Matthew M. Colless

The 2dF Galaxy Redshift Survey: hierarchical galaxy clustering

We use the Two-Degree Field Galaxy Redshift Survey (2dFGRS) to test the hierarchical scaling hypothesis: namely, that the p-point galaxy correlation functions can be written in terms of the two-point correlation function or variance. This scaling is expected if an initially Gaussian distribution of density fluctuations evolves under the action of gravitational instability. We measure the volume-averaged p-point correlation functions using a counts-in-cells technique applied to a volume-limited sample of 44 931 L-* galaxies. We demonstrate that L-* galaxies display hierarchical clustering up to order p= 6 in redshift space. The variance measured for L-* galaxies is in excellent agreement with the predictions from a Lambda-cold dark matter N-body simulation. This applies to all cell radii considered, 0.3 < (R/h(-1) Mpc) < 30. However, the higher order correlation functions of L-* galaxies have a significantly smaller amplitude than is predicted for the dark matter for R < 10 h(-1) Mpc. This disagreement implies that a non-linear bias exists between the dark matter and L-* galaxies on these scales. We also show that the presence of two rare, massive superclusters in the 2dFGRS has an impact on the higher-order clustering moments measured on large scales.

A relation between the characteristic stellar ages of galaxies and their intrinsic shapes

Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum1–3. A galaxy’s mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy’s mass was assembled. Resolved stellar dynamics4 trace the change in angular momentum due to mergers, but major mergers tend to obscure the effect of earlier interactions5. With the rise of large multi-object integral field spectroscopic surveys, such as SAMI6 and MaNGA7, and single-object integral field spectroscopic surveys (for example, ATLAS3D (ref. 8), CALIFA9, MASSIVE10), it is now feasible to connect a galaxy′s star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, morphology and environment4,11,12. Using the SAMI Galaxy Survey, here we present a combined study of spatially resolved stellar kinematics and global stellar populations. We find a strong correlation of stellar population age with location in the (V/σ,

The WiggleZ Project: AA Omega and dark energy

{\boldsymbol{\epsilon}}_{{\boldsymbol{e}}}

The 6dF Galaxy Survey: Z almost equal to 0 measurements of the growth rate and sigma 8

ϵe) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well.Α combined study of spatially resolved stellar kinematics and global stellar populations with the SAMI Galaxy Survey finds a strong correlation between the characteristic stellar population age of a galaxy and its intrinsic ellipticity.