LEDA 2108986, also known by its
Case Western Reserve University designation "Case Galaxy 611" (CG 611), is an extremely isolated, early-type
dwarf galaxy
A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is so ...
with an embedded spiral structure residing in what is likely an intermediate-scale disk.
[
] The galaxy was discovered in 1987 by Sanduleak and Pesch, and is located at a distance of about in the
Boötes Void and has no significant neighbours within 2.5 Mpc.
The galaxy may be a counterpart to the rectangular-shaped galaxy
LEDA 74886, in that they both appear to contain an intermediate-scale disk. In the case of
LEDA 74886, that disk is orientated edge-on to our line-of-sight. The "early-type galaxy" class is commonly known to contain
elliptical galaxies
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 Hubble in his Hubble sequence and 1936 work ''The Real ...
(E) with no substantial stellar disk (perhaps just a small nuclear disk) and
lenticular galaxies
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. ...
(S0) with their large-scale disks that dominate the light at large radii. Bridging these two types of galaxies are the ES galaxies with their intermediate-scale disks, referred to as "Ellicular" galaxies in recent works.
[
]
Importance
LEDA 2108986 has accreted a gas disk which counter-rotates relative to its stellar disk. It also displays a young spiral pattern within this stellar disk.
The presence of such faint disk structures and rotation within some dwarf early-type galaxies in galaxy clusters has often been heralded as evidence that they were once late-type spiral or dwarf irregular galaxies prior to experiencing a cluster-induced transformation, known as galaxy harassment. The extreme isolation of LEDA 2108986 is proof that dwarf early-type galaxies can be built by accretion events, as opposed to disk-stripping scenarios within the "galaxy harassment" model.
See also
* LEDA 74886
* NGC 1271
* Mrk 1216, NGC 1277, NGC 1332, NGC 4291[Savorgnan, Giulia A.D. and Graham, Alister W. (2016)]
Explaining the reportedly overmassive black holes in early-type galaxies with intermediate-scale discs
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References
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2108986
Dwarf galaxies
Boötes