NGC 7674

NGC 7674 is a spiral galaxy located in the constellation Pegasus. It is located at a distance of circa 350 million light years from Earth, which, given its apparent dimensions, means that NGC 7674 is about 125,000 light years across. It was discovered by John Herschel on August 16, 1830.[3]

NGC 7674
NGC 7674 by the Hubble Space Telescope
Observation data (J2000 epoch)
ConstellationPegasus
Right ascension23h 27m 56.7s[1]
Declination+08° 46′ 45″[1]
Redshift0.028924 ± 0.000030 [1]
Heliocentric radial velocity8,671 ± 9 km/s[1]
Distance380 Mly (117 Mpc)[1]
Apparent magnitude (V)13.1[2]
Characteristics
TypeSA(r)bc pec [1]
Apparent size (V)1.1′ × 1.0′[1]
Notable featuresSeyfert galaxy
Other designations
UGC 12608, VV 343a, Arp 182, Markarian 533, CGCG 406-112, MCG +01-59-080, PGC 71504[1]

Characteristics

The galaxy is seen nearly face-on, at an inclination of 31 degrees. The central bar-shaped structure, measuring 15×5 arcseconds is made up of stars. The galaxy has two spiral arms that become broader as the distance increases. One arm vanishes at the point it overlaps with the nearby galaxy NGC 7674A. The shape of NGC 7674, including the long narrow streamers emanating northeast and northwest of the galaxy can be accounted for by tidal interactions with its companions. There is no dwarf galaxy seen inside the streamers.[4] It is featured in Arp's Atlas of Peculiar Galaxies as number 182, in the category "galaxies with narrow filaments".[5]

NGC 7674 has a powerful active nucleus of the kind known as a type 2 Seyfert that is perhaps fed by gas drawn into the center through the interactions with the companions.[5] In 1975, observations of excess ultraviolet emission led to designation as Markarian 533 in Markarian's catalog.[6] Later, using spectropolarimetry, emission characteristic of a hidden broad-line region (BLR), visible only in the polarized flux spectrum was detected, implying that the nucleus of NGC 7674 is an obscured type 1 Seyfert, hidden by a dust torus.[7] In the center of NGC 7674 lies a supermassive black hole whose mass is estimated to be nearly 3.63×107 M☉ based on stellar velocity dispersion.[8] When observed in radio waves, NGC 7674 features two radio jets with an S-shape, 0.7 kpc long. The reason for this shape may be a change in the black hole spin axis due to a minor merger, the presence of a binary black hole or due to interactions with the interstellar medium.[9] Two radio sources with characteristics similar to accreting supermassive black holes have been observed in the centre of NGC 7674, at a projected separation of 0.35 parsec.[10]

NGC 7674 falls into the family of luminous infrared galaxies, with its infrared luminosity being 1011.54 L☉.[11] The luminous infrared galaxies are characterised by intense star forming activity. The total star formation rate in NGC 7674 is estimated to be 54 M☉ per year, and the star formation rate at the nucleus is 4.3 M☉ per year.[9]

Two supernovae have been observed in NGC 7674, SN 2011ee (type Ic, mag 18.6) and SN 2011hb (type Ia, mag 18.8).[12]

Nearby galaxies

NGC 7674 is the brightest and largest member of the isolated Hickson 96 compact group of galaxies, consisting of four galaxies. NGC 7674 forms a pair with its smaller companion NGC 7674A, which lies 34 arcseconds to the north. NGC 7675, an elliptical galaxy, lies 2.2 arcminutes to the east.[4][13]

References
  1. "NASA/IPAC Extragalactic Database". Results for NGC 7674. Retrieved 2016-01-18.
  2. "Revised NGC Data for NGC 7674". spider.seds.org. Retrieved 25 November 2018.
  3. Seligman, Courtney. "NGC 7674 (= PGC 71504)". Celestial Atlas. Retrieved 19 November 2018.
  4. Verdes-Montenegro, L.; del Olmo, A.; Perea, J.; Athanassoula, E.; Marquez, I.; Augarde, R. (1 May 1997). "Hickson 96: a physical compact group". Astronomy and Astrophysics. 321: 409–423. arXiv:astro-ph/9702142. Bibcode:1997A&A...321..409V. ISSN 0004-6361.
  5. "HubbleSite: Image - Hubble Interacting Galaxy NGC 7674". hubblesite.org. April 24, 2008.
  6. Markaryan, B. E.; Lipovetskii, V. A. (1974). "Galaxies with ultraviolet continuum V". Astrophysics. 8 (2): 89. Bibcode:1972Ap......8...89M. doi:10.1007/BF01002156. S2CID 122248004.
  7. Miller, J. S.; Goodrich, R. W. (June 1990). "Spectropolarimetry of high-polarization Seyfert 2 galaxies and unified Seyfert theories". The Astrophysical Journal. 355: 456. Bibcode:1990ApJ...355..456M. doi:10.1086/168780.
  8. Woo, Jong-Hak; Urry, C. Megan (10 November 2002). "Active Galactic Nucleus Black Hole Masses and Bolometric Luminosities". The Astrophysical Journal. 579 (2): 530–544. arXiv:astro-ph/0207249. Bibcode:2002ApJ...579..530W. doi:10.1086/342878. S2CID 118160249.
  9. Momjian, Emmanuel; Romney, Jonathan D.; Carilli, Christopher L.; Troland, Thomas H. (10 November 2003). "Sensitive VLBI Continuum and H I Absorption Observations of NGC 7674: First Scientific Observations with the Combined Array VLBA, VLA, and Arecibo". The Astrophysical Journal. 597 (2): 809–822. arXiv:astro-ph/0307399. Bibcode:2003ApJ...597..809M. doi:10.1086/378562. S2CID 16030538.
  10. Kharb, P.; Lal, D. V.; Merritt, D. (18 September 2017). "A candidate sub-parsec binary black hole in the Seyfert galaxy NGC 7674". Nature Astronomy. 1 (10): 727–733. arXiv:1709.06258. Bibcode:2017NatAs...1..727K. doi:10.1038/s41550-017-0256-4. S2CID 119416253.
  11. Lu, Nanyao; Zhao, Yinghe; Díaz-Santos, Tanio; Xu, C. Kevin; Gao, Yu; Armus, Lee; Isaak, Kate G.; Mazzarella, Joseph M.; van der Werf, Paul P.; Appleton, Philip N.; Charmandaris, Vassilis; Evans, Aaron S.; Howell, Justin; Iwasawa, Kazushi; Leech, Jamie; Lord, Steven; Petric, Andreea O.; Privon, George C.; Sanders, David B.; Schulz, Bernhard; Surace, Jason A. (3 May 2017). "A Herschel Space Observatory Spectral Line Survey of Local Luminous Infrared Galaxies from 194 to 671 Microns". The Astrophysical Journal Supplement Series. 230 (1): 1. arXiv:1703.00005. Bibcode:2017ApJS..230....1L. doi:10.3847/1538-4365/aa6476. S2CID 28421031.
  12. List of Supernovae IAU Central Bureau for Astronomical Telegrams. Retrieved 29 December 2015.
  13. de Vaucouleurs, G.; de Vaucouleurs, A.; Corwin, J. R. (1976). "Second reference catalogue of bright galaxies". Second Reference Catalogue of Bright Galaxies. 1976. Bibcode:1976RC2...C......0D.
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