Multiple origins for the DLA at $z_\mathrm{abs}=0.313$ toward PKS
  1127$-$145 indicated by a complex dust depletion pattern of Ca, Ti, and Mn
  We investigate the dust depletion properties of optically thick gas in and
around galaxies and its origin we study in detail the dust depletion patterns
of Ti, Mn, and Ca in the multi-component damped Lyman-$\alpha$ (DLA) absorber
at $z_\mathrm{abs}=0.313$ toward the quasar PKS 1127$-$145.} We performed a
detailed spectral analysis of the absorption profiles of CaII, MnII, TiII, and
NaI associated with the DLA toward PKS 1127$-$145, based on optical
high-resolution data obtained with the UVES instrument at the Very Large
Telescope (VLT). We obtained column densities and Doppler-parameters for the
ions listed above and determine their gas-phase abundances, from which we
conclude on their dust depletion properties. We compared the Ca and Ti
depletion properties of this DLA with that of other DLAs. One of the six
analyzed absorption components shows a striking underabundance of Ti and Mn in
the gas-phase, indicating the effect of dust depletion for these elements and a
locally enhanced dust-to-gas ratio. In this DLA and in other similar absorbers,
the MnII abundance follows that of TiII very closely, implying that both ions
are equally sensitive to the dust depletion effects. Our analysis indicates
that the DLA toward PKS 1127$-$145 has multiple origins. With its narrow line
width and its strong dust depletion, component 3 points toward the presence of
a neutral gas disk from a faint LSB galaxy in front of PKS 1127$-$145, while
the other, more diffuse and dust-poor, absorption components possibly are
related to tidal gas features from the interaction between the various,
optically confirmed galaxy-group members. In general, the Mn/CaII ratio in
sub-DLAs and DLAs possibly serves as an important indicator to discriminate
between dust-rich and dust-poor in neutral gas in and around galaxies.
