We present the detection and analysis of a weak low-ionization absorber at $z = 0.12122$ along the blazar sightline PG~$1424+240$, using spectroscopic data from both $HST$/COS and STIS. The absorber is a weak Mg II analogue, with incidence of weak C II and Si II, along with multi-component C IV and O VI. The low ions are tracing a dense ($n_{ H} \sim 10^{ -3}$ cm$^{ -3}$) parsec scale cloud of solar or higher metallicity. The kinematically coincident higher ions are either from a more diffuse ($n_{ H} \sim 10^{ -5} - 10^{ -4}$ cm$^{ -3}$) photoionized phase of kiloparsec scale dimensions, or are tracing a warm (T $\sim 2 \times 10^{ 5}$ K) collisionally ionized transition temperature plasma layer. The absorber resides in a galaxy overdense region, with 18 luminous ($> L^*$) galaxies within a projected radius of $5$ Mpc and $750$ km s$^{ -1}$ of the absorber. The multi-phase properties, high metallicity and proximity to a $1.4$ $L^*$ galaxy, at $\rho \sim 200$ kpc and $|\Delta v| = 11$ km s$^{ -1}$ separation, favors the possibility of the absorption tracing circumgalactic gas. The absorber serves as an example of weak Mg II - O VI systems as a means to study multiphase high velocity clouds in external galaxies.
Categories: astro-ph.GA