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Cavendish Astrophysics


The Astrophysics Group is actively involved with ALMA , a submillimetre interferometer in northern Chile.

One of the most important features of ALMA is that it can make high-quality images with very good angular resolution.  This picture shows the disc of gas and dust surrounding a young star.  The whole image is less than two arcseconds across and the resolution is about 0.03 arcseconds.

This high resolution makes it possible to see that the disc is made up of a series of bright rings with gaps in between them - careful examination shows at least 7 separate rings.  It is very likely that this pattern is a result of the fact that planets are starting to form out of the disc.  Although the planets themselves are too small to be seen, we should be able to learn more about their properties and the process of planet formation through detailed analysis of this image and similar ones of other young stars that should be obtained by ALMA in the coming years.

Roberto Maiolino has been leading a study using ALMA to detect the [CII]158 μm line and continuum emission in galaxies at z~7 (i.e well within the epoch of re-ionisation). These galaxies have very low star formation rates (~10 Msun/yr) and so are more representative of the galaxy population at high redshifts than those studied in previous investigation, which tend to be extreme objects.

By targeting the [CII] line with ALMA (left) we have detected clumps of neutral gas (middle) spatially offset from the primary galaxy at z=7.107 previously identified through Lyα and UV continuum emission (which is tracing the ionised gas). Such observations are indeed predicted by recent models (right) of primeval galaxy formation according to which molecular clouds in primeval galaxies are disrupted by stellar feedback, while accreting/satellite clumps of neutral gas survive in the vicinity of the galaxy and are detectable through their [CII] emission. These results imply that our observations are probing galaxy formation at their very early stages.

In addition, using our deep ALMA continuum maps, as well as a collection of deep observations from the archive, we have studied the faint end number counts and believe we have been able to resolve close to 100% of the Cosmic Infrared Background. Both sets of results will help in further constraining models of galaxy formation and identifying the key components in galaxy evolutionary scenarios.

If you are interested in doing research in this area, please visit our Graduate Research Opportunities web pages.

We also host the UK’s project scientist, and the group has developed phase correction techniques described on our ALMA Project pages.

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