| Abstract | H I observations of the Local Group dwarf elliptical galaxy, Tucana, have been obtained with the Australia Telescope Compact Array. Within the optical extent of this galaxy, no H I was detected. The upper limit on the H I mass to blue luminosity ratio, M_HI_/L_B_ , is then ~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 Group dwarfs with dominant old stellar populations. However, an H I cloud was detected, some 15' to the north-east of Tucana, at a heliocentric velocity of 130+/-2 km s^-1^. CCD observations of the central regions of this cloud, which has a maximum extent of ~20' x 10', did not reveal any obvious optical counterpart. The cloud has a faint tail 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 ~1.5 x 10^6^ M_sun_. We prefer the alternative interpretation that this H I cloud is a foreground high- velocity cloud, probably associated with the Magellanic Stream complex that pervades this part of the southern sky. |
