E. Thommes

Probing the Distribution of Dark Matter in the A901/902 Supercluster with Weak Lensing

We present a weak-shear analysis of the A901/902 supercluster, composed of three rich clusters at z = 0.16. Using a deep R-band image from the 05 × 05 MPG/ESO Wide Field Imager together with supplementary B-band observations, we build up a comprehensive picture of the light and mass distributions in this region. We find that, on average, the light from the early-type galaxies traces the dark matter fairly well, although one cluster is a notable exception to this rule. The clusters themselves exhibit a range of mass-to-light (M/L) ratios, X-ray properties, and galaxy populations. We attempt to model the relation between the total mass and the light from the early-type galaxies with a simple scale-independent linear biasing model. We find M/LB = 130h for the early-type galaxies with zero stochasticity, which, if taken at face value, would imply Ωm < 0.1. However, this linear relation breaks down on small scales and on scales equivalent to the average cluster separation (~1 Mpc), demonstrating that a single M/L ratio is not adequate to fully describe the mass-to-light relation in the supercluster. Rather, the scatter in M/L ratios observed for the clusters supports a model incorporating nonlinear biasing or stochastic processes. Finally, there is a clear detection of filamentary structure connecting two of the clusters, seen in both the galaxy and dark matter distributions, and we discuss the effects of cluster-cluster and cluster-filament interactions as a means to reconcile the disparate descriptions of the supercluster.

Multi-color classification in the calar alto deep imaging survey

We use a multi-color classification method introduced by Wolf et al. ([CITE]) to reliably identify stars, galaxies and quasars in the up to 16-dimensional color space provided by the filter set of the Calar Alto Deep Imaging Survey (CADIS). The samples of stars, galaxies and quasars obtained this way have been used for dedicated studies which are published in separate papers. The classification is good enough to detect quasars rather completely and efficiently without confirmative spectroscopy. The multi-color redshifts are accurate enough for most statistical applications, e.g. evolutionary studies of the galaxy luminosity function. Also, the separation between stars and galaxies reaches deeper than with morphological criteria, so that studies of the stellar population can be extended to fainter levels. We characterize the dataset presently available on the CADIS 1 h-, 9 h- and 16 h-fields. Using Monte-Carlo simulations we model the classification performance expected for CADIS. We present a summary of the classification results on the CADIS database and discuss unclassified objects. More than 99% of the whole catalog sample at R < 22 (more than 95% at R < 23) are successfully classified matching the expectations derived from the simulations. A small number of peculiar objects challenging the classification is discussed in detail. Spectroscopic observations are used to check the reliability of the multi-color classification (6 mistakes among 151 objects with R < 24). From these, we also determine the accuracy of the multi-color redshifts which are rather good for galaxies (σ_z ≈ 0.03) and useful for quasars. We find that the classification performance derived from the simulations compares well with results from the real survey. Finally, we locate areas for potential improvement of the classification.

The Calar Alto Deep Imaging Survey:

We present K-band number counts for the faint galaxies in the Calar Alto Deep Imaging Survey (CADIS). We covered 4 CADIS fields, a total area of 0.2 deg^2, in the broad band filters B, R and K. We detect about 4000 galaxies in the K-band images, with a completeness limit of K = 19.75 mag, and derive the K-band galaxy number counts in the range of 14.25 18 mag. We also find that most of the K = 18 – 20 mag galaxies have a B - K color bluer than the prediction of a no-evolution model for an L⋆ Sbc galaxy, implying either significant evolution, even for massive galaxies, or the existence of an extra population of small galaxies.

K

The Calar Alto Deep Imaging Survey (CADIS) employs a combination of deep exposures in three broad bands (B,R,K) and up to 13 medium bands (R = λ/Δλ = 25... 50) with spectroscopic scans through an imaging Fabry-Perot-Interferometer (R ≃ 450). The survey will cover 10 fields of > 100□′, i.e. a total area of 0.3 □°. Although primarily designed to detect faint emission line galaxies at various intermediate (z = 0.2 ...1.4) and very high redshifts (z = 4.7, 5.7, 6.5) its multi-color strategy will also allow the detection and classification of hundreds of early type galaxies, faint QSOs, and extremely faint stars in our Galaxy. This contribution outlines the survey concept and its principal goals and then focuses on the expectations and first results of the search for “primeval” Ly-α emitting galaxies at z ≳ 5. More details about the data analysis and first results on faint field galaxies at intermediate redshift are presented in the contributions by Fockenbrock et al. and Thommes et al. to these proceedings.

-band Galaxy number counts

The Calar Alto Deep Imaging Survey (CADIS) is a very deep emission line survey (using a Fabry-Perot (FP)) combined with deep broad- and medium-band photometry (for details see Meisenheimer et. al., these proceedings). Though this survey project is specifically designed to detect primeval galaxies it will in addition produce a large data base for investigations of faint galaxies at intermediate redshifts (0.2 < z < 1.2). In this contribution we present some first results concerning these forground objects which we got from the first data recorded with the CADIS strategy. These data were taken with the 2.2m telescope at Calar Alto in the CADIS field 9H. Due to delays in getting the 2k×2k CCDs, we employed an a 1k×1k CCD (field of view 8′×8′). We got four FP settings in the wavelength region 814nm to 818.5nm (resolution=1.8nm). Every setting consists of 7 individual exposures of 1500 s integration. We reached a 5σ detection limit of S lim (5σ) ≈ 5×10-20W/m2. To get an estimate of the continuum near the emissions lines detected in the FP, we did exposures with a filter λ/Δλ=812/17 nm (F lim (5σ) ≈ 5.8 × 10-21W/(m2nm)). The FP exposures were supplemented by broad band exposures with the filters BV (centered at 500 nm, 5σ limit ≈ 25. m 8), Rc (5σ limit ≈ 25. m 0) and I (5σ limit ≈ 23. m 1). Further narrow band exposures with the filters 466/9 (F lim (5σ) ≈ 10.7 × 10-21W/(m2nm)), 612/10 (F lim (5σ) ≈ 10.8 10-21W/(m2nm)) and 614/28 (F lim (5σ) ≈ 6.6 × 10-21W/(m2nm)) enable to detect further emission lines of foreground objects.

The Calar Alto Deep Imaging Survey for Primeval Galaxies

The Calar Alto Deep Imaging Survey (CADIS) is a very deep emission line survey using a Fabry-Perot (FP), combined with deep broad- and medium-band photometry (for an overview see Hippelein et al. 1996). This survey is specifically designed to detect primeval galaxies, but it will in addition produce a large data base for investigations of faint galaxies at intermediate redshifts (0.2 < z < 1.2). We present some first results from the initial data recorded with the CADIS strategy.