Number density of bright lyman-break galaxies at z ∼ 6 in the Subaru Deep field

Abstract

We report on bright Lyman-break galaxies (LBGs) selected in a 767 arcmin2 area of the Subaru Deep Field. The selection was made in the i - ZR versus ZB - ZR plane, where Z B and ZR are new bandpasses with a central wavelength of 8842 Å and 9841 Å, respectively. We detected 12 LBG candidates down to ZR = 25.4, and calculated the normalization of the rest-frame far-ultraviolet (FUV: ≃ 1400 Å) luminosity function at M FUV = -21.6 to be φ (-21.6) = (2.6 ± 0.7) × 10 -5 mag-1 Mpc-3. This must be the most reliable measurement ever obtained of the number density of bright z ∼ 6 LBGs, because it is more robust against both contamination and cosmic variance than previous values. The FUV luminosity density contributed from LBGs brighter than MFUV = -21.3 is (2.8 ± 0.8) × 1024erg s -1 Hz-1Mpc-3, which is equivalent to a star-formation rate density of (3.5 ± 1.0) × 10-4 M ⊙yr-1 Mpc-3. We find that the FUV luminosity density of bright galaxies increases by an order of magnitude from z ∼ 6 to ∼ 3, and then drops by 103 from z ∼ 3 to the present epoch. The evolutionary behavior of bright LBGs resembles that of luminous dusty star-forming galaxies and bright QSOs. The redshift of z ∼ 3 appears to be a remarkable era in the cosmic history when massive galaxies were being intensively formed. © 2005. Astronomical Society of Japan.