H-I OBSERVATIONS OF THE TUCANA DWARF ELLIPTIC GALAXY

H I observations of the Local Group dwarf elliptical galaxy, Tucana, h ave been obtained with the Australia Telescope Compact Array. Within t he optical extent of this galaxy, no H I was detected. The upper limit on the H I mass to blue luminosity ratio, M(H I)/L(B), is then simila r to 10(-2) for Tucana, a value similar to those of the Galactic dwarf spheroidal companions. This nondetection contrasts with the modest H I contents of Phoenix and LGS3, the other relatively isolated Local Gr oup dwarfs with dominant old stellar populations. However, an H I clou d was detected, some 15' to the north-east of Tucana, at a heliocentri c velocity of 130+/-2 km s(-1) CCD observations of the central regions of this cloud, which has a maximum extent of similar to 20' x 10', di d not reveal any obvious optical counterpart. The cloud has a faint ta il of emission that points in the general direction of Tucana, and if it is at the same distance as the dE galaxy, then the H I mass is simi lar to 1.5 x 10(6) M. We prefer the alternative interpretation that th is H I cloud is a foreground high-velocity cloud, probably associated with the Magellanic Stream complex that pervades this part of the sout hern sky. (C) 1996 American Astronomical Society.