A Search for Lyman alpha Emitters at Redshift 3.7

Abstract

We present the results of a survey for emission-line objects based on optical intermediate-band (${\lambda }_{\mathrm{c}}$ = 5736 Å~ and $\Delta \lambda$ = 280 Å) and broad-band ($B$, $V$, $R$, and $i^{\prime }$) observations of the Subaru/XMM-Newton Deep Field on the 8.2 m Subaru telescope with the Subaru Prime Focus Camera, Suprime-Cam. All the data were obtained during the guaranteed time observations of the Suprime-Cam instrument. The intermediate-band image covered a sky area with 10\minpoint62 $\times 12\minpoint40 \approx 132$ arcmin${}^2$ in the Subaru/XMM-Newton Deep Field (Ouchi et al.). Using this image, we have found 23 emission-line sources whose observed emission-line equivalent widths are greater than 250 Å. Their optical multicolor properties indicate that six emission-line sources are Ly$\alpha$ emitters at $z\approx$ 3.7 ($\Delta z\approx 0.22$). They are either intense starburst galaxies or active galactic nuclei like quasars at $z\approx$ 3.7. Two more emission-line sources may also be Ly$\alpha$ emitters at $z\approx$ 3.7 although their multicolor properties are marginal. Among the remaining 15 emission-line objects, eight objects appear strong emission-line galaxies at lower redshift; e.g., [O {\sc ii}] $\lambda$3727 emitters at $z\approx 0.54$, H$\beta$ at $z\approx 0.18$, or [O {\sc iii}]$\lambda$5007 emitters at $z\approx 0.15$. The remaining seven objects are unclassified because they are too faint to be detected in broad-band images. We discuss observational properties of these strong emission-line sources. In particular, our data allow us to estimate the star formation density at $z\approx 3.7$ for the first time.

Accepted for publication in AJ;14 pages, 26 figures (all figures are JPEG file)