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

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Abstract: Abridged We have discovered a strong DLA coincident in redshift with thefaint QSO Q2343-BX415 R = 20.2, z em = 2.57393. Follow-up observations atintermediate spectral resolution reveal that the metal lines associated withthis -proximate- DLA consist of two sets of absorption components. One set ismoving towards the quasar with velocities of ~ 150-600 km-s; this gas is highlyionized and does not fully cover the continuum source, suggesting that it isphysically close to the active nucleus. The other, which accounts for most ofthe neutral gas, is blueshifted relative to the QSO, with the strongestcomponent at ~ -160 km-s. We consider the possibility that the PDLA arises inthe outflowing interstellar medium of the host galaxy of Q2343-BX415, aninterpretation supported by strong C IV and N V absorption at nearbyvelocities, and by the intense radiation field longward of the Lyman limitimplied by the high C II*-H I ratio. If Q2343-BX415 is the main source of theseUV photons, then the PDLA is located at either ~ 8 or ~ 37 kpc from the activenucleus. Alternatively, the absorber may be a foreground star-forming galaxyunrelated to the quasar and coincidentally at the same redshift, but our deepimaging and follow-up spectroscopy of the field of Q2343-BX415 has not yetproduced a likely candidate. We measure the abundances of 14 elements in thePDLA, finding an overall metallicity of ~ 1-5 solar and a normal pattern ofrelative element abundances for this metallicity. Thus, in this PDLA there isno evidence for the super-solar metallicities that have been claimed for someproximate, high ionization, systems.

Autor: Samantha A. Rix ING, Max Pettini IoA, Charles C. Steidel Caltech, Naveen A. Reddy NOAO-Caltech, Kurt L. Adelberger McKinsey, Dawn


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