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[40.19] Spectral Evidence for Widespread Galaxy Outflows at z>4

B. Frye (Princeton University), T. Benitez (Johns Hopkins), T. Broadhurst (Hebrew University)

We present discovery spectra of a sample of ten lensed galaxies at high redshift, 3.7-1 with respect to the centroid of Ly-\alpha emission. A correlation is found between this blueshift and the equivalent width of the metal lines, which we interpret as a broadening of saturated absorption lines caused by a dispersion in the outflow velocity of interstellar gas. Local starburst galaxies show similar behavior, associated with obvious gas outflows. We also find a trend of increasing equivalent-width of Ly-\alpha emission with redshift, which may be a genuine evolutionary effect towards younger stellar populations at high redshift with less developed stellar continua. No obvious emission is detected below the Lyman-limit in any of our spectra, nor in deep U or B-band images. The UV continua are reproduced well by early B-stars, although some dust absorption would allow a fit to hotter stars. If B-stars dominate, then their relatively prominent stellar absorption lines should separate in wavelength from those of the outflowing gas, requiring more detailed spectroscopy. After correcting for the lensing, we derive small physical sizes for our objects, ~ 0.5-5 kpc h^-1 for a flat cosmology with \Omega_m=0.3, \Omega_\Lambda=0.7. The lensed images are only marginally resolved in good seeing despite their close proximity to the critical curve, where large arcs are visible and hence high magnifications of up to ~0\times are inferred. Two objects show a clear spatial extension of the Ly-\alpha emission relative to the continuum starlight, indicating a ``breakout'' of the gas. The sizes of our galaxies together with their large gas motion suggests that outflows of gas are common at high redshift and associated with galaxy formation.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.