High-redshift superwinds as the source of the strongest MgII absorbers: A feasibility analysis

We present High Resolution Echelle Spectrometer/Keck profiles of four extre mely strong (W-r > 1.8 Angstrom) Mg II absorbers at 1 < z < 2. The profiles display a common kinematic structure, having a sharp drop in optical depth near the center of the profile and strong, black-bottomed absorption on ei ther side. This "symmetric-inverted" structure, with a velocity spread of s everal hundred kilometers per second, is suggestive of superwinds arising i n actively star-forming galaxies. Low-ionization absorption of similar stre ngth has been observed in local star-forming galaxies. The Mg II absorbers with W-r > 1.8 Angstrom evolve away from z = 2 to the present. We propose t hat a substantial fraction of these very strong absorbers are due to superw inds and that their evolution is related to the redshift evolution of star- forming galaxies. Based on the observed redshift number density of W-r > 1. 8 Angstrom Mg II absorbers at 1 < z < 2, we explore whether it is realistic that superwinds from starbursting galaxies could give rise to these absorb ers. Finally, we do an analysis of the superwind connection to damped Ly al pha absorbers (DLAs). DLAs and superwinds evolve differently and usually ha ve different kinematic structure, indicating that superwinds probably do no t give rise to the majority of DLAs.