, Richard F. (November 2003). "Chandra Observations of Point Sources in A2255" (in en). The Astrophysical Journal 597 (1): 202–209. doi:10.1086/378384. ISSN 0004-637X. Bibcode: 2003ApJ...597..202D. https://ui.adsabs.harvard.edu/abs/2003ApJ...597..202D/abstract. 
  4. ↑ 4.0 4.1 4.2 Harris, D. E.; Kapahi, V. K.; Ekers, R. D. (February 1980). "Westerbork synthesis observations of 8 clusters of galaxies which contain tailed radio galaxies.". Astronomy and Astrophysics, Suppl. Ser. 39 (39): 215–233. Bibcode: 1980A&AS...39..215H. https://articles.adsabs.harvard.edu/pdf/1980A%26AS...39..215H. 
  5. ↑ Pizzo, R. F.; Bruyn, A. G. de (2009-11-01). "Radio spectral study of the cluster of galaxies Abell 2255" (in en). Astronomy & Astrophysics 507 (2): 639–659. doi:10.1051/0004-6361/200912465. ISSN 0004-6361. Bibcode: 2009A&A...507..639P. https://www.aanda.org/articles/aa/abs/2009/44/aa12465-09/aa12465-09.html. 
  6. ↑ 6.0 6.1 Rubeis, E. De; Bondi, M.; Botteon, A.; Weeren, R. J. van; Jong, J. M. G. H. J. de; Rudnick, L.; Brunetti, G.; Rajpurohit, K. et al. (2025-07-01). "Revealing the intricacies of radio galaxies and filaments in the merging galaxy cluster Abell 2255 - I. Insights from deep LOFAR-VLBI sub-arcsecond resolution images" (in en). Astronomy & Astrophysics 699: A229. doi:10.1051/0004-6361/202555268. ISSN 0004-6361. Bibcode: 2025A&A...699A.229D. https://www.aanda.org/articles/aa/abs/2025/07/aa55268-25/aa55268-25.html. 
  7. ↑ 7.0 7.1 Gregory, Beatrice Terni de; Feretti, Luigina; Giovannini, Gabriele; Govoni, Federica; Murgia, Matteo; Perley, Rick A.; Vacca, Valentina (2017-11-07), "Narrow head-tail radio galaxies at very high resolution", Astronomy & Astrophysics 608: A58, doi:10.1051/0004-6361/201730878, Bibcode: 2017A&A...608A..58T 
  8. ↑ Pizzo, R. F.; Bruyn, A. G. de; Bernardi, G.; Brentjens, M. A. (2011-01-01). "Deep multi-frequency rotation measure tomography of the galaxy cluster A2255" (in en). Astronomy & Astrophysics 525: A104. doi:10.1051/0004-6361/201014158. ISSN 0004-6361. Bibcode: 2011A&A...525A.104P. https://www.aanda.org/articles/aa/pdf/2011/01/aa14158-10.pdf. 
  9. ↑ L., Feretti; H., Boehringer; G., Giovannini; D., Neumann (January 1997). "The radio and X-ray properties of Abell 2255." (in en). Astronomy and Astrophysics 317: 432. ISSN 0004-6361. Bibcode: 1997A&A...317..432F. 




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