A ${\bf 1.4}$ deg${\bf ^2}$ blind survey for CII], CIII] and CIV at ${\bf z\sim0.7-1.5}$. I: nature, morphologies and equivalent widths

Andra Stroe; David Sobral; Jorryt Matthee; João Calhau; Ivan Oteo

doi:10.1093/mnras/stx1712

paper

A $1.4$ deg $^{2}$ blind survey for CII], CIII] and CIV at $z \sim 0.7 - 1.5$ . I: nature, morphologies and equivalent widths

arXiv:1703.10169 · doi:10.1093/mnras/stx1712

Abstract

While traditionally associated with active galactic nuclei (AGN), the properties of the CII] ( $λ = 2326$ \,Å), CIII] ( $λ, λ = 1907, 1909$ \,Å) and CIV ( $λ, λ = 1549, 1551$ \,Å) emission lines are still uncertain as large, unbiased samples of sources are scarce. We present the first blind, statistical study of CII], CIII] and CIV emitters at $z \sim 0.68, 1.05, 1.53$ , respectively, uniformly selected down to a flux limit of $\sim 4 \times 1 0^{- 17}$ erg s $^{- 1}$ cm $^{- 1}$ through a narrow band survey covering an area of $\sim 1.4$ deg $^{2}$ over COSMOS and UDS. We detect 16 CII], 35 CIII] and 17 CIV emitters, whose nature we investigate using optical colours as well as HST, X-ray, radio and far infra-red data. We find that $z \sim 0.7$ CII] emitters are consistent with a mixture of blue (UV slope $β = - 2.0 \pm 0.4$ ) star forming galaxies with disky HST structure and AGN with Seyfert-like morphologies. Bright CII] emitters have individual X-ray detections as well as high average black hole accretion rates (BHAR) of $\sim 0.1$ $M_{⊙}$ yr $^{- 1}$ . CIII] emitters at $z \sim 1.05$ trace a general population of SF galaxies, with $β = - 0.8 \pm 1.1$ , a variety of optical morphologies, including isolated and interacting galaxies and low BHAR ( $< 0.02$ $M_{⊙}$ yr $^{- 1}$ ). Our CIV emitters at $z \sim 1.5$ are consistent with young, blue quasars ( $β \sim - 1.9$ ) with point-like optical morphologies, bright X-ray counterparts and large BHAR ( $0.8$ $M_{⊙}$ yr $^{- 1}$ ). We also find some surprising CII], CIII] and CIV emitters with rest-frame equivalent widths which could be as large as $50 - 100$ Å. AGN or spatial offsets between the UV continuum stellar disk and the line emitting regions may explain the large EW. These bright CII], CIII] and CIV emitters are ideal candidates for spectroscopic follow up to fully unveil their nature.

Accepted for publication to MNRAS. Comments welcome! 17 pages, 12 figures, 8 tables. Paper II can be found here: https://arxiv.org/abs/1704.01124

A $1.4$ deg $^{2}$ blind survey for CII], CIII] and CIV at $z \sim 0.7 - 1.5$ . I: nature, morphologies and equivalent widths

Abstract

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A 1.4 deg2 blind survey for CII], CIII] and CIV at z∼0.7−1.5. I: nature, morphologies and equivalent widths

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A $1.4$ deg $^{2}$ blind survey for CII], CIII] and CIV at $z \sim 0.7 - 1.5$ . I: nature, morphologies and equivalent widths