Correlations with metallicity and implications for galactic winds at z ≈ 2–3
Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre et Marie Curie, 98bis Bd. Arago, 75014 Paris, France e-mail: firstname.lastname@example.org
2 European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago 19, Chile
3 LERMA, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France
4 IUCAA, Post Bag 4, Ganesh Khind, Pune 411 007, India
Accepted: 27 July 2007
We present a study of absorption in a sample of 63 damped Lyman-α (DLA) systems and 11 sub-DLAs in the redshift range , using a dataset of high-resolution (6.6 km s-1 FWHM), high signal-to-noise VLT/UVES spectra. The complex absorption line profiles show both narrow and broad components, indicating the presence of both warm, photoionized and hot, collisionally ionized gas. We report new correlations between the metallicity (measured in the neutral-phase) and each of the column density, the total line width, and the maximum velocity. We explore the effect on these correlations of the sub-DLAs, the proximate DLAs (defined as those within 5000 km s-1 of the quasar), the saturated absorbers, and the metal line used to measure the metallicity, and we find the correlations to be robust. There is no evidence for any difference between the measured properties of DLA and sub-DLA . In 25 DLAs and 4 sub-DLAs, covering 2.5 dex in [Z/H], we directly observe moving above the escape speed, where vesc is derived from the total line width of the neutral gas profiles. These high-velocity clouds, unbound from the central potential well, can be interpreted as highly ionized outflowing winds, which are predicted by numerical simulations of galaxy feedback. The distribution of column density in DLAs and sub-DLAs is similar to the distribution in Lyman Break galaxies, where winds are directly observed, supporting the idea that supernova feedback creates the ionized gas in DLAs. The unbound absorbers show a median mass flow rate of ~22 (r/40 kpc) yr-1, where r is the characteristic radius. Their kinetic energy fluxes are large enough that a star formation rate (SFR) of ~2 yr-1 is required to power them.
Key words: galaxies: quasars: absorption lines / galaxies: high-redshift / galaxies: halos / galaxies: ISM / galaxies: kinematics and dynamics
Based on observations taken with the Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) Unit 2 (Kueyen) at Paranal, Chile, operated by ESO.
© ESO, 2007