CIII] Emission in Star-forming Galaxies at z ∼ 1

The C III]lambda lambda 1907, 1909 rest-frame UV emission doublet has recently been detected in galaxies during the epoch of reionization (z > 6), with a high equivalent width (EW; 10 angstrom, 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 C III] emission. We present the first statistical sample of C III] emission measurements in star-forming galaxies at z similar to 1. Our sample is drawn from the DEEP2 survey and spans the redshifts 0.64 <= z <= 1.35 (< z > =1.08). We find that the median EW of individual C III] detections in our sample (1.30 angstrom) is much smaller than the typical value observed thus far at z > 6. Furthermore, out of 184 galaxies with coverage of C III], only 40 have significant detections. Galaxies with individual C III] detections have bluer colors and lower luminosities on average than those without, implying that strong C III] emitters are in general young and low-mass galaxies without significant dust extinction. Using stacked spectra, we further investigate how C III] strength correlates with multiple galaxy properties (M-B , U - B, M-*, star formation rate, specific star formation rate) and rest-frame near-UV (Fe II* and Mg II) and optical ([O III] and H beta) emission line strengths. These results provide a detailed picture of the physical environment in star-forming galaxies at z similar to 1, and motivate future observations of strong C III] emitters at similar redshifts.