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Register a new userChandra Spectroscopy and Mass Estimation of the Lensing Cluster of Galaxies CL0024+17
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Naomi Ota
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We present the X-ray analysis and the mass estimation of the lensing cluster of galaxies CL0024+17 with Chandra. We found that the temperature profile is consistent with being isothermal and the average X-ray temperature is 4.47 (+0.83, -0.54) keV. The X-ray surface brightness profile is represented by the sum of emissions associated with the central three bright elliptical galaxies and the emission from intracluster medium (ICM) which can be well described by a spherical beta-model. Assuming the ICM to be in the hydrostatic equilibrium, we estimated the X-ray mass and found it is significantly smaller than the strong lensing mass by a factor of 3.
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We present a detailed analysis of Chandra X-ray observations of the lensing cluster of galaxies CL0024+17 at z=0.395. We found that the radial temperature profile is consistent with being isothermal out to ~600 kpc and that the average X-ray temperature is 4.47 (+0.83, -0.54) keV. The X-ray surface brightness profile is represented by the sum of extended emission centered at the central bright elliptical galaxy with a small core of 50 kpc and more extended emission which can be well described by a spherical beta-model with a core radius of about 210 kpc. Assuming the X-ray emitting gas to be in hydrostatic equilibrium, we estimated the X-ray mass within the arc radius and found it is significantly smaller than the strong lensing mass by a factor of about 2--3. We detected a strong redshifted iron K line in the X-ray spectrum from the cluster for the first time and find the metal abundance to be 0.76 (+0.37, -0.31) solar.
We present a detailed analysis of the mass distribution in the rich and distant cluster of galaxies Cl0024+17. X-ray data come from both a deep ROSAT/HRI image of the field (Bohringer et al. 1999) and ASCA spectral data. Using a wide field CCD image of the cluster, we optically identify all the faint X-ray sources, whose counts are compatible with deep X-ray number counts. In addition we marginally detect the X-ray counter-part of the gravitational shear perturbation detected by Bonnet et al. (1994) at a 2.5 $sigma$ level. A careful spectral analysis of ASCA data is also presented. In particular, we extract a low resolution spectrum of the cluster free from the contamination by a nearby point source located 1.2 arcmin from the center. The X-ray temperature deduced from this analysis is $T_X = 5.7 ^{+4.9}_{-2.1}$ keV at the 90% confidence level. The comparison between the mass derived from a standard X-ray analysis and from other methods such as the Virial Theorem or the gravitational lensing effect lead to a mass discrepancy of a factor 1.5 to 3. We discuss all the possible sources of uncertainties in each method of mass determination and give some indications on the way to reduce them. A complementary study of optical data is in progress and may solve the X-ray/optical discrepancy through a better understanding of the dynamics of the cluster.
We derive an accurate mass distribution of the rich galaxy cluster Cl0024+1654 (z=0.395) based on deep Subaru BR_{c}z imaging and our recent comprehensive strong lensing analysis of HST/ACS/NIC3 observations. We obtain the weak lensing distortion and magnification of undilted samples of red and blue background galaxies by carefully combining all color and positional information. Unlike previous work, the weak and strong lensing are in excellent agreement where the data overlap. The joint mass profile continuously steepens out to the virial radius with only a minor contribution sim 10% in the mass from known subcluster at a projected distance of sim 700kpc/h. The projected mass distribution for the entire cluster is well fitted with a single Navarro-Frenk-White model with a virial mass, M_{vir} = (1.2 pm 0.2) times 10^{15} M_{sun}/h, and a concentration, c_{vir} = 9.2^{+1.4}_{-1.2}. This model fit is fully consistent with the depletion of the red background counts, providing independent confirmation. Careful examination and interpretation of X-ray and dynamical data strongly suggest that this cluster system is in a post collision state, which we show is consistent with our well-defined mass profile for a major merger occurring along the line of sight, viewed approximately 2-3Gyr after impact when the gravitational potential has had time to relax in the center, before the gas has recovered and before the outskirts are fully virialized. Finally, our full lensing analysis provides a model-independent constraint of M_{2D}(<r_{vir}) = (1.4 pm 0.3) times 10^{15} M_{sun}/h for the projected mass of the whole system, including any currently unbound material beyond the virial radius, which can constrain the sum of the two pre-merger cluster masses when designing simulations to explore this system.
We present a new method for measuring the projected mass distributions of galaxy clusters. The gravitational amplification is measured by comparing the joint distribution in redshift and magnitude of galaxies behind the cluster with that of field galaxies. We show that the total amplification is directly related to the surface mass density in the weak field limit, and so it is possible to map the mass distribution of the cluster. The method is shown to be limited by discreteness noise and galaxy clustering behind the lens. Galaxy clustering sets a lower limit to the error along the redshift direction, but a clustering independent lensing signature may be obtained from the magnitude distribution at fixed redshift. Statistical techniques are developed for estimating the surface mass density of the cluster. We extend these methods to account for any obscuration by cluster halo dust, which may be mapped independently of the dark matter. We apply the method to a series of numerical simulations and show the feasibility of the approach. We consider approximate redshift information, and show how the mass estimates are degraded.
We investigate the supercluster MS0302+17 (z~0.42) using weak lensing analysis and deep wide field CFH12k BVR photometry. Using (B-V) - (V-R) evolution tracks we identify supercluster early-types members. We derive a R band weak lensing background galaxies sample. We compute the correlations functions of light and mass and show that light traces mass on supercluster scales. The zeta-statistics applied in cluster centers and global correlation analyses over the whole field converge toward the simple relation M/L_B=300+/-30. This independently confirms the earlier results obtained by Kaiser et al.(1998). We model dark matter halos around each galaxy by truncated isothermal spheres and find the linear relation M L still holds. However, their averaged halo truncation radius is s* ~< 200 kpc close to clusters cores, whereas it reaches a lower limit of ~ 300 kpc at the periphery. This change of s_* as function of radial distance gives indications on tidal stripping but the lack of informations on the late-type galaxies sample prevents us to separate contributions. Though all the data at hands are consistent with mass is traced by light from early-type galaxies, we are not able to describe in details the contributions of late type galaxies. We however found it to be small.
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