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We analyse high-resolution VLT +UVES spectra of the low-ionization intrinsic absorber observed in the BAL QSO SDSS J001130.56 +005550.7. Two narrow absorption systems at velocities −600 km s−1 and−22 000 km s−1 are detected. The low-velocity system is part of the broad absorption line (BAL), while the high-velocity one is well detached. While most narrow absorption components are only detected in the high-ionization species, the lowest velocity component is detected in both highand low-ionization species, including in the excited Si  and C lines. From the analysis of doublet lines, we find that the narrow absorption lines at the low-velocity end of the BAL trough are completely saturated but do not reach zero flux, their profiles being dominated by a velocity-dependent covering factor. The covering factor is significantly smaller for Mg  than for Si  and N, which demonstrates the intrinsic nature of absorber. From the analysis of the excited Si  and C lines in the lowest velocity component, we find an electron density '103 cm−3. Assuming photoionization equilibrium, we derive a distance '20 kpc between the low-ionization region and the quasar core. The correspondence in velocity of the highand low-ionization features suggests that all these species must be closely associated, hence formed at the same distance of ∼20 kpc, much higher than the distance usually assumed for BAL absorbers.

VLT + UVES spectroscopy of the low-ionization intrinsic absorber in SDSS J001130.56+005550.7