NGC 7679 explained

NGC 7679
Credit:HST/NASA/ESA.
Epoch:J2000
Type:SB0 pec[1]
Dist Ly:191 ± 11 Mly (58.6 ± 3.3 Mpc)
Z:0.017139 ± 0.000013
H Radial V:5,138 ± 4 km/s
Appmag V:12.5[2]
Size V:1.3 × 0.9
Constellation Name:Pisces
Notes:Seyfert galaxy, starburst

NGC 7679 is a lenticular galaxy with a peculiar morphology in the constellation Pisces. It is located at a distance of about 200 million light years from Earth, which, given its apparent dimensions, means that NGC 7679 is about 60,000 light years across. It was discovered by Heinrich d'Arrest on September 23, 1864.[3] The total infrared luminosity is, and thus it is categorised as a luminous infrared galaxy.[4] NGC 7679 is both a starburst galaxy and a Seyfert galaxy.[5]

Characteristics

NGC 7679 is a barred lenticular galaxy seen face on, and is noted for its distorted shape. The galaxy has two plumes in opposite directions, possibly the result of tidal interaction with NGC 7682, and smooth outer arms. The inner region is of high surface brightness with many knots and a high star formation rate.[6] The star formation rate of the galaxy is estimated to be 80 per year based on the x-ray luminosity observed by XMM-Newton,[7] and on the H-alpha luminosity of 21.2 ± 0.2 per year while observations in infrared indicate a star formation of 11.35 ± 0.6 per year.[8]

There is evidence of massive starburst activity in the circumnuclear region, with 35% of the stars there being aged less than 10 million years.[9] A ring of ionised gas dominates both the optical and infrared wavelengths and is the locus of the starburst activity.[10]

Nucleus

The nucleus of NGC 7679 has been found to be active and has been categorised as a Seyfert galaxy. The most accepted theory for the energy source of Seyfert galaxies is the presence of an accretion disk around a supermassive black hole. NGC 7679 is believed to host a supermassive black hole whose mass is estimated to be (106.77) based on velocity dispersion.[11]

The X-ray spectrum from BeppoSAX shows no significant absorption above 2 MeV and the iron Ka line was marginally detected.[12] However, the galaxy shows signs of obstruction in visual light, as it lacks broad emission lines. Two possible reasons are the presence of dust or the accretion disk that produces X-rays is not obstructed but the broad line region is.[13] The lack of X-ray absorption along with the presence of broad H-alpha lines but not broad H-beta mean that it cannot be easily categorised as a particular type of Seyfert galaxy.[5]

Nearby galaxies

NGC 7679 forms a pair with NGC 7682. NGC 7682 lies at a distance of 269.7 arcseconds, which corresponds to a projected distance of 97 kpc.[7] The two galaxies are connected by a hydrogen bridge, a sign of a closer encounter in the past 500 million years.[10] It is possible that the interaction of the two galaxies caused star formation in NGC 7679.[14] A fainter galaxy has been found superimposed on the eastern arm of the galaxy, but it is actually located in the background.[10]

See also

Notes and References

  1. Web site: NASA/IPAC Extragalactic Database . Results for NGC 7679 . 2020-11-03.
  2. Web site: Revised NGC Data for NGC 7679 . spider.seds.org . 25 November 2018.
  3. Web site: Seligman . Courtney . NGC 7679 (= PGC 71554) . Celestial Atlas . 19 November 2018.
  4. Sanders . D. B. . Mazzarella . J. M. . Kim . D.-C. . Surace . J. A. . Soifer . B. T. . The IRAS Revised Bright Galaxy Sample . The Astronomical Journal . October 2003 . 126 . 4 . 1607–1664 . 10.1086/376841. 2003AJ....126.1607S . astro-ph/0306263 . 14825701 .
  5. Della Ceca . R. . Pellegrini . S. . Bassani . L. . Beckmann . V. . Cappi . M. . Palumbo . G. G. C. . Trinchieri . G. . Wolter . A. . Unveiling the AGN powering the "Composite" Seyfert/Star-forming galaxy NGC 7679: BeppoSAX and ASCA results . Astronomy & Astrophysics . September 2001 . 375 . 3 . 781–790 . 10.1051/0004-6361:20010913. astro-ph/0106444 . 2001A&A...375..781D . free .
  6. Sandage, A., Bedke, J. (1994), The Carnegie Atlas of Galaxies. Volume I, Carnegie Institution of Washington
  7. Ricci . C. . Bauer . F. E. . Treister . E. . Schawinski . K. . Privon . G. C. . Blecha . L. . Arevalo . P. . Armus . L. . Harrison . F. . Ho . L. C. . Iwasawa . K. . Sanders . D. B. . Stern . D. . Growing supermassive black holes in the late stages of galaxy mergers are heavily obscured . Monthly Notices of the Royal Astronomical Society . 23 January 2017 . stx173 . 10.1093/mnras/stx173. free . 20.500.11850/213867 . free .
  8. Davies . Rebecca L. . Groves . Brent . Kewley . Lisa J. . Dopita . Michael A. . Hampton . Elise J. . Shastri . Prajval . Scharwächter . Julia . Sutherland . Ralph . Kharb . Preeti . Bhatt . Harish . Jin . Chichuan . Banfield . Julie . Zaw . Ingyin . James . Bethan . Juneau . Stéphanie . Srivastava . Shweta . Dissecting galaxies: spatial and spectral separation of emission excited by star formation and AGN activity . Monthly Notices of the Royal Astronomical Society . 21 October 2016 . 462 . 2 . 1616–1629 . 10.1093/mnras/stw1754. free . 1607.05731 .
  9. Gu . Q. S. . Huang . J. H. . de Diego . J. A. . Dultzin-Hacyan . D.. Deborah Dultzin . Lei . S. J. . Benítez . E.. Erika Benítez. The nuclear starburst activity in the Seyfert 2 galaxy NGC 7679 . Astronomy & Astrophysics . August 2001 . 374 . 3 . 932–935 . 10.1051/0004-6361:20010806. astro-ph/0106165 . 2001A&A...374..932G . free .
  10. Buson . L. M. . Cappellari . M. . Corsini . E. M. . Held . E. V. . Lim . J. . Pizzella . A. . NGC 7679: an anomalous, composite Seyfert 1 galaxy whose X-ray luminous AGN vanishes at optical wavelengths . Astronomy & Astrophysics . February 2006 . 447 . 2 . 441–451 . 10.1051/0004-6361:20053204. astro-ph/0510034 . 2006A&A...447..441B . free .
  11. Alonso-Herrero . Almudena. Almudena Alonso-Herrero . Pereira-Santaella . Miguel . Rieke . George H. . Diamond-Stanic . Aleksandar M. . Wang . Yiping . Hernán-Caballero . Antonio . Rigopoulou . Dimitra . Local luminous infrared galaxies. III. Co-evolution of black hole growth and star formation activity? . The Astrophysical Journal . 19 February 2013 . 765 . 2 . 78 . 10.1088/0004-637X/765/2/78. 1301.4015 . 2013ApJ...765...78A . 10261/109183 . 119215482 . free .
  12. Dadina . M. . BeppoSAX observations in the 2–100 keV band of the nearby Seyfert galaxies: an atlas of spectra . Astronomy & Astrophysics . January 2007 . 461 . 3 . 1209–1252 . 10.1051/0004-6361:20065734. 2007A&A...461.1209D . free .
  13. Risaliti . G. . The BeppoSAX view of bright Compton-thin Seyfert 2 galaxies . Astronomy & Astrophysics . May 2002 . 386 . 2 . 379–398 . 10.1051/0004-6361:20020170. astro-ph/0202392 . 2002A&A...386..379R . free .
  14. Yankulova . I. M. . Golev . V. K. . Jockers . K. . The luminous infrared composite Seyfert 2 galaxy NGC 7679 through the [O III] λ 5007 emission line . Astronomy & Astrophysics . July 2007 . 469 . 3 . 891–898 . 10.1051/0004-6361:20077440. free . 0704.0768 .

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