The Sightline to Q2343-BX415: Clues to Galaxy Formation in a Quasar Environment

Abstract

(Abridged) We have discovered a strong DLA coincident in redshift with the faint QSO Q2343-BX415 (R = 20.2, z_em = 2.57393). Follow-up observations at intermediate spectral resolution reveal that the metal lines associated with this 'proximate' DLA consist of two sets of absorption components. One set is moving towards the quasar with velocities of ~ 150-600 km/s; this gas is highly ionized and does not fully cover the continuum source, suggesting that it is physically close to the active nucleus. The other, which accounts for most of the neutral gas, is blueshifted relative to the QSO, with the strongest component at ~ -160 km/s. We consider the possibility that the PDLA arises in the outflowing interstellar medium of the host galaxy of Q2343-BX415, an interpretation supported by strong C IV and N V absorption at nearby velocities, and by the intense radiation field longward of the Lyman limit implied by the high C II*/H I ratio. If Q2343-BX415 is the main source of these UV photons, then the PDLA is located at either ~ 8 or ~ 37 kpc from the active nucleus. Alternatively, the absorber may be a foreground star-forming galaxy unrelated to the quasar and coincidentally at the same redshift, but our deep imaging and follow-up spectroscopy of the field of Q2343-BX415 has not yet produced a likely candidate. We measure the abundances of 14 elements in the PDLA, finding an overall metallicity of ~ 1/5 solar and a normal pattern of relative element abundances for this metallicity. Thus, in this PDLA there is no evidence for the super-solar metallicities that have been claimed for some proximate, high ionization, systems.

Accepted for publication in the Astrophysical Journal. 27 pages, 8 tables, 21 postscript figures

References in corpus (4)

• H-alpha Observations of a Large Sample of Galaxies at z~2: Implications for Star Formation in High Redshift Galaxies
• Velocity-Metallicity Correlation for high-z DLA Galaxies: Evidence for a Mass-Metallicity Relation?
• Hot Halos around High Redshift Protogalaxies: Observations of O VI and N V Absorption in Damped Lyman Alpha systems
• Metallicity as a criterion to select H2 bearing Damped Lyman-alpha systems

Cited by in corpus (4)

• C, N, O Abundances in the Most Metal-Poor Damped Lyman alpha Systems
• A downturn in intergalactic CIV as redshift 6 is approached
• A z = 3 Lyman Alpha Blob Associated with a Damped Lyman Alpha System Proximate to its Background Quasar
• Measurements of CaII absorption, metals, and dust in a sample of z~1 DLAs and subDLAs