The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing

We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg^2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M_(1450) directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6^(+0.8)_(–0.6). Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = –24.1^(+0.7)_(–1.9), approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts

Thermal fluctuation field for current-induced domain wall motion

Current-induced domain wall motion in magnetic nanowires is affected by thermal fluctuation. In order to account for this effect, the Landau-Lifshitz-Gilbert equation includes a thermal fluctuation field and literature often utilizes the fluctuation-dissipation theorem to characterize statistical properties of the thermal fluctuation field. However, the theorem is not applicable to the system under finite current since it is not in equilibrium. To examine the effect of finite current on the thermal fluctuation, we adopt the influence functional formalism developed by Feynman and Vernon, which is known to be a useful tool to analyze effects of dissipation and thermal fluctuation. For this purpose, we construct a quantum mechanical effective Hamiltonian describing current-induced domain wall motion by generalizing the Caldeira-Leggett description of quantum dissipation. We find that even for the current-induced domain wall motion, the statistical properties of the thermal noise is still described by the fluctuation-dissipation theorem if the current density is sufficiently lower than the intrinsic critical current density and thus the domain wall tilting angle is sufficiently lower than pi/4. The relation between our result and a recent result, which also addresses the thermal fluctuation, is discussed. We also find interesting physical meanings of the Gilbert damping alpha and the nonadiabaticy parameter beta; while alpha characterizes the coupling strength between the magnetization dynamics (the domain wall motion in this paper) and the thermal reservoir (or environment), beta characterizes the coupling strength between the spin current and the thermal reservoir.Comment: 16 page, no figur

Holographic interacting dark energy in the braneworld cosmology

We investigate a model of brane cosmology to find a unified description of the radiation-matter-dark energy universe. It is of the interacting holographic dark energy with a bulk-holographic matter $\chi$. This is a five-dimensional cold dark matter, which plays a role of radiation on the brane. Using the effective equations of state $\omega^{\rm eff}_{\rm \Lambda}$ instead of the native equations of state $\omega_{\rm \Lambda}$, we show that this model cannot accommodate any transition from the dark energy with $\omega^{\rm eff}_{\rm \Lambda}\ge-1$ to the phantom regime $\omega^{\rm eff}_{\rm \Lambda}<-1$. Furthermore, the case of interaction between cold dark matter and five dimensional cold dark matter is considered for completeness. Here we find that the redshift of matter-radiation equality $z_{\rm eq}$ is the same order as $z^{\rm ob}_{\rm eq}=2.4\times10^{4} \Omega_{\rm m}h^2$. Finally, we obtain a general decay rate $\Gamma$ which is suitable for describing all interactions including the interaction between holographic dark energy and cold dark matter.Comment: 17 pages, 4 figure

Geometrically Induced Multiple Coulomb Blockade Gaps

We have theoretically investigated the transport properties of a ring-shaped array of small tunnel junctions, which is weakly coupled to the drain electrode. We have found that the long range interaction together with the semi-isolation of the array bring about the formation of stable standing configurations of electrons. The stable configurations break up during each transition from odd to even number of trapped electrons, leading to multiple Coulomb blockade gaps in the the $I-V$ characteristics of the system.Comment: 4 Pages (two-columns), 4 Figures, to be published in Physical Review Letter

A Detailed Study of Photometric Redshifts for GOODS-South Galaxies

We use the deepest and the most comprehensive photometric data currently available for GOODS-South galaxies to measure their photometric redshifts. The photometry includes VLT/VIMOS (U-band), HST/ACS (F435W, F606W, F775W, and F850LP bands), VLT/ISAAC (J-, H-, and Ks-bands), and four Spitzer/IRAC channels (3.6, 4.5, 5.8, and 8.0 micron). The catalog is selected in the z-band (F850LP) and photometry in each band is carried out using the recently completed TFIT algorithm, which performs PSF matched photometry uniformly across different instruments and filters, despite large variations in PSFs and pixel scales. Photometric redshifts are derived using the GOODZ code, which is based on the template fitting method using priors. The code also implements "training" of the template SED set, using available spectroscopic redshifts in order to minimize systematic differences between the templates and the SEDs of the observed galaxies. Our final catalog covers an area of 153 sq. arcmin and includes photometric redshifts for a total of 32,505 objects. The scatter between our estimated photometric and spectroscopic redshifts is sigma=0.040 with 3.7% outliers to the full z-band depth of our catalog, decreasing to sigma=0.039 and 2.1% outliers at a magnitude limit m(z)<24.5. This is consistent with the best results previously published for GOODS-S galaxies, however, the present catalog is the deepest yet available and provides photometric redshifts for significantly more objects to deeper flux limits and higher redshifts than earlier works. Furthermore, we show that the photometric redshifts estimated here for galaxies selected as dropouts are consistent with those expected based on the Lyman break technique.Comment: 62 pages, 21 figures. Minor changes to match version to be published in Ap

The Most Massive Galaxies at 3.0<z<4.0 in the NEWFIRM Medium-Band Survey: Properties and Improved Constraints on the Stellar Mass Function

[Abridged] We use the NEWFIRM Medium-Band Survey (NMBS) to characterize the properties of a mass-complete sample of 14 galaxies at 3.0<z<4.0 with M_star>2.5x10^11 Msun, and to derive more accurate measurements of the high-mass end of the stellar mass function (SMF) of galaxies at z=3.5, with significantly reduced contributions from photometric redshift errors and cosmic variance to the total error budget of the SMF. The typical very massive galaxy at z=3.5 is red and faint in the observer's optical, with median r=26.1, and rest-frame U-V=1.6. About 60% of the sample have optical colors satisfying either the U- or the B-dropout color criteria, although ~50% of these galaxies have r>25.5. About 30% of the sample has SFRs from SED modeling consistent with zero. However, >80% of the sample is detected at 24 micron, with total infrared luminosities in the range (0.5-4.0)x10^13 Lsun. This implies the presence of either dust-enshrouded starburst activity (with SFRs of 600-4300 Msun/yr) and/or highly-obscured active galactic nuclei (AGN). The contribution of galaxies with M_star>2.5x10^11 Msun to the total stellar mass budget at z=3.5 is ~8%. We find an evolution by a factor of 2-7 and 3-22 from z~5 and z~6, respectively, to z=3.5. The previously found disagreement at the high-mass end between observed and model-predicted SMFs is now significant at the 3sigma level. However, systematic uncertainties dominate the total error budget, with errors up to a factor of ~8 in the densities, bringing the observed SMF in marginal agreement with the predicted SMF. Additional systematic uncertainties on the high-mass end could be introduced by either 1) the intense star-formation and/or the very common AGN activities as inferred from the MIPS 24 micron detections, and/or 2) contamination by a significant population of massive, old, and dusty galaxies at z~2.6.Comment: 20 pages, 11 figures. Accepted in ApJ. Minor changes to colors of figures to match accepted versio

Contribution of actin filaments and microtubules to cell elongation and alignment depends on the grating depth of microgratings

Additional file 1: Figure S1. (A) A phase contrast image of TCPS surface. Bar, 100 μm. (B) An imageshowing FN-lines (1 μm line and spacing) obtained by Atomic Force Microscopy (AFM) (Dimension 3100with a Nanoscope III controller, Digital Instruments) using silicon cantilevers (spring constant; 50 Nm-1)(RTESP, Veeco Probes) in contact mode. (C-E) SEM (Scanning electron microscopy) (6010 LV, JEOL)images showing the cross section of three different microgratings; 1 μm gratings with 0.35 um depth (C) and1 μm depth (D) and 2 μm gratings with 2 μm depth (E). Figure S2. (A) Fluorescence image of a RPE-1 cell stably expressing GFP/centrin cell on 1 μm gratings (1 μm deep). Bar, 30 μm. A yellow arrow indicates the direction of cell elongation. (B) Average cell aspect ratio (R) of cells on 1 μm gratings (0.35 or 1 μm deep) and 2 μm gratings with/without CD treatment. n: number of cells. ***P < 0.001. Data were analyzed using one-way ANOVA and a Bonferroni post hoc test. Error bar denotes the standard deviation of the mean. Figure S3. Alignment of actin and vinculin to the different substrates (Flat TCPS surface, FN-lines, and 1 μm gratings (0.35 or 1μm deep)). The alignment angle was measured as an angle difference of actin or vinculin orientation to the long axis of a cell on flat PDMS surface or the long axis of the FN-line or each micrograting. #: the number of cells. Error bar denotes the standard deviation of the mean. Figure S4. Merged image of MTs (Green fluorescence) and pattern (phase contrast) of cells on 1 μm grating (1 μm deep) in the presenceof CD at 1 μM

Future cosmological evolution in f(R)f(R) gravity using two equations of state parameters

We investigate the issues of future oscillations around the phantom divide for $f(R)$ gravity. For this purpose, we introduce two types of energy density and pressure arisen from the $f(R)$-higher order curvature terms. One has the conventional energy density and pressure even in the beginning of the Jordan frame, whose continuity equation provides the native equation of state $w_{\rm DE}$. On the other hand, the other has the different forms of energy density and pressure which do not obviously satisfy the continuity equation. This needs to introduce the effective equation of state $w_{\rm eff}$ to describe the $f(R)$-fluid, in addition to the native equation of state $\tilde{w}_{\rm DE}$. We confirm that future oscillations around the phantom divide occur in $f(R)$ gravities by introducing two types of equations of state. Finally, we point out that the singularity appears ar $x=x_c$ because the stability condition of $f(R)$ gravity violates.Comment: 23 pages, 10 figures, correcting typing mistake in titl

The NEWFIRM Medium-Band Survey: Filter Definitions and First Results

Deep near-infrared imaging surveys allow us to select and study distant galaxies in the rest-frame optical, and have transformed our understanding of the early Universe. As the vast majority of K- or IRAC-selected galaxies is too faint for spectroscopy, the interpretation of these surveys relies almost exclusively on photometric redshifts determined from fitting templates to the broad-band photometry. The best-achieved accuracy of these redshifts Delta(z)/(1+z) ~ 0.06 at z>1.5, which is sufficient for determining the broad characteristics of the galaxy population but not for measuring accurate rest-frame colors, stellar population parameters, or the local galaxy density. We have started a near-infrared imaging survey with the NEWFIRM camera on the Kitt Peak 4m telescope to greatly improve the accuracy of photometric redshifts in the range 1.5<z<3.5. The survey uses five medium-bandwidth filters, which provide crude "spectra" over the wavelength range 1-1.8 micron for all objects in the 27.6 x 27.6 arcmin NEWFIRM field. In this first paper, we illustrate the technique by showing medium band NEWFIRM photometry of several galaxies at 1.7<z<2.7 from the near-infrared spectroscopic sample of Kriek et al. (2008). The filters unambiguously pinpoint the location of the redshifted Balmer break in these galaxies, enabling very accurate redshift measurements. The full survey will provide similar data for ~8000 faint K-selected galaxies at z>1.5 in the COSMOS and AEGIS fields. The filter set also enables efficient selection of exotic objects such as high redshift quasars, galaxies dominated by emission lines, and very cool brown dwarfs; we show that late T and candidate "Y" dwarfs could be identified using only two of the filters.Comment: Accepted for publication in PASP. 9 pages, 5 figure

Geographical interdependence, international trade and economic dynamics: the Chinese and German solar energy industries

The trajectories of the German and Chinese photovoltaic industries differ significantly yet are strongly interdependent. Germany has seen a rapid growth in market demand and a strong increase in production, especially in the less developed eastern half of the country. Chinese growth has been export driven. These contrasting trajectories reflect the roles of market creation, investment and credit and the drivers of innovation and competitiveness. Consequent differences in competiveness have generated major trade disputes