Showing papers by "Nabila Aghanim published in 2001"
TL;DR: In this article, a methodology for spatially resolved spectroscopy of extended sources, adapted to XMM background and vignetting characteristics, was proposed to correct for particle induced background.
Abstract: Using the PV observation of A1795, we illustrate the capability of XMM-EPIC to measure cluster temperature profiles, a key ingredient for the determination of cluster mass profiles through the equation of hydrostatic equilibrium. We develop a methodology for spatially resolved spectroscopy of extended sources, adapted to XMM background and vignetting characteristics. The effect of the particle induced background is discussed. A simple unbiased method is proposed to correct for vignetting effects, in which every photon is weighted according to its energy and location on the detector. We were able to derive the temperature profile of A1795 up to 0.4 times the virial radius. A significant and spatially resolved drop in temperature towards the center () is observed, which corresponds to the cooling flow region of the cluster. Beyond that region, the temperature is constant with no indication of a fall-off at large radii out to 1.2 Mpc.
152 citations
TL;DR: In this article, a temperature map and a temperature profile of the central part (r < 20' or 1/4 virial radius) of the Coma cluster were presented, where five overlapping pointings made with XMM/EPIC/MOS and extracted spectra were combined.
Abstract: We present a temperature map and a temperature profile of the central part (r < 20' or 1/4 virial radius) of the Coma cluster. We combined 5 overlapping pointings made with XMM/EPIC/MOS and extracted spectra in boxes of 3.5' x 3.5'. The temperature distribution around the two central galaxies is remarkably homogeneous (r < 10'), contrary to previous ASCA results, suggesting that the core is actually in a relaxed state. At larger distance from the cluster center we do see evidence for recent matter accretion. We confirm the cool area in the direction of NGC 4921, probably due to gas stripped from an infalling. group. We find ir;dications of a hot front in the South West, in the direction of NGC 4839, probably due to an adiabatic compression.
141 citations
TL;DR: In this paper, the authors present the first analysis of the XMM-Newton EPIC-MOS data of the galaxy group around NGC 4839, which lies at a projected distance to the Coma cluster center of 1.6h 1 50 Mpc.
Abstract: We present here the rst analysis of the XMM-Newton EPIC-MOS data of the galaxy group around NGC 4839, which lies at a projected distance to the Coma cluster center of 1.6h 1 50 Mpc. In our analysis, which includes imaging, spectro-imaging and spectroscopy we nd compelling evidence for the sub group being on its rst infall onto the Coma cluster. The complex temperature structure around NGC 4839 is consistent with simulations of galaxies falling into a cluster environment. We see indications of a bow shock and of ram pressure stripping around NGC 4839. Furthermore our data reveal a displacement between NGC 4839 and the center of the hot gas in the group of about 300h 1 50 kpc. With a simple approximation we can explain this displacement by the pressure force originating from the infall, which acts much stronger on the group gas than on the galaxies.
124 citations
TL;DR: The Coma cluster of galaxies was observed with XMM-Newton in 12 partially overlapping pointings as discussed by the authors, and the resulting X-ray map in different energy bands and discuss the large scale structure of this cluster.
Abstract: The Coma cluster of galaxies was observed with XMM-Newton in 12 partially overlapping pointings. We present here the resulting X-ray map in different energy bands and discuss the large scale structure of this cluster. Many point sources were found throughout the observed area, at least 11 of them are coincident with bright galaxies. We also give a hardness ratio map at the so far highest angular resolution obtained for a cluster of galaxies. In this map we found soft regions at the position of bright galaxies, little variation in the central 15 arcmin, but some harder regions north of the line NGC 4874 -NGC 4889.
76 citations
TL;DR: In this paper, the authors used the standard scaling relations of cluster properties with z and temperature, with the empirical slope of the Mgas-T relation derived by Neumann & Arnaud (2001), to study the ROSAT surface brightness profiles of a sample of 25 distant (0.3 3.5keV) clusters.
Abstract: We study the ROSAT surface brightness profiles of a sample of 25 distant (0.3 3.5keV) clusters. For both open and flat cosmological models, the derived emission measure profiles are scaled according to the self-similar model of cluster formation. We use the standard scaling relations of cluster properties with z and temperature, with the empirical slope of the Mgas-T relation derived by Neumann & Arnaud (2001). Using a \chi^2 test, we perform a quantitative comparison of the scaled emission measure profiles of distant clusters with a reference profile derived from the sample of 15 hot nearby clusters compiled by Neumann & Arnaud (1999), which were found to obey self-similarity. For a low density flat universe, the distant cluster scaled data were found to be consistent, both in shape and normalisation, with the reference local profile.It indicates that hot clusters constitute a homologous family up to high z, and supports the standard picture of structure formation for the dark matter component. Because of the intrinsic regularity in the hot cluster population, the scaled profiles can be used as distance indicators, the correct cosmology being the one for which the profiles at different redshifts coincide. The present data allow us to put a tight constraint on Omega0 for a flat Universe: Omega0=0.40^{+0.15}_{-0.12} at 90% confidence level (statistical errors only). The critical model was excluded at the 98% confidence level. Consistently, the observed evolution of the normalisation of the Lx-T relation was found to comply with the self-similar model for Omega0=0.4, Lambda=0.6. The constraint derived on Omega0 is in remarkable agreement with the constraint obtained from SNI or from combined analysis of the power spectrum of the 2dFGRS and the CMB anisotropy. ABRIDGED
67 citations
TL;DR: In this paper, the authors evaluate the error in the individual radial peculiar velocities determined with Sunyaev-Zel'dovich measurements for three cosmological models, including the errors induced by the major contributing signals (primary Cosmic Microwave Background anisotropies, SZ components, residuals from component separation and instrumental noise).
Abstract: The Sunyaev-Zel'dovich eect is a powerful tool for cosmology that can be used to measure the radial peculiar velocities of galaxy clusters, and thus to test, and constrain theories of structure formation and evolution. This requires, in principle, an accurate measurement of the eect, a good separation between the Sunyaev- Zel'dovich components, and a good understanding of the sources contributing to the signal and their eect on the measured velocity. In this study, we evaluate the error in the individual radial peculiar velocities determined with Sunyaev-Zel'dovich measurements. We estimate, for three cosmological models, the errors induced by the major contributing signals (primary Cosmic Microwave Background anisotropies, Sunyaev-Zel'dovich eect due to the background cluster population, residuals from component separation and instrumental noise). We generalise our results to estimate the error in the bulk velocity on large scales. In this context, we investigate the limitation due to the Sunyaev-Zel'dovich source (or spatial) confusion in a Planck-like instrumental conguration. Finally, we propose a strategy based on the future all-sky Sunyaev-Zel'dovich survey, that will be provided by the Planck mission, to measure accurately the bulk velocities on large scales up to redshift 1, or more.
62 citations
TL;DR: It turns out that the multi-scale wavelet decomposition is a sensitive method, and it is found that the detection of the non-Gaussian signature is ``marginal\'\' with a probability of at most 99%.
Abstract: A very important property of a statistical distribution is to know whether it obeys Gaussian statistics or not. On the one hand, it is of paramount importance in the context of CMB anisotropy studies, since deviations from a Gaussian distribution could indicate the presence of uncorrected measurement systematics, of remaining fluctuations contributed by foregrounds, of deviations from the simplest models of inflation or of topological defects. On the other hand, looking for a non-Gaussian signal is a very ill-defined task and performances of various assessment methods may differ widely when applied in different contexts. In previous studies, we introduced a sensitive wavelet-based method which we apply here to the COBE/DMR data set, already extensively studied, using different approaches. This provides an objective way to compare methods. It turns out that our multi-scale wavelet decomposition is a sensitive method. Yet we show that the results are rather sensitive to the choice of both the decomposition scheme and the wavelet basis. We find that the detection of the non-Gaussian signature is ``marginal\'\' with a probability of at most 99%.
25 citations
Posted Content•
TL;DR: In this paper, a new radial temperature profile is derived from an XMM-Newton mosaic observation of A2163, from which the issue of background subtraction is addressed as a proper treatment of the background is essential for the derivation of correct temperatures, and thus, of the correct total cluster mass.
Abstract: XMM-Newton, with its high throughput and excellent spatial and spectral resolution, is an ideal instrument for spectro-imaging observation of clusters. Presented here is an XMM-Newton mosaic observation of A2163, from which a new radial temperature profile is derived. The issue of background subtraction is addressed in some detail as a proper treatment of the background is essential for the derivation of correct temperatures, and thus, of the correct total cluster mass.
8 citations
TL;DR: The Diabolo photometer as discussed by the authors is a dual-channel photometer working at 1.2 and 2.1 mm and dedicated to high angular resolution measurements of the Sunyaev-Zel'dovich effect towards distant clusters.
Abstract: The millimetric atmospheric windows at 1 and 2 mm are interesting targets for cosmological studies. Two broad areas appear leading this field: 1) the search for high redshift star-forming galaxies and 2) the measurement of Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies at all redshifts. The Diabolo photometer is a dual-channel photometer working at 1.2 and 2.1 mm and dedicated to high angular resolution measurements of the Sunyaev--Zel'dovich effect towards distant clusters. It uses 2 by 3 bolometers cooled down to 0.1 K with a compact open dilution cryostat. The high resolution is provided by the IRAM 30 m telescope. The result of several Winter campaigns are reported here, including the first millimetric map of the SZ effect that was obtained by Pointecouteau et al. (2001) on RXJ1347-1145, the non-detection of a millimetric counterpart to the radio decrement towards PC1643+4631 and 2 mm number count upper limits. We discuss limitations in ground-based single-dish millimetre observations, namely sky noise and the number of detectors. We advocate the use of fully sampled arrays of (100 to 1000) bolometers as a big step forward in the millimetre continuum science. Efforts in France are briefly mentionned.
3 citations
TL;DR: In this article, the authors review the basic assumptions that have been made to model this physical process and discuss the main effects of the reionisation on the CMB, including the effects of different assumptions.
2 citations
01 Jan 2001
TL;DR: In this article, a new radial temperature profile is derived from an XMM-Newton mosaic observation of A2163, from which the issue of background subtraction is addressed as a proper treatment of the background is essential for the derivation of correct temperatures, and thus, of the correct total cluster mass.
Abstract: XMM-Newton, with its high throughput and excellent spatial and spectral resolution, is an ideal instrument for spectro-imaging observation of clusters. Presented here is an XMM-Newton mosaic observation of A2163, from which a new radial temperature profile is derived. The issue of background subtraction is addressed in some detail as a proper treatment of the background is essential for the derivation of correct temperatures, and thus, of the correct total cluster mass.
TL;DR: In this article, the error in the individual radial peculiar velocities determined with Sunyaev-Zel'dovich measurements was evaluated for three cosmological models, and the errors induced by the major contributing signals (primary Cosmic Microwave Background anisotropies, SZ effect due to the background cluster population, residuals from component separation and instrumental noise).
Abstract: The Sunyaev-Zel'dovich effect is a powerful tool for cosmology that can be used to measure the radial peculiar velocities of galaxy clusters, and thus to test, and constrain, theories of structure formation and evolution. This requires, in principle, an accurate measurement of the effect, a good separation between the Sunyaev-Zel'dovich components, and a good understanding of the sources contributing to the signal and their effect on the measured velocity. In this study, we evaluate the error in the individual radial peculiar velocities determined with Sunyaev-Zel'dovich measurements. We estimate, for three cosmological models, the errors induced by the major contributing signals (primary Cosmic Microwave Background anisotropies, Sunyaev-Zel'dovich effect due to the background cluster population, residuals from component separation and instrumental noise). We generalise our results to estimate the error in the bulk velocity on large scales. In this context, we investigate the limitation due to the Sunyaev-Zel'dovich source (or spatial) confusion in a Planck-like instrumental configuration. Finally, we propose a strategy based on the future all-sky Sunyaev-Zel'dovich survey, that will be provided by the Planck mission, to measure accurately the bulk velocities on large scales up to redshift 1, or more.