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The existence and detection of optically dark galaxies by 21-cm surveys

Davies, Jonathan Ivor, Disney, Michael John, Minchin, R. F., Auld, Robbie Richard and Smith, R. 2006. The existence and detection of optically dark galaxies by 21-cm surveys. Monthly Notices of the Royal Astronomical Society 368 (3) , pp. 1479-1488. 10.1111/j.1365-2966.2006.10247.x

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One explanation for the disparity between cold dark matter (CDM) predictions of galaxy numbers and observations could be that there are numerous dark galaxies in the Universe. These galaxies may still contain baryons, but no stars, and may be detectable in the 21-cm line of atomic hydrogen. The results of surveys for such objects, and simulations that do/do not predict their existence, are controversial. In this paper, we use an analytical model of galaxy formation, consistent with CDM, to first show that dark galaxies are certainly a prediction of the model. Secondly, we show that objects like VIRGOHI21, a dark galaxy candidate recently discovered by us, while rare are predicted by the model. Thirdly, we show that previous ‘blind’ H i surveys have placed few constraints on the existence of dark galaxies. This is because they have either lacked the sensitivity and/or velocity resolution or have not had the required detailed optical follow up. We look forward to new 21-cm blind surveys [Arecibo Legacy Fast ALFA (ALFALFA) survey and Arecibo Galactic Environments Survey (AGES)] using the Arecibo multibeam instrument which should find large numbers of dark galaxies if they exist.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Galaxy: formation; dark matter
Publisher: Wiley
ISSN: 0035-8711
Last Modified: 04 Jun 2017 04:17

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