Wide-field spectroscopy of A1689 and A1835 with VIMOS: First results

We are using VIMOS to conduct a wide-field spectroscopic survey covering fields of 0.5 x 0.5 sqdeg around the X-ray luminous clusters of galaxies Abell 1689 (z = 0.185) and Abell 1835 (z = 0.25). Here we describe the observations and first results on the redshift distribution of subsamples of cluster galaxies to R~22 for which we at present have obtained secure redshifts. These subsamples constitute ~40% of the total spectroscopic sample and contain 525 and 630 cluster members in Abell 1689 and Abell 1835, respectively, placing them amongst the largest redshift samples available for any cluster of galaxies.Comment: 6 pages, 4 figures, to appear in Proc. of IAU Colloq. 195: "Outskirts of Galaxy Clusters: Intense Life in the Suburbs", ed. A. Diaferio et al., Turin 12-16 March 200

Quantifying dwarf satellites through gravitational imaging: the case of SDSS J120602.09+514229.5

SDSS J120602.09+514229.5 is a gravitational lens system formed by a group of galaxies at redshift z=0.422 lensing a bright background galaxy at redshift z=2.001. The main peculiarity of this system is the presence of a luminous satellite near the Einstein radius, that slightly deforms the giant arc. This makes SDSS J120602.09+514229.5 the ideal system to test our grid-based Bayesian lens modelling method, designed to detect galactic satellites independently from their mass-to-light ratio, and to measure the mass of this dwarf galaxy despite its high redshift. Thanks to the pixelized source and potential reconstruction technique of Vegetti and Koopmans 2009a we are able to detect the luminous satellite as a local positive surface density correction to the overall smooth potential. Assuming a truncated Pseudo-Jaffe density profile, the satellite has a mass M=(2.75+-0.04)10^10 M_sun inside its tidal radius of r_t=0.68". We determine for the satellite a luminosity of L_B=(1.6+-0.8)10^9 L_sun, leading to a total mass-to-light ratio within the tidal radius of (M/L)_B=(17.2+-8.5) M_sun/L_sun. The central galaxy has a sub-isothermal density profile as in general is expected for group members. From the SDSS spectrum we derive for the central galaxy a velocity dispersion of sigma_kinem=380+-60 km/s within the SDSS aperture of diameter 3". The logarithmic density slope of gamma=1.7+0.25-0.30 (68% CL), derived from this measurement, is consistent within 1-sigma with the density slope of the dominant lens galaxy gamma~1.6, determined from the lens model. This paper shows how powerful pixelized lensing techniques are in detecting and constraining the properties of dwarf satellites at high redshift.Comment: Submitted to MNRAS; Abstract abridge

A combined HST/CFH12k/XMM survey of X-ray luminous clusters of galaxies at z~0.2

We describe a project to study a sample of X-ray luminous clusters of galaxies at redshift z~0.2 at several scales (with HST/WFPC2 and CFHT/CFH12k) and wavebands (optical and X-ray). The main aims of the project are (i) to determine the mass profiles of the clusters on scales ranging from ~10 kpc/h to >1.5 Mpc/h using weak and strong lensing, thereby testing theoretical predictions of a ``universal mass profile'', and (ii) to calibrate the M_tot - T_X relation in view of future application in the study of the evolution of the cluster mass function at higher redshift.Comment: 4 pages, 2 figures, Proceedings of the XXth Moriond Astrophysics Meeting ``Cosmological Physics with Gravitational Lensing'', J.-P. Kneib, Y. Mellier, M. Moniez and J. Tran Thanh Van eds., 200

CLASH-VLT: Is there a dependence in metallicity evolution on galaxy structures?

We investigate the environmental dependence of the mass-metallicty (MZ) relation and it's connection to galaxy stellar structures and morphologies. In our studies, we analyze galaxies in massive clusters at z~0.4 from the CLASH (HST) and CLASH-VLT surveys and measure their gas metallicities, star-formation rates, stellar structures and morphologies. We establish the MZ relation for 90 cluster and 40 field galaxies finding a shift of ~-0.3 dex in comparison to the local trends seen in SDSS for the majority of galaxies with logM<10.5. We do not find significant differences of the distribution of 4 distinct morphological types that we introduce by our classification scheme (smooth, disc-like, peculiar, compact). Some variations between cluster and field galaxies in the MZ relation are visible at the high mass end. However, obvious trends for cluster specific interactions (enhancements or quenching of SFRs) are missing. In particular, galaxies with peculiar stellar structures that hold signs for galaxy interactions, are distributed in a similar way as disc-like galaxies - in SFRs, masses and O/H abundances. We further show that our sample falls around an extrapolation of the star-forming main sequence (the SFR-M* relation) at this redshift, indicating that emission-line selected samples do not have preferentially high star-formation rates (SFRs). However, we find that half of the high mass cluster members (M*>10^10Msun) lie below the main sequence which corresponds to the higher mass objects that reach solar abundances in the MZ diagram.Comment: Proceedings of IAU Symposium 309, Vienna, ed. B.L. Ziegler, F. Combes, H. Dannerbauer, M. Verdug

SimCADO - an instrument data simulator package for MICADO at the E-ELT

MICADO will be the first-light wide-field imager for the European Extremely Large Telescope (E-ELT) and will provide difiraction limited imaging (7mas at 1.2mm) over a ~53 arcsecond field of view. In order to support various consortium activities we have developed a first version of SimCADO: an instrument simulator for MICADO. SimCADO uses the results of the detailed simulation efforts conducted for each of the separate consortium-internal work packages in order to generate a model of the optical path from source to detector readout. SimCADO is thus a tool to provide scientific context to both the science and instrument development teams who are ultimately responsible for the final design and future capabilities of the MICADO instrument. Here we present an overview of the inner workings of SimCADO and outline our plan for its further development.Comment: to appear in Ground-based and Airborne Instrumentation for Astronomy VI, eds. Evans C., Simard L., Takami H., Proc. SPIE vol. 9908 id 73; 201

A CFH12k lensing survey of X-ray luminous galaxy clusters. II. Weak lensing analysis and global correlations

Aims. We present a wide-field multi-color survey of a homogeneous sample of eleven clusters of galaxies for which we measure total masses and mass distributions from weak lensing. This sample, spanning a small range in both X-ray luminosity and redshift, is ideally suited to determining the normalisation of scaling relations between X-ray properties of clusters and their masses (the M − T_X and the M − L_X relations) and also estimating the scatter in these relations at a fixed luminosity. Methods. The eleven clusters in our sample are all X-ray luminous and span a narrow redshift range at z = 0.21 ± 0.04. The weak lensing analysis of the sample is based on ground-based wide-field imaging obtained with the CFH12k camera on CFHT. We use the methodology developed and applied previously on the massive cluster Abell 1689. A Bayesian method, implemented in the Im2shape software, is used to fit the shape parameters of the faint background galaxies and to correct for PSF smearing. A multi-color selection of the background galaxies is applied to retrieve the weak lensing signal, resulting in a background density of sources of ~10 galaxies per square arc minute. With the present data, shear profiles are measured in all clusters out to at least 2 Mpc (more than 15 from the center) with high confidence. The radial shear profiles are fitted with different parametric mass profiles and the virial mass M_(200) is estimated for each cluster and then compared to other physical properties. Results. Scaling relations between mass and optical luminosity indicate an increase of the M/L ratio with luminosity (M/L ∝ L^(0.8)) and a LX−M_(200) relation scaling as L_X ∝ M^(0.83±0.11)_(200) while the normalization of the M_(200) ∝ T^(3/2)_X relation is close to the one expected from hydrodynamical simulations of cluster formation as well as previous X-ray analyses. We suggest that the dispersion in the M_(200) − T_X and M_(200) − L_X relations reflects the different merging and dynamical histories for clusters of similar X-ray luminosities and intrinsic variations in their measured masses. Improved statistics of clusters over a wider mass range are required for a better control of the intrinsic scatter in scaling relations

Weighing the Giants II: Improved Calibration of Photometry from Stellar Colors and Accurate Photometric Redshifts

We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colors as well as to adjust the instrument flat field. By developing a spectroscopic model for the SDSS stellar locus in color-color space, synthesizing an expected stellar locus, and simultaneously solving for all unknown zeropoints when fitting to the instrumental locus, we increase the calibration accuracy of stellar locus matching. We also use a new combined technique to estimate improved flat-field models for the Subaru SuprimeCam camera, forming `star flats' based on the magnitudes of stars observed in multiple positions or through comparison with available SDSS magnitudes. These techniques yield galaxy magnitudes with reliable color calibration (< 0.01 - 0.02 mag accuracy) that enable us to estimate photometric redshift probability distributions without spectroscopic training samples. We test the accuracy of our photometric redshifts using spectroscopic redshifts z_s for ~5000 galaxies in 27 cluster fields with at least five bands of photometry, as well as galaxies in the COSMOS field, finding sigma((z_p - z_s)/(1 + z_s)) ~ 0.03 for the most probable redshift z_p. We show that the full posterior probability distributions for the redshifts of galaxies with five-band photometry exhibit good agreement with redshifts estimated from thirty-band photometry in the COSMOS field. The growth of shear with increasing distance behind each galaxy cluster shows the expected redshift-distance relation for a flat Lambda-CDM cosmology. Photometric redshifts and calibrated colors are used in subsequent papers to measure the masses of 51 galaxy clusters from their weak gravitational shear. We make our Python code for stellar locus matching available at http://big-macs-calibrate.googlecode.com; the code requires only a catalog and filter functions.Comment: Accepted by MNRAS with only minor revisions. Code available: http://big-macs-calibrate.googlecode.com (v2 latex symbols removed from abstract