科研之友
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摘要
We analyze rest-frame optical morphologies and gas-phase kinematics as traced by rest-frame far-UV and optical spectra for a sample of 204 star-forming galaxies in the redshift range z similar to 2-3 drawn from the Keck Baryonic Structure Survey. We find that spectroscopic properties and gas-phase kinematics are closely linked to morphology: compact galaxies with semimajor axis radii r less than or similar to 2 kpc are substantially more likely than their larger counterparts to exhibit Ly alpha in emission. Although Ly alpha emission strength varies widely within galaxies of a given morphological type, all but one of 19 galaxies with Ly alpha equivalent width W-Ly alpha %26gt; 20 angstrom have compact and/or multiple-component morphologies with r %26lt;= 2.5 kpc. The velocity structure of absorption lines in the galactic continuum spectra also varies as a function of morphology. Galaxies of all morphological types drive similarly strong outflows (as traced by the blue wing of interstellar absorption line features), but the outflows of larger galaxies are less highly ionized and exhibit larger optical depth at the systemic redshift that may correspond to a decreasing efficiency of feedback in evacuating gas from the galaxy. This upsilon similar to 0 km s(-1) gas is responsible both for shifting the mean absorption line redshift and attenuating W-Ly alpha (via a longer resonant scattering path) in galaxies with larger rest-optical half-light radii. In contrast to galaxies at lower redshifts, there is no evidence for a correlation between outflow velocity and inclination, suggesting that outflows from these puffy and irregular systems may be poorly collimated. Our observations are broadly consistent with theoretical models of inside-out growth of galaxies in the young universe, in which typical z similar to 2-3 star-forming galaxies are predominantly unstable, dispersion-dominated, systems fueled by rapid gas accretion that later form extended rotationally supported disks when stabilized by a sufficiently massive stellar component.
- 出版日期2012-11-1
