We compose a 265-sight-line Milky Way CIV line-shape sample using the Hubble Space Telescope/Cosmic Origins Spectrograph archive, which is complementary to the existing SiIV samples. CIV has a higher ionization potential (47-64eV) than SiIV (33-45eV), so it also traces warm gas, which is roughly cospatial with SiIV. The spatial density distribution and kinematics of CIV are identical to those SiIV within ~2{sigma}. CIV is more sensitive to the warm gas density distribution at large radii with a higher element abundance. Applying the kinematical model to the CIV sample, we find two possible solutions of the density distribution, which are distinguished by the relative extension along the disk midplane and the normal-line direction. Both solutions can reproduce the existing sample and suggest a warm gas disk mass of logM(M_{sun})~8 and an upper limit of logM(M{sun}_)<9.3 within 250kpc, which is consistent with SiIV. There is a decrease in the CIV/SiIV column density ratio from the Galactic center to the outskirts by 0.2-0.3dex, which may suggest a phase transition or different ionization mechanisms for CIV and SiIV. Also, we find that the difference between CIV and SiIV is an excellent tracer of small-scale features, and we find a typical size of 5{deg}-10{deg} for possible turbulence within individual clouds (~1kpc).

Cone search capability for table J/ApJ/924/86/table1 (Column density measurements of the matched CIV and SiIV sample)