Transiting Clouds as a Potential Explanation for the Lack of Correlations in LoBAL Groups

One potential explanation for the lack of correlations in our LoBAL groups could be the presence of clouds that pass in front of our line of sight. Several observational peculiarities support this explanation. For example, if a P V BAL is observed at the same velocity as a variable C IV BAL, it provides evidence for the transit scenario (Capellupo et al., 2014, 2017). The presence of a P V BAL suggests that the corresponding C IV BAL is highly saturated. A highly saturated C IV BAL is not easily influenced by small changes in ionization, but can exhibit variations due to the transiting of outflows. Similarly, the detection of variability in a highly optically thick C IV BAL also supports the transit scenario (McGraw et al., 2018).