Abstract
The CIIIłambdałambda1907, 1909 rest-frame UV emission doublet has
recently been detected in galaxies during the epoch of reionization (z > 6),
with high equivalent width (>10 \AA, rest frame). Currently, it is possible
to obtain much more detailed information for star-forming galaxies at
significantly lower redshift. Accordingly, studies of their far-UV spectra are
useful for understanding the factors modulating the strength of CIII emission.
We present the first statistical sample of CIII emission measurements in
star-forming galaxies at z ~ 1. Our sample is drawn from the DEEP2 survey and
spans the redshift 0.64 < z < 1.35 (<z> = 1.08). We find that the median
equivalent width (EW) of individual CIII detections in our sample (1.30 \AA)
is much smaller than the typical value observed thus far at z > 6. Furthermore,
out of 184 galaxies with coverage of CIII, only 40 have significant
detections. Galaxies with individual CIII detections have bluer colors and
lower luminosities on average than those without, implying that strong CIII
emitters are in general young and low-mass galaxies without significant dust
extinction. Using stacked spectra, we further investigate how CIII strength
correlates with multiple galaxy properties (M_B, U-B, M*, star-formation rate,
specific star-formation rate) and rest-frame near-UV (FeII* and MgII) and
optical OIII and H\beta) emission line strengths. These results provide a
detailed picture of the physical environment in star-forming galaxies at z ~ 1,
and motivate future observations of strong CIII emitters at similar redshifts.
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