The Sightline to Q2343-BX415: Clues to Galaxy Formation in a Quasar Environment
Abstract
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 (PDLA) consist of two sets of absorption components. One set is moving toward the quasar with velocities of ~150-600 km s^(-1); 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^(-1). 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 supersolar metallicities that have been claimed for some proximate, high-ionization, systems.
Additional Information
© 2007 The American Astronomical Society. Received 2007 February 22; accepted 2007 July 23. It is a pleasure to acknowledge illuminating discussions with Bob Carswell, Gary Ferland, and Paul Hewett, and valuable suggestions from the referee, which have improved this paper. We are indebted to Art Wolfe, who generously helped with the interpretation of the C ii* absorption. Part of this work was carried out during visits by Sam Rix and Art Wolfe to the Institute of Astronomy, Cambridge, supported by the Institute's visitors' grant. S. Rix also acknowledges the support of a PPARC Postdoctoral Research Fellowship. We thank the staff of the Keck Observatory for their expert assistance with the ESI and NIRSPEC observations, and the Hawaiian people for the opportunity to observe from Mauna Kea. Without their hospitality, this work would not have been possible.Attached Files
Published - RIXapj07.pdf
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Additional details
- Eprint ID
- 16629
- Resolver ID
- CaltechAUTHORS:20091109-143310813
- Institute of Astronomy, Cambridge
- Particle Physics and Astronomy Research Council (PPARC)
- Created
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2009-11-16Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field