NGC 1672

NGC 1672 is a barred spiral galaxy located in the constellation Dorado. It was originally thought to be a member of the Dorado Group,[2] however, this membership was later rejected.[3] NGC 1672 has a large bar which is estimated to measure around 20 kpc.[4] It has very strong radio emissions emanating from its nucleus, bar, and the inner portion of the spiral arm region.[4] The nucleus is Seyfert type 2 and is engulfed by a starburst region.[4] The strongest polarized emissions come from the northeastern region which is upstream from its dust lanes.[4] Magnetic field lines are at large angles with respect to the bar and turn smoothly to the center.[4]

NGC 1672
NGC 1672 HST
A Hubble Space Telescope (HST) image of NGC 1672.
Observation data (J2000 epoch)
ConstellationDorado
Right ascension 04h 45m 42s[1]
Declination−59° 14′ 56″[1]
Redshift1331 ± 3 km/s[1]
Apparent magnitude (V)10.3[1]
Characteristics
Type(R')SB(r)bc[1]
Apparent size (V)6′.6 × 5′.5[1]
Other designations
PGC 15941[1]
NGC 1672 GALEX WikiSky
A GALEX ultraviolet image of NGC 1672

General structure

The center of the galaxy contains a high surface brightness bar, and four filament-like spiral arms extend outward from the ends of this bar. The spiral arms are asymmetric; one of the arms in the northeast part of the disk is significantly brighter than its counterpart on the other side. The spiral arms also contain numerous star formation regions, some of which may be as large as 4′′.[5]

Nucleus

The classification of the nucleus of NGC 1672 is uncertain. Most galaxies may be classified by their spectra as having one of three different types of nuclei:[6]

NGC 1672, however, is one of several nearby galaxies that does not fit into this classification scheme, as its spectrum appears intermediary between these three classes of objects.[6] It may in fact contain both nuclear star formation regions and an AGN. In some wave bands (such as in ultraviolet light), the star formation regions are the primary source of emission.[7]

See also

References

  1. ^ a b c d e f g "NASA/IPAC Extragalactic Database". Results for NGC 1672. Retrieved 2007-04-04.
  2. ^ Huchra, J. P.; Geller, M. J. (June 15, 1982). "Groups of galaxies. I - Nearby groups". Astrophysical Journal. 257 (Part 1): 423–437. Bibcode:1982ApJ...257..423H. doi:10.1086/160000.
  3. ^ Maia, M. A. G.; da Costa, L. N.; Latham, David W. (April 1989). "A catalog of southern groups of galaxies". Astrophysical Journal Supplement Series. 69: 809–829. Bibcode:1989ApJS...69..809M. doi:10.1086/191328. ISSN 0067-0049.
  4. ^ a b c d e Beck, R.; Shoutenkov, V.; Ehle, M.; Harnett, J. I.; et al. (August 2002). "Magnetic fields in barred galaxies. I. The atlas". Astronomy and Astrophysics. 391 (1): 83–102. arXiv:astro-ph/0207201. Bibcode:2002A&A...391...83B. doi:10.1051/0004-6361:20020642.
  5. ^ A. Sandage; J. Bedke (1994). Carnegie Atlas of Galaxies. Washington, D.C.: Carnegie Institution of Washington. ISBN 978-0-87279-667-6.
  6. ^ a b P. Veron; A. C. Goncalves; M. P. Veron-Cetty (1997). "AGNs with composite spectra". Astronomy and Astrophysics. 319: 52–66. Bibcode:1997A&A...319...52V.
  7. ^ A. L. Kinney; R. C. Bohlin; D. Calzetti; N. Panagia; et al. (1993). "An atlas of ultraviolet spectra of star-forming galaxies". Astrophysical Journal Supplement Series. 86: 5–93. Bibcode:1993ApJS...86....5K. doi:10.1086/191771.

External links

Dorado Group

The Dorado Group is a loose concentration of galaxies containing both spirals and ellipticals. It is generally considered a 'galaxy group' but may approach the size of a 'galaxy cluster'. It lies primarily in the southern constellation Dorado and is one of the richest galaxy groups of the Southern Hemisphere. Gérard de Vaucouleurs was the first to identify it in 1975 as a large complex nebulae II in the Dorado region, designating it as G16.

NGC 1300

NGC 1300 is a barred spiral galaxy located about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across (about the same size of the Milky Way). It is a member of the Eridanus Cluster, a cluster of 200 galaxies. It was discovered by John Herschel in 1835.In the core of the larger spiral structure of NGC 1300, the nucleus shows a "grand-design" spiral structure that is about 3,300 light-years long. Only galaxies with large-scale bars appear to have these grand-design inner disks — a spiral within a spiral. Models suggest that the gas in a bar can be funneled inwards, and then spiral into the center through the grand-design disk, where it can potentially fuel a central supermassive black hole (SMBH). NGC 1300 is not known to have an active nucleus, indicating that its central black hole is not accreting matter. The SMBH has a mass of 7.3+6.9−3.5×107 M☉.

Seyfert galaxy

Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. They have quasar-like nuclei (very luminous, distant and bright sources of electromagnetic radiation) with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, their host galaxies are clearly detectable.Seyfert galaxies account for about 10% of all galaxies and are some of the most intensely studied objects in astronomy, as they are thought to be powered by the same phenomena that occur in quasars, although they are closer and less luminous than quasars. These galaxies have supermassive black holes at their centers which are surrounded by accretion discs of in-falling material. The accretion discs are believed to be the source of the observed ultraviolet radiation. Ultraviolet emission and absorption lines provide the best diagnostics for the composition of the surrounding material.Seen in visible light, most Seyfert galaxies look like normal spiral galaxies, but when studied under other wavelengths, it becomes clear that the luminosity of their cores is of comparable intensity to the luminosity of whole galaxies the size of the Milky Way.Seyfert galaxies are named after Carl Seyfert, who first described this class in 1943.

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