The Velocity Dispersion Function for Quiescent Galaxies in the Local Universe

We investigate the distribution of central velocity dispersions for quiescent galaxies in the SDSS at $0.03 \leq z \leq 0.10$. To construct the field velocity dispersion function (VDF), we construct a velocity dispersion complete sample of quiescent galaxies with Dn4000$> 1.5$. The sample consists of galaxies with central velocity dispersion larger than the velocity dispersion completeness limit of the SDSS survey. Our VDF measurement is consistent with previous field VDFs for $\sigma > 200$ km s$^{-1}$. In contrast with previous results, the VDF does not decline significantly for $\sigma < 200$ km s$^{-1}$. The field and the similarly constructed cluster VDFs are remarkably flat at low velocity dispersion ($\sigma < 250$ km s$^{-1}$). The cluster VDF exceeds the field for $\sigma > 250$ km s$^{-1}$ providing a measure of the relatively larger number of massive subhalos in clusters. The VDF is a probe of the dark matter halo distribution because the measured central velocity dispersion may be directly proportional to the dark matter velocity dispersion. Thus the VDF provides a potentially powerful test of simulations for models of structure formation.Comment: Accepted for publication in ApJ. 10 pages, 8 figures. Comments welcom

슬로언 밀집 은하군의 분광학적 특성 연구

학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부 천문학전공, 2015. 8. 이명균.Compact groups of galaxies are the densest among the known systems of galaxies and they have a few member galaxies within tens of kiloparsec. Previous studies suggest that compact groups are favored regions for galaxy interaction and may suffer from merging instability. Frequent galaxy interactions in compact groups make them an ideal target to study the effects of galaxy interactions in the evolution of galaxies. Furthermore, it is a challenge to explain the existence of compact groups because they are dynamically unstable systems that can collapse in a very short time scale (< 2 Gyr). To study environmental effects of the interaction-frequent environments of com- pact groups, I investigate the nuclear activity of galaxies in local compact groups. A spectroscopic sample of 238 galaxies in 58 compact groups from the Sloan Digital Sky Survey (SDSS) data release 7 (DR7) is used to estimate the fraction of active galactic nucleus (AGN) host galaxies in compact groups, and to compare it with those in cluster and field regions. The AGN host galaxies are identified using the emission-line ratio diagrams and the AGN fraction of compact group galaxies is estimated to be 17-42% depending on the AGN classification method. The AGN fraction in compact groups is not the highest among the galaxy environments. This trend remains in the subsamples segregated by galaxy morphology and optical luminosity. The AGN fraction for early-type galaxies decreases with increasing galaxy number density, but the fraction for late-type galaxies changes little. There is no mid-infrared detected AGN host galaxies in Wide-field Infrared Survey Explorer data for our sample of compact groups. These results suggest that the nuclear activity of compact group galaxies (mostly early types) is not strong because of the lack of gas supply even though they may experience frequent galaxy?galaxy interactions and mergers that could trigger nuclear activity. Dynamical analysis of compact groups provides important tests of models of compact group formation and evolution. To study this issue, a catalog of compact groups with complete spectroscopic redshifts in the redshift range 0.01 < z < 0.22 is constructed by identifying 2037 redshifts from FLWO/FAST, from the literature, and from SDSS DR12 in the fields of compact groups in McConnachie et al. (2009). A secure sample of 332 compact groups includes 192 groups with N ≥ 4 member galaxies and 140 groups with 3 members. The physical properties of our sample compact groups including size, number density, velocity dispersion, and local environment are similar to those derived for the original Hickson compact groups, but they differ from the compact groups in the second Palomar Observatory Sky Survey. Differences result from subtle differences in the way the group candidates were originally selected. The velocity dispersion and space density of the compact groups change little with redshift over the range covered by this sample. The approximate constancy of the space density for this sample is potential constraint on the evolution of compact groups on a few Gigayear timescale. To have a compact group sample without using previous selection criteria based only on the photometric information, a new catalog of compact groups selected from a complete, magnitude-limited redshift survey of SDSS DR12 is constructed by applying the friend-of-friend algorithm. This is the largest catalog of compact groups with complete redshifts. The identification of compact groups from redshift surveys without using Hicksons criteria results in a complete sample of compact groups without bias against the groups in nearby universe and in high-density regions. The surface galaxy number density (Σ5) distribution of compact groups show that the local environments of them are diverse. The physical properties of compact groups (e.g. redshift, size, density, velocity dispersion) in different environments are similar to each other. However, the compact groups in the denser region contain more early- type galaxies and redder galaxies, suggesting that embedded compact groups consist of more evolved galaxy populations.ABSTRACT iii LIST OF FIGURES xii 1 INTRODUCTION 1 1.1 Compact Groups of Galaxies 1 1.2 Compact Group Surveys 2 1.3 The Large-Scale Environments of Compact Groups 5 1.4 Galaxy Evolution in Compact Groups 6 1.5 Purpose of the Thesis 8 2 ACTIVITY IN GALACTIC NUCLEI OF COMPACT GROUP GALAXIES IN THE LOCAL UNIVERSE 11 2.1 INTRODUCTION 11 2.2 DATA 15 2.3 AGN SELECTION 18 2.3.1 Strong emission-line galaxy classification 18 2.3.2 Weak emission-line galaxy classification 19 2.4 RESULTS 21 2.4.1 AGN fraction in compact groups 21 2.4.2 Comparison of AGN fractions in various environments 23 2.5 DISCUSSION 31 2.5.1 AGN fraction in compact groups: comparison with other studies 31 2.5.2 Are the compact groups favored environments for the activity in galactic nuclei 37 2.6 SUMMARY 40 3 COMPACT GROUPS OF GALAXIES WITH COMPLETE SPECTROSCOPIC REDSHIFTS IN THE LOCAL UNIVERSE 43 3.1 INTRODUCTION 43 3.2 DATA 47 3.2.1 Parent Sample 47 3.2.2 Redshift Data: FLWO/FAST Observation 49 3.3 A SAMPLE OF COMPACT GROUPS WITH REDSHIFTS 51 3.4 RESULTS 59 3.4.1 The Physical Properties of Compact Groups 59 3.4.2 Comparison with Other Compact Group Samples 69 3.5 SUMMARY 77 4 COMPACT GROUPS OF GALAXIES FROM REDSHIFT SURVEYS 81 4.1 INTRODUCTION 81 4.2 DATA 83 4.3 COMPACT GROUP SELECTION 87 4.3.1 The friend-of-friend method 87 4.3.2 A Sample of Compact Groups with Complete Redshifts 88 4.4 RESULTS 94 4.4.1 Comparison with Other Compact Groups 94 4.4.2 The Large-Scale Environments of Compact Groups 100 4.5 DISCUSSION 105 4.5.1 Isolation Criteria 105 4.5.2 Environmental Effects on the Properties of Compact Groups 106 4.6 SUMMARY 110 5 SUMMARY 113 BIBLIOGRAPHY 117 요약 127Docto

A Complete Spectroscopic Census of Abell 2029: A Tale of Three Histories

A rich spectroscopic census of members of the local massive cluster Abell 2029 includes 1215 members of A2029 and its two infalling groups, A2033 and a Southern Infalling Group (SIG). The two infalling groups are identified in spectroscopic, X-ray and weak lensing maps. We identify active galactic nuclei (AGN), star-forming galaxies, E+A galaxies, and quiescent galaxies based on the spectroscopy. The fractions of AGN and post-starburst E+A galaxies in A2029 are similar to those of other clusters. We derive the stellar mass ($M_{*}$)-metallicity of A2029 based on 227 star-forming members; A2029 members within $10^{9} M_{\odot} < M _{*} < 10^{9.5} M_{\odot}$ are more metal rich than SDSS galaxies within the same mass range. We utilize the spectroscopic index $D_{n}4000$, a strong age indicator, to trace past and future evolution of the A2029 system. The median $D_{n}4000$ of the members decreases as the projected clustercentric distance increases for all three subsystems. The $D_{n}4000 - M_{*}$ relations of the members in A2029 and its two infalling groups differ significantly indicating the importance of stochastic effects for understanding the evolution of cluster galaxy populations. In the main cluster, an excess around $D_{n}4000 \sim 1.8$ indicates that some A2029 members became quiescent galaxies 2-3 Gyr ago consistent with the merger epoch of the X-ray sloshing pattern.Comment: 17 pages, 11 figures, submitted to Ap

The HectoMAP Cluster Survey - I. redMaPPer Clusters

We use the dense HectoMAP redshift survey to explore the properties of 104 redMaPPer cluster candidates. The redMaPPer systems in HectoMAP cover the full range of richness and redshift (0.08 $< z <$ 0.60). Fifteen systems included in the Subaru/Hyper Suprime-Cam public data release are bona fide clusters. The median number of spectroscopic members per cluster is $\sim20$. We include redshifts of 3547 member candidates listed in the redMaPPer catalog whether they are cluster members or not. We evaluate the redMaPPer membership probability spectroscopically. The scaled richness ({\lambda}rich/S) provided by redMaPPer correlates tightly with the spectroscopic richness regardless of the cluster redshift and appears to be a better mass proxy than the original richness, {\lambda}rich. The purity (number of real systems) in redMaPPer exceeds 90% even at the lowest richness; however, there is some incompleteness. Five massive galaxy clusters (M $\gtrsim 2 \times 10^{13}$ M$_{\odot}$) associated with X-ray emission in the HectoMAP region are missing from the catalog.Comment: submitted to ApJ, a revised version in response to the referee's comments, 15 pages, 14 figures, 3 tables; data will be available when the paper is accepte

Constructing a Galaxy Cluster Catalog in IllustrisTNG-300 using the Mulguisin Algorithm

We present a new simulated galaxy cluster catalog based on the IllustrisTNG simulation. We use the Mulguisin (MGS) algorithm to identify galaxy overdensities. Our cluster identification differs from the previous FoF cluster identification in two aspects; 1) we identify cluster halos based on the galaxy subhalos instead of unobservable dark matter particles, and 2) we use the MGS algorithm that separates galaxy overdensities hosted by massive galaxies. Our approach provides a cluster catalog constructed similar to the observed cluster catalogs using spectroscopic surveys. The MGS cluster catalog lists 303 halos with M$_{200} > 10^{14}$ M$_{\odot}$, including $\sim 10\%$ more than the FoF. The MGS catalog includes more systems because we separate some independent massive MGS cluster halos that are bundled into a single FoF algorithm. These independent MGS halos are apparently distinguishable in galaxy spatial distribution and the phase-space diagram. Because we constructed a refined cluster catalog that identifies local galaxy overdensities, we evaluate the effect of MGS clusters on the evolution of galaxies better than using the FoF cluster catalog. The MGS halo identification also enables effective identifications of merging clusters by selecting systems with neighboring galaxy overdensities. We thus highlight that the MGS cluster catalog is a useful tool for studying clusters in cosmological simulations and for comparing with the observed cluster samples.Comment: 15 pages, 9 figures, 2 tables, Submitted to Ap