In:
Publications of the Astronomical Society of Japan, Oxford University Press (OUP), Vol. 55, No. 2 ( 2003-04-25), p. L17-L21
Abstract:
We performed a deep optical imaging survey using a narrow-band filter (NB921) centered at $\lambda = 9196 \,$Å together with $i^\prime$ and $z^\prime$ broadband filters covering an $814 \,\mathrm{arcmin}^2$ area of the Subaru Deep Field. We obtained a sample of 73 strong NB921-excess objects based on the following two color criteria:$z^\prime-\mathit{NB}\,921 \gt 1$$z^\prime-\mathit{NB}\,921 \gt 1$ and $i^\prime-z^\prime \gt 1.3$$i^\prime-z^\prime \gt 1.3$. We then obtained optical spectroscopy of nine objects in our NB921-excess sample, and identified at least two Ly$\alpha$ emitters at $z=6.541 \pm 0.002$ and $z=6.578 \pm 0.002$, each of which shows the characteristic sharp cutoff together with continuum depression at wavelengths shortward of the line peak. The latter object is more distant than HCM-6A at $z=6.56$, which is the most distant known object that has been found so far. These new data allow us to estimate the first meaningful lower limit of the star-formation rate density beyond redshift 6; $\rho_\mathrm{SFR} \sim 5.2 \times 10^{-4} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1} \,\mathrm{Mpc}^{-3}$. Since it is expected that the actual density is several times higher than this value, our new observation reveals that a moderately high level of star formation activity already occurred at $z \sim 6.6$.
Type of Medium:
Online Resource
ISSN:
2053-051X
,
0004-6264
DOI:
10.1093/pasj/55.2.L17
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2003
detail.hit.zdb_id:
2206640-8
detail.hit.zdb_id:
2083084-1
SSG:
16,12