- 'Noah Brosch & Elchanan Almoznino'
- 'Bogdan Wszolek & Konrad Rudnicki'
title: The Nature of a Dusty Ring in Virgo
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Introduction
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The nature of non-luminous matter that is not part of detected and catalogued galaxies remains unsolved by modern astrophysics. As mentioned in a recent thesis, low surface brightness (LSB) objects may prove to be the “icebergs” of the extragalactic world (de Blok 1997). Some searches for non-luminous matter have been successful, the detection of a giant HI ring around the small group of galaxies in Leo centered on M96 (Schneider 1983), extended HI emission in the M81 group (Lo & Sargent 1979), HI companions to dwarf galaxies (for $\sim$25% of the cases: Taylor 1996), and a large neutral hydrogen cloud in the southern outskirts of the Virgo cluster (HI 1225+01: Giovanelli & Haynes 1989).

Along with HI clouds, a few large LSB galaxies have been identified: Malin-1 (Bothun 1987), F568-6 (Bothun 1990), and 1226+0105 (Sprayberry 1993). Their typical star formation rates are $\sim$0.1 M$_{\odot}$/yr and the metallicities are $\sim$1/3 solar. The HI rotation curves, measured by de Block (1997) and by Pickering (1997), indicate that their gaseous component is dynamically significant at all 