Number Density of Bright Lyman-Break Galaxies at z~6 in the Subaru Deep Field

We report on the bright Lyman-break galaxies (LBGs) selected in a 767 arcmin^2 area of the Subaru Deep Field. The selection is made in the i-zR vs zB-zR plane, where zB and zR are new bandpasses with a central wavelength of 8842A and 9841A, respectively. This set of bandpasses enables us to separate well z~6 LBGs from foreground galaxies and Galactic cool stars. We detect 12 LBG candidates down to zR=25.4, and calculate the normalization of the rest-frame far-ultraviolet (FUV: 1400A) luminosity function at MFUV = -21.6 to be \phi(-21.6) = (2.6+/-0.7) x 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) x 10^{24} ergs/s/Hz/Mpc^3, which is equivalent to a star formation rate density of (3.5+/-1.0) x 10^{-4} Msun/yr/Mpc^3. Combining our measurement with those at z<6 in the literature, we find that the FUV luminosity density of bright galaxies increases by an order of magnitude from z~6 to z~3 and then drops by 10^3 from z~3 to the present epoch, while the evolution of the total luminosity density is much milder. 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.Comment: 12 pages, accepted for PASJ, a high resolution version is available at http://hikari.astron.s.u-tokyo.ac.jp/~shima/z6LBGs

Subaru Deep Survey VI. A Census of Lyman Break Galaxies at z=4 and 5 in the Subaru Deep Fields: Clustering Properties

We investigate the clustering properties of 2,600 Lyman Break Galaxies (LBGs) at z=3.5-5.2 in two large blank fields, the Subaru Deep Field and the Subaru/XMM Deep Field (600arcmin^2 each). The angular correlation functions of these LBGs show a clear clustering at both z~4 and 5. The correlation lengths are r_0= 4.1^{+0.2}_{-0.2} and 5.9^{+1.3}_{-1.7} h_{100}^{-1} Mpc (r_0= 5.1^{+1.0}_{-1.1} and 5.9^{+1.3}_{-1.7} h_{100}^{-1} Mpc) for all the detected LBGs (for L>L* LBGs) at z~4 and 5, respectively. These correlation lengths correspond to galaxy-dark matter biases of b_g= 2.9^{+0.1}_{-0.1} and 4.6^{+0.9}_{-1.2} (b_g=3.5^{+0.6}_{-0.7} and 4.6^{+0.9}_{-1.2}), for all the detected LBGs (for L>L^* LBGs) at z~4 and 5, respectively. These results, combined with estimates for z~3 LBGs in the literature, show that the correlation length of L>L^* LBGs is almost constant, ~5 h_{100}^{-1} Mpc, over z~3-5, while the bias monotonically increases with redshift at z>3. We also find that for LBGs at z~4 the clustering amplitude increases with UV-continuum luminosity and with the amount of dust extinction. We estimate the mass of dark halos hosting various kinds of high-z galaxies including LBGs with the analytic model given by Sheth & Tormen (1999). We find that the typical mass of dark halos hosting L>L^* LBGs is about 1x10^{12} h_{70}^{-1}Msol over z~3-5, which is comparable to that of the Milky Way Galaxy. A single dark halo with ~10^{12} h_{70}^{-1} Msol is found to host 0.1-0.3 LBG on average but host about four K-band selected galaxies.Comment: 33 pages, 12 figures, ApJ in press. Paper with high resolution figures is available at http://hikari.astron.s.u-tokyo.ac.jp/~ouchi/work/astroph/SDS_V_VI/SDS_VI.pdf (PDF) (The abstract was reduced by the revision.

Critical dynamics of phase transition driven by dichotomous Markov noise

An Ising spin system under the critical temperature driven by a dichotomous Markov noise (magnetic field) with a finite correlation time is studied both numerically and theoretically. The order parameter exhibits a transition between two kinds of qualitatively different dynamics, symmetry-restoring and symmetry-breaking motions, as the noise intensity is changed. There exist regions called channels where the order parameter stays for a long time slightly above its critical noise intensity. Developing a phenomenological analysis of the dynamics, we investigate the distribution of the passage time through the channels and the power spectrum of the order parameter evolution. The results based on the phenomenological analysis turn out to be in quite good agreement with those of the numerical simulation.Comment: 27 pages, 12 figure

Large-scale Filamentary Structure around the Protocluster at Redshift z=3.1

We report the discovery of a large-scale coherent filamentary structure of Lyman alpha emitters in a redshift space at z=3.1. We carried out spectroscopic observations to map the three dimensional structure of the belt-like feature of the Lyman alpha emitters discovered by our previous narrow-band imaging observations centered on the protocluster at z=3.1. The feature was found to consist of at least three physical filaments connecting with each other. The result is in qualitative agreement with the prediction of the 'biased' galaxy-formation theories that galaxies preferentially formed in large-scale filamentary or sheet-like mass overdensities in the early Universe. We also found that the two known giant Lyman alpha emission-line nebulae showing high star-formation activities are located near the intersection of these filaments, which presumably evolves into a massive cluster of galaxies in the local Universe. This may suggest that massive galaxy formation occurs at the characteristic place in the surrounding large-scale structure at high redshift.Comment: 11 pages, 3 figures, accepted for publication in ApJ Letter

The Subaru Ly-alpha blob survey: A sample of 100 kpc Ly-alpha blobs at z=3

We present results of a survey for giant Ly-alpha nebulae (LABs) at z=3 with Subaru/Suprime-Cam. We obtained Ly-alpha imaging at z=3.09+-0.03 around the SSA22 protocluster and in several blank fields. The total survey area is 2.1 square degrees, corresponding to a comoving volume of 1.6 x 10^6 Mpc^3. Using a uniform detection threshold of 1.4 x 10^{-18} erg s^{-1} cm^{-2} arcsec^{-2} for the Ly-alpha images, we construct a sample of 14 LAB candidates with major-axis diameters larger than 100 kpc, including five previously known blobs and two known quasars. This survey triples the number of known LABs over 100 kpc. The giant LAB sample shows a possible "morphology-density relation": filamentary LABs reside in average density environments as derived from compact Ly-alpha emitters, while circular LABs reside in both average density and overdense environments. Although it is hard to examine the formation mechanisms of LABs only from the Ly-alpha morphologies, more filamentary LABs may relate to cold gas accretion from the surrounding inter-galactic medium (IGM) and more circular LABs may relate to large-scale gas outflows, which are driven by intense starbursts and/or by AGN activities. Our survey highlights the potential usefulness of giant LABs to investigate the interactions between galaxies and the surrounding IGM from the field to overdense environments at high-redshift.Comment: MNRAS Letters accepted (6 pages, 4 figures, 2 tables