Physical properties of galactic winds using background quasars
  Background quasars are potentially sensitive probes of galactic outflows
provided that one can determine the origin of the absorbing material since both
gaseous disks and strong bipolar outflows can contribute to the absorption
cross-section. Using a dozen quasars passing near spectroscopically identified
galaxies at $z\sim0.1$, we find that the azimuthal orientation of the quasar
sight-lines with strong MgII absorption (with EW>0.3 \AA) is bi-modal: about
half the MgII sight-lines are aligned with the major axis and the other half
are within 30deg. of the minor axis, showing that bipolar outflows contribute
significantly to the MgII cross-section. This bi-modality is also present in
the instantaneous star-formation rates (SFRs) of the hosts. For the sight-lines
aligned along the minor axis, a simple bi-conical wind model is able to
reproduce the observed MgII kinematics and the MgII dependence with impact
parameter b, (EW $\propto b^{-1}$). Using our wind model, we can directly
extract key wind properties such as the de-projected outflow speed $V_{out}$ of
the cool material traced by MgII and the outflow rates. The outflow speeds are
found to be 150-300 \kms, i.e. of the order of the circular velocity, and
smaller than the escape velocity by a factor of ~2. The outflow rates are
typically two to three times the instantaneous SFRs. Our results demonstrates
how background quasars can be used to measure wind properties with high
precision.
