[구 GC-01] Satellites of Isolated Early-type Galaxies and the Missing Satellite Galaxy Problem
Changbom Park1, Ho Seong Hwang1, Hyunbae Park2, Jong Chul Lee2
1Korea Institute for Advanced Study, 2Korea Astronomy and Space Science Institute
The standard hierarchical galaxy formation scenario in the popular LCDM cosmogony has been very successful in explaining the large-scale distribution of galaxies. However, one of the failures of the theory is that it predicts too many satellite galaxies associated with massive galaxies compared to observations, which is called the missing satellite galaxy problem. Isolated groups of galaxies hosted by passively evolving massive early-type galaxies are ideal laboratories for finding the missing physics in the current theory.
We discover through a deep spectroscopic survey of galactic satellite systems that bright isolated early-type galaxies have almost no satellite galaxies fainter than the r-band absolute magnitude of about Mr=-14. The cutoff is at somewhat brighter magnitude of about Mr=-15 when only early-type satellites are used. Such a cutoff is not observed in the luminosity function of galaxies in the field. Physical properties of the observed satellites depend sensitively on the host-centric distance. All these are strong evidence that galactic satellites can become invisible due to astrophysics of satellite-host galaxy interaction. A recent state-of-the-art hydrodynamic simulation of galaxy formation does not reproduce such a cutoff in the satellite galaxy luminosity function. But the past history of the simulated satellites shows that many satellite galaxies near or somewhat fainter than the cutoff magnitude have recently become extinct through fatal encounters with the host or other satellite galaxies. Our observation indicates that the missing satellite galaxy problem could be mitigated if the astrophysics of galaxy interaction is more elaborated in the theory.
[구 GC-02] A Hyper Suprime-Cam View of the Interacting Galaxies of the M81 Group – Structures and Stellar Populations
Nobuo Arimoto1,3 and Sakurako Okamoto2
These components are naturally predicted in models of hierarchical galaxy assembly, and their observed properties place important constraints on the amount, nature, and history of satellite accretion. One of the most effective ways of mapping the peripheral regions of galaxies is through resolved star studies. Using wide-field cameras equipped to 8 m class telescopes, it has recently become possible to extend these studies to systems beyond the Local Group. Located at a distance of 3.6 Mpc, M81 is a prime target for wide-field mapping of its resolved stellar content.
In this talk, we present the detailed results from our deep wide-field imaging survey of the M81 group with the Hyper Suprime-Cam (HSC), on the Subaru Telescope. We report on the analysis of the structures, stellar populations, and metallicities of old dwarf galaxies such as NGC3077, IKN, KDG061, as well as young stellar systems such as Arp’s Loop and Holmberg IX. Several candidates for yet-undiscovered faint dwarf galaxies and young stellar clumps in the M81 group will also be introduced. The peculiar galaxy NGC3077 has been classified as the irregular galaxy. Okamoto et al.
(2015, ApJ 809, L1) discovered an extended halo structure with S-shape elongated tails, obvious feature of tidal interaction. With a help of numerical simulation by Penarrubia et al. (2009, ApJ 698, 222), we will demonstrate that this tidal feature was formed during the latest close encounters between M81, M82, and NGC 3077, which induced star formation in tidally stripped gas far from the main bodies of galaxies. It is not clear whether the latest tidal interaction was the first close encounters of three galaxies. If NGC3077 is still surrounded by the dark matter halo, it implies that NGC3077 has undergone the first tidal stripping by larger companions. Kinematic studies of inter galactic globular clusters and planetary nebulae would tell us the past history of tidal
National University, Republic of Korea
2AIP, Potsdam, Germany
Ultra-diffuse galaxies (UDGs) are an unusual galaxy population. They are ghostlike galaxies with fainter surface brightness than normal dwarf galaxies, but they are as large as MW-like galaxies.
The key question on UDGs is whether they are 'failed' giant galaxies or 'extended' dwarf galaxies.
To answer this question, we study UDGs in massive color-magnitude relations show that most UDGs have old stellar population with red colors, while a few of them show bluer colors implying the existence of young stars. The stellar masses of UDGs show that they have less massive stellar components than the bright red sequence galaxies.
The radial number density profiles of UDGs exhibit a drop in the central region of clusters, suggesting some of them were disrupted by strong gravitational potential. Their spatial distributions are not homogeneous, which implies UDGs are not Cosmology Centre (Denmark), 4University of Sussex
Massive early-type galaxies (ETG) have been spectroscopically confirmed up to z>3 which, together with their ages and abundances at z>1.5, implies that their progenitors must have converted gas into stars on short timescales. The termination of star formation in these galaxies can occur through several channels, but they remain largely conjectural, in part due to the current lack of dust than their local counterparts, which suggests the presence of substantial amounts of gas and a low star formation efficiency.
[구 GC-05] Star-formation Properties of High-redshift (z~1) Galaxy Clusters Connected to the Large-scale Structure
Seong-Kook Lee1, Myungshin Im1, Minhee Hyun1, Bomi Park2, Jae-woo Kim3, Dohyung Kim1,
Yongjung Kim1
1Center for the Exploration of the Origin of the Universe, Department of Physics and Astronomy, Seoul National University,
2Department of Astronomy and Space Science, Kyung Hee University,
3Korea Astronomy and Space Science Institute At local, majority of galaxies in the dense environment, such as galaxy cluster, are red and quiescent with little star-formation (SF) activity.
However, a different picture emerges as we go to high redshift: (1) there exist non-negligible fraction of galaxies still forming stars actively even in dense environment, and (2) there is a significant cluster-by-cluster variation in the SF properties, such as quiescent galaxy fraction.
In this presentation, we show the results of our study about the variation of quiescent galaxy fraction among high-redshift (z~1) galaxy clusters, based on the multi-object spectroscopic (MOS) observation with IMACS on the Magellan telescope.
Our main result is that galaxy clusters which are connected with significant large-scale structure (LSS), well beyond the cluster scale, are more Zabludoff3, Alexander Karim2, Benjamin Magnelli2
1KASI, 2Affiliation Argelander Institut für Astronomie, Universität Bonn, 3Steward Observatory, University of Arizona
Bright Lyα blobs often reside in overdensities of compact Lyα emitters (LAEs) that may be galaxy protoclusters. The number density, variance, and internal kinematics of LABs suggest that they
themselves trace group-like halos. Here we test this hierarchical picture, presenting deep, wide-field Lyα narrowband imaging of a 1°×0.5° estimation method, we discover a large-scale overdensity (Boötes J1430+3522) with a surface density contrast of δ(Σ) = 2.7, a volume density contrast of δ ~ 10.4, and a projected diameter of
~20 comoving Mpc. Comparing with cosmological simulations, we conclude that this LAE overdensity will evolve into a present-day Coma-like cluster with log(M/M⊙) ~ 15.1±0.2. In this and three other wide-field LAE surveys re-analyzed here, the extents and peak amplitudes of the largest LAE overdensities are similar, not increasing with survey size, implying that they were indeed the
Weak Lensing with Subaru Observation
Mincheol Kim, Myungkook J. Jee Yonsei University
We present weak-lensing analysis of the merging galaxy cluster Abell 115 at z=0.197 based on Subaru i and V band images. As merging clusters often show, Abell 115’s merging signatures include radio relics, double X-ray peaks, and large offsets between the cluster member galaxies and the X-ray distributions. A weak-lensing study provides underlying dark matter distribution, the key information to determine the complex merging scenario of the cluster. In this work, we present 2D mass reconstruction of the cluster, which reveals two distinct mass peaks consistent with galaxy distributions. We measure the first weak-lensing mass of each subcluster. Our weak-lensing total mass estimate is a few factors lower than the published dynamical mass obtained from velocity dispersion. This large mass discrepancy may be attributed to a significant departure from dynamical equilibrium. We also re-analyze the archival chandra data and find that the result is consistent with weak-lensing mass.
[구 GC-08] Mapping the Mass of the Double configuration requires a complex merging scenario. A key to gaining insight into the events G287.0+32.9. Our investigation detects five significant mass structures. The mass is dominated by a primary structure that is centered near the and relate their distributions to the intracluster medium and galaxy distributions. In addition, we J0205-5829 and MOO1014+0038, with HST Observations
Seojin F. Kim and Myungkook J. Jee Yonsei University
The mass function of massive high-z clusters is extremely sensitive to the cosmological parameters.
However, it is challenging to estimate their
accurate masses. The “See Change” HST the instrumental effect. We successfully detect weak lensing signals which produce cluster masses consistent with those from non-lensing methods based on hydrostatic equilibrium.
[구 GC-10] A redshift survey of the nearby galaxy cluster Abell 2199: comparison of the spatial and kinematic distributions of
galaxies and intracluster medium
Hyunmi Song(송현미)1, Ho Seong Hwang(황호성)2, Changbom Park(박창범)3, Takayuki Tamura4
1Korea Astronomy and Space Science Institute (KASI; 한국천문연구원), 2Quantum Universe Center, Korea Institute for Advanced Study(QUC KIAS;
고등과학원 양자우주센터), 3School of Physics, Korea redsults in high spectroscopic completeness at rpetro,0<20.5 (77%). We use these data to study the kinematics and clustering of galaxies, focusing on the comparison with those of the intracluster medium (ICM) from Suzaku X-ray observations. We identify 406 member galaxies of A2199 at R<30’
using the caustic technique. The velocity dispersion profile of cluster members appears smoothly connected to the stellar velocity dispersion profile of the cD galaxy. The luminosity such rotation. We apply a friends-of-friends
algorithm to the cluster galaxy sample at R<60’ and identify 32 group candidates, and examine the spatial correlation between the galaxy groups and X-ray emission. This extensive survey in the Northeastern Region of the Large Magellanic Cloud
Jaeyeong Kim
Kyung Hee University, Korea,
The Large Magellanic Cloud (LMC) is a unique influence the star formation process. Measuring polarization of the background stars behind interstellar medium allows us to describe the existence of magnetic fields through the polarization vector map.
In this presentation, I introduce the near-infrared polarimetric results for the 39′☓69′
field of the northeastern region of the LMC and the N159/N160 star-forming complex therein. The polarimetric observations were conducted at IRSF/SIRPOL 1.4 m telescope. These results allow us to examine both the global geometry of the large-scale magnetic field in the northeastern region and the close structure of the magnetic field in the complex. Prominent patterns of polarization vectors mainly follow dust emission features in the mid-infrared bands, which imply that the large-scale magnetic fields are highly involved in the structure of the dust cloud in the LMC. In addition, local magnetic field structures in the N159/N160 star-forming complex are investigated with the comparison between polarization vectors and molecular cloud emissions, suggesting that the magnetic fields are resulted from the sequential formation history of this complex. I propose that ionizing radiation from massive stellar clusters and the expanding bubble of the ionized gas and dust in this complex probably affect the nascent magnetic field structure.
[구 GC-12] Lyα Radiative Transfer and The Wouthuysen-Field effect
Kwang-Il Seon1 (선광일), Chang-Goo Kim2 (김창구)
1Korea Astronomy and Space Science Institute (한국천문연구원), 2Princeton University, USA
A three-dimensional (3D) Lyα radiative transfer code is developed to study the Wouthuysen-Field plane-parallel ISM model, which is appropriate for the neutral ISM of our Galaxy, is used to calculate formation of early-type galaxies
Young-Wook Lee, Seungsoo Hong, Dongwook Lim Yonsei University, Seoul 03722, Korea
We report our discovery of a significant early-type galaxies in the hierarchical merging paradigm.
[구 GC-14] Three-Dimensional Structure of Star-Forming Regions in NGC 6822 Hubble V
2Korea Astronomy & Space Science institute,
3Department of Physics and Astronomy, Seoul National University, 4Department of Astronomy, the University of Texas, 5National Astronomical Observatory of Japan excited surface of clouds by far-ultraviolet photons, photodissociation region (PDR). We present three-dimensional maps of emission line distributions through multi slit scanning data and compare these results with the previous study.
This presentation shows the physical structure of the star-forming regions and we discuss a PDR
1Department of Astronomy and Atmospheric sciences, Kyungpook National University, 2Division of Science Education, Pusan National University
Bar fractions depend on the properties of host galaxies. However, the observational studies did not provide consistent tendency. We investigated the bar fractions and their dependence on properties of host galaxies using three bar classifications: visual inspection, ellipse fitting method and Fourier analysis from a volume-limited sample of 1,698 disk galaxies brighter than Mr=-15.2 within z = 0.01 from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We found two causes to make the discrepancy in previous studies. One is caused by
the difficulty in automatically identifying bars for bulge-dominated galaxies. In particular, ellipse fitting methods could miss early-type barred galaxies when a large bulge weakens the transition late-type spirals which are blue, disk-dominate and less-concentrated. Therefore, how much weak bars they contain affects the trend of bar fraction non-axisymmetric stellar bar potential, and the evolution of the stellar bar is influenced by mass inflows to the center and central star formation.
To study how the presence of the gas affects the evolution of the stellar bar, we use the mesh-free hydrodynamics code GIZMO and run fully self-consistent three-dimensional simulations. To explore the evolution with differing initial conditions, we vary the fraction of the gas and newly-created stars with low velocity dispersion.
However, the central mass concentration also quickly increases as the bar grows in these unstable models, resulting in fast bar dissolution in gas rich models. We will discuss our results in comparison with previous work.
[구 GC-17] The Most Massive Active Galactic Nuclei at 1<z<2
Hyunsung Jun
Korea Institute for Advanced Study, Seoul, Korea We obtained near-infrared spectra of 26 SDSS quasars at 0.7<z<2.5 with reported rest-frame ultraviolet black hole mass (MBH)~10^¹⁰M⊙ to critically examine the systematic effects involved with their mass estimations. We find that active galactic nuclei (AGNs) heavier than 10^¹⁰M⊙ often display double-peaked Hα emission, extremely broad FeII complex emission around MgII, and highly blueshifted and broadened CIV emission.
The weight of this evidence, combined with previous studies, cautions against the use of MBH values based on any emission line with a width over 8000 km/s. Also, the MBH estimations are not positively biased along the presence of ionized narrow line outflows, anisotropic radiation, or the use of line FWHM instead of σ for our sample, and unbiased with variability, scatter in broad line equivalent width, or obscuration for general type-1 quasars. Removing the systematically uncertain MBH values, ~10^¹⁰M⊙ BHs in 1<z<2 AGNs can still be explained by anisotropic motion of the broad line region from ~10^⁹·⁵M⊙ BHs, although current observations support they are intrinsically most massive, and overmassive to the host's bulge mass.
[구 GC-18] Are Quasars Growing Fast in the Early Universe?: The Lowest Eddington Ratio Quasar at z~6 Universe (CEOU), 2Astronomy Program, FPRD, Department of Physics & Astronomy, Seoul National University, 3LOCOOP, Inc., 4Korea
Astronomy and Space Science Institute, 5University of Science and Technology, 6Korea Institute for Advanced Study, 7Nature Astronomy, 8Arizona State University, School of Earth and Space Exploration, 9Subaru Telescope, National Astronomical Observatory of Japan, 10School of Space Research and Institute of Natural Sciences, Kyung Hee University…
To date, luminous quasars at z ~ 6 have been
found to be in maximal accretion with the Eddington ratios, λEdd ~ 1, suggesting enhanced nuclear activities in the early universe. However, this may not be the whole picture of supermassive black hole (SMBH) growth since previous studies have not reached on faint quasars that are more likely to harbor SMBHs with low λEdd. To understand the accretion activities in quasars at high redshift, we obtained the deep near-infrared short-duration super-Eddington accretion events (λEdd > 10).
[구 GC-19] What we have learned about Gamma-ray bright AGNs using the iMOGABA program
Sang-Sung Lee1,2
1Korea Astronomy and Space Science Institute,
2Korea University of Science and Technology A Korean VLBI Network Key Science Program, the Interferometric Monitoring of Gamma-ray Bright AGNs (iMOGABA) program continues to aim specific sources. From those highlighted works, we find that the Gamma-ray bright AGNs become fainter at higher frequencies, yielding optically thin spectra at mm wavelengths. Based on the studies on specific sources, taking into account the synchrotron self-absorption model of the
relativistic jet, we estimated the magnetic field strength in the mas emission region during the Seoul 03722, Korea; jinsu.rhee@yonsei.ac.kr
2European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile
3Universidad de Valparaso, Blanco 951, Valparaso, Chile
4UK Astronomy Technology Centre, Royal
Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK Received 2016 November 25; revised 2017 April 11;
accepted 2017 April 12; published 2017 July 13 Using the latest cosmological hydrodynamic N-body simulations of groups and clusters, we phase-space diagrams remains even when projected quantities are used (i.e.,line of sight velocities, and projected distances from the cluster). We provide figures that can be directly compared with observed samples of cluster galaxies and we also provide the data used to make
[구 GC-21] Evolution of late-type galaxies in cluster environment: Effects of high-speed multiple interactions with early-type galaxies
Jeong-Sun Hwang1, Changbom Park2, Arunima Banerjee3, Ho Seong Hwang4
1Department of Physics and Astronomy, Sejong University, 2School of Physics, Korea Institute for Advanced Study, 3Indian Institute of Science Education and Research, Tirupati, India, 4Quantum Universe Center, Korea Institute for Advanced Study
Late-type galaxies falling into a cluster would evolve being influenced by the interactions with both the cluster and the nearby cluster member interacting with neighbouring early-type galaxies, using N-body, hydrodynamical simulations. Based on the information about the typical galaxy encounters obtained by using the galaxy catalog of Coma cluster, we run the simulations for the cases where a Milky Way Galaxy-like late-type galaxy, flying either edge-on or face-on, experiences six consecutive collisions with twice more massive early-type galaxies having hot gas in their halos.
Our simulations show that the evolution of the late-type galaxy can be significantly affected by the high-speed multiple collisions with the early-type galaxies, such as on the cold gas content and the star formation activity, particularly through the hydrodynamic interactions between the cold disk and the hot gas halos. By comparing our simulation results with those of others, we claim that the role of the galaxy-galaxy interactions on the evolution of late-type galaxies in clusters could be comparable with that of the galaxy-cluster interactions, depending on the dynamical history.
Our simulations show that the evolution of the late-type galaxy can be significantly affected by the high-speed multiple collisions with the early-type galaxies, such as on the cold gas content and the star formation activity, particularly through the hydrodynamic interactions between the cold disk and the hot gas halos. By comparing our simulation results with those of others, we claim that the role of the galaxy-galaxy interactions on the evolution of late-type galaxies in clusters could be comparable with that of the galaxy-cluster interactions, depending on the dynamical history.