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The MUSE Hubble Ultra Deep Field Survey: IV. Global properties of C III emitters

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(2017)cite arxiv:1710.06432Comment: 16 pages and 13 figures, accepted for publication in A&A.

Abstract

The C III 1907,1909 emission doublet has been proposed as an alternative to Lyman-alpha in redshift confirmations of galaxies at z > 6 since it is not attenuated by the largely neutral intergalactic medium at these redshifts and is believed to be strong in the young, vigorously star-forming galaxies present at these early cosmic times. We present a statistical sample of 17 C III-emitting galaxies beyond z~1.5 using 30 hour deep VLT/MUSE integral field spectroscopy covering 2 square arcminutes in the Hubble Deep Field South (HDFS) and Ultra Deep Field (UDF), achieving C III sensitivities of ~2e-17 erg/s/cm^2 in the HDFS and ~7e-18 erg/s/cm^2 in the UDF. The rest-frame equivalent widths range from 2 to 19 Angstroms. These 17 galaxies represent ~3% of the total sample of galaxies found between 1.5 < z < 4. They also show elevated star formation rates, lower dust attenuation, and younger mass-weighted ages than the general population of galaxies at the same redshifts. Combined with deep slitless grism spectroscopy from the HST/WFC3 in the UDF, we can tie the rest-frame ultraviolet C III emission to rest-frame optical emission lines, namely O III 5007, finding a strong correlation between the two. Down to the flux limits that we observe (~1e-18 erg/s/cm^2 with the grism data in the UDF), all objects with a rest-frame O III 4959,5007 equivalent width in excess of 250 Angstroms, the so-called Extreme Emission Line Galaxies, have detections of C III in our MUSE data. More detailed studies of the C III-emitting population at these intermediate redshifts will be crucial to understand the physical conditions in galaxies at early cosmic times and to determine the utility of C III as a redshift tracer.

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