2005ApJ...622..267K

We present new H I 21 cm absorption data and ultraviolet spectroscopy from Hubble Space Telescope/Space Telescope Imaging Spectrograph of the QSO/galaxy pair 3C 232/NGC 3067. The QSO sight line lies near the minor axis and 1'.8 (11 h^–1₇₀kpc) above the plane of NGC 3067, a nearby luminous (cz=1465±5 km/s, L=0.5L^*) starburst galaxy with a moderate star formation rate of 1.4 M_☉/yr. The UV spectra show that the Si IV and C IV doublets have the same three velocity components at cz=1369, 1417, and 1530 km/s found in Ca II H and K, Na I D, Mg I, Mg II, and Fe II, implying that the low- and high-ionization gas are both found in three distinct absorbing clouds (only the strongest component at 1420 km/s is detected in H I 21 cm). The new Lyα observation allows the first measurements of the spin and kinetic temperatures of halo gas: T_s=435±140 K and T_k/T_s~1. However, while a standard photoionization model can explain the low ions, the C IV and Si IV are explained more easily as collisionally ionized boundary layers of the photoionized clouds. Because of their small inferred space velocity offsets (Δv=-260, -130, and +170 km/s) relative to the nucleus of NGC 3067 and the spatial coincidence of low- and high-ionization gas, we propose that these absorbers are analogous to Galactic high-velocity clouds (HVCs). A comparison of the NGC 3067 clouds and Galactic HVCs finds similar H I column densities, kinematics, metallicities, spin temperatures, and inferred sizes. We find no compelling evidence that any halo gas along this sight line is escaping the gravitational potential of NGC 3067, despite its modest starburst.