50 research outputs found
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
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
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
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
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 â T_X and the M â 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 â L^(0.8)) and a LXâM_(200) relation scaling as L_X â M^(0.83±0.11)_(200) while the normalization of the M_(200) â 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) â T_X and M_(200) â 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
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
Two-dimensional kinematics of SLACS lenses: I. Phase-space analysis of the early-type galaxy SDSS J2321-097 at z=0.1
We present the first results of a combined VLT VIMOS integral-field unit and
Hubble Space Telescope (HST)/ACS study of the early-type lens galaxy SDSS
J2321-097 at z=0.0819, extending kinematic studies to a look-back time of 1
Gyr. This system, discovered in the Sloan Lens ACS Survey (SLACS), has been
observed as part of a VLT Large Programme with the goal of obtaining
two-dimensional stellar kinematics of 17 early-type galaxies to z~0.35 and Keck
spectroscopy of an additional dozen lens systems. Bayesian modelling of both
the surface brightness distribution of the lensed source and the
two-dimensional measurements of velocity and velocity dispersion has allowed
us, under the only assumptions of axisymmetry and a two-integral stellar
distribution function (DF) for the lens galaxy, to dissect this galaxy in three
dimensions and break the classical mass--anisotropy, mass-sheet and
inclination--oblateness degeneracies. Our main results are that the galaxy (i)
has a total density profile well described by a single power-law rho propto
r^{-gamma'} with gamma'=2.06^{+0.03}_{-0.06}; (ii) is a very slow rotator
(specific stellar angular momentum parameter lambda_R = 0.075); (iii) shows
only mild anisotropy (delta ~ 0.15); and (iv) has a dark matter contribution of
~30 per cent inside the effective radius. Our first results from this large
combined imaging and spectroscopic effort with the VLT, Keck and HST show that
the structure of massive early-type galaxies beyond the local Universe can now
be studied in great detail using the combination of stellar kinematics and
gravitational lensing. Extending these studies to look-back times where
evolutionary effects become measurable holds great promise for the
understanding of formation and evolution of early-type galaxies.Comment: 16 pages, 12 figures; accepted for publication in MNRAS; corrected
typo