VLT+UVES spectroscopy of the Ca II low-ionization broad absorption line quasar SDSS J030000.56+004828.0

We study high-resolution spectra of the "overlapping-trough'' low-ionization broad absorption line (LoBAL) quasar SDSS J030000.56+004828.0. The Ca II, Mg II, and Mg I column densities in this object are the largest reported to date for any BAL outflow. The broad Ca II absorption is mildly blended, but the blending can be disentangled to measure the Ca II column density, which is large enough that the outflow must include a strong hydrogen ionization front. The outflow begins at a blueshift of similar to1650 km s(-1) from the systemic redshift. The lowest velocity BAL region produces strong Ca II absorption but does not produce significant excited Fe II absorption, while the higher velocity excited Fe II absorption region produces very little Ca II absorption. We have found that only a disk wind outflow can explain this segregation. Whether the outflow is smooth or clumpy, we conclude that the Ca II BAL region has a density high enough to populate excited levels of Fe II but a temperature low enough to prevent them from being significantly populated. This requirement means the Ca II BAL region has T less than or similar to 1100 K, and perhaps even T less than or similar to 550 K. This quasar also has an associated absorption line system (AAL) that exhibits partial covering and therefore is likely located near the central engine. Its association with the BAL outflow is unclear. Blending of the AAL with the BAL trough shows that the spatial region covered by the BAL outflow can vary over velocity differences of similar to1700 km s(-1).