TY - JOUR
T1 - Searching for z ≃ 6 objects with the Hubble Space Telescope advanced camera for surveys
T2 - Preliminary analysis of a deep parallel field
AU - Yan, Haojing
AU - Windhorst, Rogier
AU - Cohen, Seth H.
N1 - Funding Information:
The authors would like to thank the anonymous referee for the helpful comments. We thank H. J. A. Röttgering for carefully reading the manuscript. We acknowledge funding from NASA/JWST grant NAG5-12460.
PY - 2003/3/10
Y1 - 2003/3/10
N2 - Recent results suggest that z ≃ 6 marks the end of the reionization era. A large sample of objects at z ≃ 6, therefore, will be of enormous importance, as it will enable us to observationally determine the exact epoch of the reionization and the sources that are responsible for it. With the Hubble Space Telescope Advanced Camera for Surveys (ACS) coming on-line, we now have a unique opportunity to discover a significant number of objects at z ≃ 6. The pure parallel mode implemented for the Wide-Field Camera (WFC) has greatly enhanced this ability. We present our preliminary analysis of a deep ACS/WFC parallel field at |b| = 74°.4. We find 30 plausible z ≃ 6 candidates, all of which have signal-to-noise ratios greater than 7 in the F850LP band. The major source of contamination could be faint cool Galactic dwarfs, and we estimated that they would contribute at most four objects to our candidate list. We derived the cumulative number density of galaxies at 6.0 ≤ z ≤ 6.5 as 2.3 arcmin-2 to a limit of 28.0 mag in the F850LP band, which is slightly higher than our prediction. If this is not due to an underestimated contamination rate, it could possibly imply that the faint-end slope of the z ≃ 6 luminosity function is steeper than α = -1.6. At the very least, our result suggests that galaxies with L < L* do exist in significant numbers at z ≃ 6 and that they could be the major sources that contributed the reionizing photons.
AB - Recent results suggest that z ≃ 6 marks the end of the reionization era. A large sample of objects at z ≃ 6, therefore, will be of enormous importance, as it will enable us to observationally determine the exact epoch of the reionization and the sources that are responsible for it. With the Hubble Space Telescope Advanced Camera for Surveys (ACS) coming on-line, we now have a unique opportunity to discover a significant number of objects at z ≃ 6. The pure parallel mode implemented for the Wide-Field Camera (WFC) has greatly enhanced this ability. We present our preliminary analysis of a deep ACS/WFC parallel field at |b| = 74°.4. We find 30 plausible z ≃ 6 candidates, all of which have signal-to-noise ratios greater than 7 in the F850LP band. The major source of contamination could be faint cool Galactic dwarfs, and we estimated that they would contribute at most four objects to our candidate list. We derived the cumulative number density of galaxies at 6.0 ≤ z ≤ 6.5 as 2.3 arcmin-2 to a limit of 28.0 mag in the F850LP band, which is slightly higher than our prediction. If this is not due to an underestimated contamination rate, it could possibly imply that the faint-end slope of the z ≃ 6 luminosity function is steeper than α = -1.6. At the very least, our result suggests that galaxies with L < L* do exist in significant numbers at z ≃ 6 and that they could be the major sources that contributed the reionizing photons.
KW - Cosmology: observations
KW - Galaxies: high-redshift
KW - Galaxies: luminosity function
KW - Mass function
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U2 - 10.1086/374371
DO - 10.1086/374371
M3 - Review article
AN - SCOPUS:0043030274
SN - 0004-637X
VL - 585
SP - L93-L96
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 II
ER -