@article{4338, abstract = {Mosaic hybrid zones arise when ecologically differentiated taxa hybridize across a network of habitat patches. Frequent interbreeding across a small-scale patchwork can erode species differences that might have been preserved in a clinal hybrid zone. In particular, the rapid breakdown of neutral divergence sets an upper limit to the time for which differences at marker loci can persist. We present here a case study of a mosaic hybrid zone between the fire-bellied toads Bombina bombina and B. variegata (Anura: Discoglossidae) near Apahida in Romania. In our 20 × 20 km study area, we detected no evidence of a clinal transition but found a strong association between aquatic habitat and mean allele frequencies at four molecular markers. In particular, pure populations of B. bombina in ponds appear to cause massive introgression into the surrounding B. variegata gene pool found in temporary aquatic sites. Nevertheless, the genetic structure of these hybrid populations was remarkably similar to those of a previously studied transect near Pescenica (Croatia), which had both clinal and mosaic features: estimates of heterozygote deficit and linkage disequilibrium in each country are similar. In Apahida, the observed strong linkage disequilibria should stem from an imperfect habitat preference that guides most (but not all) adults into the habitats to which they are adapted. In the absence of a clinal structure, the inferred migration rate between habitats implies that associations between selected loci and neutral markers should break down rapidly. Although plausible selection strengths can maintain differentiation at those loci adapting the toads to either permanent or temporary breeding sites, the divergence at neutral markers must be transient. The hybrid zone may be approaching a state in which the gene pools are homogenized at all but the selected loci, not dissimilar from an early stage of sympatric divergence.}, author = {Vines, Timothy and Kohler, S C and Thiel, M and Ghira, Ioan and Sands, T R and Maccallum, Catriona and Barton, Nicholas H and Nürnberger, Beate}, issn = {0014-3820}, journal = {Evolution}, number = {8}, pages = {1876 -- 1888}, publisher = {Wiley-Blackwell}, title = {{On the maintenance of reproductive isolation in a mosaic hybrid zone between the toads Bombina bombina and B. variegata}}, doi = {10.1111/j.0014-3820.2003.tb00595.x}, volume = {57}, year = {2003}, } @article{17741, abstract = {The recent discovery of a Gunn-Peterson (GP) trough in the spectrum of the redshift 6.28 SDSS quasar has raised the tantalizing possibility that we have detected the reionization of the universe. However, a neutral fraction (of hydrogen) as small as 0.1% is sufficient to cause the GP trough; hence, its detection alone cannot rule out reionization at a much earlier epoch. The cosmic microwave background (CMB) polarization anisotropy offers an alternative way to explore the dark age of the universe. We show that for most models constrained by the current CMB data and by the discovery of a GP trough (showing that reionization occurred at z > 6.3), Microwave Anisotropy Probe (MAP) can detect the reionization signature in the polarization power spectrum. The expected 1 σ error on the measurement of the electron optical depth is around 0.03 with a weak dependence on the value of that optical depth. Such a constraint on the optical depth will allow MAP to achieve a 1 σ error on the amplitude of the primordial power spectrum of 6%. MAP with 2 yr (Planck with 1 yr) of observation can distinguish a model with 50% (6%) partial ionization between redshifts of 6.3 and 20 from a model in which hydrogen was completely neutral at redshifts greater than 6.3. Planck will be able to distinguish between different reionization histories even when they imply the same optical depth to electron scattering for the CMB photons.}, author = {Kaplinghat, Manoj and Chu, Mike and Haiman, Zoltán and Holder, Gilbert P. and Knox, Lloyd and Skordis, Constantinos}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {24--32}, publisher = {American Astronomical Society}, title = {{Probing the reionization history of the universe using the cosmic microwave background polarization}}, doi = {10.1086/344927}, volume = {583}, year = {2003}, } @article{17748, abstract = {Recent results by the WMAP satellite suggest that the intergalactic medium was significantly reionized at redshifts as high as z~17. At this early epoch, the first ionizing sources likely appeared in the shallow potential wells of mini-halos with virial temperatures T < 10^4 K. Once such an ionizing source turns off, its surrounding HII region Compton cools and recombines. Nonetheless, we show that the ``fossil'' HII regions left behind remain at high adiabats, prohibiting gas accretion and cooling in subsequent generations of mini-halos. Thus, early star formation is self-limiting. We quantify this effect to show that star formation in mini-halos cannot account for the bulk of the electron scattering opacity measured by WMAP, which must be due to more massive objects. We argue that gas entropy, rather than IGM metallicity, regulates the evolution of the global ionizing emissivity, and impedes full reionization until lower redshifts. We discuss several important consequences of this early entropy floor for reionization. It reduces gas clumping, curtailing the required photon budget for reionization. An entropy floor also prevents H2 formation and cooling, due to reduced gas densities: it greatly enhances feedback from UV photodissociation of H2. An early X-ray background would also furnish an entropy floor to the entire IGM; thus, X-rays impede rather than enhance H2 formation. Future 21cm observations may probe the topology of fossil HII regions.}, author = {Oh, S. Peng and Haiman, Zoltán}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {456--472}, publisher = {Oxford University Press}, title = {{Fossil H ii regions: Self-limiting star formation at high redshift}}, doi = {10.1046/j.1365-2966.2003.07103.x}, volume = {346}, year = {2003}, } @article{17750, abstract = {We present the discovery of three new quasars at z>6 in 1300 deg^2 of SDSS imaging data, J114816.64+525150.3 (z=6.43), J104845.05+463718.3 (z=6.23) and J163033.90+401209.6 (z=6.05). The first two objects have weak Ly alpha emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to 0.05 and could be affected by the presence of broad absorption line systems. The last object has a Ly alpha strength more typical of lower redshift quasars. Based on a sample of six quasars at z>5.7 that cover 2870 deg^2 presented in this paper and in Paper I, we estimate the comoving density of luminous quasars at z 6 and M_{1450} < -26.8 to be (8 +/- 3)x10^{-10} Mpc^{-3} (for H_0 = 50 km/s/Mpc, Omega = 1). HST imaging of two z>5.7 quasars and high-resolution ground-based images (seeing 0.4'') of three additional z>5.7 quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshfit quasar sample suggests the bright end slope of the quasar luminosity function at z 6 is shallower than Psi L^{-3.5} (2-sigma), consistent with the absence of strongly lensed objects.}, author = {Fan, Xiaohui and Strauss, Michael A. and Schneider, Donald P. and Becker, Robert H. and White, Richard L. and Haiman, Zoltán and Gregg, Michael and Pentericci, Laura and Grebel, Eva K. and Narayanan, Vijay K. and Loh, Yeong-Shang and Richards, Gordon T. and Gunn, James E. and Lupton, Robert H. and Knapp, Gillian R. and Ivezić, Željko and Brandt, W. N. and Collinge, Matthew and Hao, Lei and Harbeck, Daniel and Prada, Francisco and Schaye, Joop and Strateva, Iskra and Zakamska, Nadia and Anderson, Scott and Brinkmann, Jon and Bahcall, Neta A. and Lamb, Don Q. and Okamura, Sadanori and Szalay, Alex and York, Donald G.}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {4}, pages = {1649--1659}, publisher = {American Astronomical Society}, title = {{A survey of z > 5.7 quasars in the Sloan Digital Sky Survey. II. Discovery of three additional quasars at z > 6}}, doi = {10.1086/368246}, volume = {125}, year = {2003}, } @article{17754, abstract = {The recent discovery of a high optical depth tau to Thomson scattering from the WMAP data implies that significant reionization took place at redshifts z~15. This discovery has important implications for the sources of reionization, and allows, for the first time, constraints to be placed on physical reionization scenarios out to redshift z~20. Using a new suite of semi-analytic reionization models, we show that the high value of tau requires a surprisingly high efficiency epsilon of the first generation of UV sources for injecting ionizing photons into the intergalactic medium. We find that no simple reionization model can be consistent with the combination of the WMAP result with data from the z<6.5 universe. Satisfying both constraints requires either of the following: (i) H_2 molecules form efficiently at z~20, survive feedback processes, and allow UV sources in halos with virial temperatures below Tvir=10^4 K to contribute substantially to reionization, or (ii) the efficiency epsilon in halos with Tvir>10^4K decreased by a factor of ~ 30 between (z~20) and (z~6). We discuss the relevant physical issues to produce either scenario, and argue that both options are viable, and allowed by current data. In detailed models of the reionization history, we find that the evolution of the ionized fractions in the two scenarios have distinctive features that Planck can distinguish at 3 sigma significance. At the high WMAP value for tau, Planck will also be able to provide tight statistical constraints on reionization model parameters, and elucidate much of the physics at the end of the Dark Ages. The sources responsible for the high optical depth discovered by WMAP should be directly detectable out to z~15 by the James Webb Space Telescope.}, author = {Haiman, Zoltán and Holder, Gilbert P.}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {1--12}, publisher = {American Astronomical Society}, title = {{The reionization history at high redshifts. I. Physical models and new constraints from cosmic microwave background polarization}}, doi = {10.1086/377337}, volume = {595}, year = {2003}, } @article{17759, abstract = {The cosmic microwave background (CMB) has provided a precise template for features in the linear power spectrum: the matter-radiation turnover, sound horizon drop, and acoustic oscillations. In a two-dimensional power spectrum in redshift and angular space, the features appear as distorted rings, and yield simultaneous, purely geometric, measures of the Hubble parameter 𝐻⁡(𝑧) and angular diameter distance 𝐷𝐴⁡(𝑧) via an absolute version of the Alcock-Paczynski test. Employing a simple Fisher matrix tool, we explore how future surveys can exploit these rings of power for dark energy studies. High-z CMB determinations of H and 𝐷𝐴 are best complemented at moderate to low redshift (𝑧≲0.5) with a population of objects that are at least as abundant as clusters of galaxies. We find that a sample similar to that of the ongoing SDSS luminous red galaxy survey can achieve statistical errors at the ∼5% level for 𝐷𝐴⁡(𝑧) and 𝐻⁡(𝑧) in several redshift bins. This, in turn, implies errors of 𝜎⁡(𝑤)=0.03–0.05 for a constant dark energy equation of state in a flat universe. Deep galaxy cluster surveys such as the planned South Pole Telescope survey can extend this test out to 𝑧∼1 or as far as redshift follow-up is available. We find that the expected constraints are at the 𝜎⁡(𝑤)=0.04–0.08 level, comparable to those of galaxies and complementary in redshift coverage.}, author = {Hu, Wayne and Haiman, Zoltán}, issn = {0556-2821}, journal = {Physical Review D}, number = {6}, publisher = {American Physical Society}, title = {{Redshifting rings of power}}, doi = {10.1103/physrevd.68.063004}, volume = {68}, year = {2003}, } @article{17760, abstract = {In light of the recent inference of a high optical depth τ to Thomson scattering from the Wilkinson Microwave Anisotropy Probe (WMAP) data, we investigate the effects of extended periods of partial ionization and ask if the value of τ inferred by assuming a single sharp transition is an unbiased estimate. We construct and consider several representative ionization models and evaluate their signatures in the cosmic microwave background (CMB). If τ is estimated with a single sharp transition, we show that there can be a significant bias in the derived value (and, therefore, a bias in σ8 as well). For WMAP noise levels, the bias in τ is smaller than the statistical uncertainty, but for Planck or a cosmic variance limited experiment the τ bias could be much larger than the statistical uncertainties. This bias can be reduced in the ionization models we consider by fitting a slightly more complicated ionization history, such as a two-step ionization process. Assuming this two-step process, we find that the Planck satellite can simultaneously determine the initial redshift of reionization to ±2 and τ to ±0.01. Uncertainty about the ionization history appears to provide a limit of ~0.005 on how well τ can be estimated from CMB polarization data, much better than expected from WMAP but significantly worse than expected from cosmic variance limits.}, author = {Holder, Gilbert P. and Haiman, Zoltán and Kaplinghat, Manoj and Knox, Lloyd}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {13--18}, publisher = {American Astronomical Society}, title = {{The reionization history at high redshifts. II. Estimating the optical depth to Thomson scattering from cosmic microwave background polarization}}, doi = {10.1086/377338}, volume = {595}, year = {2003}, } @article{17767, abstract = {Galaxy cluster surveys provide a powerful means of studying the density and nature of the dark energy. The redshift distribution of detected clusters in a deep, large solid angle SZE or X-ray survey is highly sensitive to the dark energy equation of state. Accurate constraints at the 5% level on the dark energy equation of state require that systematic biases in the mass estimators must be controlled at better than the ∼10% level. Observed regularity in the cluster population and the availability of multiple, independent mass estimators suggests these precise measurements are possible. Using hydrodynamical simulations that include preheating, we show that the level of preheating required to explain local galaxy cluster structure has a dramatic effect on X-ray cluster surveys, but only a mild effect on SZE surveys. This suggests that SZE surveys may be optimal for cosmology while X-ray surveys are well suited for studies of the thermal history of the intracluster medium.}, author = {Mohr, Joseph J and O'Shea, Brian and Evrard, August E and Bialek, John and Haiman, Zoltán}, issn = {0920-5632}, journal = {Nuclear Physics B - Proceedings Supplements}, pages = {63--67}, publisher = {Elsevier BV}, title = {{Studying dark energy with galaxy cluster surveys}}, doi = {10.1016/s0920-5632(03)02078-4}, volume = {124}, year = {2003}, } @article{17780, abstract = {We study contributions from inhomogeneous (patchy) reionization to arcminute-scale (1000 < l < 10,000) cosmic microwave background (CMB) anisotropies. We show that inhomogeneities in the ionization fraction, rather than in the mean density, dominate both the temperature and the polarization power spectra. Depending on the ionization history and the clustering bias of the ionizing sources, we find that rms temperature fluctuations range from 2 to 8 μK and the corresponding values for polarization are over 2 orders of magnitude smaller. Reionization can significantly bias cosmological parameter estimates and degrade gravitational lensing potential reconstruction from temperature maps but not from polarization maps. We demonstrate that a simple modeling of the reionization temperature power spectrum may be sufficient to remove the parameter bias. The high-l temperature power spectrum will contain some limited information about the sources of reionization.}, author = {Santos, Mario G. and Cooray, Asantha and Haiman, Zoltán and Knox, Lloyd and Ma, Chung‐Pei}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {756--766}, publisher = {American Astronomical Society}, title = {{Small‐scale cosmic microwave background temperature and polarization anisotropies due to patchy reionization}}, doi = {10.1086/378772}, volume = {598}, year = {2003}, } @article{17796, abstract = {The recent measurement by WMAP of a large electron-scattering optical depth τe = 0.17 ± 0.04 is consistent with a simple model of reionization in which the intergalactic medium (IGM) is ionized at redshift z ~ 15 and remains highly ionized thereafter. Here we show that existing measurements of the IGM temperature from the Lyα forest at z ~ 2-4 rule out this "vanilla" model. Under reasonable assumptions about the ionizing spectrum, as long as the universe is reionized before z = 10 and remains highly ionized thereafter, the IGM reaches an asymptotic thermal state that is too cold compared to observations. To simultaneously satisfy the cosmic microwave background and Lyα forest constraints, the reionization history must be complex: reionization begins early at z ≳ 15, but there must have been significant (order-of-unity) changes in fractions of neutral hydrogen and/or helium at 6 < z < 10 and/or singly ionized helium at 4 < z < 10. We describe a physically motivated reionization model that satisfies all current observations. We also explore the impact of a stochastic reionization history and show that a late epoch of (He → He ) reionization induces a significant scatter in the IGM temperature, but the scatter diminishes with time quickly. Finally, we provide an analytic formula for the thermal asymptote and discuss possible additional heating mechanisms that might evade our constraints.}, author = {Hui, Lam and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, pages = {9--18}, publisher = {American Astronomical Society}, title = {{The thermal memory of reionization history}}, doi = {10.1086/377229}, volume = {596}, year = {2003}, } @article{17800, abstract = {Deep mid-infrared (MIR) observations could reveal a population of faint, high-redshift (z > 3), dusty starburst galaxies that are the progenitors of present-day spheroids or bulges and are beyond the reach of current instruments. We utilize a semianalytic galaxy formation scheme to find a range of models for the MIR galaxy counts, down to a flux level of a few nanojanskys. The models incorporate the formation of heavily dust-enshrouded stellar populations at high redshift and are consistent with existing observations, including faint counts at 1.6 μm in the NICMOS Hubble Deep Field, and the upper limit on the extragalactic MIR background from TeV gamma rays. Our models predict ~0.04-0.4 galaxies arcsec-2 at the threshold of 100 nJy at 6 μm, with a comparable or larger surface density at longer MIR wavelengths. We conclude that a significant new population of high-redshift galaxies could be detected by the James Webb Space Telescope. Such a population would constitute background noise for the Terrestrial Planet Finder (TPF) and could necessitate repeat observations: every TPF resolution element would have a chance of up to ~10% of being contaminated by a background galaxy.}, author = {Haiman, Zoltán and Spergel, David N. and Turner, Edwin L.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, pages = {630--637}, publisher = {American Astronomical Society}, title = {{Predictions for the counts of faint, high‐redshift galaxies in the mid‐infrared}}, doi = {10.1086/346201}, volume = {585}, year = {2003}, } @inproceedings{18324, abstract = {We present a novel 3D face recognition approach based on geometric invariants introduced by Elad and Kimmel. The key idea of the proposed algorithm is a representation of the facial surface, invariant to isometric deformations, such as those resulting from different expressions and postures of the face. The obtained geometric invariants allow mapping 2D facial texture images into special images that incorporate the 3D geometry of the face. These signature images are then decomposed into their principal components. The result is an efficient and accurate face recognition algorithm that is robust to facial expressions. We demonstrate the results of our method and compare it to existing 2D and 3D face recognition algorithms.}, author = {Bronstein, Alexander and Bronstein, Michael M. and Kimmel, Ron}, booktitle = {4th International Conference on Audio- and Video-Based Biometric Person Authentication}, isbn = {9783540403029}, issn = {1611-3349}, location = {Guildford, United Kingdom}, pages = {62--70}, publisher = {Springer Nature}, title = {{Expression-invariant 3D face recognition}}, doi = {10.1007/3-540-44887-x_8}, volume = {2688}, year = {2003}, } @article{18410, abstract = {The authors consider detection of high-energy photons in positron emission tomography using thick scintillation crystals. Parallax effect and multiple Compton interactions in such crystals significantly reduce the accuracy of conventional detection methods. In order to estimate the photon line of flight based on photomultiplier responses, the authors use asymptotically optimal nonlinear techniques, implemented by feedforward and radial basis function neural networks. Incorporation of information about angles of incidence of photons significantly improves accuracy of estimation. The proposed estimators are fast enough to perform detection, using conventional computers. Monte Carlo simulation results show that their approach significantly outperforms the conventional Anger algorithm.}, author = {Bronstein, Alexander and Bronstein, M.M. and Zibulevsky, M. and Zeevi, Y.Y.}, issn = {1558-1578}, journal = {IEEE Transactions on Nuclear Science}, number = {3}, pages = {421--426}, publisher = {Institute of Electrical and Electronics Engineers}, title = {{Optimal nonlinear line-of-flight estimation in positron emission tomography}}, doi = {10.1109/tns.2003.812434}, volume = {50}, year = {2003}, } @inproceedings{18428, author = {Bronstein, Alexander and Bronstein, Michael M. and Zibulevsky, Michael and Zeevi, Yehoshua Y.}, booktitle = {SPIE Proceedings}, editor = {Unser, Michael A. and Aldroubi, Akram and Laine, Andrew F.}, issn = {1996-756X}, location = {San Diego, CA, United States}, number = {1}, pages = {292 -- 296}, publisher = {SPIE}, title = {{Separation of reflections via sparse ICA}}, doi = {10.1117/12.505210}, volume = {5207}, year = {2003}, }