NGC 4395 explained

NGC 4395
Epoch:J2000
Ra:[1]
Constellation Name:Canes Venatici[2]
Z:319 ± 1 km/s
Dist Ly:~14 million light-years
Type:SA(s)m
Appmag V:10.6
Size V:13.2 × 11.0
Size:50,000 ly (diameter)
Names:NGC 4395, UGC 7542, PGC 40596

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.[3] 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.[4]

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.[5]

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

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. 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 .[10] However, a recent study found a black hole mass of just 10,000 .[11] The low-mass black hole in NGC 4395 would make it a so-called "intermediate-mass black hole".[12] The black hole may have a truncated disk. [13]

External links

Notes and References

  1. Web site: NASA/IPAC Extragalactic Database . Results for . 2006-11-04.
  2. Celestia version 1.4.1. Laurel, Chris, 2006.
  3. 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. en. 127. 4. 2322–2343. 10.1086/382244. astro-ph/0401558. 2004AJ....127.2322T. 14631171. 0004-6256.
  4. 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. 10.1086/375361. 20 August 2020. astro-ph/0303429. 2003ApJ...588L..13F. 14411746.
  5. Book: Kepple , George Robert . Glen W. Sanner . The Night Sky Observer's Guide, Volume 2 . Willmann-Bell, Inc. . 1998 . 978-0-943396-60-6 . 48.
  6. 1920ApJ....51..276P Page 17. The Astrophysical Journal. 1920ApJ....51..276P. Pease. F. G.. 1920. 51. 276. 10.1086/142552. free.
  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. en. 194. 559–568. 10.1086/153275. 1974ApJ...194..559S. 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. en. 342. L11. 10.1086/185472. 1989ApJ...342L..11F. 0004-637X.
  9. Book: Merritt, David. David Merritt. Dynamics and Evolution of Galactic Nuclei. 2013. Princeton University Press. Princeton, NJ. 9781400846122.
  10. Peterson. Bradley. etal . Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass. The Astrophysical Journal . 2005 . 632 . 2. 799–808 . 10.1086/444494. astro-ph/0506665 . 2005ApJ...632..799P . 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. en. 3. 8. 755–759. 10.1038/s41550-019-0790-3. 2397-3366. 1905.00145. 2019NatAs...3..755W. 189762554.
  12. Shih . D. C. . Iwasawa . K. . Fabian . A. C. . 2003-05-21 . Evidence for an intermediate-mass black hole and a multi-zone warm absorber in NGC 4395 . Monthly Notices of the Royal Astronomical Society . 341 . 3 . 973–980 . 10.1046/j.1365-8711.2003.06482.x . free . 0035-8711. astro-ph/0302108 . 2003MNRAS.341..973S .
  13. McHardy . I M . Beard . M . Breedt . E . Knapen . J H . Vincentelli . F M . Veresvarska . M . Dhillon . V S . Marsh . T R . Littlefair . S P . Horne . K . Glew . R . Goad . M R . Kammoun . E . Emmanoulopoulos . D . 2022-11-22 . First detection of the outer edge of an AGN accretion disc: very fast multiband optical variability of NGC 4395 with GTC/HiPERCAM and LT/IO:O . Monthly Notices of the Royal Astronomical Society . 519 . 3 . 3366–3382 . 10.1093/mnras/stac3651 . free . 0035-8711. 2212.08015 .

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