Solar-Metallicity Gas in the Extended Halo of a Galaxy at \(z \sim 0.12\)

• Published in: arXiv.org 2020-02
• Main Authors: Jayadev Pradeep, Sankar, Sriram, Umasree, T M, Narayanan, Anand, Khaire, Vikram, Gebhardt, Matthew, Sameer, Charlton, Jane C
• Format: Article
• Language: English
• Subjects: Absorbers; Galactic halos; Galaxies; Metallicity; Multiphase; Photoionization; Stars & galaxies; Tracing; Transition temperature
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2001.10558

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.