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Perrott Y.C.,Astrophysics Group | Scaife A.M.M.,University of Southampton | Hurley-Walker N.,Curtin Institute of Radio Astronomy | Grainge K.J.B.,Astrophysics Group
Advances in Astronomy | Year: 2013

The Planck 28.5 GHz maps were searched for potential Anomalous Microwave Emission (AME) regions on the scale of 3° or smaller, and several new regions of interest were selected. Ancillary data at both lower and higher frequencies were used to construct spectral energy distributions (SEDs), which seem to confirm an excess consistent with spinning dust models. Here we present higher resolution observations of two of these new regions with the Arcminute Microkelvin Imager Small Array (AMI SA) between 14 and 18 GHz to test for the presence of a compact (10 arcmin or smaller) component. For AME-G107.1+5.2, dominated by the Hii region S140, we find evidence for the characteristic rising spectrum associated with either the spinning dust mechanism for AME or an ultra- /hypercompact Hii region across the AMI frequency band; however, for AME-G173.6+208 we find no evidence for AME on scales of 2-10 arcmin. © 2013 Yvette C. Perrott et al.

Rodriguez-Gonzalvez C.,Astrophysics Group | Rodriguez-Gonzalvez C.,California Institute of Technology | Shimwell T.W.,Astrophysics Group | Shimwell T.W.,CSIRO | And 20 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We present detailed 16-GHz interferometric observations using the Arcminute Microkelvin Imager (AMI) of 19 clusters with L X > 7 × 10 37W (h 50 = 1) selected from the Local Cluster Substructure Survey (LoCuSS; 0.142 ≤ z ≤ 0.295) and of Abell 1758b, which is in the field of view of Abell 1758a. We detect and resolve Sunyaev-Zel'dovich (SZ) signals towards 17 clusters, with peak surface brightnesses between 5σ and 23σ. We use a fast, Bayesian cluster analysis to obtain cluster parameter estimates in the presence of radio point sources, receiver noise and primordial cosmic microwave background (CMB) anisotropy. We fit isothermal β-models to our data and assume the clusters are virialized (with all the kinetic energy in gas internal energy). Our gas temperature, T AMI, is derived from AMI SZ data and not from X-ray spectroscopy. Cluster parameters internal to r 500 are derived under the assumption of hydrostatic equilibrium. We find the following. (i) Different generalized Navarro-Frenk-White (gNFW) parametrizations yield significantly different parameter degeneracies. (ii) For h 70 = 1, we find the classical virial radius, r 200, to be typically 1.6 ± 0.1Mpc and the total mass M T(r 200) typically to be 2.0-2.5× M T(r 500). (iii) Where we have found M T(r 500) and M T(r 200) X-ray and weak-lensing values in the literature, there is good agreement between weak-lensing and AMI estimates (with MT, AMI /MT, WL =1.2-0.3+0.2 and 1.0 ± 0.1 for r 500 and r 200, respectively). In comparison, most Suzaku/Chandra estimates are higher than for AMI (with M T, X/M T, AMI = 1.7 ± 0.2 within r 500), particularly for the stronger mergers. (iv) Comparison of T AMI to T X sheds light on high X-ray masses: even at large radius, T X can substantially exceed T AMI in mergers. The use of these higher T X values will give higher X-ray masses. We stress that large-radius T AMI and T X data are scarce and must be increased. (v) Despite the paucity of data, there is an indication of a relation between merger activity and SZ ellipticity. (vi) At small radius (but away from any cooling flow) the SZ signal (and T AMI) is less sensitive to intracluster medium disturbance than the X-ray signal (and T X) and, even at high radius, mergers affect n 2-weighted X-ray data more than n-weighted SZ, implying that significant shocking or clumping or both occur in even the outer parts of mergers. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Scaife A.M.M.,University of Southampton | Scaife A.M.M.,Dublin Institute for Advanced Studies | Buckle J.V.,Astrophysics Group | Buckle J.V.,Kavli Institute for Cosmology | And 25 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We present deep 1.8cm (16GHz) radio continuum imaging of seven young stellar objects in the Taurus molecular cloud. These objects have previously been extensively studied in the submm to near-infrared range and their spectral energy distributions modelled to provide reliable physical and geometrical parameters. We use these new data to constrain the properties of the long-wavelength tail of the greybody spectrum, which is expected to be dominated by emission from large dust grains in the protostellar disc. We find spectra consistent with the opacity indices expected for such a population, with an average opacity index of β= 0.26 ± 0.22 indicating grain growth within the discs. We use spectra fitted jointly to radio and submm data to separate the contributions from thermal dust and radio emission at 1.8cm and derive disc masses directly from the cm-wave dust contribution. We find that disc masses derived from these flux densities under assumptions consistent with the literature are systematically higher than those calculated from submm data, and meet the criteria for giant planet formation in a number of cases. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Hurley-Walker N.,Astrophysics Group | Hurley-Walker N.,Curtin Institute of Radio Astronomy | Bridle S.,University College London | Cypriano E.S.,University of Sao Paulo | And 22 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We present an analysis of observations made with the Arcminute Microkelvin Imager (AMI) and the Canada-France-Hawaii Telescope (CFHT) of six galaxy clusters in a redshift range of 0.16-0.41. The cluster gas is modelled using the Sunyaev-Zel'dovich (SZ) data provided by AMI, while the total mass is modelled using the lensing data from the CFHT. In this paper, we (i) find very good agreement between SZ measurements (assuming large-scale virialization and a gas-fraction prior) and lensing measurements of the total cluster masses out to r 200; (ii) perform the first multiple-component weak-lensing analysis of A115; (iii) confirm the unusual separation between the gas and mass components in A1914 and (iv) jointly analyse the SZ and lensing data for the relaxed cluster A611, confirming our use of a simulation-derived mass-temperature relation for parametrizing measurements of the SZ effect. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Burke-Spolaor S.,CSIRO | Ekers R.,CSIRO | MacQuart J.-P.,Curtin Institute of Radio Astronomy
2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011 | Year: 2011

A publication in the Astrophysical Journal [1] reported the discovery of swept-frequency, terrestrial emission in a search for astrophysical pulses. The emission's origin has yet to be determined; its attributes are atypical of known sources of terrestrial signals. We review the observed properties of the emission and present a simple model for a physical mechanism that could occur in the atmosphere to produce it. If this mechanism is the cause of the emission, its origin may lie in secondary effects of lightning production in the upper atmosphere. © 2011 IEEE.

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