The location of NGC 4945 (labelled in red)

NGC 4945 is a widely-studied[7] barred spiral galaxy in the constellation Centaurus, visible near the optical double star Xi Centauri.[9] It is also known as Caldwell 83. The galaxy was discovered by Sottish astronomer James Dunlop in 1826.[10] It is located at a distance of approximately 11.0 million light-years (3.36 Mpc) from the Milky Way.[4] NGC 4945 hosts one of the closest active galactic nuclei to Earth and is classified as a Seyfert 2 galaxy.[7]

NGC 4945 one of the brightest galaxies of the Centaurus A/M83 Group, a large, nearby group of galaxies. The galaxy is the second brightest galaxy in the subgroup centered on Centaurus A.[5] [11]

Observations

The morphological classification of NGC 4945 is SB(s)cd?edge,[4] indicating this is a barred spiral galaxy (SB) with no inner ring structure (s) and possibly loosely-wound spiral arms (cd?). It is inclined at an angle of 90° to the plane of the sky, which means the galactic plane is being viewed edge-on.[4] NGC 4945 is thought to be similar to the Milky Way Galaxy, although the maximum rotation rate of ~ 180 km/s is lower.[12] It has a combined estimated mass of 1.4+1.4
−0.7×1011 M☉.[6] The stellar mass of the galaxy is 3.8×1010 M☉, or 38 billion times the mass of the Sun.[12]

In 1964, this galaxy was classified as a radio source at the Parkes Observatory.[13] The nucleus was obscured in the optical band but was found to be a quite prominent source of infrared emission.[14] It is the third brightest galaxy in the IRAS point source catalogue, with most of the emission coming from the core.[15] Most of the Galaxy shows a linear rotation curve, although the southwest region showed an infall suggestive of a bar.[16]

In 1979, strong H2O maser emission was detected from the central region.[17] The properties of the nuclear region are suggestive of both a Seyfert type galaxy and an intence starburst region with a complex structure.[18] The active nucleus is heavily obscured by dust. These dust lanes approach the nucleus, forming a tightly-wound structure in the inner 650 ly (200 pc).[7] X-ray emission from the nuclear region indicates a Type 2 Seyfert galaxy. It is a strong emitter of hard X-rays, second only to NGC 4151,[15] and likely harbors a supermassive black hole.[19]

The starburst region is thought to be at least 5×106 years old and contributes at least half of the luminosity coming from the core.[20] It is concentrated in the central 330 ly (100 pc) and includes a conical cavity likely produced by supernovae-driven winds.[21] This is taking place in a region of dense molecular clouds,[22] forming a disk of dust and gas, along with many rich star clusters.[23][24] A hot wind of gas from the nuclear region is carrying away 1.6 M☉ per year.[25]

NGC 4945 was the first galaxy outside the Local Group to have stars resolved within its galactic halo. The halo mass is relatively large at ~ 3.5×109 M☉ and it is metal-rich, both of which are typical for a Milky Way-like galaxy. It appears to be counter-rotating compared to the main disk, suggesting the halo has been accreted. The mass of the dominant satellite accreted into the halo is ~ 1.5×109 M☉, which is roughly the same as the Large Magellanic Cloud.[12]

Two supernovae have been observed in NGC 4945. Type II-P supernova SN 2005af was discovered by CEAMIG/REA Supernovae Search on 8 February 2005, reaching a peak magnitude of 12.8.[26][27][28] Type II-P supernova SN 2011ja was discovered by Libert "Berto" Monard on 18 December 2011, and achieved a maximum magnitude of 14.[29][30] The progenitor star for 2011ja may have been massive at 25 M☉ and located within a massive stellar cluster.[31]

"NGC 4945" is the title of a song by Brett Domino on the album Funk.

References

  1. ^ a b Skrutskie, Michael F.; et al. (February 1, 2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708. ISSN 0004-6256. S2CID 18913331.
  2. ^ de Vaucouleurs, G.; et al. (2016). Third Reference Catalogue of Bright Galaxies. 9. New York: Springer-Verlag. Retrieved 2025-03-08.{{cite book}}: CS1 maint: multiple names: authors list (link)
  3. ^ a b c d "NASA/IPAC Extragalactic Database". Results for NGC 4945. Retrieved 2006-11-25.
  4. ^ a b c d e f Crowther, Paul A. (January 2013). "On the association between core-collapse supernovae and H II regions". Monthly Notices of the Royal Astronomical Society. 428 (3): 1927–1943. arXiv:1210.1126. Bibcode:2013MNRAS.428.1927C. doi:10.1093/mnras/sts145.
  5. ^ a b Karachentsev, I. D.; Sharina, M. E.; Dolphin, A. E.; Grebel, E. K.; et al. (2002). "New distances to galaxies in the Centaurus A group". Astronomy and Astrophysics. 385 (1): 21–31. Bibcode:2002A&A...385...21K. doi:10.1051/0004-6361:20020042.
  6. ^ a b Graham, Alister W. (November 2008). "Populating the Galaxy Velocity Dispersion - Supermassive Black Hole Mass Diagram: A Catalogue of (Mbh, σ) Values". Publications of the Astronomical Society of Australia. 25 (4): 167–175. arXiv:0807.2549. Bibcode:2008PASA...25..167G. doi:10.1071/AS08013. S2CID 89905.
  7. ^ a b c d Gaspar, G.; et al. (May 2022). "An Infrared View of the Obscured AGN Environment in NGC 4945". The Astronomical Journal. 163 (5). id. 230. arXiv:2203.03678. Bibcode:2022AJ....163..230G. doi:10.3847/1538-3881/ac5ea4.
  8. ^ "NGC 4945", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2025-03-08.
  9. ^ "NGC 4945". DOCdb :Deep Sky Observer's Companion – the online database. Retrieved 2025-03-08.
  10. ^ "Caldwell 83". science.nasa.gov. NASA. 10 September 2020. Retrieved 2025-03-12.
  11. ^ Karachentsev, I. D. (2005). "The Local Group and Other Neighboring Galaxy Groups". Astronomical Journal. 129 (1): 178–188. arXiv:astro-ph/0410065. Bibcode:2005AJ....129..178K. doi:10.1086/426368. S2CID 119385141.
  12. ^ a b c Beltrand, Camila; et al. (October 2024). "First resolved stellar halo kinematics of a Milky Way-mass galaxy outside the Local Group: The flat counter-rotating halo in NGC 4945". Astronomy & Astrophysics. 690. id. A115. arXiv:2406.17533. Bibcode:2024A&A...690A.115B. doi:10.1051/0004-6361/202450626.
  13. ^ Bolton, J. G.; et al. (September 1964). "The Parkes catalogue of radio sources, declination zone -20° to -60°". Australian Journal of Physics. 17 (3): 340. Bibcode:1964AuJPh..17..340B. doi:10.1071/PH640340.
  14. ^ Shobbrook, R. R.; Shaver, P. A. (August 1967). "The nucleus of the southern spiral NGC 4945". The Observatory. 87: 169–170. Bibcode:1967Obs....87..169S.
  15. ^ a b Done, C.; et al. (June 1996). "NGC 4945: The brightest Seyfert 2 galaxy at 100 keV". Astrophysical Journal Letters. 463 (2): L63. Bibcode:1996ApJ...463L..63D. doi:10.1086/310056.
  16. ^ Peterson, C. J. (August 1980). "Observations of the kinematics of the excited gas in the late-type spiral galaxy NGC 4945". Publications of the Astronomical Society of the Pacific. 92: 397–408. Bibcode:1980PASP...92..397P. doi:10.1086/130685.
  17. ^ Moorwood, A. F. M.; Glass, I. S. (June 1984). "Infrared activity in Circinus and NGC 4945 : two galaxies containing luminous H2 O masers". Astronomy and Astrophysics. 135: 281–288. Bibcode:1984A&A...135..281M.
  18. ^ Whiteoak, J. B. (1986). "NGC 4945 – a galaxy with a nucleus full of surprises". Astronomical Society of Australia, Proceedings. 6 (4): 467–471. Bibcode:1986PASA....6..467W. doi:10.1017/S1323358000018403.
  19. ^ "Milky Way's Not-So-Distant Cousin Likely Harbors Supermassive Black Hole". Science Daily. Retrieved 2025-03-08.
  20. ^ Spoon, H. W. W.; et al. (May 2000). "Mid-infrared ISO spectroscopy of NGC 4945". Astronomy and Astrophysics. 357: 898–908. arXiv:astro-ph/0003457. Bibcode:2000A&A...357..898S.
  21. ^ Wang, M.; et al. (August 2004). "Dense gas in nearby galaxies. XVI. The nuclear starburst environment in NGC 4945". Astronomy and Astrophysics. 422 (3): 883–905. arXiv:astro-ph/0405346. Bibcode:2004A&A...422..883W. doi:10.1051/0004-6361:20035722.
  22. ^ Cunningham, M. R.; Whiteoak, J. B. (November 2005). "The nuclear molecular clouds of NGC4945". Monthly Notices of the Royal Astronomical Society. 364 (1): 37–46. Bibcode:2005MNRAS.364...37C. doi:10.1111/j.1365-2966.2005.09502.x.
  23. ^ Gaspar, G.; et al. (2022). "An Infrared View of the Obscured AGN Environment in NGC 4945". The Astronomical Journal. 163 (5): 230. arXiv:2203.03678. Bibcode:2022AJ....163..230G. doi:10.3847/1538-3881/ac5ea4. S2CID 247315251.
  24. ^ Emig, Kimberly L.; et al. (November 2020). "Super star clusters in the central starburst of NGC 4945". The Astrophysical Journal. 903 (1). id. 50. arXiv:2009.05154. Bibcode:2020ApJ...903...50E. doi:10.3847/1538-4357/abb67d.
  25. ^ Porraz Barrera, Natalia; et al. (June 2024). "Hot Gas Outflow Properties of the Starburst Galaxy NGC 4945". The Astrophysical Journal. 968 (2). id. 54. arXiv:2312.08444. Bibcode:2024ApJ...968...54P. doi:10.3847/1538-4357/ad4606.
  26. ^ Jacques, C.; Pimentel, E. (2005). "Possible Supernova in NGC 4945". International Astronomical Union Circular (8482): 1. Bibcode:2005IAUC.8482....1J.
  27. ^ "SN 2005af". Transient Name Server. IAU. Retrieved 8 December 2024.
  28. ^ Pereyra, A.; et al. (August 2006). "Optical polarimetric monitoring of the type II-plateau SN 2005af". Astronomy and Astrophysics. 454 (3): 827–831. arXiv:astro-ph/0604511. Bibcode:2006A&A...454..827P. doi:10.1051/0004-6361:20065207.
  29. ^ Monard, L. A. G.; et al. (2011). "Supernova 2011ja in NGC 4945 = PSN J13051112-4931270". Central Bureau Electronic Telegrams (2946): 1. Bibcode:2011CBET.2946....1M.
  30. ^ "SN 2011ja". Transient Name Server. IAU. Retrieved 8 December 2024.
  31. ^ Andrews, J. E.; et al. (April 2016). "Early dust formation and a massive progenitor for SN 2011ja?". Monthly Notices of the Royal Astronomical Society. 457 (3): 3241–3253. arXiv:1509.06379. Bibcode:2016MNRAS.457.3241A. doi:10.1093/mnras/stw164.

Further reading

Allikas: http://en.wikipedia.org/wiki/Caldwell_83
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