Galaxy and Mass Assembly (GAMA): Demonstrating the power of WISE in the study of Galaxy Groups to z < 0.1

Combining high-fidelity group characterisation from the Galaxy and Mass Assembly (GAMA) survey and source-tailored z < 0.1 photometry from the WISE survey, we present a comprehensive study of the properties of ungrouped galaxies, compared to 497 galaxy groups (4≤ NFoF ≤ 20) as a function of stellar and halo mass. Ungrouped galaxies are largely unimodal in WISE color, the result of being dominated by star-forming, late-type galaxies. Grouped galaxies, however, show a clear bimodality in WISE color, which correlates strongly with stellar mass and morphology. We find evidence for an increasing earlytype fraction, in stellar mass bins between 1010 .Mstellar . 1011 M , with increasing halo mass. Using ungrouped, late-type galaxies with star-forming colors (W2−W3>3), we define a star-forming mainsequence (SFMS), which we use to delineate systems that have moved below the sequence (“quenched” for the purposes of this work). We find that with increasing halo mass, the relative number of latetype systems on the SFMS decreases, with a corresponding increase in early-type, quenched systems at high stellar mass (Mstellar > 1010.5 M ), consistent with mass quenching. Group galaxies with masses Mstellar < 1010.5 M show evidence of quenching consistent with environmentally-driven processes. The stellar mass distribution of late-type, quenched galaxies suggests they may be an intermediate population as systems transition from being star-forming and late-type to the “red sequence”. Finally, we use the projected area of groups on the sky to extract groups that are (relatively) compact for their halo mass. Although these show a marginal increase in their proportion of high mass and early-type galaxies compared to nominal groups, a clear increase in quenched fraction is not evident

Star formation suppression in compact group galaxies: A new path to quenching?

We present CO(1-0) maps of 12 warm H2-selected Hickson Compact Groups (HCGs), covering 14 individually imaged warm H2 bright galaxies, with the Combined Array for Research in Millimeter Astronomy. We found a variety of molecular gas distributions within the HCGs, including regularly rotating disks, bars, rings, tidal tails, and possibly nuclear outflows, though the molecular gas morphologies are more consistent with spirals and early-type galaxies than mergers and interacting systems. Our CO-imaged HCG galaxies, when plotted on the Kennicutt-Schmidt relation, shows star formation (SF) suppression of distributed bimodally, with five objects exhibiting suppressions of 10 and depletion timescales 10 Gyr. This SF inefficiency is also seen in the efficiency per freefall time of Krumholz et al. We investigate the gas-to-dust ratios of these galaxies to determine if an incorrect LCO-M(H2) conversion caused the apparent suppression and find that HCGs have normal gas-to-dust ratios. It is likely that the cause of the apparent suppression in these objects is associated with shocks injecting turbulence into the molecular gas, supported by the fact that the required turbulent injection luminosity is consistent with the bright H2 luminosity reported by Cluver et al. Galaxies with high SF suppression ( 10) also appear to be those in the most advanced stages of transition across both optical and infrared color space. This supports the idea that at least some galaxies in HCGs are transitioning objects, where a disruption of the existing molecular gas in the system suppresses SF by inhibiting the molecular gas from collapsing and forming stars efficiently. These observations, combined with recent work on poststarburst galaxies with molecular reservoirs, indicates that galaxies do not need to expel their molecular reservoirs prior to quenching SF and transitioning from blue spirals to red early-type galaxies. This may imply that SF quenching can occur without the need to starve a galaxy of cold gas first

The 6dF galaxy survey: fundamental plane data

We report the 6dFGS Fundamental Plane (6dFGSv) catalogue that is used to estimate distances and peculiar velocities for nearly 9000 early-type galaxies in the local (z < 0.055) universe. Velocity dispersions are derived by cross-correlation from 6dF V-band spectra with typical S/N of 12.9 Å−1 for a sample of 11 315 galaxies; the median velocity dispersion is 163 km s−1 and the median measurement error is 12.9 per cent. The photometric Fundamental Plane (FP) parameters (effective radii and surface brightnesses) are determined from the JHK 2MASS images for 11 102 galaxies. Comparison of the independent J- and K-band measurements implies that the average uncertainty in XFP, the combined photometric parameter that enters the FP, is 0.013 dex (3 per cent) for each band. Visual classification of morphologies was used to select a sample of nearly 9000 early-type galaxies that form 6dFGSv. This catalogue has been used to study the effects of stellar populations on galaxy scaling relations, to investigate the variation of the FP with environment and galaxy morphology, to explore trends in stellar populations through, along and across the FP, and to map and analyse the local peculiar velocity field

Discovery of a supercluster in the Zone of Avoidance in Vela

We report the discovery of a potentially major supercluster that extends across the Galactic plane in the constellation of Vela, at a mean recessional velocity of ~18 000 km s-1. Recent multiobject spectroscopic observations of this Vela supercluster (VSCL), using AAOmega+2dF and the Southern African Large Telescope, confirm an extended galaxy overdensity in the Zone of Avoidance (ZOA) located where residual bulk flows predict a considerable mass excess. We present a preliminary analysis of ~4500 new spectroscopic galaxy redshifts obtained in the ZOA centred on the Vela region (l = 272. ° 5 ± 20°, b = 0° ± 10°). The presently sparsely sampled data set traces an overdensity that covers 25° in Galactic longitude on either side of the Galactic plane, suggesting an extent of 25 × 20 deg2, corresponding to ~ 115×90 h70 Mpc at the supercluster redshift. In redshift space, the overdensity appears to consist of two merging wall-like structures, interspersed with clusters and groups. Both the velocity histogram and the morphology of the multibranching wall structure are consistent with a supercluster classification. Ks o galaxy counts show an enhancement of ~1.2 over the survey area for galaxies brighter than MK * at the VSCL distance, and a galaxy overdensity of δ = 0.50-0.77 within a photometric redshift shell around the VSCL, when compared with various Two Micron All-Sky Survey samples. Taking account of selection effects, the VSCL is estimated to contribute vLG ≳ 50 km s-1 to the motion of the Local GroupRCK-K, THJ, and MEC acknowledge research support from the NRF. MB is supported through grants #614.001.451 from the NWO, FP7 #279396 from the ERC, and #UMO-2012/07/D/ST9/02785 from the NC

The detection of a massive chain of dark H I Clouds in the GAMA G23 Field

Interstellar matter and star formatio

Galaxy And Mass Assembly (GAMA): data release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions

Galaxie