NGC 5728 is an active barred spiral galaxy located 146^[2] million light years away in the southern constellationofLibra. It was discovered on May 7, 1787 by William Herschel. The designation comes from the New General CatalogueofJ. L. E. Dreyer, published in 1888.^[7] It has an apparent visual magnitude of 13.40^[3] and spans an angle of 3.4 arcminutes. The galaxy shows a red shift of 0.00935 and has a heliocentric radial velocity of 2,803 km/s.^[2] It has an estimated mass of 72^[5] billion times the mass of the Sun and stretches around 30 kpc across.^[4]

The morphological classification of this galaxy is SAB(r)a?,^[4] which indicates a weakly barred spiral galaxy (SAB) with a ring-like structure (r) and possible tightly wound arms (a?). The Spitzer galactic survey lists a morphology code of (R₁)SB(r′l,bl,nr,nb)0/a, meaning a barred spiral having a closer outer ring and an inner pseudo-ring/lens, plus a nuclear ring and bar/bar-lens.^[5] Vera Rubin described it as having a "distinct elliptical structure intermediate between a spheroid and a disk".^[8] Asymmetrical gas distribution in the galaxy suggests it has undergone a minor merger event that did not produce tidal tails.^[9]

In addition to the main bar, there is what appears to be a counter-rotating nuclear bar in the inner ~10″, which is at an angle of 60° from the main bar.^[10] There is evidence of star formation, but that has nearly ceased in the nuclear region due to the molecular gas being all but exhausted. The nuclear bar, if it exists, now consists of stars with little surrounding gas.^[9]

This is a Seyfert galaxy of type 2, indicating it has an obscured active galactic nucleus (AGN) powered by a supermassive black hole at the center. The estimated mass of this object is 3.4×10⁷ M_☉ and it is accreting mass at the rate of 2.7×10⁻² M_☉·yr⁻¹.^[11] Energy released by the AGN is visible in the form of ionized cones that extend outward from the nucleus to a distance of more than 2.5 kpc, and lie across the line of sight from the Earth. X-ray and radio jets have been detected. The nucleus is being fed by spiraling filaments and dust lanes from the surrounding galaxy. The AGN itself is hidden behind a bar of dust approximately 64 pc in length.^[5] The outflow from the core is encountering the galactic ring at a distance of 1 kpc and is significantly enhancing star formation in that region compared to other parts of the ring.^[12]

The type Ia supernova SN 2009Y was reported in February 2009, before it reached maximum.^[13] It was magnitude 16.0 at discovery and located 24.7″ north and 9.3″ east of the center of NGC 5728.^[14]

References[edit]

^ ^a ^b Evans, I. N.; et al. (July 2010), "The Chandra Source Catalog", The Astrophysical Journal Supplement, 189 (1): 37–82, arXiv:1005.4665, Bibcode:2010ApJS..189...37E, doi:10.1088/0067-0049/189/1/37, S2CID 16151642.

^ ^a ^b ^c ^d ^e Catinella, Barbara; et al. (September 2005), "Rotational Widths for Use in the Tully-Fisher Relation. I. Long-Slit Spectroscopic Data", The Astronomical Journal, 130 (3): 1037–1048, arXiv:astro-ph/0506148, Bibcode:2005AJ....130.1037C, doi:10.1086/432543, S2CID 17643127.

^ ^a ^b ^c ^d Véron-Cetty, M. -P.; Véron, P. (July 2010), "A catalogue of quasars and active nuclei", Astronomy and Astrophysics, 518 (13th ed.), Bibcode:2010A&A...518A..10V, doi:10.1051/0004-6361/201014188, A10.

^ ^a ^b ^c ^d de Vaucouleurs, G.; et al. (1991), Third Reference Catalogue of Bright Galaxies, New York, NY: Springer, pp. 1–723, doi:10.1007/978-1-4757-4360-9_1, ISBN 978-1-4757-4362-3

^ ^a ^b ^c ^d ^e Durré, Mark; Mould, Jeremy (November 2018), "The AGN Ionization Cones of NGC 5728. I. Excitation and Nuclear Structure", The Astrophysical Journal, 867 (2): 26, arXiv:1810.03258, Bibcode:2018ApJ...867..149D, doi:10.3847/1538-4357/aae68e, S2CID 117916655, 149.

^ "NGC 5728". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-11-25.

^ ^a ^b Seligman, Courtney, NGC Objects, retrieved 2019-11-27.

^ Rubin, V. C. (June 1980), "Velocities and mass distribution in the barred spiral NGC 5728", Astrophysical Journal, 238: 808–817, Bibcode:1980ApJ...238..808R, doi:10.1086/158041.

^ ^a ^b Petitpas, Glen R.; Wilson, Christine D. (August 2002), "Molecular Gas in Candidate Double-barred Galaxies. I. The Diverse Morphology and Dynamics of NGC 2273 and NGC 5728", The Astrophysical Journal, 575 (2): 814–825, arXiv:astro-ph/0204413, Bibcode:2002ApJ...575..814P, doi:10.1086/341335, S2CID 16574000.

^ Prada, F.; Gutiérrez, C. M. (January 1997), "Counterrotating Bulges in NGC 7331 and NGC 5728", Bulletin of the American Astronomical, 29, American Astronomical Society, 189th AAS Meeting: 734, Bibcode:1997AAS...18912202P, 122.02.

^ Durré, Mark; Mould, Jeremy (January 2019), "The AGN Ionization Cones of NGC 5728. II. Kinematics", The Astrophysical Journal, 870 (1): 21, arXiv:1811.04513, Bibcode:2019ApJ...870...37D, doi:10.3847/1538-4357/aaf000, S2CID 119219822, 37.

^ Shin, Jaejin; et al. (August 2019), "Positive and Negative Feedback of AGN Outflows in NGC 5728", The Astrophysical Journal, 881 (2): 13, arXiv:1907.00982, Bibcode:2019ApJ...881..147S, doi:10.3847/1538-4357/ab2e72, S2CID 195776340, 147.

^ Martin, R.; et al. (February 2009), Green, D. W. E. (ed.), "Supernova 2009Y in NGC 5728", Central Bureau Electronic Telegrams, 1684: 1, Bibcode:2009CBET.1684....1M.