A 1.4 deg(2) blind survey for CII], CIII] and CIV at z similar to 0.7-1.5-I. Nature, morphologies and equivalent widths

作者：Stroe Andra; Sobral David; Matthee Jorryt; Calhau Joao; Oteo Ivan

来源：Monthly Notices of the Royal Astronomical Society, 2017, 471(3): 2558-2574.

DOI：10.1093/mnras/stx1712

• galaxies: active
• galaxies: high-redshift
• quasars: emission lines
• galaxies: star formation
• cosmology: observations

While traditionally associated with active galactic nuclei (AGN), the properties of the C II] (lambda = 2326 angstrom), CIII] (lambda, lambda = 1907, 1909 angstrom) and C IV (lambda, lambda = 1549, 1551 angstrom) emission lines are still uncertain as large, unbiased samples of sources are scarce. We present the first blind, statistical study of C II], CIII] and C IV emitters at z similar to 0.68, 1.05, 1.53, respectively, uniformly selected down to a flux limit of similar to 4 x 10(-17) erg s(-1) cm(-1) through a narrow-band survey covering an area of similar to 1.4 deg(2) over COSMOS and UDS. We detect 16 C II], 35 C III] and 17 C IV emitters, whose nature we investigate using optical colours as well as Hubble Space Telescope (HST), X-ray, radio and far-infrared data. We find that z similar to 0.7 C II] emitters are consistent with a mixture of blue (UV slope beta = -2.0 +/- 0.4) star-forming (SF) galaxies with discy HST structure and AGN with Seyfert-like morphologies. Bright C II] emitters have individual X-ray detections as well as high average black hole accretion rates (BHARs) of similar to 0.1 M-circle dot yr(-1). CIII] emitters at z similar to 1.05 trace a general population of SF galaxies, with beta = -0.8 +/- 1.1, a variety of optical morphologies, including isolated and interacting galaxies and low BHAR (<0.02 M-circle dot yr(-1)). Our CIV emitters at z similar to 1.5 are consistent with young, blue quasars (beta similar to -1.9) with point-like optical morphologies, bright X-ray counterparts and large BHAR (0.8 M-circle dot yr(-1)). We also find some surprising C II], CIII] and C IV emitters with rest-frame equivalent widths (EWs) that could be as large as 50-100 angstrom. AGN or spatial offsets between the UV continuum stellar disc and the line-emitting regions may explain the large EW. These bright C II], CIII] and C IV emitters are ideal candidates for spectroscopic follow-up to fully unveil their nature.

• 出版日期2017-11