18702340
SUBARU MID-INFRARED IMAGING OF THE QUADRUPLE LENSES PG 1115+080 AND B1422+231: LIMITS ON SUBSTRUCTURE LENSING
We present mid-infrared imaging at 11.7 μm for the quadruple lens systems PG 1115+080 and B1422+231 using the cooled mid-infrared camera and spectrometer (COMICS) attached on the Subaru Telescope. These lensed QSOs are characterized by their anomalous optical and radio flux ratios, as obtained for A1 and A2 images of PG 1115+080 and A, B, and C images of B1422+231, respectively, i.e., such flux ratios are hardly able to be reproduced by lens models with a smooth mass distribution. Our mid-infrared observations for these images have revealed that the mid-infrared flux ratio A2/A1 of PG 1115+080 is virtually consistent with smooth lens models (but inconsistent with the optical flux ratio), whereas for B1422+231, the mid-infrared flux ratios among the A, B, and C images are in good agreement with the radio flux ratios. We also identify a clear infrared bump in the spectral energy distributions of these QSOs, thereby indicating that the observed mid-infrared fluxes originate from a hot dust torus around a QSO nucleus. Based on the size estimate of the dust torus, we place limits on the mass of a substructure in these lens systems causing the anomalous optical or radio flux ratios. For PG 1115+080, the mass of a substructure inside an Einstein radius ME is 16 M☉, corresponding to either a star or a low-mass CDM subhalo having a mass of M 2.2 × 104 M☉ inside a radius of 100 pc if modeled as a singular isothermal sphere (SIS). For B1422+231, we obtain ME 209 M☉, indicating that a CDM subhalo is more likely, having a mass of M 7.4 × 104 M☉.
17147602
How large is our universe
We reexamine constraints on the spatial size of closed toroidal models with cold dark matter and the cosmological constant from cosmic microwave background. We carry out Bayesian analyses using the Cosmic Background Explorer (COBE) data properly taking into account the statistically anisotropic correlation, i.e., off-diagonal elements in the covariance. We find that the COBE constraint becomes more stringent in comparison with that using only the angular power spectrum, if the likelihood is marginalized over the orientation of the observer. For some limited choices of orientations, the fit to the COBE data is considerably better than that of the infinite counterpart. The best-fit matter normalization is increased because of large-angle suppression in the power and the global anisotropy of the temperature fluctuations. We also study several deformed closed toroidal models in which the fundamental cell is described by a rectangular box. In contrast to the cubic models, the large-angle power can be enhanced in comparison with the infinite counterparts if the cell is sufficiently squashed in a certain direction. It turns out that constraints on some slightly deformed models are less stringent. We comment on how these results affect our understanding of the global topology of our universe.
15697946
SUBARU MID-INFRARED IMAGING OF THE QUADRUPLE LENSES. II. UNVEILING LENS STRUCTURE OF MG0414+0534 AND Q2237+030*
We present mid-infrared imaging at 11.7 μm for the quadruple lens systems, MG0414+0534 and Q2237+030, using the cooled mid-infrared camera and spectrometer attached on the Subaru telescope. MG0414+0534 is characterized by a bright pair of lensed images (A1, A2) and their optical flux ratio A2/A1 deviates significantly from the prediction of a smooth-lens model. Q2237+030 is the Einstein Cross being comprised of four lensed images, which are significantly affected by microlensing in a foreground lensing galaxy. Our mid-infrared observations of these lensed images have revealed that the mid-infrared flux ratio for A2/A1 of MG0414+0534 is nearly unity (0.90 ± 0.04). We find that this flux ratio is systematically small, at 4-5σ level, compared with the prediction of a best smooth-lens model (1.09) represented by a singular isothermal ellipsoid and external shear. The smooth-lens model, which also considers the additional lensing effect of the possible faint satellite, object X, still provides a large flux ratio of A2/A1=1.06, thereby suggesting the presence of more substructures that can explain our observational result. In contrast, for Q2237+030, our high signal-to-noise observation indicates that the mid-infrared flux ratios between all the four images of Q2237+030 are virtually consistent with the prediction of a smooth-lens model. Based on the size estimate of the dust torus surrounding the nuclei of these QSOs, we set limits on the mass of a substructure in these lens systems, which can cause anomalies in the flux ratios. For MG0414+0534, since the required mass of a substructure inside its Einstein radius is 360 M ☉, millilensing by a cold dark matter substructure is most likely. If it is modeled as a singular isothermal sphere, the mass inside a radius of 100 pc is given as 1.0 × 105 M ☉. For Q2237+030, there is no significant evidence of millilensing, so the reported anomalous flux ratios in shorter wavelengths are entirely caused due to microlensing by stars.
17834566
Temperature correlations in a compact hyperbolic universe
The effect of a non-trivial topology on the temperature correlations of the cosmic microwave background (CMB) in a small compact hyperbolic universe with volume comparable to the cube of the curvature radius is investigated. Because the bulk of large-angle CMB fluctuations are produced at the late epoch in low-Ω0 models, the effect of a long-wavelength cut-off owing to the periodic structure does not lead to significant suppression of large-angle power as in compact flat models. The angular power spectra are consistent with COBE data for Ω00.1.
55953444
Evidence of Quasi-linear Super-structures in the Cosmic Microwave Background and Galaxy Distribution
Recent measurements of hot and cold spots on the cosmic microwave background (CMB) sky suggest the presence of super-structures on (>100 h –1 Mpc) scales. We develop a new formalism to estimate the expected amplitude of temperature fluctuations due to the integrated Sachs-Wolfe (ISW) effect from prominent quasi-linear structures. Applying the developed tools to the observed ISW signals from voids and clusters in catalogs of galaxies at redshifts z < 1, we find that they indeed imply a presence of quasi-linear super-structures with a comoving radius of 100 ~ 300 h –1 Mpc and a density contrast |δ| ~ O(0.1). We also find that the observed ISW signals are at odds with the concordant Λ cold dark matter model that predicts Gaussian primordial perturbations at 3σ level. We confirm that the mean temperature around the CMB cold spot in the southern Galactic hemisphere filtered by a compensating top-hat filter deviates from the mean value at ~3σ level, implying that a quasi-linear supervoid or an underdensity region surrounded by a massive wall may reside at low redshifts z < 0.3 and the actual angular size (16°-17°) may be larger than the apparent size (4°-10°) discussed in literature. Possible solutions are briefly discussed.
44010185
Geometric Gaussianity and non-Gaussianity in the cosmic microwave background
In this paper, the Gaussianity of eigenmodes and non-Gaussianity in the cosmic microwave background (CMB) temperature fluctuations in the two smallest compact hyperbolic (CH) models are investigated. First, it is numerically found that the expansion coefficients of low-lying eigenmodes on the two CH manifolds behave as if they are Gaussian random numbers in almost all places. Next, the non-Gaussianity of the temperature fluctuations in the $(l,m)$ space in these models is studied. Assuming that the initial fluctuations are Gaussian, the real expansion coefficients ${b}_{\mathrm{lm}}$ of the temperature fluctuations in the sky are found to be distinctively non-Gaussian. In particular, the cosmic variances are found to be much larger than for Gaussian models. On the other hand, the anisotropic structure is vastly erased if one averages the fluctuations at a number of different observation points because of the Gaussian pseudorandomness of the eigenmodes. Thus the dominant contribution to the two-point correlation functions comes from the isotropic terms described by the angular power spectra ${C}_{l}.$ Finally, topological quantities, the total length and the genus of isotemperature contours are investigated. The variances of total length and genus at high and low threshold levels are found to be considerably larger than that of Gaussian models while the means almost agree with them.
18698664
Observational Constraints on the ICM Temperature Enhancement by Cluster Mergers
We present results from a combined weak lensing and X-ray analysis of the merging cluster A1914 at a redshift of z = 0.1712, based on R-band imaging data with Subaru/Suprime-Cam and archival Chandra X-ray data. Using the weak-lensing and X-ray data we explore the relationships between cluster global properties, namely the gravitational mass, the bolometric X-lay luminosity and temperature, the gas mass and the gas mass fraction, as a function of radius. We found that the gas mass fractions within r2500 and rvir are consistent with the results of earlier X-ray cluster studies and with cosmic microwave background studies based on the WMAP observations, respectively. However, the observed X-ray temperature, kBTave = 9.6±0.3keV, is signi?cantly higher than the virial temperature, kBTvir = 4.7 ± 0.3keV derived from the weak lensing distortion measurement. The X-ray bolometric luminosity-temperature (LX - T) relation is consistent with the LX - T relation derived by previous statistical X-ray studies of galaxy clusters. Such correlations among the global cluster properties are invaluable observational tools for studying the cluster merger physics. Our results demonstrate that the combination of X-ray and weak-lensing observations is a promising, powerful probe of the physical processes associated with cluster mergers as well as of their mass properties.