GMASS ultradeep spectroscopy of galaxies at z ~ 2 - VII. Star formation,
  extinction, and gas outflows from UV spectra
  We use rest-frame UV spectroscopy to investigate the properties related to
large-scale gas outflows, and to the dust extinction and star-formation rates
of a sample of z ~ 2 star-forming galaxies from the Galaxy Mass Assembly
ultradeep Spectroscopic Survey (GMASS). Dust extinction is estimated from the
rest-frame UV continuum slope and used to obtain dust-corrected star-formation
rates for the galaxies of the sample. For the entire sample, a mean value of
the continuum slope <\beta> = -1.11 \pm 0.44 (r.m.s.) was derived, while the
average SFR was found to be <SFR> = 52 \pm 48 M_sun/yr (r.m.s.). A positive
correlation between SFR and stellar mass was observed, in agreement with other
works, the logarithmic slope of the relation being 1.10 \pm 0.10.
Low-ionization absorption lines, associated with the interstellar medium, were
found to be blueshifted, with respect to the rest frame of the system, which
indicates that there is outflowing gas with typical velocities of the order of
~ 100 km/s. Finally, investigating correlations between galaxy UV spectral
characteristics and galaxy general properties, we report a possible correlation
between the equivalent width of the interstellar absorption lines and SFR,
stellar mass, and colour excess similar to that seen to hold at different
redshifts.
