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

TL;DR

This study analyzes dust depletion patterns of Ti, Mn, and Ca in a complex DLA at z=0.313, revealing multiple origins including a neutral gas disk and tidal features, with implications for understanding dust-rich and dust-poor gas in galaxy environments.

Contribution

It provides detailed spectral analysis of dust depletion in a specific DLA, highlighting multiple origins and the potential of Mn/CaII ratio as a diagnostic tool.

Findings

One absorption component shows strong dust depletion and a neutral gas disk origin.

MnII and TiII are similarly affected by dust depletion, indicating their use as tracers.

The Mn/CaII ratio can distinguish dust-rich from dust-poor gas in galaxy environments.

Abstract

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.