NGC 2841

NGC 2841 is an unbarred spiral galaxy in the northern circumpolar constellation of Ursa Major. It was discovered on 9 March 1788 by German-born astronomer William Herschel. J. L. E. Dreyer, the author of the New General Catalogue, described it as, "very bright, large, very much extended 151°, very suddenly much brighter middle equal to 10th magnitude star".[7] Initially thought to be about 30 million light-years distant, a 2001 Hubble Space Telescope survey of the galaxy's Cepheid variables determined its distance to be approximately 14.1 megaparsecs or 46 million light-years.[4] The optical size of the galaxy is 8.′1 × 3.′5.[6]

NGC 2841
Hubble image of NGC 2841
Observation data (J2000 epoch)
ConstellationUrsa Major
Right ascension09h 22m 02.655s[1]
Declination+50° 58′ 35.32″[1]
Redshift0.002130[2]
Helio radial velocity638 km/s[3]
Distance46.0 ± 4.9 Mly (14.1 ± 1.5 Mpc)[4][5]
Apparent magnitude (V)10.1[3]
Characteristics
TypeSAa[2]
Mass7×1010 M☉[6] M☉
Apparent size (V)8.′1 × 3.′5[6]
Notable featuresFlocculent galaxy with LINER nucleus
Other designations
UGC 4966, PGC 26512[3]

This is the prototype for the flocculent spiral galaxy,[5] a type of spiral galaxy whose arms are patchy and discontinuous.[8] The morphological class is SAa, indicating a spiral galaxy with no central bar and very tightly-wound arms. There is no grand design structure visible in the optical band, although some inner spiral arms can be seen in the near infrared.[5] It is inclined by an angle of 68° to the line of sight from the Earth, with the major axis aligned along a position angle of 148°.[5]

The properties of NGC 2841 are similar to those of the Andromeda Galaxy.[4] It is home to a large population of young blue stars, and a few H II regions.[9] The luminosity of the galaxy is 2×1010 M☉ and it has a combined mass of 7×1010 M☉.[6] Its disk of stars can be traced out to a radius of around 228 kly (70 kpc). This disk begins to warp at a radius of around 98 kly (30 kpc), suggesting the perturbing effect of in-falling matter from the surrounding medium.[5]

The rotational behavior of the galaxy suggests there is a massive nuclear bulge,[6] with a low-ionization nuclear emission-line region (LINER) at the core; a type of region that is characterized by spectral line emission from weakly ionized atoms.[10] A prominent molecular ring is orbiting at a radius of 7–20 kly (2–6 kpc), which is providing a star-forming region of gas and dust.[6] The nucleus appears decoupled and there is a counter-rotating element of stars and gas in the outer parts of the nucleus, suggesting a recent interaction with a smaller galaxy.[6]

References
  1. Skrutskie, M. F.; et al. (February 2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708.
  2. Ann, H. B.; et al. (2015). "A Catalog of Visually Classified Galaxies in the Local (z ∼ 0.01) Universe". The Astrophysical Journal Supplement Series. 217 (2): 27. arXiv:1502.03545. Bibcode:2015ApJS..217...27A. doi:10.1088/0067-0049/217/2/27. S2CID 119253507.
  3. "NASA/IPAC Extragalactic Database". Results for NGC 2841. Retrieved 2006-10-04.
  4. Macri, L. M.; Stetson, P. B.; Bothun, G. D.; Freedman, W. L.; et al. (September 2001). "The Discovery of Cepheids and a New Distance to NGC 2841 Using the Hubble Space Telescope". Astrophysical Journal. 559 (1): 243–259. arXiv:astro-ph/0105491. Bibcode:2001ApJ...559..243M. doi:10.1086/322395. ISSN 0004-637X. S2CID 15546458.
  5. Zhang, Jielai; et al. (March 2018). "The Dragonfly Nearby Galaxies Survey. IV. A Giant Stellar Disk in NGC 2841". The Astrophysical Journal. 855 (2): 8. arXiv:1802.02583. Bibcode:2018ApJ...855...78Z. doi:10.3847/1538-4357/aaac81. S2CID 58889554. 78.
  6. Kaneda, H.; et al. (October 2007). "Far-Infrared Distributions in Nearby Spiral Galaxies NGC 2841 and NGC 2976 Observed with AKARI/Far-Infrared Surveyor (FIS)". Publications of the Astronomical Society of Japan. 59 (s2): S463. arXiv:0706.0068. Bibcode:2007PASJ...59S.463K. doi:10.1093/pasj/59.sp2.S463. S2CID 17966955.
  7. Seligman, Courtney. "NGC Objects: NGC 2800 - 2849". Celestial Atlas. Retrieved 2016-03-01.
  8. Elmegreen, Debra. A Near-Infrared Atlas of Spiral Galaxies. Retrieved 23 April 2010. See CH3. Discussion.
  9. Marochnik, Leonid; Suchkov, Anatoly (1995-11-01). Milky Way Galaxy (1st ed.). Routledge. p. 267. ISBN 978-2-88124-931-0.
  10. Ho, L. C.; et al. (1997). "A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". Astrophysical Journal Supplement. 112 (2): 315–390. arXiv:astro-ph/9704107. Bibcode:1997ApJS..112..315H. doi:10.1086/313041. S2CID 17086638.

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