A blind detection of a large, complex, Sunyaev–Zel’dovich structure

We present an interesting Sunyaev–Zel’dovich (SZ) detection in the first of the Arcminute Microkelvin Imager (AMI) ‘blind’, degree-square fields to have been observed down to our target sensitivity of 100 µJy beam-1. In follow-up deep pointed observations the SZ effect is detected with a maximum...

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Main Authors:	Shimwell, T., Barker, R., Biddulph, P., Bly, D., Boysen, R., Brown, A., Brown, M., Clementson, C., Crofts, M., Culverhouse, T., Czeres, J., Dace, R., Davies, M., D’Alessandro, R., Doherty, P., Duggan, K., Ely, J., Felvus, M., Feroz, F., Flynn, W., Franzen, Thomas, Geisbusch, J., Genova-Santos, R., Grainge, K., Grainger, W., Hammett, D., Hobson, M., Holler, C., Hurley-Walker, Natasha, Jilley, R., Kaneko, T., Kneissl, R., Lancaster, K., Lasenby, A., Marshall, P., Newton, F., Norris, O., Northrop, I., Odell, D., Olamaie, M., Perrott, Y., Pober, J., Pooley, G., Pospieszalski, M., Quy, V., Rodriguez-Gonzalvez, C., Saunders, R., Scaife, A., Schammel, M., Schofield, J., Scott, P., Shaw, C., Smith, H., Titterington, D., Velic, M., Waldram, E., West, S., Wood, B., Yassin, G., Zwart, J.
Format:	Journal Article
Published:	Oxford University Press 2012
Subjects:	galaxies: clusters: general cosmology: observations
Online Access:	http://hdl.handle.net/20.500.11937/4941

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author	Shimwell, T. Barker, R. Biddulph, P. Bly, D. Boysen, R. Brown, A. Brown, M. Clementson, C. Crofts, M. Culverhouse, T. Czeres, J. Dace, R. Davies, M. D’Alessandro, R. Doherty, P. Duggan, K. Ely, J. Felvus, M. Feroz, F. Flynn, W. Franzen, Thomas Geisbusch, J. Genova-Santos, R. Grainge, K. Grainger, W. Hammett, D. Hobson, M. Holler, C. Hurley-Walker, Natasha Jilley, R. Kaneko, T. Kneissl, R. Lancaster, K. Lasenby, A. Marshall, P. Newton, F. Norris, O. Northrop, I. Odell, D. Olamaie, M. Perrott, Y. Pober, J. Pooley, G. Pospieszalski, M. Quy, V. Rodriguez-Gonzalvez, C. Saunders, R. Scaife, A. Schammel, M. Schofield, J. Scott, P. Shaw, C. Smith, H. Titterington, D. Velic, M. Waldram, E. West, S. Wood, B. Yassin, G. Zwart, J.
author_facet	Shimwell, T. Barker, R. Biddulph, P. Bly, D. Boysen, R. Brown, A. Brown, M. Clementson, C. Crofts, M. Culverhouse, T. Czeres, J. Dace, R. Davies, M. D’Alessandro, R. Doherty, P. Duggan, K. Ely, J. Felvus, M. Feroz, F. Flynn, W. Franzen, Thomas Geisbusch, J. Genova-Santos, R. Grainge, K. Grainger, W. Hammett, D. Hobson, M. Holler, C. Hurley-Walker, Natasha Jilley, R. Kaneko, T. Kneissl, R. Lancaster, K. Lasenby, A. Marshall, P. Newton, F. Norris, O. Northrop, I. Odell, D. Olamaie, M. Perrott, Y. Pober, J. Pooley, G. Pospieszalski, M. Quy, V. Rodriguez-Gonzalvez, C. Saunders, R. Scaife, A. Schammel, M. Schofield, J. Scott, P. Shaw, C. Smith, H. Titterington, D. Velic, M. Waldram, E. West, S. Wood, B. Yassin, G. Zwart, J.
author_sort	Shimwell, T.
building	Curtin Institutional Repository
collection	Online Access
description	We present an interesting Sunyaev–Zel’dovich (SZ) detection in the first of the Arcminute Microkelvin Imager (AMI) ‘blind’, degree-square fields to have been observed down to our target sensitivity of 100 µJy beam-1. In follow-up deep pointed observations the SZ effect is detected with a maximum peak decrement greater than eight times the thermal noise. No corresponding emission is visible in the ROSAT all-sky X-ray survey and no cluster is evident in the Palomar all-sky optical survey. Compared with existing SZ images of distant clusters, the extent is large (˜10 arcmin) and complex; our analysis favours a model containing two clusters rather than a single cluster. Our Bayesian analysis is currently limited to modelling each cluster with an ellipsoidal or spherical ß model, which does not do justice to this decrement. Fitting an ellipsoid to the deeper candidate we find the following. (a) Assuming that the Evrard et al. approximation to Press & Schechter correctly gives the number density of clusters as a function of mass and redshift, then, in the search area, the formal Bayesian probability ratio of the AMI detection of this cluster is 7.9 × 104:1; alternatively assuming Jenkins et al. as the true prior, the formal Bayesian probability ratio of detection is 2.1 × 105:1. (b) The cluster mass is MT,200 = 5.5+1.2 -1.3 × 1014h -1 70 M. (c) Abandoning a physical model with number density prior and instead simply modelling the SZ decrement using a phenomenological ß model of temperature decrement as a function of angular distance, we find a central SZ temperature decrement of -295+36 -15 µK – this allows for cosmic microwave background primary anisotropies, receiver noise and radio sources.We are unsure if the cluster system we observe is a merging system or two separate clusters.
first_indexed	2025-11-14T06:04:56Z
format	Journal Article
id	curtin-20.500.11937-4941
institution	Curtin University Malaysia
institution_category	Local University
last_indexed	2025-11-14T06:04:56Z
publishDate	2012
publisher	Oxford University Press
recordtype	eprints
repository_type	Digital Repository
spelling	curtin-20.500.11937-49412017-09-13T14:45:10Z A blind detection of a large, complex, Sunyaev–Zel’dovich structure Shimwell, T. Barker, R. Biddulph, P. Bly, D. Boysen, R. Brown, A. Brown, M. Clementson, C. Crofts, M. Culverhouse, T. Czeres, J. Dace, R. Davies, M. D’Alessandro, R. Doherty, P. Duggan, K. Ely, J. Felvus, M. Feroz, F. Flynn, W. Franzen, Thomas Geisbusch, J. Genova-Santos, R. Grainge, K. Grainger, W. Hammett, D. Hobson, M. Holler, C. Hurley-Walker, Natasha Jilley, R. Kaneko, T. Kneissl, R. Lancaster, K. Lasenby, A. Marshall, P. Newton, F. Norris, O. Northrop, I. Odell, D. Olamaie, M. Perrott, Y. Pober, J. Pooley, G. Pospieszalski, M. Quy, V. Rodriguez-Gonzalvez, C. Saunders, R. Scaife, A. Schammel, M. Schofield, J. Scott, P. Shaw, C. Smith, H. Titterington, D. Velic, M. Waldram, E. West, S. Wood, B. Yassin, G. Zwart, J. galaxies: clusters: general cosmology: observations We present an interesting Sunyaev–Zel’dovich (SZ) detection in the first of the Arcminute Microkelvin Imager (AMI) ‘blind’, degree-square fields to have been observed down to our target sensitivity of 100 µJy beam-1. In follow-up deep pointed observations the SZ effect is detected with a maximum peak decrement greater than eight times the thermal noise. No corresponding emission is visible in the ROSAT all-sky X-ray survey and no cluster is evident in the Palomar all-sky optical survey. Compared with existing SZ images of distant clusters, the extent is large (˜10 arcmin) and complex; our analysis favours a model containing two clusters rather than a single cluster. Our Bayesian analysis is currently limited to modelling each cluster with an ellipsoidal or spherical ß model, which does not do justice to this decrement. Fitting an ellipsoid to the deeper candidate we find the following. (a) Assuming that the Evrard et al. approximation to Press & Schechter correctly gives the number density of clusters as a function of mass and redshift, then, in the search area, the formal Bayesian probability ratio of the AMI detection of this cluster is 7.9 × 104:1; alternatively assuming Jenkins et al. as the true prior, the formal Bayesian probability ratio of detection is 2.1 × 105:1. (b) The cluster mass is MT,200 = 5.5+1.2 -1.3 × 1014h -1 70 M. (c) Abandoning a physical model with number density prior and instead simply modelling the SZ decrement using a phenomenological ß model of temperature decrement as a function of angular distance, we find a central SZ temperature decrement of -295+36 -15 µK – this allows for cosmic microwave background primary anisotropies, receiver noise and radio sources.We are unsure if the cluster system we observe is a merging system or two separate clusters. 2012 Journal Article http://hdl.handle.net/20.500.11937/4941 10.1111/j.1365-2966.2012.20970.x Oxford University Press fulltext
spellingShingle	galaxies: clusters: general cosmology: observations Shimwell, T. Barker, R. Biddulph, P. Bly, D. Boysen, R. Brown, A. Brown, M. Clementson, C. Crofts, M. Culverhouse, T. Czeres, J. Dace, R. Davies, M. D’Alessandro, R. Doherty, P. Duggan, K. Ely, J. Felvus, M. Feroz, F. Flynn, W. Franzen, Thomas Geisbusch, J. Genova-Santos, R. Grainge, K. Grainger, W. Hammett, D. Hobson, M. Holler, C. Hurley-Walker, Natasha Jilley, R. Kaneko, T. Kneissl, R. Lancaster, K. Lasenby, A. Marshall, P. Newton, F. Norris, O. Northrop, I. Odell, D. Olamaie, M. Perrott, Y. Pober, J. Pooley, G. Pospieszalski, M. Quy, V. Rodriguez-Gonzalvez, C. Saunders, R. Scaife, A. Schammel, M. Schofield, J. Scott, P. Shaw, C. Smith, H. Titterington, D. Velic, M. Waldram, E. West, S. Wood, B. Yassin, G. Zwart, J. A blind detection of a large, complex, Sunyaev–Zel’dovich structure
title	A blind detection of a large, complex, Sunyaev–Zel’dovich structure
title_full	A blind detection of a large, complex, Sunyaev–Zel’dovich structure
title_fullStr	A blind detection of a large, complex, Sunyaev–Zel’dovich structure
title_full_unstemmed	A blind detection of a large, complex, Sunyaev–Zel’dovich structure
title_short	A blind detection of a large, complex, Sunyaev–Zel’dovich structure
title_sort	blind detection of a large, complex, sunyaev–zel’dovich structure
topic	galaxies: clusters: general cosmology: observations
url	http://hdl.handle.net/20.500.11937/4941

A blind detection of a large, complex, Sunyaev–Zel’dovich structure

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