Talks

Bernardo Cervantes-Sodi

(Shanghai Astronomical Observatory)

"The galactic spin through empirical distributions"

Using a simple and general model to describe the structure of disc galaxies, we are able to estimate the spin parameter of large samples extracted from the SDSS, study their empirical distributions and show that several internal physical parameters depend directly on this parameter. With the aim of studying the evolution of this parameter, we selected a sample of high-redshift galaxies in the fields of the Great Observatories Origins Deep Survey in the redshift range 0.4 ≤ z ≤ 1.2 and find that the mass and environmental dependences of the spin of our high-redshift galaxies are similar to those of low-z galaxies. These results lead us to conclude that although individual disc galaxies might occasionally suffer strong evolution, they evolve in such a way that the overall spin distribution of the galactic population remains constant from z ∼ 1 to the present epoch.

Xuelei Chen

(National Astronomical Observatories, CAS)

"Researches on 21cm cosmology"

Pravabati Chingangbam

(Indian Institute of Astrophysics)

"Non-Gaussianity from residual foreground contamination in WMAP data"

Yun-Young Choi

(Kyung Hee University)

"Topology of SDSS Luminous Red Galaxies: genus statistics and non-Gaussianity"

Gayoung Chon

(Max-Planck-Institut fuer extraterrestrische Physik)

"X-ray cluster science from ROSAT to eROSITA"

Galaxy clusters are ideal tracers of the large-scale matter distribution and the growth of cosmic structures in the Universe. Therefore they can be used as sensitive probes to test cosmological models. X-ray observations provide an efficient way of detecting and characterising galaxy clusters. Based on the first all-sky X-ray survey from the ROSAT mission we compiled a flux-limited catalogue of galaxy clusters that we use to assess the abundance and clustering of galaxy clusters and apply these results to constrain cosmological parameters. We give an overview of our current activities with the extended ROSAT-ESO Flux Limited X-ray (REFLEX II) galaxy cluster survey. This cluster survey is most sensitive to constrain the matter density of the Universe and the amplitude of dark matter density fluctuations. The upcoming eROSITA All-Sky X-ray Survey is expected to be about 30 times deeper than the survey of ROSAT. This data set will in particular allow us to trace the redshift evolution of the galaxy cluster population which will provide tight constraints on the properties of Dark Energy. We provide forecasts of the potential of the eROSITA mission.

Matthew Colless

(Australian Astronomical Observatory)

"The local density and velocity fields from the 6dF Galaxy Survey"

The 6dF Galaxy Survey (6dFGS) has measured redshifts for 125,000 galaxies down to K=12.65 over the southern sky. It also obtains peculiar velocities for 9000 early-type galaxies within 16000 km/s using the Fundamental Plane. I report results on the density and velocity fields in the local universe derived from these surveys. The redshift survey leads to a precise and independent new estimate of the local Hubble constant based on the baryon acoustic oscillation scale. Redshift space distortions provide a low-redshift estimate of the growth rate of structure, and constraints on the normalisation of the power spectrum and the galaxy bias parameter. The Fundamental Plane survey yields Bayesian estimates of the peculiar velocity for 9000 galaxies and maps of the local velocity field. The observed velocities are fit by models combining the reconstructed velocities from the redshift density map with a residual dipole from more distant masses. We obtain new estimates of the local dipole motion and the beta parameter.

Sudeep Das

(Argonne National Laboratory)

"The Scientific Potential of CMB Lensing"

Recent advances in cosmic microwave background (CMB) observations have enabled us to use the CMB as a unique probe of large scale structure -- through the gravitational lensing of CMB photons. I will discuss the progress in the field, the detection, and various first applications of this effect. I will conclude with an outlook toward the future, specially the synergy of this new probe with the other probes of large scale structure.

Rafael de Souza

(Korea Astronomy and Space Science Institute)

"Dark Matter Halo Environment for Primordial Star Formation"

We study the statistical properties (such as shape and spin) of high-z halos likely hosting the first (PopIII) stars with cosmological simulations including detailed gas physics. In the redshift range considered ($11 < z < 16$) the average sphericity is $<s> = 0.3 \pm 0.1$, and for more than 90% of halos the triaxiality parameter is $T \lesssim 0.4$, showing a clear preference for oblateness over prolateness. Larger halos in the simulation tend to be both more spherical and prolate: we find $s \propto M_h^{\alpha_s}$ and $T \propto M_h^{\alpha_T}$, with $\alpha_s \approx 0.128$ and $\alpha_T= 0.276$ at z = 11. The spin distributions of dark matter and gas are considerably different at $z=16$, with the baryons rotating slower than the dark matter. At lower redshift, instead, the spin distributions of dark matter and gas track each other almost perfectly, as a consequence of a longer time interval available for momentum redistribution between the two components. The spin of both the gas and dark matter follows a lognormal distribution, with a mean value at z=16 of $<\lambda> =0.0184$, virtually independent of halo mass. This is in good agreement with previous studies. Using the results of two feedback models (MT1 and MT2) by McKee & Tan (2008) and mapping our halo spin distribution into a PopIII IMF, we find that at high-$z$ the IMF closely tracks the spin lognormal distribution. Depending on the feedback model, though, the distribution can be centered at $\approx 65 M_\odot$ (MT1) or $\approx 140 M_\odot$ (MT2). At later times, model MT1 evolves into a bimodal distribution with a second prominent peak located at $35-40 M_\odot$ as a result of the non-linear relation between rotation and halo mass. We conclude that the dark matter halo properties might be a key factor shaping the IMF of the first stars.

Ken Ganga

(APC Paris)

"Planck"

The Planck Satellite, created to measure the anisotropies in the temperature and polarization of the cosmic microwave background, was launched in May of 2009 and has performed well. Some early, non-CMB results have been published already. The first set of CMB temperature data and papers will be released early in 2013. The full data set, including polarization, is scheduled to be made public in 2014. Galactic and other astronomical results will continue to be released throughout this period. I will review the non-CMB results which have been released to date and give previews of what we hope to be able to do with the cosmological data releases.

Raphael Gobat

(CEA Saclay)

"Galaxy and cluster formation at z~2"

The redshift range z=1.5-2, and especially around z~2, is particularly interesting as a formative epoch where the first "true" clusters acquire their distinctive characteristics. Processes considered as crucial for the formation of the core population are thought to occur, and thus be most easily studiable, at this stage. The most distant X-ray detected cluster confirmed so far, Cl J1449+0856 at z=2, bridges the gap between the massive virialized structures of the last 9 Gyr and the vigorously active protoclusters of the early Universe and offers thus a unique laboratory to study the coevolution of cluster galaxies and their host structure close to their formation epoch. I will discuss its properties, focusing on the galaxy population content, its interactions with the young environment and the implications for both galaxy and cluster formation.

Jinn-Ouk Gong

(CERN/ APCTP)

"Non-linear and non-Gaussian contributions to galaxy bias"

The observational advances in large scale structure in the universe are bringing the era of precision cosmology with the LSS data. Being intrinsically highly non-linear, galaxy clustering demands deeper understanding of non-linear perturbations. We first present a general account on the galaxy clustering using the functional integration approach, and apply it to the non-Gaussian density field. This approach is extended to more refined criteria of galaxy clustering in the context of peak correlations, and the scale dependent corrections to the bias are presented.

Alireza Hojjati

(Inst. for the early universe)

"Cosmological tests of General Relativity: a principal component analysis"

Future cosmological surveys will have the ability to measure the growth of large-scale structure with accuracy sufficient for discriminating between different models of dark energy and modified gravity. The principal component analysis can be an efficient way of storing information about the linear growth of structure in a model-independent way. I describe how one can test different models of large-scale structure formation using the information stored in the principal components of linear growth and be used to constrain some modified gravity models.

Sungwook E. Hong

(Chungnam Nat'l University)

"Effect of the Cosmological Constant on the number density of Milky-Way-like galaxies"

We estimated the number density of the galaxies whose properties are similar to the Milky Way as a function of the cosmological constant, by using a series of N-body simulations with different value of the cosmological constant. The estimated number density of the Milky-Way-sized galaxies, with neighbor galaxies whose mass and distance are identical to the Andromeda, is exponentially decreased at $\Lambda \gtrsim 3 \Lambda_0$. If above characteristics are anthropically favored, the typicality of our observed value of the cosmological constant is about 90%.

Ho Seong Hwang

(Harvard-Smithsonian Center for Astrophysics)

"Infrared bright galaxies in galaxy redshift surveys"

Many observational studies indicate that the majority of star formation and nuclear activity took place in dusty environments (i.e. infrared bright galaxies) over cosmic time. The combination of infrared and redshift surveys provides valuable, large samples of infrared-detected galaxies without ambiguity in projection along the line of sight, an important basis for studying the optical/infrared properties of infrared bright galaxies and their environmental dependence. However, most wide-field surveys are shallow, and many small-area surveys yield meaningful results only for high-z galaxies because of small pencil-beam volumes. Therefore, a large sample of infrared bright galaxies at intermediate redshift is necessary, bridging the gap between nearby and high-z infrared galaxies. In this talk, I present the results from a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4 deg^2 region of a deep imaging survey, the Deep Lens Survey (DLS). By combining these data with recent Wide-field Infrared Survey Explorer (WISE) data, we obtain a nearly complete identification of optical counterparts of WISE 22 micron sources. We discuss the properties of these WISE selected galaxies and their environmental dependence at intermediate redshift.

Jai-chan Hwang

(Kyungpook Nat'l University)

"Exact and fully nonlinear cosmological perturbations"

We introduce exact and fully nonlinear perturbation formulation in the Friedmann world model. Newtonian and first-order post-Newtonian equations naturally follow from this formulation. Several applications in the large-scale cosmic structures will be displayed in the talk.

Jeong-Sun Hwang

(KIAS)

"On the effects of a hot gas halo in the evolution of isolated galaxy models"

We present our numerical study on how a gaseous halo component included in isolated galaxy models affects their evolution. In the work we construct several Milky Way-like galaxy models containing a gas halo (as well as both gaseous and stellar disks, a dark matter halo, and a stellar bulge) following either an isothermal or an NFW density profile with varying mass and initial spin. In addition, galactic winds associated with star formation are tested in some of the simulations. We use two independent numerical codes for this work, first the ZENO code to create initial galaxy models, and second the GADGET-3 code (an early version) to evolve the models. We compare the evolution of our galaxy models, in particular star formation rates, focusing on the effects of the hot gas halo.

Ilian T. Iliev

(University of Sussex)

"Early Structure Formation and Cosmic Reionization at Large Scales"

Simulations of the early structure formation and the Epoch of Reionization have now reached sufficient volume, dynamic range and resolution to make reliable predictions of the fundamental features and observable signatures of these epochs at the full range of relevant scales. I will summarize important recent progress we have made in this area, including performing a series of simulations of early structure formation on all scales from minihaloes up to very large volumes of hundreds of Mpc, with up 5488^3=165 billion particles, largest by far simulations of this epoch. This allowed us to derive a precise high-z halo mass function and halo clustering and halo sub-structures, all of which have important implications for the observational signatures of reionization. These structure formation simulations were then used as basis for performing state-of-the-art radiative transfer simulations in volumes of up to (607 Mpc)^3, comparable to the full volume of the LOFAR EoR experiment, but including all atomically-cooling ionizing sources. These simulations enabled us for the first time to study numerically the very large-scale structure of reionization. Our results indicate that large-scale fluctuations missed in smaller-volume simulations can boost the EoR 21-cm signal significantly, which yields signatures which should facilitate the LOFAR detection of the EoR signal. Finally, I will present some recent simulation results on the effect of primordial non-Gaussianity of the local type on the formation of early structures and reionization. Our results indicate that non-gaussianity as small as f_NL=50 can have a substantial effect on the formation of rare, bright sources, the source clustering and the reionization history and patchiness.

Myungshin Im

(Seoul Nat'l University)

"Massive Structures of Galaxies at High Redshift"

If the universe is dominated by cold dark matter and dark energy as favored today as in the LCDM universe, it is expected that massive structures such as galaxy clusters emerge slowly at z ~ 1. We searched for massive structures of galaxies (MSGs) at z=0.7 - 4.5 in the GOODS fields, and identify 59 MSGs with ~10^14 Msun. The comparison with the simulation data shows that the observed number of MSGs is a factor of 3 more than the simulation at z > 2. Possible implications of the discrepancy are discussed.

Emille Ishida

(University of Sao Paulo)

"kernel PCA and the SNe photometric classification problem"

The problem of photometric identification will be extremely important for large surveys in the next decade. In this work, we propose the use of KPCA combined with k = 1 nearest neighbour algorithm (KPCA+1NN) as a framework for SNe photometric classification, aiming at a final SNe Ia sample with maximum purity. The method does not rely on information about redshift or local environmental variables, so it is less sensitive to bias than its template fitting counterparts. We applied the method to different instances of the Supernova Photometric Classification Challenge (SNPCC) data set. Results show that our method provide extremely good purity results in all samples analysed, when SNR>5. As a consequence, we can state that if a sample as the SNPCC were available today, we would be able to classify $\approx15\%$ of the initial sample with purity higher than 90\%. This makes our algorithm ideal for a first approach to a completely unknown data or to be used as a complement in increasing the training sample from other algorithms. Results are sensitive to the information contained in each light curve, as a consequence, higher quality the data points lead to higher successful classification rates. The method is flexible enough to be applied to other astrophysical transients, as long as a training and a template sample are provided.

Donghui Jeong

(Johns Hopkins University)

Alex G. Kim

(Lawrence Berkeley Nat'l Laboratory)

"The Bright Future of Supernova Cosmology"

The discovery of the accelerating expansion of the universe was made using Type Ia Supernovae as distance indicators. SNe Ia continue to provide the tightest constraints on the dark energy responsible for that expansion. Improvements in experimental design and analysis methodology will increase the probative power of future projects such as the Dark Energy Survey, Large Synoptic Survey Telescope, and Euclid.

Juhan Kim

(KIAS)

"The Horizon Run Simulations"

Young-Rae Kim

(KIAS)

"Modeling the non-linear systematic effects on genus statistics for large scale structure topology."

The genus, as a quantitative measure of large scale structure topology, has been known to be insensitive to systematic effects. However, it is necessary to characterize these effects on genus statistics and remove them before we use it for a cosmological probe since we are in the era of precision cosmology where we are trying to constrain cosmological parameters within a percent-level accuracy. Using Horizon run 2 simulation, we investigated non-linear systematic effects caused by the non-linear gravitational evolution, pixel effects, shot noise and redshift-space distortion. We successfully modeled these effects using Hermite polynomials. We compare our results with analytic prediction by Matsubara who derived analytical fomulae for non-linear effects using the second order perturbation theory.

Akito Kusaka

(Princeton University)

"Ground based search for CMB B modes from primordial gravitational waves"

Cosmic microwave background (CMB) polarization is the ultimate probe of primordial gravitational waves in the early universe, via the B-mode (or parity odd) signal on degree angular scales. A detection of such a signal would be strong evidence of the inflation scenario and represent indirect observation of a fundamentally new phenomenon near the grand unification energy scale. In order to detect the subtle B-mode signal, control of the instrumental systematics and understanding of the galactic foregrounds are critical. In this talk, I review the suborbital activities for the CMB polarization measurements, including the latest result from QUIET collaboration.

Hyung Mok Lee

(Seoul Nat'l University)

"Cosmic Near Infrared Background Radiation from AKARI Surveys as an Indicator of First Galaxies"

When and how the first galaxies are formed are not well known because of lack of observational data. Using the deep images taken by AKARI at near infrared bands, we obtained the background radiation after removing all point or extended sources. We found excess fluctuating component over the shot noise at angular scale greater than 100 arcseconds. Our results are consistent with the Spitzer data at 3.6 and 4.5 microns.  The fluctuating component observed at large angular scales has a blue stellar spectrum which is similar to that of the spectrum of the excess isotropic emission. A significant spatial correlation between wavelength bands was found, and the slopes of the linear correlations are consistent with the spectrum of the excess fluctuation. These findings indicate that the detected fluctuation could be attributed to the first stars of the universe, i.e., Population III stars. The observed fluctuation provides an important constraint on the era of the first galaxies.

Seokcheon Lee

(KIAS)

"Probing cosmic acceleration with galaxy clusters"

Clusters are the largest virialized objects in the Universe with their abundance and evolution simply related to the linear matter power spectrum. Thus, the abundance of clusters and their distribution in redshift should be determined purely by the geometry of the Universe and the power spectrum of initial density fluctuations. As a result, the clusters of galaxies provide a useful probe of the fundamental cosmological parameters including the investigation into the dark energy equation of state ω, because the linear growth factor Dg, the cosmological volume element, as well as the primordial scalar amplitude at horizon crossing δ depend on ω. We briefly review the effects of quintessence field on the matter power spectrum. We directly show the effects of the quintessence field on the σ8(M) due to the change in δ. We also show the effects of quintessence field on both the background evolution and the growth factor. From the above, we investigate the resulting changes in the cluster abundance.

Benjamin L’Huillier

(KIAS)

"Galaxy mass assembly: the role of gas accretion"

Galaxies accrete their mass by means of both smooth accretion from the cosmic web, and the mergers of smaller entities. We wish to quantify the respective role of these two modes of accretion, which could determine the morphological types of galaxies observed today. Multi-zoom cosmological simulations are used to estimate as a function of time the evolution of mass in bound systems, for dark matter as well as baryons. The baryonic contents of dark matter haloes are studied. Merger histories are followed as a function of external density, and the different ways in which mass is assembled in galaxies and the stellar component accumulated are quantified. We find that most galaxies assemble their mass through smooth accretion, and only the most massive galaxies also grow significantly through mergers. The mean fraction of mass assembled by accretion is 77 %, and by mergers 23 %. We present typical accretion histories of hundreds of galaxies: masses of the most massive galaxies increase monotonically in time, mainly through accretion, many intermediate-mass objects also experience mass-loss events such as tidal stripping and evaporation. However, our simulations suffer from the overcooling of massive galaxies caused by the neglect of active galaxy nuclei (AGN) feedback. The time by which half of the galaxy mass has assembled, both in dark matter and baryons, is a decreasing function of mass, which is compatible with the observations of a so-called downsizing. At every epoch in the universe, there are low-mass galaxies actively forming stars, while more massive galaxies form their stars over a shorter period of time within half the age of the universe.

Cheng Li

(Shanghai Astronomical Observatory)

"Linking galaxies to dark matter halos with stellar mass or with stellar velocity dispersion?"

It was recently suggested that, compared to its stellar mass (M*), the central stellar velocity dispersion (sigma*) of a galaxy might be a better indicator for its host dark matter halo mass. Here we test this hypothesis by estimating the dark matter halo mass for central galaxies in groups as a function of M* and sigma*. For this we have estimated the redshift-space cross-correlation function (CCF) between the central galaxies at given M* and sigma* and a reference galaxy sample, from which we determine both the projected CCF, w_p(r_p), and the velocity dispersion profile (VDP). A halo mass is then obtained from the average velocity dispersion within the virial radius. At fixed
M*, we find very weak or no correlation between halo mass and sigma*. In contrast, strong mass dependence is clearly seen even when sigma* is limited to a narrow range. Our results thus firmly demonstrate that the stellar mass of central galaxies is still a good (if not the best) indicator for dark matter halo mass, better than the stellar velocity dispersion. The dependence of galaxy clustering on sigma* at fixed M*, as recently discovered by Wake et al. (2012), may be attributed to satellite galaxies, for which the tidal stripping occurring within halos has stronger effect on stellar mass than on central stellar velocity dispersion."

Yin-Zhe Ma

(University of British Columbia and CITA/Canada)

"Comparing Planck First Results with WMAP"

Planck collaboration released its first results in Jan/2011, in which the early Sunyaev-Zeldovich catalogue is one of the most important new releases of the survey. Planck gives a detection of each cluster as a signal-to-noise ratio around 3 \sigma, but one of the important questions is, why we didn't find such clusters in WMAP? As a Planck team member, I will present here a study of Sunyaev-Zeldovich effect in 7-year WMAP W-band data with the assistant of the Planck ESZ catalogue. We employ a matched filter technique to WMAP data to suppress the noise in the maps and calculate the universal profile for galaxy clusters. We then obtain the map of Compton y-parameter in which we can calculate the significance of detection for each cluster in the WMAP. By comparing the values of Compton y-parameter between the two experiments, we find excellent agreement between them and the result strongly suggests that WMAP beam profile is well calibrated and be able to detect the SZ signals. This method will be extended to investigate and separate components of the SZ effect in the future Planck maps.

Shude Mao

(National Astronomical Observatories, CAS)

"Dynamical modelling of the Milky Way and external galaxies"

I will discuss some recent observations and results of  the Milky Way and external galaxies using both Schwarzschild and the made-to-measure methods. I will highlight how we explain some of the observed features in the Milky Way in the dynamical modelling.

Teppei Okumura

(Inst. for the Early Universe)

"Distribution function approach to redshift space distortions"

Galaxy redshift surveys are one of the most powerful tools to probe cosmological models. Particularly measurement of redshift space distortions (RSD), caused by peculiar velocities of galaxies, offers an attractive method to directly probe the cosmic growth history of density perturbations. A distribution function approach where RSD can be written as a sum over density weighted velocity moment correlators has recently been developed. In this talk, first I present the redshift-space power spectrum of dark matter based on this approach using N-body simulations and show that this formalism predicts the true power spectrum up to sufficiently small scales. Next, I show the results extended to biased objects such as dark matter halos and galaxies, generalizing the concept of the bias in density-density power spectra.

Camilla Pacifici

(MPI/ Yonsei University)

"Relative merits of different types of multi-wavelength observations to constrain galaxy physical parameters"

We present a new approach to constrain galaxy physical parameters from the combined interpretation of stellar and nebular emission in wide ranges of observations. This approach relies on the Bayesian analysis of galaxy spectral energy distributions using a comprehensive library of synthetic spectra. This library is assembled using state-of-the-art models of star formation and chemical enrichment histories, stellar population synthesis, nebular emission and attenuation by dust. We focus on the constraints set by 5-band photometry and low- and medium-resolution spectroscopy at optical rest wavelengths on a few physical parameters characterizing the stars and interstellar medium. Since these parameters cannot be known a priori for any galaxy sample, we assess the accuracy to which they can be retrieved by simulating `pseudo-observations' using models with known parameters. Assuming that these models are good approximations of true galaxies, we find that the combined analysis of stellar and nebular emission in low-resolution (50A FWHM) galaxy spectra provides valuable constraints on all physical parameters. Our approach can be extended to the analysis of any type of observation across the wavelength range covered by spectral evolution models.

 Danny Pan

(Shanghai Astronomical Observatory)

Changbom Park

(KIAS)

"The Challenge of the Largest Structures in the Universe to Cosmology"

Chan-Gyung Park

(Chonbuk Nat'l University)

"Observational effects of the early episodically dominating dark energy"

Hyunbae Park

(Univ. of Texas at Austin)

"The Kinetic Sunyaev-Zel'dovich effect as the Probe of the Reionization Epoch"

We present our calculation of the angular power spectrum of the Cosmic Microwave Background (CMB) fluctuation induced by the kinetic Sunyaev-Zel'dovich effect from the reionization era. We use our N-body+radiative transfer simulations to model the inhomogeneity of the reionization. In comparison to previous approach generating a sky map to calculating the signal, we present our new method that takes the ionized momentum power spectrum from each simulation snapshot and integrates along the line of sight. Out approach guarantees the full usage of statistical information of the simulation and avoids non-trivial interpolation and connection of maps and enables us to see how much contribution comes from a given time by looking at the integrand. We show a way to correct for the missing bulk velocity power due to finiteness of the simulation box. The accuracy of the correction is confirmed by comparing the signals from different sizes of simulations with the same reionization prescription. We first show that the inhomogeneity boosts the signal by an order of magnitude with the maximum contribution from when the IGM is about half ionized. Then, we examine the impact on the kSZ signal of the "self-regulation" of reionization, which results if low-mass dwarf galaxies (10^8 solar mass < M < 10^9 solar mass) or mini halos (10^4 solar mass < M < 10^8 solar mass) are suppressed as sources of reionization if they form in regions that were already ionized or Lyman-Werner dissociated. The CMB fluctuation power for the multipole moment, l, of 3000 is not sensitive to those self-regulated sources, but, for higher l's, is significantly enhanced. The enhancement at l=10000 is 60% and 25% by the low-mass dwarf galaxies and mini halos, respectively, in terms of C_l possibly distinguishable with a measurement of the power over a range of several thousands in l with 10% level of accuracy. Insensitivity of the signal at l=3000 to the self-regulating sources with sensitivity of the duration of reionization to them warns the simplified approach of Zahn et al. (2011) Mesinger et al. (2012) that parameterize the kSZ signal only with the duration and timing of the reionization. kSZ signal computed with our simulations are, in general, lower than their values with the same sets of duration and timing of reionization and fits into the SPT upper bound.

Graziano Rossi

(CEA Saclay)

"Cosmic web statistics and halo triaxiality: new insights"

I will present a new algorithm to sample the constrained eigenvalues of the initial shear field associated with Gaussian statistics, called the ‘peak/dip excursion-set- based’ algorithm, at positions which correspond to peaks or dips of the correlated density field. The algorithm, derived from a novel extension of Doroshkevich’s (1970) formulae, offers new insights into the statistical description of the cosmic web, and has important implications for models of structure formation. In particular, I will discuss how the standard distributions of shape parameters in triaxial halo/void models (i.e. ellipticity and prolateness) are modified in the presence of the constraint, and what this implies for the morphology of the cosmic web.

Margus Saal

(Institute of Physics University of Tartu)

"Scalar-tensor cosmological models converging to general relativity: potential dominated and matter dominated cases"

We consider Friedmann-Lema&#305;tre-Robertson-Walker flat cosmological models in the framework of general Jordan frame scalar-tensor theories of gravity in two different cases: in the dust matter dominated era and in the potential dominated era. Motivated by the local weak field constraints and by cosmological observations, we develop and use an approximation scheme for the regime close to the so-called limit of general relativity. The ensuing nonlinear approximate equations for the scalar field and the Hubble parameter can be solved analytically in cosmological time in both cases. We find criteria for the functions &#969; and V characterizing a scalar-tensor theory, to determine whether the theory does or does not possess solutions converging to general relativity asymptotically in time. The converging solutions can be subsumed under two principal classes: exponential or polynomial convergence, and damped oscillations around general relativity. The classes of scalar-tensor theories of gravity which contain these types of solutions and satisfy observational constraints, are candidates to explain possible deviations from the standard &#923;CDM model. Finally, the effective equation of state parameter weff is used to illustrate possible asymptotic cosmological dynamics.

Cristiano Sabiu

(KIAS)

"Constraining the halo model using higher order statistics"

David J. Schlegel

(Lawrence Berkeley Nat'l Laboratory)

"BOSS, BigBOSS and Beyond"

The Baryon Oscillation Spectroscopic Survey (BOSS) is a Stage III dark energy experiment on the Sloan Telescope. For the five years from 2009-2014, we are mapping 1.5 million galaxies at z<0.7. A simultaneous survey of 160,000 quasars is mapping hydrogen gas in absorption at redshifts 2 < z < 3. BOSS will provide the definitive measurement of the low redshift (z<0.7) BAO distance scale, and is pioneering a new method of measuring BAO at high redshift. First results from each will be presented. BigBOSS is a Stage IV dark energy experiment that will extend this map to 25 million objects spanning the full redshift range 0 < z < 3.5. The instrument is a 5000-fiber spectrograph on a 7 square degree field of the Mayall 4-m telescope. I will describe this survey and its technical status.

Tiit Sepp

(Tartu Observatory)

"On the formation of superclusters"

We aim to understand better the large-scale effects that are dominant in the Universe, for the formation and evolution of superclusters. For that, we use N-body smoothed particle hydrodynamics simulations to model the formation and evolution of a galaxy supercluster and its inner structure, both at the galaxy cluster/group scales. We use constrained simulations to model an observed supercluster, optimizing both the initial conditions and border conditions to simulate the evolution of a supercluster. This will allow us to obtain a more detailed understanding of structure formation at supercluster scales and to better compare simulations and observations. It will also be important for better understanding of the connection between the properties of a supercluster and those of its galaxies and galaxy clusters (environmental effects). The highly parallel n-body SPH (smoothed particle hydrodynamics) simulation code GADGET2 is used for simulating the evolution of our system on the Louhi supercomputer in the CSC computing centre in Finland. The simulation is the highest resolution supercluster evolution simulation carried out so far and contains more particles both for the observable matter (gas) and dark matter than any other supercluster formation simulation. Possible constraint construction techniques are presented for creating cosmologically correct initial conditions for supercluster formation.

Arman Shafieloo

(Inst. for the Early Universe/ APCTP)

"Cosmographic Degeneracy"

We examine the dark energy and matter densities allowed by precision measurements of distances out to various redshifts, in the presence of spatial curvature and (near) arbitrary behavior of the dark energy equation of state. Degeneracies among the parameters permit a remarkably large variation in their values when using only distance measurements of the late time universe and making no assumptions about the dark energy or curvature. Going beyond distance measurements to a lower limit on the growth of structure bounds the allowed region significantly but still leaves considerable freedom to match a flat LCDM model with dark energy very different from a cosmological constant. The combination of distances with Hubble parameter, gravitational lensing or other large scale structure data is essential to determining robustly the cosmological model.

Owain Snaith

(Observatoire de Paris-Meudon)

"Formation and structure of a simulated polar disc galaxy"

Polar disc galaxies are extreme objects, and so provide a useful test of current theories of galaxy formation. We present an analysis of the formation processes and properties of the simulated poplar disc galaxy first presented in Brook et al. (2008). Polar disc galaxies are characterized by two orthogonal stellar discs. We study the shape of the dark matter halo and relate this property to the observable line-of-sight velocity of the two discs. This provides an effective test the robustness of using polar disc galaxies to identify the properties of the inner regions of dark matter halos. By using a SPH simulation we follow the polar disc galaxy through time and explore the different events experienced by the galaxy during its formation. We identify the key processes which give rise to the polar disc structure. This analysis confirms that the polar disc structure forms due to a major merger misaligning the old stars, followed by a resumption of gas infall. I would also like to present a Poster on the following: Poster title: Cold Gas Accretion onto Galaxy Discs Recent research has found that a significant fraction of galaxy gas is accreted from cold flows rather than spherical inflow. We present preliminary work, using toy models, of the characteristic effects of cold accretion on the properties of galaxies. We compare the effect of cold accretion on the heating of the galaxy disc with the effect of minor mergers. The angle and rate of infall of the cold gas has been varied, and the effect of this on the properties of the galaxy disc is presented.

 Yong-Seon Song

(Korea Astronomy and Space Science Institute)

"Unplugged determination of expansion history of the universe using redshift distortions."

The observed spectra in redshift space include a mixture of information: fluctuations of density--density and velocity--velocity spectra, and distance measures of perpendicular and parallel components to the line of sight. Unfortunately it is hard to measure all the components simultaneously without any specific prior assumption. Common prior assumptions include a linear/quasi-linear model of redshift distortions or a model for the shape of the power spectra, which eventually breaks down on small scales at later epochs where nonlinear structure formation disturbs coherent growth. The degeneracy breaking between the effect of cosmic distances and redshift distortions for example depends on the prior we assume. An incorrect model for various nonlinear effects will likely bias the measurements of dark energy as well as the estimated effect of the velocity fields. As an alternative approach is to utilize the cosmological principle inscribed in the heart of the Friedman universe (hereafter, FRW prior), that is, the specific relation between the angular diameter distance and the Hubble parameter, in this degeneracy breaking. While baryon acousic oscillations is a robust feature that enables us to distinguish the effect of cosmic distances from the effect of redshift distortions, the additional nonlinear damping of the BAO feature along the line of sight direction weakens the precision in the Hubble parameter. We show that utilizing this FRW prior early in the step of distinguishing the distance effect from redshift distortions help us improve the detectability of power spectra and distance measures with no leaning on combination of other experiments.

Curtis Struck

(Iowa State University)

"Some Secular Drivers of Galaxy Evolution"

The chief drivers of galaxy evolution are currently believed to be mergers and cold accretion. I will describe the work of my group and others on the roles of several other processes in disk galaxy evolution, whose actions occur on relatively long time scales. These include the effects of: fall-back from long tidal tails, weak tidal spirals in high Toomre Q disks, and of waves induced by ram pressure compression of a disk. The first of these is similar to cold accretion, and may teach us about how that process works at high redshift. The second teaches us about the effects of weak or fast tidal encounters, and the last has hardly begun to be studied.

Yasushi Suto

(The Univ. of Tokyo)

"Detection of Far Infrared Emission from SDSS Galaxies in the SFD Galactic Extinction Map"

We have performed stacking image analyses of galaxies over the Galactic extinction map constructed by Schlegel, Finkbeiner & Davis (1998). We select  10 million galaxies from the Sloan Digital Sky Survey (SDSS) DR7 photometric catalog. We detect clear signatures of the enhancement of the extinction in r-band around galaxies, indicating that the extinction map is contaminated by their FIR (far infrared) emission.
The average amplitude of the contamination per galaxy is on the order of milli-magnitude. Although it is very small, it is directly associated with galaxies and may have a systematic effect on galaxy statistics. Indeed this correlated contamination leads to a relatively large anomaly of galaxy surface number densities against the SFD extinction discovered by Yahata et al. (2007).
We model the radial profiles of stacked galaxy images, and find that the FIR signal around each galaxy does not originate from the central galaxy alone, but is dominated by the contributions of nearby galaxies via galaxy angular clustering. The separation of the single galaxy and the clustering terms enables us to infer the statistical relation of the FIR and r-band fluxes of galaxies and also to probe the flux-weighted cross-correlation of galaxies, down to the magnitudes that are difficult to probe directly for individual objects. We repeat the same stacking analysis for SDSS DR6 photometric quasars and discovered the similar signatures but with a weaker amplitude.

István Szapudi

(Institute for Astronomy, Univ. of Hawaii)

"Cross-correlation of WMAP7 and the WISE Full Data Release"

We measured the cross-correlation of the Wilkinson Microwave Anisotropy Probe (WMAP) 7 year temperature map and the full sky release of the Wide-field Infrared Survey Explorer (WISE) galaxy map. Using careful mapmaking and masking techniques we find a positive cross-correlation signal with ∼1.0σ significance. The results are fully consistent with a ΛCDM Universe, although not statistically significant. Our findings are robust against changing the galactic latitude cut from |b| > 10 to |b| > 20 and no color dependence was detected when we used WMAP Q, V or W maps. I appears that the best explanation is cosmic variance for the lower significance compared to the Preliminary Data Release analysis.

Takayuki Tamura

(Institute of Space and Astronautical Science, JAXA)

"X-ray study of Gas Dynamics in Galaxy Clusters"

X-ray studies of velocity structures of the intracluster medium is one of the primary goals for future X-ray missions. High resolution spectroscopies will provide measurements of energy distributions not only in thermal but also in kinematic forms. We have detected a motion of a sub component with a velocity of about 1500 km/s for the first time by X-ray based on the Suzaku observations of a X-ray bright merging cluster, Abell2256 (Tamura et al. 2011, PASJ, 63, S1009). Prospect for future spectroscopy focusing on the ASTRO-H performance will also be introduced.

Atsushi Taruya

(Research Center for the Early Universe,

The Univ. of Tokyo)

"Precision calculations for cosmological power spectrum in real and redshift spaces"

We summarize our recent development of precision calculation of cosmological power spectra in weakly nonlinear regime. In particular, we present a specific prescription based on the multipoint propagator expansion, and develop an algorithm that allows us to accelerate the power spectrum calculation. We show that newly developed prescription, with a help of regularized treatment of the propagators, gives robust and accurate predictions which agree with N-body simulations at percent level in the weakly nonlinear regime. The prescription is also applied to the calculation of redshift-space power spectrum, and a good agreement with N-body simulations is found.

Sanil Unnikrishnan

(IISER, Trivandrum)

"Improving inflation using non-canonical scalar fields"

We discuss inflation driven by non canonical scalar fields. Our results emphasize the fact that non-canonical scalars can significantly improve the viability of inflationary models. They accomplish this by decreasing the tensor-to-scalar ratio while simultaneously increasing the value of the scalar spectral index, thereby redeeming models which are incompatible with the cosmic microwave background (CMB) in their canonical version. For instance, the non-canonical version of the chaotic inflationary model with a quartic potential is found to agree with observations for values of the coupling constant as large as unity !  The exponential potential can also provide a reasonable fit to CMB observations. A central result of this study is that steep potentials (such as inverse power law potentials) usually associated with dark energy, can drive inflation in the non-canonical setting. This could open up the possibility of constructing quintessential inflation models based on non canonical scalars.

reference:

Sanil Unnikrishnan, Varun Sahni & Aleksey Toporensky [arXiv:1205.0786v3]

Yougang Wang

(National Astronomical Observatories, CAS)

"Dynamical model of the Milky Way bar"

I will report our recent studies on the dynamical model of the Milky Way Bar by using Schwarzschild's orbit-superposition method. Our model can fit the BRAVA data well, but the model has some problems on the proper motion and the stability.

Melody Wolk

(Institut d’Astrophysique de Paris)

"Hierarchical amplitudes in the CFHTLS Wide survey: evolution since z~1"

I will present the most accurate measurements to date of the higher order moments of the galaxy distribution at intermediate redshift (0.2<z<1.0) using the four fields of the CFHTLS Wide. In order to better understand these results, I extend the analytic "halo model" to make predictions of the high order galaxy clustering. I will show that using a simple HOD model fitted on the two point correlation function, we are able to successfully reproduce the amplitude and the main features of higher-order moments including their dependence on angular scale and redshift. I will discuss these results in the context of galaxy formation and evolution.

Jaswant K. Yadav

(National Astronomical Observatories, CAS)

"H I  as a probe of LSS in post reionization universe"

I will present a model to describe the large-scale distribution of neutral hydrogen (H I) in the post-reionization universe in a hierarchical model of galaxy formation. The model is implemented in the form of semi-analytic prescriptions describing various physical processes on top of gravity only N-body simulations. The model is calibrated with observations of the Tully-Fisher relation, and of the Milky Way, at z=0. We find that our prediction for the H I density parameter is in good agreement with observations in the local universe. We predict a peak value of this parameter to be about 10^-3 at around z = 5. In our model, the H I  distribution is strongly biased at high  redshift. This enhances the H I  power spectrum as compared to the dark matter power spectrum. The enhanced H I power spectrum predicts better prospects for a detection using instruments like the GMRT and MWA.

Kazuhiro Yamamoto

(Hiroshima University)

"Testing modified gravity model with cluster of galaxies"

We investigate theoretical predictions of modified gravity models proposed to explain the accelerated expansion of the universe, focusing on the scales of cluster of galaxies. Observational constraints will also be discussed by confronting with X-ray observations of clusters of galaxies.

Xiaohu Yang

(Shanghai Astronomical Observatory)

"Mapping the star formation histories of the Universe"

Based on a self consistent modeling of the conditional stellar mass functions across the cosmic time carried out by Yang et al. (2012), we made reliable model predictions of the star formation histories (SFHs) of the central galaxies in halos of different masses. In establishing these SFHs, two key ingredients are needed: (i) the mass assembly histories of the central galaxies as well as the accreted and survived satellite galaxies; and (ii) the local observational constraints of the star formation rate for central galaxies in different mass halos. Upon these SFHs, a universal fitting formula, which is directly applicable to the dark matter halos of different cosmologies or the galaxies in observations, is provided. This SFH formula allows us to make various useful predictions regarding the galaxy formations: (1) the star formation rate (SFR) map, stellar mass density (SMD) map, star formation efficiency (SFE) map, the specific star formation rate (SSFR) map, etc., (2) the cosmic star formation rate density, and (3) the fraction of in situ formed stars in central galaxies across the cosmic time, etc.

Jaiyul Yoo

(University of Zürich)

"Going beyond the Kaiser Redshift-Space Distortion Formula"

Kaiser redshift-space distortion formula describes well the clustering of galaxies in redshift surveys on small scales, but there are numerous additional terms that arise on large scales. Some of these terms can be described using Newtonian dynamics and have been discussed in the literature, while the others require proper general relativistic description that was only recently developed. Accounting for these terms in galaxy clustering is the first step toward tests of general relativity on horizon scales. The effects can be classified as two terms that represent the velocity and the gravitational potential contributions. Their amplitude is determined by effects such as the volume and luminosity distance fluctuation effects and the time evolution of galaxy number density and Hubble parameter. We compare the Newtonian approximation often used in the redshift-space distortion literature to the fully general relativistic equation, and show that Newtonian approximation accounts for most of the terms contributing to velocity effect. We perform a Fisher matrix analysis of detectability of these terms and show that in a single tracer survey they are completely undetectable. To detect these terms one must resort to the recently developed methods to reduce sampling variance and shot noise. We show that in an all-sky galaxy redshift survey at low redshift the velocity term can be measured at a few sigma if one can utilize halos of mass M>10^12 Msun (this can increase to 10-sigma or more in some more optimistic scenarios), while the gravitational potential term itself can only be marginally detected. We also demonstrate that the general relativistic effect is not degenerate with the primordial non-Gaussian signature in galaxy bias, and the ability to detect primordial non-Gaussianity is little compromised.

Posters

Ali Banijamali

(Babol univ. of technology)

"Bouncing Cosmology with Tachyon and Non-minimal Derivative Coupling"

The bouncing cosmology provides a successful solution of the cosmological singularity problem. In this paper, we study the bouncing behavior of a single scalar field model with tachyon field non-minimally coupled to itself, its derivative and to the curvature. By utilizing the numerical calculations we will show that the bouncing solution can appear in the universe dominated by such a quintom matter with equation of state crossing the phantom divide line. We also investigate the classical stability of our model using the phase velocity of the homogeneous perturbations of the tachyon scalar field.

Jungyeon Cho

(Chungnam National Univ.)

"Turbulence and Magnetic Field in the Large-scale Structure of the Universe"

Turbulence is believed to play important roles in the origin of cosmic magnetism, which may split into two parts - the origin of seed magnetic fields and their amplification. Here I will focus on the second part. First, I will consider growth of uniform seed magnetic fields in turbulence. Second, I will consider growth of localized seed magnetic fields in turbulence. Our results shows that, regardless of the shape of the seed fields, fast magnetization is possible in turbulent systems, such as large-scale structure of the universe or galaxies.

Behnaz Fazlpour

(Babol univ. of technology)

"Tachyonic Teleparallel Dark Energy"

Teleparallel gravity is an equivalent formulation of general relativity in which instead of the Ricci scalar $R$, one uses the torsion scalar $T$ for the Lagrangian density. Recently teleparallel dark energy has been proposed. In the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. We find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. Using the numerical calculations we display such a behavior of the model explicitly.

Sungwook E. Hong

(Chungnam Nat'l University)

"Structure Formation and Cosmological Accretion Shocks in Clusters of Galaxies"

Authors: Sungwook E. Hong, Dongsu Ryu (Chungnam National University) & Hyesung Kang (Pusan National University)

During the structure formation process, cosmological shock waves are formed in and around the clusters of galaxies. Using numerical simulations for large-scale structure formation, we simulated the cosmological shocks and studied their properties. We showed the accretion shocks, which are formed around ~r_200 by warm gas flowing through the filament into the cluster center, may be strong sources the cosmic ray population.

Naseer Iqbal

(University of Kashmir)

"Correlations functions and Galaxy Clusters in an expanding Universe"

We inquire the phenomena of clustering of galaxies in an expanding universe from a theoretical point of view on the basis of thermodynamics and correlation functions. The partial differential equation is developed both for the point mass and extended mass structures of a two-point correlation function by using thermodynamic equations in combination with the equation of state taking gravitational interaction between particles into consideration. The unique solution physically satisfies a set of boundary conditions for correlated systems and provides a new insight into the gravitational clustering problem.

Sungeun Kim

(Sejong University)

"Structure Determination of the Interstellar Medium and Its Implications for Understanding the Large-Scale Structure of the Universe."

We review the current tools of determining structures that underlie in the interstellar medium (ISM) in our Galaxy and in the external galaxies. The tools in the present review include cloud detection algorithms with temperature threshold, clump finding algorithms, the kernel principal component analysis (PCA), the spectral correlation function, the power spectrum analysis, and complex analysis. We summarize the different outcomes of the diverse tools of determining structures in the ISM and the prospects for analyzing the large-scale structures present in the universe.

Young-Lo Kim

(Yonsei University)

"The Luminosity of Type Ia Supernova as a Function of Host-Galaxy Morphology"

Authors: Young-Lo Kim, Yijung Kang, Dongwook Lim, and Young-Wook Lee

(Center for Galaxy Evolution Research & Department of Astronomy, Yonsei University)

We have employed SNANA supernova analysis package to make YONSEI Supernova Catalogue 1, which contains distance modulus, light-curve shape parameters, and color or extinction values of each supernova. The redshift range of the catalogue is 0.010 < z < 1.555, and we use three light-curve fitters: SALT2, MLCS2k2 (R_v = 3.1), and MLCS2k2 (R_v = 1.7). This database is used to study the dependence of Type Ia supernovae (SNe Ia) luminosities on the host-galaxy morphologies. We find a systematic difference in the Hubble residual (HR) of 0.12 ± 0.033 mag between E-S0 and Scd/Sd/Irr host-galaxies, and of 0.15 ± 0.058 mag between passive and star-burst host-galaxies. This difference is significant over the 3σ level. Considering the significant difference in the mean age of stellar population between these morphological types, the difference in the HR reported here suggests that the evolution effect of SNe Ia luminosity should be considered in the cosmological application of SNe Ia data.

Anthony Moraghan

(Yonsei University)

"Simulating SZ intensity maps of giant AGN cocoons"

We perform relativistic hydrodynamic simulations of the formation and evolution of active galactic nucleus (AGN) cocoons produced by very light powerful jets. We calculate the intensity maps of the Sunyaev-Zel&quot;dovich (SZ) effect at high frequencies for the simulated AGN cocoons using the relativistically correct Wright formalism. Our fully relativistic calculations demonstrate that the contribution from the high-temperature gas (kbTe &#8771; 100 keV) to the SZ signal from AGN cocoons at high frequencies is stronger than that from the shocked ambient intercluster medium owing to the fact that the relativistic spectral functions peak at these temperature values. We present simulations of the SZ effect from AGN cocoons at various frequencies, and demonstrate that SZ observations at 217 GHz and at higher frequencies, such as 857 GHz, will provide us with knowledge about the dynamically dominant component of AGN cocoons.

Jihye Shin

(Kyung Hee University)

"Properties of the mini-halos in dwarf ellipticals obtained from cosmological hydrodynamic simulations"

We have performed cosmological hydrodynamic simulations that include the effects of radiative heating/cooling, star formation, feedback by supernova explosions, and metallicity evolution. Our simulations cover a cubic box of a side length 4 Mpc/h with 130 million particles. The mass of each particle is 3.4 x 104 Msun, thus sub-galactic mini-halos can be resolved with more than hundred particles. Our simulation follows the whole formation process of the mini-halos (M<10^7 Msun) around dwarf galaxies. We discuss various properties of the mini halos such as mass function, specific frequency, baryon-to-dark matter ratio, metallicity, spatial distribution, and orbit eccentricity distribution as functions of redshift and host galaxy mass. We also discuss how the formation and evolution of the mini halos are affected by the epoch of the reionization.

Owain Snaith

(Observatoire de Paris-Meudon)

"Cold Gas Accretion onto Galaxy Discs"

Recent research has found that a significant fraction of galaxy gas is accreted from cold flows rather than spherical inflow. We present preliminary work, using toy models, of the characteristic effects of cold accretion on the properties of galaxies. We compare the effect of cold accretion on the heating of the galaxy disc with the effect of minor mergers. The angle and rate of infall of the cold gas has been varied, and the effect of this on the properties of the galaxy disc is presented.

Curtis Struck

(Iowa State University)

"Observations and Models of Interacting Galaxies: Creating Beads, Rings, Hinges, and Dwarfs"

Authors: Curtis Struck (Iowa State), Beverly J. Smith (ETSU), Mark L. Giroux (ETSU), and Ryen Lapham (New Mexico Tech)

Interacting galaxies exhibit a wide variety of exotic star forming environments that typically are not seen in isolated galaxies. We use both analytical models and numerical simulations to understand these structures, comparing with multi-wavelength images for a set of nearby strongly interacting galaxies.