OPTICAL AND 21-CM OBSERVATIONS OF HIGH-VELOCITY GAS TOWARDS SUBDWARFS IN THE HALO AND EARLY-TYPE STARS IN THE DISK

We present a study of high-velocity gas in the direction of 13 halo sub-dwarfs located at \z\ similar or equal to 0.5 - 2 kpc and of 8 early-type stars in the Galactic disk at d similar or equal to 1 - 4 kpc. For each line of sight of our sample we collected Ca II and Na I absorption spectra with the 2.5-m Isaac Newton Telescope at La Palma (Spain) and H I 21-cm emission profiles with the 100-m radiotelescope at Effelsberg (Germany). The faint sub-dwarfs (m(V) similar or equal to 11-14) are observed for the first time at relatively high spectral resolution (similar or equal to 25 - 30 km s(-1)) in the optical. By comparing the optical absorptions (or upper limits) with the 21-cm emissions, we constrain the distances to the concentrations of neutral gas at high velocity named Complex C, Complex H, and for high velocity gas located between the Cohen Stream and the Magellanic Stream, We find new evidence for gas at intermediate velocity in the halo and in the disk of our Galaxy.