YZiCS: Preprocessing of Dark Halos in the Hydrodynamic Zoom-in Simulation of Clusters

Authors: Han, San; Smith, Rory; Choi, Hoseung; Cortese, Luca; Catinella, Barbara; Contini, Emanuele; Yi, Sukyoung K.

Publication: The Astrophysical Journal, 2018 October

Introduction (Kor): 은하단 확대 시뮬레이션 YZiCS를 이용한 암흑 헤일로의 전처리 및 질량 손실에 관한 연구

Introduction (Eng): To understand the galaxy population in clusters today, we should also consider the impact of previous environments prior to cluster infall, namely preprocessing. We use the Yonsei Zoom-in Cluster Simulation, a hydrodynamic high-resolution zoom-in simulation of 15 clusters, and focus on the tidal stripping suffered by the dark matter halos of cluster members due to preprocessing. We find that ∼48% of today’s cluster members were once satellites of other hosts. This is slightly higher than previous estimates, in part because we consider not just group-mass hosts but hosts of all masses. Thus, we find that the preprocessed fraction is poorly correlated with cluster mass and is instead related to each cluster’s recent mass growth rate. Hosts less massive than groups are significant contributors, providing more than one-third of the total preprocessed fraction. We find that halo mass loss is a clear function of the time spent in hosts. However, two factors can increase the mass-loss rate considerably: the mass ratio of a satellite to its host and the cosmological epoch when the satellite was hosted. The latter means we may have previously underestimated the role of high-redshift groups. From a sample of heavily tidally stripped members in clusters today, nearly three-quarters were previously in a host. Thus, visibly disturbed cluster members are more likely to have experienced preprocessing. Being hosted before cluster infall enables cluster members to experience tidal stripping for extended durations compared to direct cluster infall and at earlier epochs when hosts were more destructive.



Assembling the Milky Way Bulge from Globular Clusters: Evidence from the Double Red Clump

Authors: Young-Wook Lee, Seungsoo Hong, Dongwook Lim, Chul Chung, Sohee Jang, Jenny, J. Kim, and Seok-Joo Joo

Publication: The Astrophysical Journal Letters, 862, L8, 2018 July

Introduction (Kor): Double red clump 연구를 통한 우리은하 Bulge 형성 기원 연구

Introduction (Eng): Two red clumps (RCs) observed in the color–magnitude diagram of the Milky Way bulge are widely accepted as evidence for an X-shaped structure that originated from the bar instability. A drastically different interpretation has been suggested, however, based on the He-enhanced multiple stellar population phenomenon as is observed in globular clusters (GCs). Because these two scenarios imply very different pictures of the formation of the bulge and elliptical galaxies, understanding the origin of the double RC is of crucial importance. Here we report our discovery that the stars in the two RCs show a significant (>5.3σ) difference in CN-band strength, in stark contrast to that expected in the X-shaped bulge scenario. The difference in CN abundance and the population ratio between the two RCs are comparable to those observed in GCs between the first- and later-generation stars. Because CN-strong stars trace a population with enhanced N, Na, and He abundances that originated in GCs, this is direct evidence that the double RC is due to the multiple population phenomenon, and that a significant population of stars in the Milky Way bulge were assembled from disrupted proto-GCs. Our result also calls for the major revision of the 3D structure of the Milky Way bulge, given that the current view is based on the previous interpretation of the double RC phenomenon.



Evidence for the existence of abundant intracluster light at z= 1.24

Authors : Jongwan Ko and M. James Jee

Publication: Astrophysical Journal, 2018 August

Introduction (Kor) : 가장 먼 은하단에서의 ICL 검출을 통해 그 기원을 연구

Introduction (Eng) : Intracluster stars are believed to be unbound from their progenitor galaxies and diffused throughout the galaxy cluster, creating intracluster light (ICL). However, when and how these stars form are still in debate. To directly constrain the origin, one powerful method is to study clusters at the epoch when mature galaxy clusters began to appear. We report measurements of the spatial distribution, color, and quantity of diffuse intracluster stars for a massive galaxy cluster at a redshift of 1.24. This is the most distant galaxy cluster to date for which those three properties of the ICL have been quantified simultaneously. Our detection of the significant ICL fraction in this unprecedentedly high redshift regime strongly indicates that intracluster stars, contrary to most previous studies, might have formed during a short period and early in the history of the Virgo-like massive cluster formation and might be concurrent with the formation of the brightest cluster galaxy.




Authors : Hoseung Choi, Sukyoung K. Yi, Yohan Dubois, Taysun Kimm, Julien. E. G. Devriendt, and Christophe Pichon

Publication: Astrophysical Journal, 2018 April

Introduction (Kor) : Horizon-AGN 시뮬레이션을 활용한 타원은하 회전의 환경 영향에 대한 연구

Introduction (Eng) : The diversity in the ETG spin has drawn much attention for the last decade. We analyzed the Horizon-AGN simulation, a cosmological galaxy formation simulation of 100Mpc/h cube, to investigate the differences in the evolution of ETGs with different spin properties. We found that massive central ETGs form through numerous mergers and are preferentially very slowly rotating. However, group and cluster satellite ETGs, which are multiple times more numerous than the massive central ETGs, show slow rotation not because of mergers but because of environmental tidal interactions such as fly-bys or tidal force of the cluster potential. This differential evolutionary track may appear as distinct features in spin versus stellar mass plot, for example.



MC2: Subaru and Hubble Space Telescope Weak-lensing Analysis of the Double Radio Relic Galaxy Cluster PLCK G287.0+32.9

Authors : Kyle Finner, M. James Jee, Nathan Golovich, David Wittman, William Dawson, Daniel Gruen, Anton M. Koekemoer, Brian C. Lemaux, and Stella Seitz

Publication: Astrophysical Journal, 2017 December

Introduction (Kor) : 허블 우주망원경과 수바루 망원경을 이용하여 하늘에서 두번째로 SZ 효과가 큰 PLCK G287.0+32.9 은하단의 암흑물질 연구

Introduction (Eng) : The second most significant detection of the Planck Sunyaev−Zel'dovich survey, PLCK G287.0+32.9 (z = 0.385), boasts two similarly bright radio relics and a radio halo. A key missing puzzle for the merging scenario reconstruction is the underlying dark matter distribution in high resolution. We present a joint Subaru Telescope and Hubble Space Telescope weak-lensing analysis of the cluster. Our analysis shows that the mass distribution features four significant substructures.



First Weak-lensing Results from “See Change”: Quantifying Dark Matter in the Two z ≳ 1.5 High-redshift Galaxy Clusters SPT-CL J2040-4451 and IDCS J1426+3508

Authors : Jee, M. James; Ko, Jongwan; Perlmutter, Saul; Gonzalez, Anthony; Brodwin, Mark; Linder, Eric; Eisenhardt, Peter

Publication: Astrophysical Journal, 2017 October

Introduction (Kor) : 허블 우주망원경을 이용한 고 적색편이 은하단의 암흑물질 함량 결정

Introduction (Eng) : First use of the Wide Field Camera 3 (WFC3) on Hubble to quantify dark matter in two interesting high-z clusters



Star Formation of Merging Disk Galaxies with AGN Feedback Effects

Authors : Jongwon Park, Rory Smith, Sukyoung K. Yi

Publication: Astrophysical Journal, 2017 August

Introduction (Kor) : AGN FB 효과를 고려하면, 충돌하는 두 원반 은하의 별 생성률이 예상보다 적게 증가한다.

Introduction (Eng) : Using numerical hydrodynamics simulations, we studied the effect of AGN feedback on the evolution of merging disk galaxies with various conditions.



Phase-space Analysis in the Group and Cluster Environment: Time Since Infall and Tidal Mass Loss

Authors : Jinsu Rhee, Rory Smith, Hoseung Choi, Sukyoung K. Yi, Yara Jaffe, Geame Candlish, and Ruben Sanchez-Janssen

Publication: Astrophysical Journal, 2017 July

Introduction (Kor) : 우주론적 유체역학 수치모사의 결과를 이용하여, 은하단에 병합한 은하들의 특징등을 위상공간분석을 통해 분석하는 논문입니다.

Introduction (Eng) : Using cosmological hydrodynamic simulations, we provide phase-space diagrams as a tool for understanding cluster environmental effects which can be directly compared with real observations of galaxy clusters. Link


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