Yuko KAKAZU
(University of Chicago)
We present the metallicity and kinematics studies of star-forming galaxies at $3.5 < z < 5.5$ in the COSMOS field.
Our analysis is based on the composite spectra of rest-frame ultraviolet spectra of $\sim$400 galaxies obtained with the Keck/DEIMOS spectrograph.
Majority of bright galaxies ($z'_{AB}<25$) in our sample exhibit prominent P Cygni stellar wind lines of CIV and SiIV,
suggesting the ubiquity of Galactic outflow among massive star-forming galaxies at high-redshift.
The composite spectrum of 216 galaxies at $<z_{spec}> = 4.6$ with Ly$\alpha$ emission shows remarkably similar absorption profiles of both low ionization and high ionization interstellar lines to the stacked spectrum of $z\sim3$ Lyman break galaxies of Shapley et al (2013).
The HST/ACS images of these galaxies show that they are compact and have very high star formation surface density.
We further split our galaxy sample based on various galaxy parameters (such as UV luminosity, stellar mass, Ly$\alpha$ equivalent width, SFR density, selection criteria) and investigate systemic effects of these paramters on absorption line strengths and physical properties of galaxies.