IC 1101 is a class S0 supergiant ( cD)

lenticular galaxy A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. L ...

at the center of the Abell 2029

galaxy cluster A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity, with typical masses ranging from 1014 to 1015 solar masses. They are the second-l ...

. It has an isophotal diameter at about . It possesses a diffuse core which is the largest known core of any galaxy to date, and also hosts a supermassive black hole that is one of the largest black holes known. The galaxy is located at from Earth. The galaxy was discovered on 19 June 1790, by the British astronomer

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...

Characteristics

Morphology

The galaxy is classified as a supergiant elliptical (E) to lenticular (S0) and is the brightest galaxy in A2029 (hence its other designation A2029-BCG; BCG meaning ''

brightest cluster galaxy A brightest cluster galaxy (BCG) is defined as the brightest galaxy in a cluster of galaxies. BCGs include the most massive galaxies in the universe. They are generally elliptical galaxies which lie close to the geometric and kinematical center ...

''). The galaxy's morphological type is debated due to it possibly being shaped like a flat disc but only visible from Earth at its broadest dimensions. A morphology of S0- (Hubble stage -2; see Hubble stage for details) has been given by the Third Reference Catalogue of Bright Galaxies (RC3) in 1991.

Size

IC 1101 is considered a large galaxy characterized by an extensive, diffuse halo. Defining the size of a galaxy varies according to the method used in the astronomical literature.

Photographic plate Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinn ...

s of blue light from the galaxy (sampling stars excluding the diffuse halo) yield an

effective radius Galaxy effective radius or half-light radius (R_e) is the radius at which half of the total light of a galaxy is emitted. This assumes the galaxy has either intrinsic spherical symmetry or is at least circularly symmetric as viewed in the plane o ...

(the radius within which half the light is emitted) of based on an earlier distance measurement. The galaxy has a very large halo of much lower intensity "diffuse light" extending to a radius of . The authors of the study identifying the halo conclude that IC 1101 is "possibly one of the largest and most luminous galaxies in the universe", though this figure was based on an earlier assumed distance of More recent measurements, using the 25.0 magnitude/arcsec² standard (commonly known as ''D₂₅'', a method recommended by R.O. Redman in 1936) has been utilized by the RC3 in the B-band, with a measured major axis (log 2a+1) of 1.08 (equivalent to 72.10 arcseconds), translating to a diameter of . Another calculation by the

Two Micron All-Sky Survey The Two Micron All-Sky Survey, or 2MASS, was an astronomical survey of the whole sky in infrared light. It took place between 1997 and 2001, in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and ...

using the "total" aperture at the K-band yield a much larger size of . Both measurements are based on the currently-accepted distance to IC 1101. This would make it one of the largest and most luminous galaxies known, though there are other galaxies with larger isophotal diameter measurements (such as

NGC 623 NGC 623 is a large elliptical galaxy located in the Sculptor constellation at a distance of about 400 million light-years away from the Milky Way. It was discovered by British astronomer An astronomer is a scientist in the field of astronomy ...

Abell 1413 Abell 1413 is a galaxy cluster in the Abell catalogue. The Abell catalogue was published by George O. Abell in 1958 while working on his PhD at California Institute of Technology. The catalogue has two different surveys. The Northern survey was do ...

BCG, and

ESO 306-17 ESO 306-17 is a fossil group giant elliptical galaxy An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the four main classes of galaxy described by Edwin ...

Distance

The distance to IC 1101 has also been uncertain, with different methods across different wavelengths producing varying results. An earlier distance calculation from 1980 using the galaxy's photometric property yield a distance of and a redshift of z = 0.077, based on a Hubble constant value H₀ of 60 km/s/Mpc. The RC3 catalogue gave a nearly similar value of z=0.078, based on optical emission lines, a value conformed to as recently as 2017 based on luminosity, stellar mass, and velocity dispersion functions, all yielding distances of based on the modern value of the Hubble constant H₀ = 67.8 km/s/Mpc; the currently accepted values. Lower redshifts have been calculated for other wavelengths such as the photometric redshift measurement by the Two Micron All-Sky Survey ( 2MASS) in 2014, which gave a value of z = 0.045, translating to a distance of . A measurement made in 2005 by the

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science F ...

using the 21-cm hydrogen emission line yields a redshift of z = 0.021, and hence a distance of . Like most large galaxies, IC 1101 is populated by a number of metal-rich stars, some of which are seven billion years older than the Sun, making it appear golden yellow in color. It has a bright radio source at the center, which is likely associated with an

ultramassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical obj ...

in the mass range of measured using core dynamical models, or alternatively at using gas accretion rate and growth modelling., which would make IC 1101's black hole one of the most massive known to date. The authors also say that the galaxy is one of the most luminous and largest cD-galaxies. A 2017 paper suggests that IC 1101 has the largest core size of any galaxy, with a core radius of around , making its core larger than the one observed in A2261-BCG. The core is also roughly an order of magnitude larger than the cores of other large elliptical galaxies, such as

NGC 4889 NGC 4889 (also known as Caldwell 35) is an E4 supergiant elliptical galaxy. It was discovered in 1785 by the British astronomer William Herschel, Frederick William Herschel I, who catalogued it as a bright, nebulous patch. The brightest galaxy wi ...

and NGC 1600. However, when examining large and diffuse galactic cores, caution must be taken, as various estimates may differ between the computer models used. As an example, Holmberg 15A was originally claimed to have the largest galactic core of any galaxy but other studies proved otherwise.

Notes

References

External links

* * * {{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Elliptical galaxies Virgo (constellation) 1101 54167 09752 17900619