NGC 4395

NGC 4395 is a nearby low surface brightness spiral galaxy located about 14 million light-years (or 4.3 Mpc) from Earth in the constellation Canes Venatici.[4] The nucleus of NGC 4395 is active and the galaxy is classified as a Seyfert Type I known for its very low-mass supermassive black hole.[5]

NGC 4395
An ultraviolet image of NGC 4395 taken with GALEX.
Credit: GALEX/NASA
Observation data (J2000 epoch)
ConstellationCanes Venatici[1]
Right ascension12h 25m 48.9s[2]
Declination+33° 32′ 48″[2]
Redshift319 ± 1 km/s[2]
Distance~14 million light-years
Apparent magnitude (V)10.6[2]
Characteristics
TypeSA(s)m[2]
Size50,000 ly (diameter)
Apparent size (V)13′.2 × 11′.0[2]
Other designations
NGC 4395,[3] UGC 7542,[2] PGC 40596[2]

Physical characteristics

NGC 4395 has a halo that is about 8′ in diameter. It has several patches of greater brightness running northwest to southeast. The one furthest southeast is the brightest. Three of the patches have their own NGC numbers: 4401, 4400, and 4399 running east to west.[3]

The galaxy is highly unusual for Seyfert galaxies, because it does not have a bulge and is considered to be a dwarf galaxy.[5]

Observational history

NGC 4395 was imaged and classified as a "spiral nebula" in a 1920 paper by astronomer Francis G. Pease.[6] Now, it is known to be a galaxy distinct from the Milky Way (see Great Debate). Along with several other nearby galaxies, resolved stars in NGC 4395 were used to measure the expansion rate of the Universe by Allan Sandage and Gustav Andreas Tammann in their 1974 paper.[7] More recently, NGC 4395 was discovered to contain a very low-luminosity active galactic nucleus.[8] Since then, its nucleus has been the subject of several academic papers and attempts to measure the mass of its central black hole.

Nucleus

NGC 4395 is one of the least luminous and nearest Seyfert galaxies known.[5] The nucleus of NGC 4395 is notable for containing one of the smallest supermassive black holes with a well-measured mass.[9] The central black hole has a mass of "only" 300,000 M☉.[10] However, a recent study found a black hole mass of just 10,000 M☉.[11] The low-mass black hole in NGC 4395 would make it a so-called "intermediate-mass black hole".

References
  1. Celestia version 1.4.1. Laurel, Chris, 2006.
  2. "NASA/IPAC Extragalactic Database". Results for. Retrieved 2006-11-04.
  3. Kepple, George Robert; Glen W. Sanner (1998). The Night Sky Observer's Guide, Volume 2. Willmann-Bell, Inc. p. 48. ISBN 978-0-943396-60-6.
  4. Thim, F.; Hoessel, J. G.; Saha, A.; Claver, J.; Dolphin, A.; Tammann, G. A. (April 2004). "Cepheids and Long-Period Variables in NGC 4395". The Astronomical Journal. 127 (4): 2322–2343. arXiv:astro-ph/0401558. Bibcode:2004AJ....127.2322T. doi:10.1086/382244. ISSN 0004-6256. S2CID 14631171.
  5. Filippenko, Alexei V.; Ho, Luis C. (25 March 2003). "A Low-Mass Central Black Hole in the Bulgeless Seyfert 1 Galaxy NGC 4395". The Astrophysical Journal Letters. 588 (1): L13. arXiv:astro-ph/0303429. Bibcode:2003ApJ...588L..13F. doi:10.1086/375361. S2CID 14411746. Retrieved 20 August 2020.
  6. "1920ApJ....51..276P Page 17". articles.adsabs.harvard.edu. Bibcode:1920ApJ....51..276P. Retrieved 2020-08-23.
  7. Sandage, A.; Tammann, G. A. (December 1974). "Steps toward the Hubble constant. IV. Distances to 39 galaxies in the general field leading to a calibration of the galaxy luminosity classes and a first hint of the value of H0". The Astrophysical Journal. 194: 559–568. Bibcode:1974ApJ...194..559S. doi:10.1086/153275. ISSN 0004-637X.
  8. Filippenko, Alexei V.; Sargent, Wallace L. W. (July 1989). "Discovery of an Extremely Low Luminosity Seyfert 1 Nucleus in the Dwarf Galaxy NGC 4395". The Astrophysical Journal. 342: L11. Bibcode:1989ApJ...342L..11F. doi:10.1086/185472. ISSN 0004-637X.
  9. Merritt, David (2013). Dynamics and Evolution of Galactic Nuclei. Princeton, NJ: Princeton University Press. ISBN 9781400846122.
  10. Peterson, Bradley; et al. (2005). "Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass". The Astrophysical Journal. 632 (2): 799–808. arXiv:astro-ph/0506665. Bibcode:2005ApJ...632..799P. doi:10.1086/444494. S2CID 13886279.
  11. Woo, Jong-Hak; Cho, Hojin; Gallo, Elena; Hodges-Kluck, Edmund; Le, Huynh Anh N.; Shin, Jaejin; Son, Donghoon; Horst, John C. (August 2019). "A 10,000-solar-mass black hole in the nucleus of a bulgeless dwarf galaxy". Nature Astronomy. 3 (8): 755–759. arXiv:1905.00145. Bibcode:2019NatAs...3..755W. doi:10.1038/s41550-019-0790-3. ISSN 2397-3366. S2CID 189762554.


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