NGC 1808

NGC 1808
A Hubble Space Telescope (HST) image of NGC 1808 taken using WFPC2.[1]
Observation data (J2000 epoch)
ConstellationColumba[2]
Right ascension05h 07m 42.343s[3]
Declination−37° 30′ 46.98″[3]
Redshift995[4]
Distance41.7 ± 3.9 Mly (12.8 ± 1.2 Mpc)[5]
Group or clusterDorado Group
Apparent magnitude (V)9.94[6]
Apparent magnitude (B)10.83[4]
Absolute magnitude (B)−20.17[7]
Characteristics
Type(R)SAB(s)a[7]
Apparent size (V)7′.41 × 3′.39[8]
Other designations
PGC 16779[9]
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NGC 1808 is a barred spiral galaxy[5] located in the southern constellation of Columba, about two degrees to the south and east of Gamma Caeli.[2] It was discovered by Scottish astronomer James Dunlop, who described it as a "faint nebula".[10] The galaxy is a member of the NGC 1808 group, which is part of the larger Dorado Group.[10]

The morphological classification of this galaxy is (R)SAB(s)a,[7] which indicates a spiral galaxy with a weak-bar around the nucleus (SAB), no ring around the bar (s), an outer ring (R), and tightly-wound spiral arms (a). It is inclined by an angle of 57° to the line of sight from the Earth, with the long axis oriented at a position angle of 324°.[5] The disk of gas and stars shows a noticeable warp, and there is a pronounced asymmetry in the distribution of neutral hydrogen and H II regions.[11]

The core region contains a suspected weak active galactic nucleus plus a circumnuclear ring containing star clusters and supernova remnants at a distance of ~280 pc from the center. These form a ring of peculiar "hot spots".[12] It was formerly identified as a possible Seyfert galaxy,[5] but evidence now points to starburst activity in a ~500 pc radius around the center.[13] A probable outflow of gas is directed to the north-east from the nucleus, forming prominent dust lanes.[5] The high level of star formation in this galaxy and the nearby NGC 1792 may indicate a recent, distant tidal interaction between the two.[11]

The type Ia supernova SN 1993af was discovered in November 1993 at 220″ east and 94″ north of the galactic nucleus.[14][15]

A Hubble Space Telescope image of the center of NGC 1808. Credit: HST/NASA/ESA.
  1. ^ Cite error: The named reference hubb was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Sinnott1997 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Skrutskie2006 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Tully2016 was invoked but never defined (see the help page).
  5. ^ a b c d e Cite error: The named reference Busch2017 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Armando2007 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Erwin2013 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Paturel2003 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference ned was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference OMeara2013 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Dahlem2001 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Salak2016 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Salak2017 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Hamuy1993 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Haumy1996 was invoked but never defined (see the help page).