Based on an extensive redshift survey for galaxy clusters Abell 2029 and Coma, we measure the luminosity functions (LFs) and stellar mass functions (SMFs) for the entire cluster member galaxies. Most importantly, we measure the velocity dispersion functions (VDFs) for quiescent members. The MMT/Hectospec redshift survey for galaxies in A2029 identifies 982 spectroscopic members; for 838 members, we derive the central velocity dispersion from the spectroscopy. Coma is the only other cluster surveyed as densely. The LFs, SMFs, and VDFs for A2029 and Coma are essentially identical. The SMFs of the clusters are consistent with simulations. The A2029 and Coma VDFs for quiescent galaxies have a significantly steeper slope than those of field galaxies for velocity dispersion  -100 km s 1 . The cluster VDFs also exceed the field at velocity dispersion  -250 km s 1 . The differences between cluster and field VDFs are potentially important tests of simulations and of the formation of structure in the universe.

Multiarmed nonlinear optical (NLO) molecules containing triphenylamine as a core and 4-(2-ethylhexylsulfonyl)benzene-(1E)-2-vinyl group or 4-{2-[4-(2-ethylhexylsulfonyl)phenyl]-(1E)-vinyl}benzene-(1E)-2-vinyl group as arms were synthesized (STEH series and SSEH series, respectively). Because triphenylamine linked to the sulfonylated stilbenic arms provided effective push-pull NLO structure and strong 2-D charge transfer, they were capable of both two-photon absorption (TPA) and photorefraction. Effective TPA cross sections of these molecules were as high as 0.94 × 10 -46 cm 4 ‚s and significantly enhanced as the number of arms and conjugation length increased. One-and two-armed STEH molecules (STEH1 and STEH2) showed moderate two-beam coupling gain coefficients (13.4 cm -1 at 45 V/µm and 17.4 cm -1 at 55 V/µm, respectively) and distinct diffraction efficiency (0.45% at 40 V/µm and 0.55% at 55 V/µm). On the other hand, the centrosymmetric three-armed STEH molecule exhibited no photorefraction at all. It is importantly claimed that the multiarmed bifunctional molecules of this work are easily fabricated into optically clear amorphous films by themselves, which is a key advantage toward potential applications such as solid-state optical limiting devices and two-photon excited photorefractive materials.

We explore connections between brightest cluster galaxies (BCGs) and their host clusters. We first construct a HeCS-omnibus cluster sample including 227 galaxy clusters within 0.02 < z < 0.30; the total number of spectroscopic members from MMT/Hectospec and SDSS observations is 52325. Taking advantage of the large spectroscopic sample, we compute physical properties of the clusters including the dynamical mass and cluster velocity dispersion (σ cl ). We also measure the central stellar velocity dispersion of the BCGs (σ * ,BCG s) to examine the relation between BCG velocity dispersion and cluster velocity dispersion for the first time. The observed relation between BCG velocity dispersion and the cluster velocity dispersion is remarkably tight. Interestingly, the σ * ,BCG /σ cl ratio decreases as a function of σ cl unlike the prediction from the numerical simulation of Dolag et al. (2010). The trend in σ * ,BCG /σ cl suggests that the BCG formation is more efficient in lower mass halos.

We explore the relations between size, stellar mass and average stellar population age (indicated by D n 4000 indices) for a sample of ∼ 11000 intermediate-redshift galaxies from the SHELS spectroscopic survey (Geller et al. 2014) augmented by high-resolution Subaru Telescope Hyper Suprime-Cam imaging. In the redshift interval 0.1 < z < 0.6, star forming galaxies are on average larger than their quiescent counterparts. The mass-complete sample of ∼ 3500 M * > 10 10 M quiescent galaxies shows that the average size of a 10 11 M quiescent galaxy increases by 25% from z ∼ 0.6 to z ∼ 0.1. This growth rate is a function of stellar mass: the most massive (M * > 10 11 M ) galaxies grow significntly more slowly in size than an order of magnitude less massive quiescent systems that grow by 70% in the 0.1 z 0.3 redshift interval. For M * < 10 11 M galaxies age and size are anti-correlated at fixed mass; more massive quiescent systems show no significant trend in size with average stellar population age. The evolution in absolute and fractional abundances of quiescent systems at intermediate redshift are also a function of galaxy stellar mass. The suite of evolutionary trends suggests that galaxies more massive than ∼ 10 11 M have mostly assembled their mass by z ∼ 0.6. Quiescent galaxies with lower stellar masses show more complex evolution that is characterized by a combination of individual quiescent galaxy size growth (through mergers) and an increase in the size of newly quenched galaxies joining the population at later times (progenitor bias). The low-mass population (M * ∼ 10 10 M ) grows predominantly as a result of progenitor bias. For more massive (M * ∼ 5 × 10 10 M ) quiescent galaxies, (predominantly minor) mergers and progenitor bias make more comparable contributions to the size growth. At intermediate redshift quiescent size growth is mass-dependent; the most massive (M * > 10 11 M ) galaxies experience the least rapid increase in size from z ∼ 0.6 to z ∼ 0.1.

We analyze the Illustris-1 hydrodynamical cosmological simulation to explore the stellar velocity dispersion of quiescent galaxies as an observational probe of dark matter halo velocity dispersion and mass. Stellar velocity dispersion is proportional to dark matter halo velocity dispersion for both central and satellite galaxies. The dark matter halos of central galaxies are in virial equilibrium and thus the stellar velocity dispersion is also proportional to dark matter halo mass. This proportionality holds even when a line-of-sight aperture dispersion is calculated in analogy to observations. In contrast, at a given stellar velocity dispersion, the dark matter halo mass of satellite galaxies is smaller than virial equilibrium expectations. This deviation from virial equilibrium probably results from tidal stripping of the outer dark matter halo. Stellar velocity dispersion appears insensitive to tidal effects and thus reflects the correlation between stellar velocity dispersion and dark matter halo mass prior to infall. There is a tight relation ( 0.2 dex scatter) between line-of-sight aperture stellar velocity dispersion and dark matter halo mass suggesting that the dark matter halo mass may be estimated from the measured stellar velocity dispersion for both central and satellite galaxies. We evaluate the impact of treating all objects as central galaxies if the relation we derive is applied to a statistical ensemble. A large fraction ( 2/3) of massive quiescent galaxies are central galaxies and systematic uncertainty in the inferred dark matter halo mass is 0.1 dex thus simplifying application of the simulation results to currently available observations.

We apply a friends-of-friends algorithm to an enhanced SDSS DR12 spectroscopic catalog including redshift from literature to construct a catalog of 1588 N ≥ 3 compact groups of galaxies containing 5179 member galaxies and covering the redshift range 0.01 < z < 0.19. This catalog contains 18 times as many systems and reaches 3 times the depth of similar catalog of Barton et al. (1996). We construct catalogs from both magnitude-limited and volume-limited galaxy samples. Like Barton et al. (1996) we omit the frequently applied isolation criterion in the compact group selection algorithm. Thus the groups selected by fixed projected spatial and rest frame line-of-sight velocity separation produce a catalog of groups with a redshift independent median size. In contrast with previous catalogs, the enhanced SDSS DR12 catalog (including galaxies with r < 14.5) includes many systems with z 0.05. The volume-limited samples are unique to this study. The compact group candidates in these samples have a median stellar mass independent of redshift. Groups with velocity dispersion 100 km s −1 show abundant evidence for ongoing dynamical interactions among the members. The number density of the volume-limited catalogs agrees with previous catalogs at the lowest redshifts but decreases as the redshift increases. The SDSS fiber placement constraints limit the catalog completeness. In spite of this issue the volume-limited catalogs provide a promising basis for detailed spatially resolved probes of the impact of galaxy-galaxy interactions within similar dense systems over a broad redshift range.

Dynamical analysis of compact groups provides important tests of models of compact group formation and evolution. By compiling 2066 redshifts from FLWO/FAST, from the literature, and from SDSS DR12 in the fields of compact groups in McConnachie et al. (2009), we construct the largest sample of compact groups with complete spectroscopic redshifts in the redshift range 0.01 < z < 0.22. This large redshift sample shows that the interloper fraction in the McConnachie et al. ( 2009) compact group candidates is ∼ 42%. A secure sample of 332 compact groups includes 192 groups with four or more member galaxies and 140 groups with three members. The fraction of early-type galaxies in these compact groups is 62%, slightly higher than for the original Hickson compact groups. The velocity dispersions of early-and late-type galaxies in compact groups change little with groupcentric radius; the radii sampled are less than 100 h −1 kpc, smaller than the radii typically sampled by members of massive clusters of galaxies. The physical properties of our sample compact groups include size, number density, velocity dispersion, and local environment; these properties slightly differ from those derived for the original Hickson compact groups and for the DPOSS II compact groups. Differences result from subtle differences in the way the group candidates were originally selected. The space density of the compact groups changes little with redshift over the range covered by this sample. The approximate constancy of the space density for this sample is a potential constraint on the evolution of compact groups on a few Gigayear timescale.

We investigate the connection between the presence of bars and AGN activity, using a volumelimited sample of ∼9,000 late-type galaxies with axis ratio b/a > 0.6 and M r < −19.5 + 5logh at low redshift (0.02 ≤ z 0.055), selected from Sloan Digital Sky Survey Data Release 7. We find that the bar fraction in AGN-host galaxies (42.6%) is ∼2.5 times higher than in non-AGN galaxies (15.6%), and that the AGN fraction is a factor of two higher in strong-barred galaxies (34.5%) than in non-barred galaxies (15.0%). However, these trends are simply caused by the fact that AGN-host galaxies are on average more massive and redder than non-AGN galaxies because the fraction of strong-barred galaxies (f SB ) increases with u − r color and stellar velocity dispersion. When u − r color and velocity dispersion (or stellar mass) are fixed, both the excess of f SB in AGN-host galaxies and the enhanced AGN fraction in strong-barred galaxies disappears. Among AGN-host galaxies we find no strong difference of the Eddington ratio distributions between barred and non-barred systems.These results indicate that AGN activity is not dominated by the presence of bars, and that AGN power is not enhanced by bars. In conclusion we do not find a clear evidence that bars trigger AGN activity.