Search

Stacking cosmic microwave background maps around known galaxy clusters and groups provides a powerful probe of the distribution of hot gas in these systems via the Sunyaev- Zel'dovich (SZ) effect. A stacking analysis allows one to detect the average SZ signal around low-mass haloes, to extend measurements out to large scales and measure the redshift dependence of the SZ background. Motivated by these exciting prospects, we measure the two-point cross-correlation function between ∼380 000 galaxy groups (at z = 0.01-0.2) from the Sloan Digital Sky Survey and Compton-y parameter maps constructed by the Planck collaboration. We find statistically significant correlations in each of six separate mass bins, with halo masses ranging from 1011.5 to 1015.5 M☉ h-1. We compare with halo models of the SZ signal, which describe the stacked measurement in terms of one-halo and two-halo contributions. The onehalo term quantifies the average pressure profile around the groups in a mass bin, while the two-halo term describes the contribution of correlated neighbouring haloes. For the massive groups, we find clear evidence for the one and two-halo regimes, while groups with mass below 1013M☉ h-1 are dominated by the two-halo term, given the resolution of Planck data. We use the signal in the two-halo regime to determine the bias-weighted electron pressure of the Universe: ≺bPe≻ = 1.50 ± 0.226 × 10-7 keV cm-3 (1σ) at z ≈ 0.15. [ABSTRACT FROM AUTHOR]

We extend the catalogue of two-dimensional, Point-Spread-Function-corrected de Vacouleurs, Sérsic, de Vacouleurs+Exponential, and Sérsic+Exponential fits of ~7 × 105 galaxies presented in Meert et al. to include the g and i bands. Fits are analysed using the physically motivated flagging system presented in the original text, making adjustments for the differing signal to noise when necessary. We compare the fits in each of the g, r, and i bands. Fixed aperture magnitudes and colours are also provided for all galaxies. The catalogues are available in electronic format. [ABSTRACT FROM AUTHOR]

Using archival data from the Hubble Space Telescope, we study the quantitative morphological evolution of spectroscopically confirmed bright galaxies in the core regions of nine clusters ranging in redshift from to . We use morphological parameters derived from two-dimensional bulge–disc decomposition to study the evolution. We find an increase in the mean bulge-to-total luminosity ratio as the Universe evolves. We also find a corresponding increase in the fraction of early-type galaxies and in the mean Sérsic index. We discuss these results and their implications to physical mechanisms for evolution of galaxy morphology. [ABSTRACT FROM AUTHOR]