Chaotic diffusion of particles with finite mass in oscillating convection flows

Deterministic diffusion in temporally oscillating convection is studied for particles with finite mass. The particles are assumed to obey a simple dissipative dynamical system and the particle diffusion is induced by the strange attractor. The diffusion constants are numerically calculated for convection models with free and rigid boundary conditions.Comment: 5 figure

Large Cosmic Variance in the Clustering Properties of Lyman Alpha Emitters at z~5

We reported in a previous paper the discovery of large-scale structure of Lyman Alpha emitters (LAEs) at z=4.86+-0.03 with a projected size of 20 Mpc x 50 Mpc in narrow-band data of a 25' x 45' area of the Subaru Deep Field (Omega_0=0.3, lambda_0=0.7, H0=70 km/s/Mpc). However, the surveyed area, which corresponds to 55 Mpc x 100 Mpc, was not large enough that we can conclude that we are seeing a typical distribution of z~5 LAEs. In this Letter, we report the results of follow-up imaging of the same sky area using a new narrow-band filter (NB704, lambda_c=7046 A and FWHM=100 A) to detect LAEs at z=4.79, i.e., LAEs lying closer to us by 39 Mpc on average than the z=4.86 objects. We detect 51 LAEs at z=4.79+-0.04 down to NB704=25.7, and find that their sky distribution is quite different from the z=4.86 LAEs'. The clustering of z=4.79 LAEs is very weak on any scales and there is no large-scale high- contrast structure. The shape and the amplitude of the angular correlation function are thus largely different between the two samples. These results demonstrate a large cosmic variance in the clustering properties of LAEs on scales of ~ 50 Mpc.Comment: 4 pages (uses emulateapj5.sty), accepted for ApJ

Climatic Conditions for modelling the Northern Hemisphere ice sheets throughout the ice age cycle

International audienceThe ice sheet-climate interaction as well as the climatic response to orbital parameters and atmospheric CO2 concentration are examined in order to drive an ice sheet model throughout an ice age cycle. Feedback processes between ice sheet and atmosphere are analyzed by numerical experiments using a high resolution General Circulation Model (GCM) under different conditions at the Last Glacial Maximum. Among the proposed processes, the ice albedo feedback, the elevation-mass balance feedback and the desertification effect over the ice sheet were found to be the dominant processes for the ice-sheet mass balance. For the elevation-mass balance feedback, the temperature lapse rate over the ice sheet is proposed to be weaker than assumed in previous studies. Within the plausible range of parameters related to these processes, the ice sheet response to the orbital parameters and atmospheric CO2 concentration for the last glacial/interglacial cycle was simulated in terms of both ice volume and geographical distribution, using a three-dimensional ice-sheet model. Careful treatment of climate-ice sheet feedback is essential for a reliable simulation of the ice sheet changes during ice age cycles

The Subaru/XMM-Newton Deep Survey (SXDS) -VII. Clustering Segregation with Ultraviolet and Optical Luminosities of Lyman-Break Galaxies at z~3

We investigate clustering properties of Lyman-break galaxies (LBGs) at z~3 based on deep multi-waveband imaging data from optical to near-infrared wavelengths in the Subaru/XMM-Newton Deep Field. The LBGs are selected by U-V and V-z' colors in one contiguous area of 561 arcmin^2 down to z'=25.5. We study the dependence of the clustering strength on rest-frame UV and optical magnitudes, which can be indicators of star formation rate and stellar mass, respectively. The correlation length is found to be a strong function of both UV and optical magnitudes with brighter galaxies being more clustered than faint ones in both cases. Furthermore, the correlation length is dependent on a combination of UV and optical magnitudes in the sense that galaxies bright in optical magnitude have large correlation lengths irrespective of UV magnitude, while galaxies faint in optical magnitude have correlation lengths decreasing with decreasing UV brightness. These results suggest that galaxies with large stellar masses always belong to massive halos in which they can have various star formation rates, while galaxies with small stellar masses reside in less massive halos only if they have low star formation rates. There appears to be an upper limit to the stellar mass and the star formation rate which is determined by the mass of hosting dark halos.Comment: 16 pages, 15 figures, accepted for publication in Ap

Searching for z~7.7 Lyman Alpha Emitters in the COSMOS Field with NEWFIRM

The study of Ly-alpha emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Ly-alpha line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Ly-alpha emitters in the COSMOS field. We have used two ultra-narrowband filters (filter width of ~8-9 {\deg}A) on the NEWFIRM camera, installed on the Mayall 4m telescope at Kitt Peak National Observatory, in order to isolate Ly-alpha emitters at z = 7.7; such ultra-narrowband imaging searches have proved to be excellent at detecting Ly-alpha emitters. We found 5-sigma detections of four candidate Ly-alpha emitters in a survey volume of 2.8 x 10^4 Mpc^3 (total survey area ~760 arcmin^2). Each candidate has a line flux greater than 8 x 10^-18 erg s^-1 cm^-2. Using these results to construct a luminosity function and comparing to previously established Ly-alpha luminosity functions at z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of the luminosity function between z = 5.7 and z = 7.7. Statistical Monte Carlo simulations suggest that half of these candidates are real z = 7.7 targets, and spectroscopic follow-up will be required to verify the redshift of these candidates. However, our results are consistent with no strong evolution in the neutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if only one or two of the z = 7.7 candidates are spectroscopically confirmed.Comment: 29 pages, 5 figures, accepted to ApJ (12/11

Characterization of the distribution of the Lly\alpha emitters in the 53W002 field at z = 2.4

We present the results of our wide-field narrow band imaging of the field around the radio galaxy 53W002 at z = 2.390 with Subaru/Suprime-Cam. A custom made filter NB413 centered at 4140 \AA\ with the width of 83 \AA\ is used to observe the 31' x 24' area around the radio galaxy. We detected 204 Ly\alpha emitters (LAEs) at z = 2.4 with a rest frame equivalent width larger than 25 \AA\ to the depth of 26 AB mag (in NB413). The entire LAE population in the 53W002 field has an average number density and distributions of equivalent width and size that are similar to those of other fields at z ~ 2. We identify a significant high density region (53W002F-HDR) that spreads over ~ 5' x 4' near 53W002 where the LAE number density is nearly four times as large as the average of the entire field. Using the probability distribution function of density fluctuation, we evaluate the rareness probability of the 53W002F-HDR to be 0.9^{+2.4}_{-0.62}%, which corresponds to a moderately rich structure. No notable environmental dependency at the comoving scale of 10 Mpc is found for the distributions of the Ly\alpha equivalent width and luminosity in the field. We also detected 4 Ly\alpha blobs (LABs), one of which is newly discovered. They are all found to be located in the rims of high density regions. The biased location and unique morphologies in Ly\alpha suggest that galaxy interaction play a key role in their formation.Comment: 26 pages, 12 figure

Large-scale structure of Lyman break galaxies around a radio galaxy protocluster at z~4

We present broad-band imaging with the Subaru Telescope of a 25'x25' field surrounding the radio galaxy TN J1338-1942 at redshift z=4.1. The field contains excesses of Lyman-alpha emitters (LAEs) and Lyman break galaxies (LBGs) identified with a protocluster surrounding the radio galaxy. Our new wide-field images provide information about the boundary of the protocluster and its surroundings. There are 874 candidate LBGs within our field, having redshifts in the range z=3.5-4.5. An examination of the brightest of these (with i'< 25.0) shows that the most prominent concentration coincides with the previously discovered protocluster. The diameter of this galaxy overdensity corresponds to ~2 Mpc at z=4, consistent with the previous estimation using LAEs. Several other concentrations of LBGs are observed in the field, some of which may well be physically connected with the z=4.1 protocluster. The observed structure in the smoothed LBG distribution can be explained as the projection of large-scale structure, within the redshift range z=3.5-4.5, comprising compact overdensities and prominent larger voids. If the 5-8 observed compact overdensities are associated with protoclusters, the observed protocluster volume density is ~5x10^-6 Mpc^-3, similar to the volume density of rich clusters in the local Universe.Comment: 5 pages, 4 figures. Accepted for publication in A&A. Full resolution version available at http://www.strw.leidenuniv.nl/~intema/files/AA_2006_4812.zi