NGC 4941 is a spiral galaxy in the constellation Virgo. The galaxy lies about 45 million light years away from Earth, which means, given its apparent dimensions, that NGC 4941 is approximately 50,000 light years across.[1] It was discovered by William Herschel on April 24, 1784.[3]

Characteristics

NGC 4941 has an elliptical bulge which appears twisted. Two spiral arms emerge from major axis of the bulge. The arms are smooth and low contrast and appear symmetric. The arms fade after about half a revolution and merge into the disk.[4] Multiple spiral fragments are visible in the disk, along with dust lanes. The galaxy has two very low surface brightness outer arms.[5] HII regions are visible along the arms.[6] The galaxy has two rings, one between 37 and 73 arcseconds from the nucleus, and one outer between 81 and 120 arcseconds from the nucleus. A weak bar is visible between the two rings.[7]

Nucleus

The nucleus of NGC 4941 has been found to be active and it has been categorised as a type II Seyfert galaxy. The most accepted theory for the energy source of active galactic nuclei is the presence of an accretion disk around a supermassive black hole. The mass of the black hole in the centre of NGC 4941 is estimated to be 106.91 (8.1 million) M☉.[8]

Imaging of the [S III] emission in the narrow-line region of the nuclues by the Gemini Multi-Object Spectrograph showed there is a blueshifted element running along a small northwest radio emission indicating there is a compact outflow associated with a radio jet. The length of the outflow is estimated to be about 150 parsec. There is a redshift element at the opposite direction, indicating there is one more outflow, but without a counterpart visible in radiowaves.[9] The radio jet is about 15 parsec long.[6]

The nucleus of NGC 4941 is a source of X-rays. The spectrum indicates it is highly absorbed. The Fe-Kα line is detectable.[10] The X-ray emission shows variability in the timescale of months to years when comparing observations by ASCA and BeppoSAX.[11] The spectrum shows a partially or fully absorbed component, a reflection from the accretion disk and from the circumnuclear torus, a scattered component and thermal plasma emission, maybe a result of increased star formation activity. The hard X-ray luminosity of the nucleus is estimated to be 4.5×1041 erg/s.[12]

Although the nucleus appears deficient in molecular gas, there is some CO(3-2) emission which corresponds to a molecular gas mass of 1.9–3.3 × 104 M☉. The CO nuclear emission shows two peaks in a butterfly shape.[13]

Nearby galaxies

NGC 4941 is a member of the NGC 4941 Group, along with NGC 4951.[14] A. M. Garcia considers the galaxy a member of the NGC 4697 Group, also known as LGG 314.[15] Other members of the group include NGC 4697, NGC 4731, NGC 4775, NGC 4951, NGC 4948, and NGC 4958.[15] It is part of a Virgo II Groups, a chain of groups extending from the Virgo Cluster.[16]

References

  1. ^ a b c d e f g h i j "Results for object NGC 4941". NASA/IPAC Extragalactic Database. NASA and Caltech. Retrieved 25 February 2025.
  2. ^ "Revised NGC Data for NGC 4941". spider.seds.org. Retrieved 30 March 2024.
  3. ^ Seligman, Courtney. "NGC 4941 (= PGC 45165)". Celestial Atlas. Retrieved 19 November 2018.
  4. ^ Eskridge, Paul B.; Frogel, Jay A.; Pogge, Richard W.; Quillen, Alice C.; Berlind, Andreas A.; Davies, Roger L.; DePoy, D. L.; Gilbert, Karoline M.; Houdashelt, Mark L.; Kuchinski, Leslie E.; Ramirez, Solange V.; Sellgren, K.; Stutz, Amelia; Terndrup, Donald M.; Tiede, Glenn P. (November 2002). "Near‐Infrared and Optical Morphology of Spiral Galaxies". The Astrophysical Journal Supplement Series. 143 (1): 73–111. doi:10.1086/342340.
  5. ^ Sandage, A., Bedke, J. (1994), The Carnegie Atlas of Galaxies. Volume I, Carnegie Institution of Washington
  6. ^ a b Schmitt, H. R.; Ulvestad, J. S.; Antonucci, R. R. J.; Kinney, A. L. (February 2001). "Jet Directions in Seyfert Galaxies: Radio Continuum Imaging Data". The Astrophysical Journal Supplement Series. 132 (2): 199–209. doi:10.1086/318957.
  7. ^ Gutiérrez, Leonel; Erwin, Peter; Aladro, Rebeca; Beckman, John E. (1 November 2011). "THE OUTER DISKS OF EARLY-TYPE GALAXIES. II. SURFACE-BRIGHTNESS PROFILES OF UNBARRED GALAXIES AND TRENDS WITH HUBBLE TYPE". The Astronomical Journal. 142 (5): 145. doi:10.1088/0004-6256/142/5/145.
  8. ^ Asmus, D.; Gandhi, P.; Smette, A.; Hönig, S. F.; Duschl, W. J. (December 2011). "Mid-infrared properties of nearby low-luminosity AGN at high angular resolution". Astronomy & Astrophysics. 536: A36. doi:10.1051/0004-6361/201116693.
  9. ^ Barbosa, F. K. B.; Storchi-Bergmann, T.; Fernandes, R. Cid; Winge, C.; Schmitt, H. (11 June 2009). "Gemini/GMOS IFU gas velocity 'tomography' of the narrow line region of nearby active galaxies". Monthly Notices of the Royal Astronomical Society. 396 (1): 2–18. doi:10.1111/j.1365-2966.2009.14485.x.
  10. ^ Maiolino, R.; Salvati, M.; Bassani, L.; Dadina, M.; della Ceca, R.; Matt, G.; Risaliti, G.; Zamorani, G. (1 October 1998). "Heavy obscuration in X-ray weak AGNs". Astronomy and Astrophysics. 338: 781–794. doi:10.48550/arXiv.astro-ph/9806055. ISSN 0004-6361.
  11. ^ Terashima, Yuichi; Iyomoto, Naoko; Ho, Luis C.; Ptak, Andrew F. (March 2002). "X‐Ray Properties of LINERs and Low‐Luminosity Seyfert Galaxies Observed with ASCA . I. Observations and Results". The Astrophysical Journal Supplement Series. 139 (1): 1–36. doi:10.1086/324373.
  12. ^ Kawamuro, Taiki; Ueda, Yoshihiro; Tazaki, Fumie; Terashima, Yuichi (6 June 2013). "BROADBAND X-RAY SPECTRA OF TWO LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI NGC 1566 AND NGC 4941 OBSERVED WITH SUZAKU". The Astrophysical Journal. 770 (2): 157. doi:10.1088/0004-637X/770/2/157.
  13. ^ García-Burillo, S.; et al. (August 2021). "The Galaxy Activity, Torus, and Outflow Survey (GATOS): I. ALMA images of dusty molecular tori in Seyfert galaxies". Astronomy & Astrophysics. 652: A98. doi:10.1051/0004-6361/202141075.
  14. ^ Makarov, Dmitry; Karachentsev, Igor (21 April 2011). "Galaxy groups and clouds in the local (z~ 0.01) Universe". Monthly Notices of the Royal Astronomical Society. 412 (4): 2498–2520. arXiv:1011.6277. Bibcode:2011MNRAS.412.2498M. doi:10.1111/j.1365-2966.2010.18071.x. S2CID 119194025. Retrieved 1 February 2025.
  15. ^ a b Garcia, A. M. (1 July 1993). "General study of group membership. II. Determination of nearby groups". Astronomy and Astrophysics Supplement Series. 100: 47–90. Bibcode:1993A&AS..100...47G. ISSN 0365-0138.
  16. ^ "The Virgo II Groups". www.atlasoftheuniverse.com. Retrieved 25 February 2025.
Allikas: http://en.wikipedia.org/wiki/NGC_4941
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