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193 results on '"Sarazin, C. L"'

151. A Deep Chandra Observation of A2052.

Author

Leibundgut, Bruno, Böhringer, H., Pratt, G.W., Finoguenov, A., Schuecker, P., Blanton, E. L., Douglass, E. M., Sarazin, C. L., Clarke, T. E., and McNamara, B. R.

Abstract

We present initial results from a long (125 ksec) Chandra observation of Abell 2052. A2052 is a bright, nearby, cooling core cluster at a redshift of z=0.0348. It was previously observed for 36 ksec with Chandra [3,4]. The longer observation reveals ripples in the surface brightness, similar to what has been seen in e.g., the Perseus cluster [5] and M87/Virgo [6]. The southern cavity now appears to be split into two cavities with the southernmost cavity likely representing a ghost bubble from earlier radio activity. There also appears to be a ghost bubble present to the NW of the cluster center. Bright emission in the X-ray corresponds very well with optical line emission, and the correlated X-ray emission is seen to continue from the N bubble edge closer to the AGN in this longer exposure, tracking the H-α emission. The energy deposited by the radio source, as determined by measuring the pressure in the bright, X-ray shells, averaged over the repetition rate of the radio source (determined from either the ripple separation or the ghost cavity distances) can easily offset the cooling in the core of the cluster. [ABSTRACT FROM AUTHOR]

Published
2007
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152. Off-axis cluster mergers.

Author

Ricker, P. M. and Sarazin, C. L.

Subjects
*GALAXY clusters, *PARAMETER estimation, *DARK matter, *STELLAR luminosity function
Abstract

We present a parameter study of offset mergers between clusters of galaxies, examining the effect of a cuspy dark matter profile on luminosity and temperature evolution and turbulence. [ABSTRACT FROM AUTHOR]

Published
2001

155. Centaurus A: Interaction of a Radio Source with its Environment

Author

Nulsen, Paul, Kraft, R. P., Stark, D., Croston, J. H., Hardcastle, M. J., Birkinshaw, M., Worrall, D. M., Sivakoff, G. R., Jordan, A., Brassington, N. J., Evans, D. A., Forman, W. R., Gilfanov, M., Goodger, J. L., Jones, C., Harris, W. E., Juett, A. M., Murray, S. S., Somak Raychaudhury, Sarazin, C. L., Voss, R., and Woodley, K. A.

156. Constraining the Cold Gas and Dust in Cluster Cooling Flows

Author

O Dea, Christopher P., Edge, A., Hamer, S., Fabian, A., Johnstone, R., Crawford, C., Oonk, R., Jaffe, W., Hatch, N., Baum, S., Mittal, R., Quillen, A., Wilman, R., Wise, M., Mcnamara, B., Bremer, M., Combes, F., Salome, P., Boehringer, H., Popesso, P., Sarazin, C. L., Allen, S., Egami, E., Donahue, M., Voit, M., Joel Bregman, and Ferland, G.

157. LOFAR, VLA, AND CHANDRA observations of the Toothbrush galaxy cluster

Author

van Weeren, R. J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G. A., Williams, W. L., Röttgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Hardcastle, M. J., Jones, C., Miley, G. K., Rafferty, D. A., Rudnick, L., Sabater, J., Sarazin, C. L., Shimwell, T. W., Bonafede, A., Best, P. N., Bîrzan, L., Cassano, R., Chyży, K. T., Croston, J. H., Dijkema, T. J., Enßlin, T., Ferrari, C., Heald, G., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orrú, E., Pizzo, R., Sridhar, S. S., Simionescu, A., Stroe, A., Tol, S. van der, White, G. J., van Weeren, R. J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G. A., Williams, W. L., Röttgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Hardcastle, M. J., Jones, C., Miley, G. K., Rafferty, D. A., Rudnick, L., Sabater, J., Sarazin, C. L., Shimwell, T. W., Bonafede, A., Best, P. N., Bîrzan, L., Cassano, R., Chyży, K. T., Croston, J. H., Dijkema, T. J., Enßlin, T., Ferrari, C., Heald, G., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orrú, E., Pizzo, R., Sridhar, S. S., Simionescu, A., Stroe, A., Tol, S. van der, and White, G. J.

Abstract

We present deep LOFAR observations between 120 and 181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of $\alpha =-0.8\pm 0.1$ at the northern edge of the main radio relic, steepening toward the south to $\alpha \approx -2$. The spectral index of the radio halo is remarkably uniform ($\alpha =-1.16$, with an intrinsic scatter of $\leq 0.04$). The observed radio relic spectral index gives a Mach number of ${ \mathcal M }={2.8}_{-0.3}^{+0.5}$, assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock (${ \mathcal M }\approx 1.2$, with an upper limit of ${ \mathcal M }\approx 1.5$). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks.

158. LOFAR, VLA, AND CHANDRA observations of the Toothbrush galaxy cluster

Author

van Weeren, R. J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G. A., Williams, W. L., Röttgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Hardcastle, M. J., Jones, C., Miley, G. K., Rafferty, D. A., Rudnick, L., Sabater, J., Sarazin, C. L., Shimwell, T. W., Bonafede, A., Best, P. N., Bîrzan, L., Cassano, R., Chyży, K. T., Croston, J. H., Dijkema, T. J., Enßlin, T., Ferrari, C., Heald, G., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orrú, E., Pizzo, R., Sridhar, S. S., Simionescu, A., Stroe, A., Tol, S. van der, White, G. J., van Weeren, R. J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G. A., Williams, W. L., Röttgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Hardcastle, M. J., Jones, C., Miley, G. K., Rafferty, D. A., Rudnick, L., Sabater, J., Sarazin, C. L., Shimwell, T. W., Bonafede, A., Best, P. N., Bîrzan, L., Cassano, R., Chyży, K. T., Croston, J. H., Dijkema, T. J., Enßlin, T., Ferrari, C., Heald, G., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orrú, E., Pizzo, R., Sridhar, S. S., Simionescu, A., Stroe, A., Tol, S. van der, and White, G. J.

Abstract

We present deep LOFAR observations between 120 and 181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of $\alpha =-0.8\pm 0.1$ at the northern edge of the main radio relic, steepening toward the south to $\alpha \approx -2$. The spectral index of the radio halo is remarkably uniform ($\alpha =-1.16$, with an intrinsic scatter of $\leq 0.04$). The observed radio relic spectral index gives a Mach number of ${ \mathcal M }={2.8}_{-0.3}^{+0.5}$, assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock (${ \mathcal M }\approx 1.2$, with an upper limit of ${ \mathcal M }\approx 1.5$). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks.

159. LOFAR Facet Calibration

Author

Weeren, R. J. van, Williams, W. L., Hardcastle, M. J., Shimwell, T. W., Rafferty, D. A., Sabater, J., Heald, G., Sridhar, S. S., Dijkema, T. J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G. A., Röttgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Jones, C., Miley, G. K., Rudnick, L., Sarazin, C. L., Bonafede, A., Best, P. N., Bîrzan, L., Cassano, R., Chyży, K. T., Croston, J. H., Ensslin, T., Ferrari, C., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orrú, E., Pizzo, R., Simionescu, A., Stroe, A., Tol, S. van der, White, G. J., Weeren, R. J. van, Williams, W. L., Hardcastle, M. J., Shimwell, T. W., Rafferty, D. A., Sabater, J., Heald, G., Sridhar, S. S., Dijkema, T. J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G. A., Röttgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Jones, C., Miley, G. K., Rudnick, L., Sarazin, C. L., Bonafede, A., Best, P. N., Bîrzan, L., Cassano, R., Chyży, K. T., Croston, J. H., Ensslin, T., Ferrari, C., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orrú, E., Pizzo, R., Simionescu, A., Stroe, A., Tol, S. van der, and White, G. J.

Abstract

LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides excellent short baseline coverage to map diffuse extended emission. However, producing high-quality deep images is challenging due to the presence of direction-dependent calibration errors, caused by imperfect knowledge of the station beam shapes and the ionosphere. Furthermore, the large data volume and presence of station clock errors present additional difficulties. In this paper we present a new calibration scheme, which we name facet calibration, to obtain deep high-resolution LOFAR High Band Antenna images using the Dutch part of the array. This scheme solves and corrects the direction-dependent errors in a number of facets that cover the observed field of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at resolution, meeting the specifications of the LOFAR Tier-1 northern survey.

175. Beam models for SS 433

Author

Begelman, M. C., primary, Hatchett, S. P., additional, McKee, C. F., additional, Sarazin, C. L., additional, and Arons, J., additional

Published
1980
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191. The 400dGalaxy Cluster Survey weak lensing programme*

Author

Israel, H., Erben, T., Reiprich, T. H., Vikhlinin, A., Hildebrandt, H., Hudson, D. S., McLeod, B. A., Sarazin, C. L., Schneider, P., and Zhang, Y.-Y.

Abstract

Context. Studying cosmological structure formation provides insights into all of the universe's components: baryonic matter, dark matter, and, notably, dark energy. Measuring the mass function of galaxy clusters at high redshifts is particularly useful probe for both learning about the history of structure formation and constraining cosmological parameters.Aims. We attempt to derive reliable masses for a high-redshift, high-luminosity sample of galaxy clusters selected from the 400dX-ray selected cluster survey. Weak gravitational lensing allows us to determine masses that can be compared with those inferred from X-rays, forming an independent test. We focus on a particular object, CL0030+2618 at z= 0.50.Methods. Using deep imaging in three passbands acquired using the Megacaminstrument at MMT, we show that Megacamis well-suited to measuring gravitational shear, i.e., the shapes of faint galaxies. A catalogue of background galaxies is constructed by analysing the photometric properties of galaxies in the g'r'i' bands.Results. Using the aperture mass technique, we detect the weak lensing signal of CL0030+2618 at 5.8σsignificance. We find significant tangential alignment of galaxies out to ~10' or a distance of >2 r200from the cluster centre. The weak lensing centre of CL0030+2618 agrees with several X-ray measurements and the position of the brightest cluster galaxy. Finally, we infer a weak lensing virial mass of M200= 7.2+3.6+2.3-2.9-2.5× 1014${M}_{\odot}$for CL0030+2618.Conclusions. Despite complications caused by a tentative foreground galaxy group along the line of sight, the X-ray and weak lensing estimates for CL0030+2618 are in remarkable agreement.

Published
2010

192. What is a cool-core cluster? a detailed analysis of the cores of the X-ray flux-limited HIFLUGCScluster sample*

Author

Hudson, D. S., Mittal, R., Reiprich, T. H., Nulsen, P. E. J., Andernach, H., and Sarazin, C. L.

Abstract

We use the largest complete sample of 64 galaxy clusters (HIghest X-ray FLUx Galaxy Cluster Sample) with available high-quality X-ray data from Chandra, and apply 16 cool-core diagnostics to them, some of them new. In order to identify the best parameter for characterizing cool-core clusters and quantify its relation to other parameters, we mainly use very high spatial resolution profiles of central gas density and temperature, and quantities derived from them. We also correlate optical properties of brightest cluster galaxies (BCGs) with X-ray properties.
To segregate cool core and non-cool-core clusters, we find that central cooling time, tcool, is the best parameter for low redshift clusters with high quality data, and that cuspiness is the best parameter for high redshift clusters. 72% of clusters in our sample have a cool core (tcool< 7.7 h71-1/2Gyr) and 44% have strong cool cores (tcool< 1.0 h71-1/2Gyr). We find strong cool-core clusters are characterized as having low central entropy and a systematic central temperature drop. Weak cool-core clusters have enhanced central entropies and temperature profiles that are flat or decrease slightly towards the center. Non-cool-core clusters have high central entropies.
For the first time we show quantitatively that the discrepancy in classical and spectroscopic mass deposition rates can not be explained with a recent formation of the cool cores, demonstrating the need for a heating mechanism to explain the cooling flow problem. 
We find that strong cool-core clusters have a distribution of central temperature drops, centered on 0.4Tvir. However, the radius at which the temperature begins to drop varies. This lack of a universal inner temperature profile probably reflects the complex physics in cluster cores not directly related to the cluster as a whole. Our results suggest that the central temperature does not correlate with the mass of the BCGs and weakly correlates with the expected radiative cooling only for strong cool-core clusters. Since 88% of the clusters in our sample have a BCG within a projected distance of 50 h71-1kpc from the X-ray peak, we argue that it is easier to heat the gas (e.g. with mergers or non-gravitational processes) than to separate the dense core from the brightest cluster galaxy.
Diffuse, Mpc-scale radio emission, believed to be associated with major mergers, has not been unambiguously detected in any of the strong cool-core clusters in our sample. Of the weak cool-core clusters and non-cool-core clusters, most of the clusters (seven out of eight) that have diffuse, Mpc-scale radio emission have a large (> 50 h71-1kpc) projected separation between their BCG and X-ray peak. In contrast, only two of the 56 clusters with a small separation between the BCG and X-ray peak (<50 h71-1kpc) show large-scale radio emission. Based on this result, we argue that a large projected separation between the BCG and the X-ray peak is a good indicator of a major merger. The properties of weak cool-core clusters as an intermediate class of objects are discussed. Finally we describe individual properties of all 64 clusters in the sample.

Published
2010

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