dwarf galaxy

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dwarf galaxy

A galaxy that is unusually faint either because of its very small size, its very low surface brightness, or both. Since galaxies exist in a continuous range of sizes from the giant ellipticals downward, the dividing line between average and dwarf is somewhat arbitrary. Since no spiral or S0 galaxies have been observed with total magnitudes below –16, this is often used as a convenient demarcation line. They contain only a few million stars and are very difficult to observe against foreground stars because they are almost completely transparent. Dwarf galaxies may make up the bulk of the cosmic population and occur in all morphologies except as spiral galaxies.

The dwarf irregulars (dI) are the most numerous of these galaxies, and contain a significant fraction of their mass as neutral hydrogen gas in a dark halo (see also LSB galaxies). Dwarf ellipticals (dE) are dominated by metal-poor halo stars, and their lack of gas or dust suggests that any star formation occurred a long time ago in these systems. In contrast, the gas-rich blue compact dwarf (BCD) galaxies are undergoing active star formation with sizes and spectra resembling giant H II regions. See also extragalactic H II region.

dwarf galaxy

[′dwȯrf ′gal·ik·sē]
(astronomy)
An elliptical galaxy with low mass and low luminosity, having at most a few tens of millions of stars.
References in periodicals archive ?
Faint dwarf galaxies also give astronomers a peek at what the earliest galaxies were like.
That's why dwarf galaxies are important in the hunt for the dark matter particle.
Professor Geraint Lewis from the University of Sydney's School of Physics, said that early in 2013 they announced their startling discovery that half of the dwarf galaxies surrounding the Andromeda Galaxy were orbiting it in an immense plane and this plane was more than a million light years in diameter, but was very thin, with a width of only 300 000 light years.
Title: A Search for Intermediate-Mass Black Holes at the Centres of Nearby Dwarf Galaxies
There are a lot of similar ultracompact dwarf galaxies, and together they may contain as many supermassive black holes as there are at the centers of normal galaxies.
The Gas Phase in Low Metallicity ISM, in Low-Metallicity Star Formation: From the First Stars to Dwarf Galaxies, eds.
Because dwarf galaxies contain so little mass, star formation there can be easily quenched by heat or ultraviolet radiation, comments astronomer Mario Mateo of the University of Michigan in Ann Arbor.
David Merritt, professor of astrophysics at Rochester Institute of Technology said that the co-orbiting satellite galaxy structures are still in conflict with the distribution of primordial dwarf galaxies.
The Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way, are at the head of the gaseous stream.
Astronomers have discovered two dwarf galaxies that are being devoured by the Milky Way.
The Yale scientists will tackle a key question next: Are these seven newly found objects dwarf galaxies orbiting around the M101 spiral galaxy, or are they located much closer or farther away, and just by chance are visible in the same direction as M101?
The movement of the stars tells us that what we are observing is the remnant of a merger between two dwarf galaxies.