NGC 3227
Encyclopedia
NGC 3227 is a spiral galaxy
that is interacting with the dwarf elliptical galaxy
NGC 3226
. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies
. Both galaxies may be found in the constellation
Leo
.
Sir William Herschel
already recognised them as a 'double nebula' and they were jointly listed as Holm 187 in the Catalogue of Double and Multiple Galaxies and Arp 94 in the Atlas of Peculiar Galaxies
. Amateur telescopes can discern them but require magnification of about a 100 times. They are situated 50' east of the well-known double star system Gamma Leonis
(i.e. Algieba).
, a type of active galactic nucleus
(AGN). Such Seyfert nuclei typically contain supermassive black hole
s.
As is typical of many AGN, the nucleus of NGC 3227 has been identified as a source of variable X-ray
emission. This variability occurs on time scales ranging from a few hours to a few months. The variability may be caused by variations in the density or ionization
of gas and dust near the AGN that absorb the X-ray emission. A substantial amount of the X-ray absorbing gas may lie within 0.4 parsec
(1.3 light-year
s) of the nucleus. An observed change in the shape of the X-ray spectrum
in 2000 and 2001 suggests that some of the X-ray absorbing gas is located within 10-100 light-days of the nucleus.
The luminosity of the nucleus reached a maximum in 1977 when evidence suggesting long-lived one-sided or two-sided gas streams was obtained.
X-ray radiation of the central accretion disc is reprocessed in one to two days to be re-emitted in the optical spectrum. Infra-red light emission from the hot dust torus lags optical light emission from the nucleus by about 20 days in NGC 3227. The temperature of the dust torus is estimated at 1500K to 1800K in NGC 3227 and similar galaxies.
This galaxy was studied by the Multicolor Active Galactic Nuclei Monitoring
2m telescope.
Spiral galaxy
A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as...
that is interacting with the dwarf elliptical galaxy
Dwarf elliptical galaxy
Dwarf elliptical galaxies, or dEs, are elliptical galaxies that are much smaller than others. They are classified as dE, and are quite common in galaxy groups and clusters, and are usually companions to other galaxies.- Examples :...
NGC 3226
NGC 3226
NGC 3226 is a dwarf elliptical galaxy that is interacting with the spiral galaxy NGC 3227. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies...
. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies
Atlas of Peculiar Galaxies
The Atlas of Peculiar Galaxies is a catalog of peculiar galaxies produced by Halton Arp. A total of 338 galaxies are presented in the atlas, which was originally published in 1966 by the California Institute of Technology....
. Both galaxies may be found in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Leo
Leo (constellation)
Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:...
.
Sir William Herschel
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...
already recognised them as a 'double nebula' and they were jointly listed as Holm 187 in the Catalogue of Double and Multiple Galaxies and Arp 94 in the Atlas of Peculiar Galaxies
Atlas of Peculiar Galaxies
The Atlas of Peculiar Galaxies is a catalog of peculiar galaxies produced by Halton Arp. A total of 338 galaxies are presented in the atlas, which was originally published in 1966 by the California Institute of Technology....
. Amateur telescopes can discern them but require magnification of about a 100 times. They are situated 50' east of the well-known double star system Gamma Leonis
Gamma Leonis
Gamma Leonis is a binary star system in the constellation Leo. It has the traditional name Algieba or Al Gieba.-Name origin and history:...
(i.e. Algieba).
Nucleus
NGC 3227 contains a Seyfert nucleusSeyfert galaxy
Seyfert galaxies are a class of galaxies with nuclei that produce spectral line emission from highly ionized gas, named after Carl Keenan Seyfert, the astronomer who first identified the class in 1943...
, a type of active galactic nucleus
Active galactic nucleus
An active galactic nucleus is a compact region at the centre of a galaxy that has a much higher than normal luminosity over at least some portion, and possibly all, of the electromagnetic spectrum. Such excess emission has been observed in the radio, infrared, optical, ultra-violet, X-ray and...
(AGN). Such Seyfert nuclei typically contain supermassive black hole
Supermassive black hole
A supermassive black hole is the largest type of black hole in a galaxy, in the order of hundreds of thousands to billions of solar masses. Most, and possibly all galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.Supermassive black holes have...
s.
As is typical of many AGN, the nucleus of NGC 3227 has been identified as a source of variable X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
emission. This variability occurs on time scales ranging from a few hours to a few months. The variability may be caused by variations in the density or ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
of gas and dust near the AGN that absorb the X-ray emission. A substantial amount of the X-ray absorbing gas may lie within 0.4 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
(1.3 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s) of the nucleus. An observed change in the shape of the X-ray spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
in 2000 and 2001 suggests that some of the X-ray absorbing gas is located within 10-100 light-days of the nucleus.
The luminosity of the nucleus reached a maximum in 1977 when evidence suggesting long-lived one-sided or two-sided gas streams was obtained.
X-ray radiation of the central accretion disc is reprocessed in one to two days to be re-emitted in the optical spectrum. Infra-red light emission from the hot dust torus lags optical light emission from the nucleus by about 20 days in NGC 3227. The temperature of the dust torus is estimated at 1500K to 1800K in NGC 3227 and similar galaxies.
This galaxy was studied by the Multicolor Active Galactic Nuclei Monitoring
Multicolor Active Galactic Nuclei Monitoring
Multicolor Active Galactic Nuclei Monitoring or MAGNUM is project started in 1995, and with observations starting in 2000 using 2m reflecting telescope for scientific study of active galactic nuclei. The telescope is run by the University of Tokyo and other Japanese academic institutions. MAGNUM...
2m telescope.
External links
- Glen Youman's Astrophotos of NGC 3226 and NGC 3227
- Cosmic Voyages webpage on NGC 3226 and NGC 3227
- Spitzer observations of the interacting galaxy pair
- Long-term variability of the optical emission lines in the nuclear spectrum of the Seyfert galaxy NGC 3227, Pronik et al., Active Galaxies Newsletter, No. 98
- Reverberation Measurements of the Inner Radius of the Dust Torus in Nearby Seyfert 1 Galaxies, Suganuma et al., ApJ, March 2006, vol. 639