NGC 5506 is a
spiral galaxy located in the constellation
Virgo. It is located at a distance of about 75 million
light years from Earth, which, given its apparent dimensions, means that NGC 5506 is about 80,000 light years across.[1] It was discovered by
William Herschel on April 15, 1787.[2] It is a
Seyfert galaxy.[1]
Characteristics
NGC 5506 is a spiral galaxy seen edge-on, with dust lanes visible south of the nucleus.[3]
Active nucleus
The nucleus of NGC 5506 has been found to be
active and it has been categorised as a narrow line type I
Seyfert galaxy, and is the brightest such nucleus.[4] The classification of the active nucleus had been an issue of debate, as it lacked broad
emission lines in the visual wavelength. However, broader lines were observed in the
infrared,[5] indicating that the broad line region is obscured in visual light.[4]
The most accepted theory for the energy source of active galactic nuclei is the presence of an
accretion disk around a
supermassive black hole. The mass of the black hole in the centre of NGC 5506 is estimated to be 8.8×107M☉ based on stellar
velocity dispersion and 5.1×106M☉ based on the
MBH–σ⋆ relation and X-ray variability.[6]
NGC 5506 is a bright
X-ray source, detected by all X-ray space observatories, starting with
Uhuru.[7] The X-ray spectrum indicates that there is both a compton-thick and a compton-thin absorber. The compton-thick absorber is a dust torus around the supermassive black hole at a distance of around one parsec, while the compton thin absorbs the softer X-rays emitted by the nucleus.[7] The soft emission by the nucleus extends to a distance of about 350 pc and is attributed to reflection of the nuclear emission by
photoionized gas.[7] The inclination of the accretion disk is estimated to be between 40° and 50°.[8] The iron line is complex, indicating emission by neutral and ionised iron.[9] A broad component of the
Fe Kα fluorescent emission line was observed by
XMM-Newton.[10]
The galaxy also emits
radiowaves. The galaxy exhibits a central source that accounts for 75% of the total emission and diffuse wing-like emission towards the north-west and east of the nucleus and a low-surface-brightness halo measuring 2.75 arcseconds in diameter that surrounds these features.[11] The features have no clear axis of symmetry.[12] The galaxy has been found to host an H2Omegamaser.[13]
Nearby galaxies
NGC 5506 is the foremost galaxy in a
galaxy group known as the
NGC 5506 Group. Other members of the group include
NGC 5507, while IC 978 lies a bit farther away.[14] Garcia identified as members of group also the galaxies
NGC 5496, and UGC 9057.[15] NGC 5506 forms a pair with NGC 5507, which lies 4 arcminutes from it.[16] The group is part of the
Virgo III Groups, a very obvious chain of galaxy groups on the left side of the Virgo cluster, stretching across 40 million light years of space.[17]
^Nikołajuk, M.; Czerny, B.; Gurynowicz, P. (21 April 2009). "NLS1 galaxies and estimation of their central black hole masses from the X-ray excess variance method". Monthly Notices of the Royal Astronomical Society. 394 (4): 2141–2152.
arXiv:0901.1442.
doi:
10.1111/j.1365-2966.2009.14478.x.
^Sun, Shangyu; Guainazzi, Matteo; Ni, Qingling; Wang, Jingchun; Qian, Chenyang; Shi, Fangzheng; Wang, Yu; Bambi, Cosimo (1 August 2018). "Multi-epoch analysis of the X-ray spectrum of the active galactic nucleus in NGC 5506". Monthly Notices of the Royal Astronomical Society. 478 (2): 1900–1910.
arXiv:1704.03716.
doi:
10.1093/mnras/sty1233.
^Guainazzi, M.; Bianchi, S.; Matt, G.; Dadina, M.; Kaastra, J.; Malzac, J.; Risaliti, G. (June 2010). "Final verdict from XMM-Newton: the X-ray obscured Seyfert galaxy NGC 5506 has a broad Fe Kα line: Broad Kα Fe line in NGC 5506". Monthly Notices of the Royal Astronomical Society: no–no.
arXiv:1004.1442.
doi:
10.1111/j.1365-2966.2010.16805.x.
^Orienti, M.; Prieto, M. A. (1 February 2010). "Radio structures of the nuclei of nearby Seyfert galaxies and the nature of the missing diffuse emission". Monthly Notices of the Royal Astronomical Society. 401 (4): 2599–2610.
arXiv:0911.0852.
doi:
10.1111/j.1365-2966.2009.15837.x.
^Braatz, J. A.; Wilson, A. S.; Henkel, C. (December 1994). "The discovery of five new H2O megamasers in active galaxies". The Astrophysical Journal. 437: L99.
doi:
10.1086/187692.