Le 28 juin 2019
De 10h30 à 12h00

Frédéric Marin Observatoire astronomique de Strasbourg Worldships are hypothetical, large,...

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Inert hydrogen clouds in the Virgo cluster : dark galaxies, tidal debris, or something else?

Le 26 octobre 2018
De 10h30 à 12h00

Rhys Taylor

Astronomical Institute, Prague


The Arecibo Galaxy Environment Survey is a large-area, blind neutral hydrogen survey, designed to observe the full range of galaxy environments without the optical biases of traditional surveys. As well as being a sensitive tracer of the effects of environment, HI can be used to detect features which are completely optically dark and cannot be detected by other methods. I will review some of the optically dark features detected so far by AGES, concentrating on a population of isolated, compact clouds in the Virgo cluster with high line widths. Such clouds are not easily explained as tidal debris owing to their high line width and isolation. One possibility is that they may be "dark galaxies", rotating HI discs embedded in dark matter halos but with a gas density too low to allow star formation. I will review the numerical work we have performed to test three proposed explanations for the clouds : tidal debris, dark galaxies, and pressure confined clouds prevented from dispersal by the pressure of the intracluster medium. 3D glasses will be provided to the audience.

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