HI Observations of Low Surface Brightness Galaxies: Probing Low Density Galaxies
HI Observations of Low Surface Brightness Galaxies: Probing Low Density Galaxies
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Date
1996
Authors
de Blok, W.J.G.
McGaugh, S.S.
van der Hulst, J.M.
Advisor
Citation
HI Observations of Low Surface Brightness Galaxies: Probing Low Density Galaxies. de Blok, W.J.G., McGaugh, S.S., & van der Hulst, J.M. 1996, MNRAS, 283, 18-54.
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Abstract
We present Very Large Array (vla) and Westerbork Synthesis Radio Telescope (wsrt)
21-cm Hi observations of 19 late-type low surface brightness (LSB) galaxies. Our main
findings are that these galaxies, as well as having low surface brightnesses, have low
Hi surface densities, about a factor of ~ 3 lower than in normal late-type galaxies. We
show that LSB galaxies in some respects resemble the outer parts of late-type normal
galaxies, but may be less evolved. LSB galaxies are more gas-rich than their high surface
brightness counterparts. The rotation curves of LSB galaxies rise more slowly than those
of HSB galaxies of the same luminosity, with amplitudes between 50 and 120 km s−1,
and are often still increasing at the outermost measured point. The shape of the rotation
curves suggests that LSB galaxies have low matter surface densities. We use the average
total mass surface density of a galaxy as a measure for the evolutionary state, and show
that LSB galaxies are among the least compact, least evolved galaxies. We show that
both MHI/LB and Mdyn/LB depend strongly on central surface brightness, consistent
with the surface brightness–mass-to-light ratio relation required by the Tully-Fisher
relation. LSB galaxies are therefore slowly evolving galaxies, and may well be low surface
density systems in all respects.