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Gas in gas-poor galaxies

Submitter: Raffaella Morganti & Tom Oosterloo
Description: The WSRT is busy at the moment with a Large Project, looking for neutral hydrogen in a large sample of nearby early-type galaxies. This type of galaxies were originally thought to be round, boring and to contain very little gas. However, the WSRT has discovered (see Daily Image 13-7-2006) that, if a good radio telescope and deep enough observations are available, neutral hydrogen can be detected in more than 60% of them! The new, large project aims to expand on this initial exciting result with a larger sample of galaxies.

The pictures show some of the new HI detections obtained: the contours represent the distribution of the neutral hydrogen, while the orange pictures represent the optical light. You can see how, in many cases, the distribution of the gas is much larger than that of the stars, and this is one of the reasons that makes the HI observations interesting and important. The distribution of the gas can also be messy, likely disturbed by the passage of a neighbouring galaxy.

The observed sample (also known as ATLAS3D) is currently studied not only with the WSRT, but also with the integral-field spectrograph SAURON on the William Herschel Telescope on La Palma. Such data will tell us how the stars and the ionised gas are behaving. All this information together will be used to understand how these galaxies form and evolve.
Copyright: Astron
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