a)–d) Column density profiles computed by adding the Gaussian velocity absorption components listed in Table 3. The components with upper limit were not included. e)–g) Abundance profiles relative to H₂. The H₂ column density was computed from the HCO⁺ column density assuming an HCO⁺ abundance of 5 × 10^-9. h)–j) Abundance profiles relative to H i. k) The H i column density was computed from comparing an H i absorption with an H i emission profile (see text).