2011.4 ~ 2012.3
The astrophysics and cosmology group of Korea Institute for Advanced Study consists of prof. Changbom Park, research prof. Juhan Kim, two assistant professors, and four research fellows. Prof. Park is leading the Korean Scientist Group participating in the Sloan Digital Sky Survey III that will continue through 2014. Prof. Park works as the director of the new KIAS computer center, Center for Advanced Computation (KIAS CAC). He is also engaged in preparation of the KIAS trans-disciplinary research program that will start in 2012. He is working as the Editor-in-Chief of Journal of the Korean Astronomical Society, which has a history of 44 years. He created and is leading a group of astronomers, the Survey Science Group, who gather together to study and plan the future major astronomical survey projects. The group held five workshops in 2011.
Individual members of the astrophysics and cosmology group have been active in his/her research in 2010-2011. Assistant Prof. Maurice H.P.M. van Putten is working on gravitational-wave physics and globular clusters, and is a member of the Large Cryogentic Gravitational-wave Telescrope (LCGT). He published joint work with the LCGT on a new detection algorithm for long bursts in gravitational waves and developed electromagnetic priors from core-collapse supernovae with Prof. M. Della Valle of the Observatory of Capodimonte, Naples, Italy. He recently published a proposed observational tests to relaxation-limited evaporation for the LSST and BigBOSS, and is now pursuing follow-up numerical simulations with Prof. Henk van Beijeren of the University of Utrecht.
Prof. Park and Research Prof. Juhan Kim made two large cosmological simulations called Horizon Run 2 and 3. Those simulations were run on a supercomputer at KISTI using 8000 cpu cores and 15 TBytes of memory. Various analyses are being done on the linux clusters of KIAS CAC. The simulations are used for various projects. For example, they are used to simulate the SDSS surveys of the luminous red galaxies to constrain the LCDM cosmological model and primordial non-Gaussianity, and to accurately estimate the non-linear systematic effects on the genus topology of large-scale structure in the universe.
Assistant Prof. Yong-Seon Song completed a test of General Relativity (GR) using CHFTLS and SDSS DR7 datasets. He showed that GR is trustable at certain level of precision, and that there is no clear evidence that cosmic acceleration is caused by Modified Gravity. In addition to this activity, he found new technique to measure the history of Hubble expansion using redshift distortions. In near future, we are able to probe it within a couple of precision with fourth generation of wide deep survey.
Dr. Graziano Rossi has been pursuing research in non-Gaussian signatures from the CMB and the LSS. Recently, he has derived new formulae for the constrained eigenvalues of the initial shear field associated with Gaussian statistics, which include the fact that those eigenvalues are related to density peak regions - extending the pioneer study of Doroshkevich (1970). Together with Prof. Park, he is currently working on the topology of the cosmic web, including applications to the BOSS survey.
Dr. Jeong-Sun Hwang has investigated the question of the duration of induced spirals by performing numerical simulations on fast flyby galaxy collisions. She has also constructed numerical models of the interactions in the compact galaxy group, Stephan's Quintet. Specifically, she has modeled the formation of the hot X-ray gas, the large-scale shock, and emission line gas as the result of a member galaxy colliding with the group. She is currently working with Prof. Park on hydrodynamic impacts in interacting galaxies.
Dr. Seong-Kook Lee has generated model galaxy catalogs at redshifts z=0.1 and z=1, using semi-analytic models of galaxy formation. Using these model galaxy catalogs, he has investigated the uncertainties and systematic biases in spectral fitting anaysis of z=0.1 galaxies (analogous to SDSS galaxies) as well as in photometric SED-fitting analysis at z=1 galaxies (analogous to GOODS survey galaxies). He has also studied environmental effects on the early-type galaxy properties, such as their size.
Prof. Park is collaborating with a guest scientist Dr. Young-Rae Kim to investigate the effects of non-linear systematics on the large scale structure topology. The accurate measurement of these effects is essential for constraining cosmology using topology. Using the Horizon Run 2 simulation, the systematic effects such as pixel effects, shot noise effects, redshift-space distortion effects, effects of halo biasing and non-linear gravitational evolution are being separated.