2019 가을 학술대회

Most of the mass is known to be occupied [포 GC-06] Velocity Dispersion Bias of Galaxy by dark matter. However, it is difficult to directly Groups classified by Machine Learning measure the mass and distribution of dark matter Algorithm in a galaxy. Recently, the velocity dispersion of the stellar population in a galaxy’s center has been Youngdae Lee1, Hyunjin Jeong2, Jongwan Ko2, Joon suggested as a possible probe of the mass of the Hyeop Lee2, Jong Chul Lee2, Hye-Ran Lee2,3, Yujin dark matter halo. In this study, we test and verify Yang2, Soo-Chang Rey1 this hypothesis using the kinematics of the satellite 1Department of Astronomy and Space Science, of isolated galaxies. We use the Chungnam National Nuniversity (CNU), 2Korea Friends-of-Friends (FoF)algorithm to build a Astronomy and Space Science Institute (KASI), catalog of primary galaxies and their satellite 3Korea University of Science and Technology (UST) galaxies from the (SDSS) DR 12. We calculate the dynamical mass of the We present a possible bias in the estimation of primary galaxies from the velocity dispersion of velocity dispersions for galaxy groups due to the their satellite galaxies. We then investigate the contribution of subgroups which are infalling into correlation between the dynamical mass and the the groups. We execute a systematic search for central velocity dispersion of the primary galaxies. flux-limited galaxy groups and subgroups based on The stellar velocity dispersion of the central host the spectroscopic galaxies with r < 17.77 mag of galaxies has a strong linear correlation with the SDSS data release 12, by using DBSCAN velocity dispersion of their satellite galaxies. Also, (Density-Based Spatial Clustering of Application the stellar velocity dispersion of the central galaxy with Noise) and Hierarchical Clustering Method is strongly correlated with the dynamical mass of which are well known unsupervised machine the galaxy, which can be described as a power law. learning algorithm. A total of 2042 groups with at The results of this study show that the central least 10 members are found and ~20% of groups velocity dispersion of the primary galaxies is a have subgroups. We found that the estimation of good proxy for tracing the mass of dark matter velocity dispersions of groups using total galaxies halo. including those in subgroups are underestimated by ~10% compared to the case of using only [포 GC-05] NGC 4517 Group: A New Galaxy galaxies in main groups. This result suggests that Group in front of the Cluster the subgroups should be properly considered for mass measurement of galaxy groups based on the Yoo Jung Kim1, Jisu Kang1, Myung Gyoon Lee1, velocity dispersion. Insung Jang2 1 2 Seoul National University, Leibniz-Institut für [포 GC-07] Submillimeter galaxies in the Astrophysik Potsdam AKARI North Ecliptic Pole survey field

We present the distance measurements of two Dongseob Lee1, Yeonsik Kim2, and Hyunjin Shim1 spiral galaxies NGC 4517, NGC 4592, and 1Department of Science Education, Kyungpook neighboring dwarf galaxies found in Hyper National University, 2Department of Astronomy and Suprime-Cam Subaru Strategic Program Atmospheric Sciences, Kyungpook National (HSC-SSP) wide field survey data. Distances to NGC University 4517 and NGC 4592 are measured by the Tip of the Red Giant Branch method from archival Hubble SCUBA-2 North Ecliptic Pole survey, one of the Space Telescope data; 9.00 Mpc for NGC 4517  ongoing JCMT large programs, is designed to  2 and 8.90 Mpc for NGC 4592. The spatial obtain 850 ㎛ imaging data over ~4 deg around the distance between NGC 4517 and NGC 4592 is 300 NEP based on the AKARI NEP-Wide survey. By kpc, which is close enough for them to be August 2019, the program is 50 % complete in considered as a group (NGC 4517 group). Using terms of observing time, increasing the resolved stellar photometry and Surface Brightness submillimeter coverage by a factor of 2 with the Fluctuation (SBF) method with HSC-SSP data, we comparable depth. The rms measured in the estimate the distances to three other dwarf deepest center is 0.92 mJy/beam, slightly above the galaxies and confirm that they are members of the 850 ㎛ confusion limit. With 4 σ detection, the group. Velocities of three of the galaxies in the source count is 50 % complete at 9 mJy. The NGC 4517 group show that this group is one of the surface density of submillimeter galaxies at this galaxy groups in the near side of the flux limit is 200 deg-2. Multi-wavelength infall region. identification of the 850 ㎛ sources was done through the likelihood analysis based on the

74 / Bull. Kor. Astron. Soc. Vol. 44 No.2, Oct. 2019 포스터발표초록 far-infrared (250-500 ㎛), mid-infrared (18 ㎛), Sextans, and Canes Venatici I. For all three near-infrared (2-4 ㎛), and optical (i-band) source galaxies, we found that metal-poor and metal-rich catalog. We are going to present morphologies and groups of red-giant-branch stars have distinct physical properties of 850 ㎛ selected submillimeter spatial distributions, in which metal-rich stars are galaxies with the help of ancillary multi-wavelength centrally concentrated while metal-poor stars are datasets over the NEP area. relatively dispersed. In Sextans, we found an off-centered peak of metal-poor stars which is [포 GC-08] Weak Lensing Mass Map presumed to be a disrupting star cluster in this Reconstruction of Merging Clusters with galaxy. We will discuss the implications of our Convolutional Neural Network results for the dwarf galaxy formation and possible directions on future work of this project. Sangnam Park1, James M. Jee2, Sungwook E. Hong1, Dongsu Bak1,3 [포 GC-10] Chemical properties of 1Natural Science Research Institute, University of star-forming galaxies in Virgo-related Seoul, 2Department of Astronomy, Yonsei large-scale filamentary structures. University, 3Department of Physics, University of Seoul Jiwon Chung1, Soo-Chang Rey2, Suk Kim2, Youngdae Lee2, Eon-Chang Sung1 We introduce a novel method for reconstructing 1Korea Astronomy and Space Science Institute, the projected dark matter mass maps of merging 2Chungnam National University galaxy clusters by applying the convolutional neural network (CNN) to their weak lensing maps. The filament is an interesting structure in the We generate synthesized grayscale images from Universe because clusters form at the nodes of given weak lensing maps that preserve their filaments and grow through the continuous averaged galaxy ellipticity. We then apply them to accretion of individual galaxies and groups from multi-layered CNN with architectures of alternating the surrounding filaments. We study the chemical convolution and trans-convolution filters to predict properties of star-forming (SF) galaxies in the five the mass maps. We train our architecture with large-scale filamentary structures (Leo II A, Leo II 1,000 Subaru/Suprime-Cam mock weak lensing B, Leo Minor, Canes Venatici, and Virgo III) related maps, and our method have better mass map with the Virgo cluster, with the spectroscopic data prediction than the Kaiser-Squires method with the taken with the SDSS DR12, and compare them with following three aspects: (1) better pixel-to-pixel those of the Virgo cluster and field galaxies. In correlation, (2) more accurate finding of density mass-metallicity relation, most of the SF galaxies peak position, and (3) free from mass-sheet in Virgo-related filaments (except Virgo III degeneracy. We also apply our method to the HST filament) show lower metallicity on average than weak lensing map of the El Gordo cluster and the Virgo cluster SF galaxies, but similar to field compare our result to the previous studies. counterparts. These chemically less evolved feature of SF galaxies in the filaments and field are [포 GC-09] Narrow-band Ca Photometry for more pronounced for lower mass galaxies. This is Dwarf Spheroidal Galaxies: Recent Results probably because low mass galaxies have low and Future Work potential wells and are therefore likely to be sensitive to cluster environmental effects. Interestingly, we find that the metallicity Hak-Sub Kim1, Sang-Il Han2, Suk-Jin Yoon2 enhancement of SF galaxies in the Virgo III 1Korea Astronomy and Space Science Institute, filament. In chemical and morphological 2Yonsei University perspectives, SF galaxies in the Virgo III thought to be transitional objects possibly transformed from This poster introduces the ongoing SF late-type galaxies and are on the way to red "Narrow-band Ca Photometry for Dwarf Spheroidal early-type galaxies in the filament environment. Galaxies" project and presents the latest results. This is the first discovery of systematic ‘chemical The project aims to explain the formation and pre-processing’ signature for filament galaxies in evolution of dwarf spheroidal galaxies by Local Universe before they fall into the cluster. examining the structural properties of stellar populations as a function of metallicity. To overcome the lack of stars with known [포 GC-11] Gas dynamics and star formation spectroscopic metallicities for dwarf spheroidal in dwarf galaxies: the case of DDO 210 galaxies, we apply the hk index as a photometric metallicity indicator to three galaxies—Draco, Se-Heon Oh1, Yun Zheng2 and Jing Wang2

한국천문학회보 제44권 2호, 2019년 10월 / 75