NGC 4993

NGC 4993 (also catalogued as NGC 4994) is a lenticular galaxy[5] located about 140 million light-years away[6] in the constellation Hydra.[7] It was discovered on 26 March 1789[8] by William Herschel[7][8] and is a member of the NGC 4993 Group.[3]

NGC 4993
NGC 4993 and GRB 170817A afterglow as taken by Hubble Space Telescope[1]
Observation data (J2000 epoch)
ConstellationHydra
Right ascension13h 09m 47.7s[2]
Declination−23° 23′ 02″[2]
Redshift0.009727[2]
Helio radial velocity2916 km/s[2]
Distance (comoving)44.1 Mpc (144 Mly)[2]
Group or clusterNGC 4993 Group[3]
Apparent magnitude (V)13.32[2]
Characteristics
Type(R')SAB0^-(rs)[2]
Size~55,000 ly (17 kpc) (estimated)[2]
Apparent size (V)1.3 x 1.1[2]
Notable featuresHost of neutron star merger detected as gravitational wave GW170817 and gamma-ray burst GRB 170817A
Other designations
NGC 4994, ESO 508-18, AM 1307-230, MCG -4-31-39, PGC 45657, WH III 766[4]

NGC 4993 starmap near ψ Hydrae, near galaxies of NGC 4968, NGC 4970, NGC 5042, IC 4180, IC 4197

NGC 4993 is the site of GW170817, the first astronomical event detected in both electromagnetic and gravitational radiation, the collision of two neutron stars, a discovery given the Breakthrough of the Year award for 2017 by the journal Science.[9][10] Detecting a gravitational wave event associated with the gamma-ray burst provided direct confirmation that binary neutron star collisions produce short gamma-ray bursts.[11]

Physical characteristics

NGC 4993 has several concentric shells of stars and large dust lane with diameter of approximately a few kiloparsecs which surrounds the nucleus and is stretched out into an "s" shape. The dust lane appears to be connected to a small dust ring with a diameter of ~330 ly (0.1 kpc).[12] These features in NGC 4993 may be the result[13] of a recent merger with a gaseous late-type galaxy that occurred about 400 million years ago.[14] However, Palmese et al. suggested that the galaxy involved in the merger was a gas-poor galaxy.[15]

Dark matter content

NGC 4993 has a dark matter halo with an estimated mass of 193.9×1010 M☉.[14]

Globular clusters

NGC 4993 has an estimated population of 250 globular clusters.[5]

The luminosity of NGC 4993 indicates that the globular cluster system surrounding the galaxy may be dominated by metal-poor globular clusters.[16]

Supermassive black hole

NGC 4993 has a supermassive black hole with an estimated mass of roughly 80 to 100 million solar masses (8×107 M☉).[17]

Galactic nucleus activity

The presence of weak O III, NII and SII emission lines in the nucleus of NGC 4993 and the relatively high ratio of [NII]λ6583/Hα suggest that NGC 4993 is a low-luminosity AGN (LLAGN).[17] The activity may have been triggered by gas from the late-type galaxy as it merged with NGC 4993.[14]

Neutron star merger observations
Main article: GW170817

In August 2017, rumors circulated[18] regarding a short gamma-ray burst designated GRB 170817A, of the type conjectured to be emitted in the collision of two neutron stars.[19] On 16 October 2017, the LIGO and Virgo collaborations announced that they had detected a gravitational wave event, designated GW170817. The gravitational wave signal matched prediction for the merger of two neutron stars, two seconds before the gamma-ray burst. The gravitational wave signal, which had a duration of about 100 seconds, was the first gravitational wave detection of the merger of two neutron stars.[1][20][21][22][23]

An optical transient, AT 2017gfo (also known as SSS 17a), was detected in NGC 4993 11 hours after the gravitational wave and gamma-ray signals, allowing the location of the merger to be determined. The optical emission is thought to be due to a kilonova. The discovery of AT 2017gfo was the first observation (and first localisation) of an electromagnetic counterpart to a gravitational wave source.[20][22][23][24][25]

GRB 170817A was a gamma-ray burst (GRB) detected by NASA's Fermi and ESA's INTEGRAL on 17 August 2017.[18][26][27][28] Although only localized to a large area of the sky, it is believed to correspond to the other two observations,[24] in part due to its arrival time 1.7 seconds after the GW event.

See also

References
  1. Chou, Felicia; Washington, Dewayne; Porter, Molly (16 October 2017). "Release 17-083 - NASA Missions Catch First Light from a Gravitational-Wave Event". NASA. Retrieved 21 October 2017.
  2. "NASA/IPAC Extragalactic Database". Results for NGC 4993. Retrieved 3 June 2018.
  3. Hjorth, Jens; Levan, Andrew J.; Tanvir, Nial R.; Lyman, Joe D.; Wojtak, Radosław; Schrøder, Sophie L.; Mandel, Ilya; Gall, Christa; Bruun, Sofie H. (16 October 2017). "The Distance to NGC 4993: The Host Galaxy of the Gravitational-wave Event GW170817". The Astrophysical Journal. 848 (2): L31. arXiv:1710.05856. Bibcode:2017ApJ...848L..31H. doi:10.3847/2041-8213/aa9110. hdl:2381/41880.
  4. Staff (2017). "Galaxy NGC 4993 - Galaxy in Hydra Constellation". dso-browser.com. Retrieved 30 September 2017.
  5. Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X. (1 December 2017). "On the Progenitor of Binary Neutron Star Merger GW170817". The Astrophysical Journal. 850 (2): L40. arXiv:1710.05838. Bibcode:2017ApJ...850L..40A. doi:10.3847/2041-8213/aa93fc.
  6. "Your NED Search Results". ned.ipac.caltech.edu. Retrieved 5 June 2018.
  7. "NGC 4993". Deep Sky Observer's Companion. Retrieved 28 August 2017.
  8. "New General Catalog Objects: NGC 4950 - 4999". cseligman.com. Retrieved 5 June 2018.
  9. "Breakthrough of the year 2017". Science | AAAS. 22 December 2017.
  10. Cho, Adrian (2017). "Cosmic convergence". Science. 358 (6370): 1520–1521. Bibcode:2017Sci...358.1520C. doi:10.1126/science.358.6370.1520. PMID 29269456.
  11. Overbye, Dennis (16 October 2017). "LIGO Detects Fierce Collision of Neutron Stars for the First Time". The New York Times. Retrieved 16 October 2017.
  12. Blanchard, P. K.; Berger, E.; Fong, W.; Nicholl, M.; Leja, J.; Conroy, C.; Alexander, K. D.; Margutti, R.; Williams, P. K. G. (16 October 2017). "The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VII. Properties of the Host Galaxy and Constraints on the Merger Timescale". The Astrophysical Journal. 848 (2): L22. arXiv:1710.05458. Bibcode:2017ApJ...848L..22B. doi:10.3847/2041-8213/aa9055.
  13. Im, Myungshin; Yoon, Yongmin; Lee, Seong-Kook J.; Lee, Hyung Mok; Kim, Joonho; Lee, Chung-Uk; Kim, Seung-Lee; Troja, Eleonora; Choi, Changsu (26 October 2017). "Distance and Properties of NGC 4993 as the Host Galaxy of the Gravitational-wave Source GW170817". The Astrophysical Journal. 849 (1): L16. arXiv:1710.05861. Bibcode:2017ApJ...849L..16I. doi:10.3847/2041-8213/aa9367.
  14. Ebrová, Ivana; Bílek, Michal (2020). "NGC 4993 the shell galaxy host of GW170817: constraints on the recent galactic merger". Astronomy & Astrophysics. 634: A73. arXiv:1801.01493. doi:10.1051/0004-6361/201935219.
  15. Palmese, A.; Hartley, W.; Tarsitano, F.; Conselice, C.; Lahav, O.; Allam, S.; Annis, J.; Lin, H.; Soares-Santos, M. (9 November 2017). "Evidence for Dynamically Driven Formation of the GW170817 Neutron Star Binary in NGC 4993". The Astrophysical Journal. 849 (2): L34. arXiv:1710.06748. Bibcode:2017ApJ...849L..34P. doi:10.3847/2041-8213/aa9660.
  16. Lee, Myung Gyoon; Kang, Jisu; Im, Myungshin (20 May 2018). "A Globular Cluster Luminosity Function Distance to NGC 4993 Hosting a Binary Neutron Star Merger GW170817/GRB 170817A". The Astrophysical Journal Letters. 859 (1): L6. arXiv:1805.01127. Bibcode:2018ApJ...859L...6L. doi:10.3847/2041-8213/aac2e9.
  17. Wu, Qingwen; Feng, Jianchao; Fan, Xuliang (6 March 2018). "The Possible Submillimeter Bump and Accretion-jet in the Central Supermassive Black Hole of NGC 4993". The Astrophysical Journal. 855 (1): 46. arXiv:1710.09590. Bibcode:2018ApJ...855...46W. doi:10.3847/1538-4357/aaac28.
  18. Drake, Nadia (25 August 2017). "Strange stars caught wrinkling spacetime? Get the facts". National Geographic. Retrieved 27 August 2017.
  19. Nakar, E. (2007). "Short-hard gamma-ray bursts". Physics Reports. 442 (1–6): 166–236. arXiv:astro-ph/0701748. Bibcode:2007PhR...442..166N. CiteSeerX 10.1.1.317.1544. doi:10.1016/j.physrep.2007.02.005.
  20. Landau, Elizabeth; Chou, Felicia; Washington, Dewayne; Porter, Molly (16 October 2017). "NASA Missions Catch First Light from a Gravitational-Wave Event". NASA. Retrieved 16 October 2017.
  21. Abbott, B.P.; et al. (16 October 2017). "GW 170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral". Physical Review Letters. 119 (16): 161101. arXiv:1710.05832. Bibcode:2017PhRvL.119p1101A. doi:10.1103/PhysRevLett.119.161101. PMID 29099225.
  22. Cho, Adrian (16 October 2017). "Merging neutron stars generate gravitational waves and a celestial light show". Science. doi:10.1126/science.aar2149. Retrieved 16 October 2017.
  23. Krieger, Lisa M. (16 October 2017). "A Bright Light Seen Across The Universe, Proving Einstein Right - Violent collisions source of our gold, silver". The Mercury News. Retrieved 16 October 2017.
  24. Overbye, Dennis (16 October 2017). "LIGO Detects Fierce Collision of Neutron Stars for the First Time". The New York Times. Retrieved 16 October 2017.
  25. Abbott, B. P.; et al. (LIGO Scientific Collaboration & Virgo Collaboration) (16 October 2017). "GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral". Physical Review Letters. 119 (16): 161101. arXiv:1710.05832. Bibcode:2017PhRvL.119p1101A. doi:10.1103/PhysRevLett.119.161101. PMID 29099225.
  26. von Kienlin, Andreas (17 August 2017). "GCN Circular Number 21520; GRB 170817A: Fermi GBM detection; 2017-08-17 20:00:07 GMT". Max Planck Institute for Extraterrestrial Physics. Retrieved 28 August 2017.
  27. Castelvecchi, Davide (25 August 2017). "Rumours swell over new kind of gravitational-wave sighting". Nature News. doi:10.1038/nature.2017.22482. Retrieved 27 August 2017.
  28. Sokol, Joshua (25 August 2017). "What Happens When Two Neutron Stars Collide?". Wired. Retrieved 28 August 2017.
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