NGC 1705

NGC 1705 is a peculiar lenticular galaxy and a blue compact dwarf galaxy (BCD)[3] in the southern constellation of Pictor, positioned less than a degree to the east of Iota Pictoris,[6] and is undergoing a starburst.[7] With an apparent visual magnitude of 12.6[4] it requires a telescope to observe. It is estimated to be approximately 17 million light-years from the Earth,[8] and is a member of the Dorado Group.[9]

NGC 1705
NGC 1705.jpg
NGC 1705. Credit: NASA.
Observation data (J2000 epoch)
Right ascension04h 54m 13.500s[1]
Declination−53° 21′ 39.82″[1]
Redshift633 ± 6 km/s[2]
Distance16.6 ± 2.0 Mly (5.1 ± 0.6 Mpc)[3]
Group or clusterDorado Group
Apparent magnitude (V)12.56±0.03[4]
TypeSA0 pec[2] or BCD[3]
Apparent size (V)1′.86 × 1′.45[5]
Other designations
PGC 16282[2]

This is a relatively isolated galaxy, with its nearest neighbors being more than 500 kpc distant. However, its neutral hydrogen disk shows a significant amount of warp, suggesting that the outer gas is still settling into place.[3] The mass models of the galaxy suggest the dominant source of mass is a dark matter halo.[10] It has a super star cluster located near the galactic center,[10] and shows strong galactic winds.[3] Designated NGC1750–1, this cluster has a maximum radius of 2.85±0.50 pc and is 12±6 Myr old.[11]

The major starburst activity is happening at the core of the galaxy, within the central ~150 pc, and this is providing the main ionizing source out to distance of ~1 kpc or more.[7] Over the last 10 million years it has added 5.7×105 M worth of stars.[3] The younger stars in the galaxy with an age below a billion years have an estimated 6×107 M and are mainly concentrated near the center, while the older star populations have 2.2×108 M and form a more extended distribution. The total mass of neutral hydrogen in the galaxy is estimated at (2.2±0.2)×108 M.[10]


  1. ^ a b Skrutskie, M. F.; et al. (2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708.
  2. ^ a b c "NASA/IPAC Extragalactic Database". Results for NGC 1705. Retrieved 2006-11-29.
  3. ^ a b c d e f Cignoni, M.; et al. (March 2018). "Star Formation Histories of the LEGUS Dwarf Galaxies. I. Recent History of NGC 1705, NGC 4449, and Holmberg II". The Astrophysical Journal. 856 (1): 17. arXiv:1802.06792. Bibcode:2018ApJ...856...62C. doi:10.3847/1538-4357/aab041. S2CID 119485664. 62.
  4. ^ a b Cook, David O.; et al. (2014). "Spitzer Local Volume Legacy (LVL) SEDs and physical properties". Monthly Notices of the Royal Astronomical Society. 445 (1): 899–912. arXiv:1409.0847. Bibcode:2014MNRAS.445..899C. doi:10.1093/mnras/stu1787.
  5. ^ Paturel, G.; et al. (December 2003). "HYPERLEDA. I. Identification and designation of galaxies". Astronomy and Astrophysics. 412: 45–55. Bibcode:2003A&A...412...45P. doi:10.1051/0004-6361:20031411.
  6. ^ Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. 1. Sky Publishing Corporation and the European Space Agency. p. 458. ISBN 0-933346-84-0.
  7. ^ a b Annibali, F.; et al. (November 2015). "Chemical Abundances and Properties of the Ionized Gas in NGC 1705". The Astronomical Journal. 150 (5): 23. arXiv:1505.05545. Bibcode:2015AJ....150..143A. doi:10.1088/0004-6256/150/5/143. S2CID 119249162. 143.
  8. ^ Nemiroff, R. & Bonnell, J., eds. (April 23, 2003). "The Stars of NGC 1705". Astronomy Picture of the Day. NASA.
  9. ^ 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.
  10. ^ a b c Elson, E. C.; et al. (March 2013). "H I synthesis observations of the blue compact dwarf NGC 1705". Monthly Notices of the Royal Astronomical Society. 429 (3): 2550–2561. arXiv:1301.2889. Bibcode:2013MNRAS.429.2550E. doi:10.1093/mnras/sts526.
  11. ^ Martins, F.; et al. (November 2012). "Near-infrared spectroscopy of the super star cluster in NGC 1705". Astronomy & Astrophysics. 547: 4. arXiv:1209.3910. Bibcode:2012A&A...547A..17M. doi:10.1051/0004-6361/201220144. S2CID 56159879. A17.

External linksEdit

Coordinates:   04h 54m 13.5s, −53° 21′ 40″