2015/09/04 by Jingzhe Ma, Paul Caucal, Pasquier Noterdaeme +12 · 37 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Extinction (optical mineralogy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Interstellar medium #Ion #Ionization #Metallicity #Milky Way #Optics #Photoionization #Physics #Population #Quasar #Space Telescope Imaging Spectrograph #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stv2073
published in Monthly Notices of the Royal Astronomical Society 454(2), 1751-1766 (Oxford University Press) · 18 pages, 17 figures, to be published in MNRAS
arxiv created 2015/09/04 · openalex publication_date 2015/10/07 · arxiv updated 2015/10/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report the detection of a strong Milky Way-type 2175-Å extinction bump at z = 2.1166 in the quasar spectrum towards SDSS J121143.42+083349.7 from the Sloan Digital Sky Survey Data Release 10. We conduct follow up observations with the Echelle Spectrograph and Imager on-board the Keck II telescope and the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope. This 2175-Å absorber is remarkable in that we simultaneously detect neutral carbon (C i), neutral chlorine (Cl i), and carbon monoxide (CO). It also qualifies as a damped Lyman α system. The J1211+0833 absorber is found to be metal rich and has a dust depletion pattern resembling that of the Milky Way disc clouds. We use the column densities of the C i fine structure states and the C ii/C i ratio (under the assumption of ionization equilibrium) to derive the temperature and volume density in the absorbing gas. A cloudy photoionization model is constructed, which utilizes additional atoms/ions to constrain the physical conditions. The inferred physical conditions are consistent with a canonical cold (T ∼ 100 K) neutral medium with a high density (n(H i) ∼ 100 cm−3) and a slightly higher pressure than the local interstellar medium. Given the simultaneous presence of C i, CO, and the 2175-Å bump, combined with the high metallicity, high dust depletion level, and overall low ionization state of the gas, the absorber towards J1211+0833 supports the scenario that the presence of the bump requires an evolved stellar population.