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Ultra-Diffuse Galaxies in the Virgo Cluster

25 Jul 2015, 23:00 UTC
Ultra-Diffuse Galaxies in the Virgo Cluster
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Recently, a large number of low surface brightness (LSB) galaxies were discovered in the Coma Cluster - a large cluster of galaxies located over 300 million light years away. Galaxies do not possess well defined boundaries. They simply get fainter and fainter towards their outer regions. As a result, the size of a galaxy is defined by its effective radius, also known as the half-light radius. The effective radius is the radius within which half of the galaxy’s luminosity is emitted.Many of the LSB galaxies in the Coma Cluster are large, with effective radii between 2 to 5 kpc. One kpc (kiloparsec) is equivalent to 3,260 light years, and for comparison, the effective radius of the Milky Way galaxy is estimated to be ~3.6 kpc. They are also extremely diffuse galaxies with central surface brightnesses between 24 to 26 mag/arcsec². LSB galaxies are vulnerable to tidal perturbations as they move through the cluster and interact with other galaxies. Tidal disruption of a LSB galaxy can strip the galaxy down to only its dense nucleus, leading to the formation of an ultra-compact dwarf (UCD) galaxy.Mihos et al. (2015) present the discovery of three LSB galaxies in the Virgo Cluster - a ...

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