NGC 4395

NGC 4395
An ultraviolet image of NGC 4395 taken with GALEX
Observation data (J2000 epoch)
Constellation	Canes Venatici[1]
Right ascension	12^h 25^m 48.9^s[2]
Declination	+33° 32′ 48″[2]
Redshift	319 ± 1 km/s[2]
Distance	~14 million light-years
Apparent magnitude (V)	10.6[2]
Characteristics
Type	SA(s)m[2]
Size	50,000 ly (diameter)
Apparent size (V)	13.2′ × 11.0′[2]
Other designations
NGC 4395,[3] UGC 7542,[2] PGC 40596[2]

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.^[1] 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.^[3]

The galaxy is highly unusual for Seyfert galaxies, because it does not have a bulge and is considered to be a dwarf galaxy.^[4]

Observational history

NGC 4395 was imaged and classified as a "spiral nebula" in a 1920 paper by astronomer Francis G. Pease.^[5] 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.^[6] More recently, NGC 4395 was discovered to contain a very low-luminosity active galactic nucleus.^[7] 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.^[4] The nucleus of NGC 4395 is notable for containing one of the smallest supermassive black holes with a well-measured mass.^[8] The central black hole has a mass of "only" 300,000 M_☉.^[9] However, a recent study found a black hole mass of just 10,000 M_☉.^[10] The low-mass black hole in NGC 4395 would make it a so-called "intermediate-mass black hole".^[11] The black hole may have a truncated disk. ^[12]

References

1. 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.
2. "NASA/IPAC Extragalactic Database". Results for. Retrieved 2006-11-04.
3. Kepple, George Robert; Sanner, Glen W. (1998). The night sky observers guide. Vol. 2. Richmond (Va.): Willmann-Bell. p. 48. ISBN 978-0-943396-60-6.
4. Filippenko, Alexei V.; Ho, Luis C. (May 2003). "A Low-Mass Central Black Hole in the Bulgeless Seyfert 1 Galaxy NGC 4395". The Astrophysical Journal. 588 (1): L13 – L16. arXiv:astro-ph/0303429. Bibcode:2003ApJ...588L..13F. doi:10.1086/375361. ISSN 0004-637X. S2CID 14411746.
5. Pease, F. G. (June 1920). "Photographs of nebulae with the 60-inch reflector, 1917-1919". The Astrophysical Journal. 51: 276. Bibcode:1920ApJ....51..276P. doi:10.1086/142552. ISSN 0004-637X.
6. 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 H sub 0". The Astrophysical Journal. 194: 559. Bibcode:1974ApJ...194..559S. doi:10.1086/153275. ISSN 0004-637X.
7. 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.
8. Merritt, David (2013). Dynamics and evolution of galactic nuclei. Princeton series in astrophysics. Princeton: Princeton University Press. ISBN 978-0-691-15860-0.
9. Peterson, Bradley M.; et al. (20 October 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. ISSN 0004-637X. S2CID 13886279.
10. Woo, Jong-Hak; et al. (10 July 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.
11. Shih, D. C.; Iwasawa, K.; Fabian, A. C. (21 May 2003). "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. arXiv:astro-ph/0302108. Bibcode:2003MNRAS.341..973S. doi:10.1046/j.1365-8711.2003.06482.x. ISSN 0035-8711.
12. McHardy, I M; et al. (9 January 2023). "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. arXiv:2212.08015. doi:10.1093/mnras/stac3651. ISSN 0035-8711.

External links

• Media related to NGC 4395 at Wikimedia Commons
• NGC4395