"HI observations of Superthin Galaxies"

Juan M. Uson (Observatoire de Paris)

Superthin galaxies are bulgeless, late-type spiral galaxies seen edge-on. HI synthesis observations probe the kinematic structure of their interstellar medium. I shall present the results of high-sensitivity VLA observations of UGC7321, IC2233, UGC3697 and UGC10043. Two of these galaxies are rather isolated while the other two are the dominant members of small groups.

We have detected a pattern of "corrugations" in IC 2233, the first such detection in neutral Hydrogen in an external galaxy. UGC 3697, the "Integral Sign" galaxy shows a spectacular S-shaped bending that has been triggered by the passage of an intruder through its disk. UGC 10043, not quite a superthin galaxy, has presented us with an unexpected, rich interaction with a previously unknown companion which is reminiscent of the M51 system (the Whirlpool galaxy) "seen from the side."

The simple structure of the superthins makes them ideal cosmological laboratories. As an example, I shall discuss briefly recent H-alpha observations of UGC7321 and UGC1281 which have allowed us to set new limits on the metagalactic UV background.