Published on August 29, 2007
Slide1: SHAPLEY OPTICAL SURVEY (SOS): LUMINOSITY AND COLOURS OF GALAXIES A. Mercurio, P. Merluzzi, C. P. Haines, A. Gargiulo, N. Krusanova, G. Busarello, F. La Barbera, The SOS project Shapley environments Luminosity function vs. environment Colour-Magnitude relation Galaxy Colours SISCO meeting - Edimburg 15/09/05 Shapley Optical Survey Project: Shapley Optical Survey Project OAC pilot project for VESUVIO VST extra-galactic survey Science goals : Global galaxy properties (luminosity function, CM relation, structural parameters) as a function of environment both in terms of local galaxy density and ICM Technical goals : 'Know-how' to reduce and analyse wide-field data rapidly and automatically. Tools to clean catalogues, extract global galaxy properties, quantify environment. SISCO meeting - Edimburg 15/09/05 Shapley Optical Survey Project: As well as being a pilot-project from the observational / technical side of VESUVIO, Shapley is a optimal system for a pilot study, because: It provides a vary large sample of galaxies associated with a single structure. There is a wealth of multi-wavelength data on the core of the Shapley Supercluster, e.g. X-ray luminosities, redshift and galaxy distributions. Many of the environments / processes we wish to study in VESUVIO superclusters are present here, e.g. cluster mergers, infalling groups, although the complex dynamics makes life difficult / interesting disentangling the different processes in action. Shapley Optical Survey Project SISCO meeting - Edimburg 15/09/05 Wide-field optical imaging of Shapley supercluster: Wide-field optical imaging of Shapley supercluster Archive ESO / WFI imaging of eight 34’x33’ fields. Pixel scale = 0.238 arcsec. Size of each field 2.0x1.9 h-270 Mpc2. 1 200s B, 1 500s R. SISCO meeting - Edimburg 15/09/05 Wide-field optical imaging of Shapley supercluster: Wide-field optical imaging of Shapley supercluster Density contours obtained from SuperCOSMOS catalogues Wide-field optical imaging of Shapley supercluster: Wide-field optical imaging of Shapley supercluster Archive ESO / WFI imaging of eight 34’x33’ fields. Pixel scale = 0.238 arcsec. Size of each field 2.0x1.9 h-270 Mpc2. 1 200s B, 1 500s R. Complete to B=23.5, R=23. Reliable to B=22.5 (andgt; M*+6; Ngal=16588), R=22.0 (andgt;M*+7; Ngal=28008) Colours determined using 17 arcsec (8 kpc) apertures. SISCO meeting - Edimburg 15/09/05 Galaxy catalogues: Developed tools to automatically clean the catalogues output by SExtractor, e.g. spurious detections, correct if Kron aperture too large, sources near bright stars / galaxies, star/galaxy blends. Critical for LF and CM studies is the ability to accurately account for the contamination from background galaxies. Using 5 deg2 of deep (BVR~27) imaging taken from the Deep Lens Survey ( Wittman et al. 2002). Provides accurate photometry and classification for andgt;100,000 galaxies to R=23. Wide area covered (2.2 deg2) means effects of cosmic variance reduced for LF determination, but increases importance of having clean and well photometrically calibrated catalogues. For this reason we use a conservative magnitude limit. Galaxy catalogues SISCO meeting - Edimburg 15/09/05 Slide8: Density map Density map shows complex dynamical system, with a trail of galaxies connecting the 2 merging clusters A3558 and A3562, wheras A3556 appears isolated, and an infalling group is apparent. Shapley supercluster environment: Shapley supercluster environment Galaxy luminosity function: Galaxy luminosity function Galaxy LF for supercluster core region determined to ~ M*+6. Best described by combination of Gaussian and Schechter functions to model giant and dwarf galaxy populations. Apparent dip at MR~ -19 as seen for rich, evolved low-z clusters (e.g. Coma), suggesting separation of the two populations Galaxy luminosity functions in different environments: Galaxy luminosity functions in different environments Dip becomes more prominent with decreasing density. Faint-end slope becomes shallower with density. Colour-magnitude relation: Statistically subtract background galaxies using the Deep Lens Survey data. Calculate probability that each galaxy is a member using : P(member) = 1 - [ ρ (R,B-R)DLS / ρ (R,B-R)Shapley ] Very strong red sequence made up of many 100s of galaxies from 3 rich cluster and 2 groups Galaxies redder than CRS are all from field, and so a simple colour cut 0.2mag redder than CRS can reduce contamination greatly for measuring local density or LF. Colour-magnitude relation Galaxy colours: Galaxy colours Red galaxies are concentrated in cluster cores, but correspond best with centres of X-ray emission (Finoguenov et al. 2004) rather than peaks in galaxy density. Mean environment as function of colours and luminosities: Mean environment as function of colours and luminosities Strong segregation between red and blue galaxies. No luminosity-dependence for environment except at the very brightest magnitudes, which are clustered in the highest density regions Comparison between blue and red galaxy distributions: Comparison between blue and red galaxy distributions Blue galaxies appear spread across the whole field, while red galaxies are highly concentrated. Comparison between blue and red galaxy distributions: Comparison between blue and red galaxy distributions Several localised overdensities of blue galaxies are apparent along the filamentary structure connecting A3562 and A3558. Blue galaxy fraction: Blue galaxy fraction Blue galaxies avoid the cluster centers and are concident with regions containing high fraction of galaxies with radio emission (Miller et al. 2005) Conclusions: Conclusions Bimodal distribution of galaxy populations as pointed out by the presence of a dip at MR ~ -19.0 in the LF. Faint-end slope becomes shallower with increasing galaxy local density. Strong colour segregation. Several localised overdensities of blue galaxies are apparent along the filamentary structure connecting A3562 and A3558. Galaxy harassment or ram-pressure stripping. Merging of the two clusters.