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Preprint typeset using L ATEX style emulateapj v. 11/26/04 QUASARS PROBING QUASARS III: NEW CLUES TO FEEDBACK, QUENCHING, AND THE PHYSICS OF MASSIVE GALAXY FORMATION

By J. Xavier Prochaska and Joseph F. Hennawi

Abstract

Galaxies hosting z ∼ 2 quasars are the high-z progenitors of today’s massive ‘red-and-dead ’ galaxies. With close pairs of quasars at different redshifts, a background quasar can be used to study a foreground quasar’s halo gas in absorption, providing a wealth of information about feedback, quenching, and the physics of massive galaxy formation. We present a Keck/HIRES spectrum of the bright background quasar in a projected pair with angular separation θ = 13.3 ′ ′ corresponding to R ⊥ = 108kpc at the redshift of the foreground quasar zfg = 2.4360±0.0005, precisely determined from Gemini/GNIRS near-IR spectroscopy. Our echelle spectrum reveals optically thick gas (NHI ≈ 10 19.7 cm −2) coincident with the foreground quasar redshift. The ionic transitions of associated metal-lines reveal the following properties of the foreground quasar’s halo: (1) the kinematics are extreme with absorption extending to +780 km s −1 relative to zfg; (2) the metallicity is nearly solar; (3) the temperature of the predominantly ionized gas is T � 20, 000K; (4) the electron density is ne ∼ 1 cm −3 indicating a characteristic size ∼ 10 − 100pc for the absorbing ‘clouds’; (7) there is little (if any) warm gas 10 5 K � T � 10 6 K; (8) the gas is unlikely illuminated by the foreground quasar, implying anisotropic or intermittent emission. The mass of cold T ∼ 10 4 K gas implied by our observations is significant, amounting to a few percent of the total expected baryonic mass density of the foreground quasar’s dark halo at r ∼ 100 kpc. The origin of this material is still unclear, and we discuss several possibilities in the context of current models of feedback and massive galaxy formation. Subject headings: quasars: general – intergalactic medium – quasars: absorption lines – cosmology: general – surveys: observations 1

Year: 2008
OAI identifier: oai:CiteSeerX.psu:10.1.1.311.3878
Provided by: CiteSeerX
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