ABSTRACTS

 

  Oct. 27

Chung Wook Kim,  Neutrino Properties from Cosmology

It is truly remarkable that we should have come so far in determining, from the passive collection of a small fraction of the photons that chance to come our way, the properties of neutrinos better than nuclear/particle physics has ever attempted in many decades. (Charles Bennett in Nature in 2006) After a brief review of the roles that neutrinos have played in the cosmic evolution, a summary of the current status on the neutrino mass limits and the effective number of neutrino flavors, based on WMAP 5-year data and others such as BAO and SN is presented.  

 

Matthew Colless, The WiggleZ Dark Energy Survey

The WiggleZ survey aims to measure the dark energy equation of state parameter w(z) in the redshift range z=0.5-1.0. The survey is using the Anglo-Australian Telescope to obtain redshifts for about 140,000 galaxies in this range, selected from UV and optical imaging over 1000 square degrees. The survey has now reached the halfway point, and I will show initial results on both the small-scale clustering and the large-scale power spectrum. Detailed forecasts indicate the survey will measure the baryon acoustic oscillation scale to better than 2% and the tangential and radial acoustic wavescales to approximately 3% and 5%. Combining the WiggleZ constraints with the 5-year WMAP measurement of the CMB shift parameter and the latest supernova data from the ESSENCE, SNLS and HST projects, the marginalized uncertainties in the cosmological model are expected to be σ(Ωm) = 0.02 and σ(w) = 0.07. The WiggleZ measurement of w constitutes a robust and precise test of the dark energy model.  Authors: Matthew Colless and the WiggleZ team  

 

Pyungwon Ko, Dark Matter Search at LHC

I review various dark matter candidates in particle physics models, and how to discover some of them at the Large Hadron Collider (LHC) at CERN.

 

   Masahiro Takada, The impact of finite-mass neutrinos on nonlinear matter power spectrum

Various laboratory experiments have shown strong evidence that neutrinos have finite mass. Such neutrinos suppress the growth in mass clustering by free- streaming out of the gravitational potential well, imprinting characteristic signatures onto large-scale structures. In this talk I will discuss how the finite-mass neutrinos affect the mass clustering in nonlinear regime, and show the application of the theoretical model to the existing data sets to obtain an upper limit on the total neutrino mass.

  

Yong-Yeon Keum, Neutrino Masses in LCDM vs Interacting Neutrino Dark-Energy Model    

We investigate whether interaction between massive neutrinos and quintessence scalar field is the origin of the late time accelerated expansion of the universe. We present explicit formulas of the cosmological linear perturbation theory in the neutrinos probes of dark-energy model, and calculate cosmic microwave background anisotropies and matter power spectra. In these models, the evolution of the mass of neutrinos is determined by the quintessence scalar field, which is responsible for a varying effective equation of states; ωeff(z) goes down lesser than -1. We consider several types of scalar field potential and put constraints on the coupling parameter between neutrinos and dark energy. By combining data from cosmic microwave background (CMB) experiments including the WMAP 3 or 5-year results, large scale structure with 2dFGRS data sets, we constrain the hypothesis of massive neutrinos in the mass-varying neutrino scenario. Assuming the flatness of the universe, the constraint we can derive from the current observation is ∑mν < 0.45 eV at 1σ (0.87 eV at 2σ) confidence level for the sum over three species of neutrinos. The dynamics of scalar field and the impact of scalar field perturbations on cosmic microwave background anisotropies are discussed. We also discuss on the instability issue and confirm that neutrinos are stable against the density fluctuation in our model.

 

Pengjie Zhang, Peculiar velocity: a window to the dark universe

Large scale peculiar velocity is an unique probe of the dark universe, since it directly responds to gravity of dark matter and clustering dark energy. In this talk, I will present powerful applications of peculiar velocity to probe dark matter, dark energy and the nature of gravity at cosmological scales. I will also discuss new methods of precision peculiar velocity measurement.

 

Yoshiaki Taniguchi, Dynamical Properties of Forming Galaxies at Redshift z>5

 

Myungshin Im, Supermassive Black Holes of Quasars at the World ..

Quasars at high redshifts are now identified out to z ~ 6.4, or about 1 Gyr after the Big Bang. However, our understanding of high redshift quasars has been limited by the lack of the rest-frame optical spectra where one can find the popular key diagnostics to derive quasar properties such as masses of supermassive black holes (SMBHs). In this talk, we present the rest-frame optical spectra of high redshift quasars taken with AKARI IR space telescope. Taking advantage of the AKARI&quot;s unique spectroscopic capability at 2-5 micron, we observed 14 quasras at 4.5 < z < 6.5, revealing for the firt time, the redshifted H-alpha emission lines of quasars at 4.5 < z < 6.5. We will present our data and discuss the implication of our results on the growth of the SMBH mass. We will also present our ongoing effort to extend this kind of study. Authors: M. Im, H. M. Lee, M. G. Lee, I. Lee, M. Kim (SNU), Y. Ohymama, X. T. Wada, T. Nakagawa (ISAS/JAXA), X. Fan (Univ. of Arizona)

 

     Ranga-Ram Chary, The First Billion Years of Galaxy Evolution

 

 Changbom Park, Spatial and Temporal Environmental Effects on Galaxy Properties

We inspect the dependence of galaxy properties on the small-scale (distance and morphology of the nearest neighbor galaxy) and the large-scale (background density smoothed over 20 nearby galaxies or clustercetric radius) environmental factors. The dependences are studied in the general and massive cluster environments and also in the high redshift universe. We find two characteristic neighbor-separation scales where the galaxy interactions cause abrupt changes in the properties of galaxies. The first scale is the virial radius of the nearest neighbor galaxy r_{vir,nei}, which is typically between 200 and 400 h^{-1} kpc for the galaxies in our sample. The second scale is the scale at which the galaxies in pairs start to merge. In the cluster environment the cluster infall region is found to be the place where the mean morphology and structure parameters of galaxies suddenly change. We find that late-type neighbors enhance the star formation activity of galaxies while early-type neighbors reduce it, and that these effects occur within r_{vir,nei}. The same phenomena are found for galaxies at redshifts between 0.4 and 1.0. In cluster environment we find the galaxy-galaxy interaction does a critical role in determining the galaxy color and star formation activity even well within the cluster virial radius. Our results demonstrate the importance of galaxy-galaxy interactions in building the correlations between the galaxy properties and environment during the past history of the universe.

 

    Hsi-Yu Schive, GPUs-Accelerated Fluid Simulation with Adaptive Mesh Refinement

 Novel use of modern graphic processing units (GPU) for acceleration of numerical calculations is becoming a widely-adopted technique in the past two years. We have implemented a parallel, GPUs-accelerated fluid simulation code with the Adaptive Mesh Refinement (AMR) scheme in a GPU cluster. The physical domain is separated into several levels of different resolutions, where the grids in each level are grouped into patches. To take advantage of the parallel architecture of GPU, hundreds of patches are evaluated in one GPU simultaneously. The entire physical domain is further divided into several sub-domains, for which each sub-domain is handled by one GPU. In the test case, we achieved 10 times speed-up ratio when comparing a single GPU with a single CPU. The parallel efficiency of this AMR code will be discussed in this talk.

 

 

 

   Oct. 28

 

Yasushi Suto, Log-normal fluctuations in intra-cluster medium and their impact on X-ray and SZ cluster observations

Log-normal fluctuations in intra-cluster medium and their impact on X-ray and SZ cluster observations he Hubble constant estimated from the combined analysis of the Sunyaev-Zel&quot;dovich effect and X-ray observations of galaxy clusters is systematically lower than those from other methods by 10-15 percent. We examine the origin of the systematic underestimate using an analytic model of the intracluster medium (ICM), and compare the prediction with idealistic triaxial models and with clusters extracted from cosmological hydrodynamic simulations. We identify three important sources for the systematic errors; density and temperature inhomogeneities in the ICM, departures from isothermality, and asphericity. In particular, the combination of the first two leads to the systematic underestimate of the ICM spectroscopic temperature relative to its emission-weighed one. We find that these three systematics well reproduce both the observed bias and the intrinsic dispersions of the Hubble constant estimated from the Sunyaev-Zeldovich effect.

 

Naoki Yoshida, Formation of primordial stars

The first generation of stars appeared very early in the history of the Universe. These stars are thought to be the first sources of light, and also the first sources of heavy elements such as carbon, oxygen, and iron. The first stars terminate the cosmic Dark Ages, set the scene for later galaxy formation, and ultimately enable the emergence of life. I present the results from recent theoretical studies on the formation of the first stars within the framework of the standard cosmology. These theories predict that tiny density fluctuations left over from the Big Bang drive the formation of cosmic primordial stars when the age of the universe was less than a few million years. I show results from state-of-the-art computer simulations. Our simulations include all the relevant atomic and molecular processes on a first-principle basis. The detailed formation process of a primordial protostar has been revealed for the first time. I discuss the implications of the results. Finally, I will discuss prospects for future observations of the first stars exploiting ground-based and space-borne telescopes.

 

Xuelei Chen, Forecasting the dark energy measurement with LAMOST

 

Takahiko Matsubara, Nonlinear perturbation theory with halo bias and redshift-space distortions via the Lagrangian picture

 

Xiaohu Yang, The halo model and galaxy formation

Galaxies are formed in cold dark matter halos. The central and satellite galaxies are closely related with the host and sub-halos respectively. In this talk I will briefly introduce the halo occupation models and show you how the local observations of the central and satellite components can be used to constrain the evolution of the satellite galaxies, especially the fate of those disrupted satellite galaxies.

 

Rien van de Weygaert, Morphology & Dynamics of the Cosmic Web

The Cosmic Web is one of the most intriguing and intricate spatial patterns in Nature. The product of the gravitational growth of tiny primordial density perturbations, it is a testimony of its key characteristics, the hierarchical buildup of structure, the void-dominated morphology and in particular the anistotropic nature of gravitational collapse. In the presentation we will address the morphological analysis and of the Cosmic Web and the insights that as a resuls we obtained on its dynamics and evolution. In particular we are interested in the intrinsic connection between the large scale tidal field shaping the cosmic web and the orientation and spin of dark halos and galaxies within the web, manifesting itself in intrinsic alignments. Our analysis of the cosmic web involves a toolset stemming from computational geometry and computational topology. The basis of our toolset is the DTFE density field reconstruction (Delaunay Tessellation Field Estimator), a naturally adaptive rendering which optimally reflects the structural characteristics of the Cosmic Web. The Multiscale Morphology Filter (MMF) dissects the cosmic web into its various components, taking into account its multiscale character, while we use the watershed transform of the density field to trace the voids with the Watershed Void Finder (WVF) and to trace its global filamentary and sheetlike outline, the web&quot;s Spine. We will pay special attention to our recent results on galaxy shape and spin alignments with respect to the filaments in the SDSS, and to the correlation between void alignments and the large scale tidal fields.

 

Luic C. Ho, The Coevolution of Black Holes and Galaxies

I will review observational progress in defining and refining the various empirical scaling relations between black hole masses and host galaxy properties.  I will emphasize ways in which the intrinsic scatter can be quantified, and whether the scatter correlates with physical properties.  I will discuss how to extend the scaling relations to active galaxies, and summarize preliminary efforts to probe the evolution of these scaling relations.  I will summarize recent detections of neutral hydrogen in AGNs and constraints they place on models of AGN feedback.

 

Michael Vogeley, Cosmic Voids and Void Galaxies

Wide-angle, moderately deep redshift surveys such as that conducted as part of the Sloan Digital Sky Survey (SDSS) allow study of the relationship between the structural elements of the large-scale distribution of galaxies - including groups, cluster, superclusters, and voids - and the dependence of galaxy formation and evolution on these environments. In this talk I will focus on the identification of voids as dynamically distinct large-scale structures and examine their properties. Then I will discuss the properties of galaxies in voids, from normal galaxies to merging galaxies and active galactic nuclei.

 

Myung Gyoon Lee, Galaxy Interaction and Star Clusters

Myung Gyoon Lee Astronomy Program, Department of Physics and Astronomy Seoul National University mglee@astro.snu.ac.kr Galaxy interaction may lead to morphological transformation of galaxies, and to formation of stars, star clusters, and dwarf galaxies. Galxy interaction started with the first generation of galaxies and still continues today. However it is not easy to derive any quantitative information on the stages of galaxy interaction. Star clusters are a powerful tool to investigate the dynamical history of galaxy interaction, because they are bright and age-datable. We highlight some recent findings of galaxy interaction based on the studies of star clusters in nearby interacting galaxies.

 

Sukyoung K. Yi, Satellite Overquenching Problem

We investigate the correlation of star formation quenching with internal galaxy properties and large scale environment (halo mass) in empirical data and theoretical models. We make use of the halo-based Group Catalog of Yang and collaborators, which is based on the Sloan Digital Sky Survey. Data from theGalaxy Evolution Explorer (GALEX) are also used to extract the recent star formation rate. In order to investigate the environmental effects, we examine the properties of ``central and ``satellite galaxies separately. For central galaxies,we find that the fractions of `` red and ``passive galaxies in the observational group catalogs are a strong function of halo mass at fixed stellar mass, and a weak function of stellar mass at fixed halo mass. For satellite galaxies, a nearly equally strong dependence on halo mass and stellar mass is seen. We make the same comparison for five different semi-analytic models based on three independently developed codes. We find that the models with AGN feedback reproduce reasonably well the dependence of the fraction of central red and passive galaxies on halo mass and stellar mass. However, for satellite galaxies, the same models badly overproduce the fraction of red/passive galaxies and do not reproduce the empirical trends with stellar mass or halo mass. This satellite overquenching problem is ubiquitous in semi-analytic models and poses another serious challenge to modelers.

 

Sungeun Kim, Maps and Results from the JCMT AzTEC 1.1 mm Surveys

We present results of AzTEC observations at the 15m James Clerk Maxwell Telescope (JCMT). AzTEC is a new large-format array composed of 144 silicon-nitride micromesh bolometers developed for a facility instrument on the Large Millimeter Telescope at the University of Massachusetts in collaboration with researchers at Caltech, Cardiff, INAOE, Sejong University, and Smith College. Here we report performance of the instrument, mapping technique, and results from blank-field continuum surveys at 1.1 mm.