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Ainsworth R.E.,Dublin Institute for Advanced Studies | Scaife A.M.M.,University of Southampton | Ray T.P.,Dublin Institute for Advanced Studies | Buckle J.V.,Astrophysics Group | And 22 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We present 16GHz (1.9cm) deep radio continuum observations made with the Arcminute Microkelvin Imager (AMI) of a sample of low-mass young stars driving jets. We combine these new data with archival information from an extensive literature search to examine spectral energy distributions (SEDs) for each source and calculate both the radio and sub-mm spectral indices in two different scenarios: (1) fixing the dust temperature (T d) according to evolutionary class; and (2) allowing T d to vary. We use the results of this analysis to place constraints on the physical mechanisms responsible for the radio emission. From AMI data alone, as well as from model fitting to the full SED in both scenarios, we find that 80percent of the objects in this sample have spectral indices consistent with free-free emission. We find an average spectral index in both T d scenarios, consistent with free-free emission. We examine correlations of the radio luminosity with bolometric luminosity, envelope mass and outflow force, and find that these data are consistent with the strong correlation with envelope mass seen in lower luminosity samples. We examine the errors associated with determining the radio luminosity and find that the dominant source of error is the uncertainty on the opacity index, β. We examine the SEDs for variability in these young objects, and find evidence for possible radio flare events in the histories of L1551 IRS 5 and Serpens SMM 1. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


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.


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.


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.


Perrott Y.C.,Astrophysics Group | Scaif A.M.M.,University of Manchester | Green D.A.,Astrophysics Group | Grainge K.J.B.,University of Manchester | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

The Arcminute Microkelvin Imager Galactic Plane Survey provides mJy-sensitivity, arcminute-resolution interferometric images of the northern Galactic plane at ≈16 GHz. The first data release covered 76° ≲ l ≲ 170° between latitudes of |b| ≲ 5°; here we present a second data release, extending the coverage to 53° ≲ l ≲ 193° and including high-latitude extensions to cover the Taurus and California giant molecular cloud regions, and the recently discovered large supernova remnant G159.6+7.3. The total coverage is now 1777 deg2 and the catalogue contains 6509 sources. We also describe the improvements to the data processing pipeline which improves the positional and flux density accuracies of the survey. © 2015 The Authors.


Perrott Y.C.,Astrophysics Group | Scaife A.M.M.,University of Southampton | Green D.A.,Astrophysics Group | Davies M.L.,Astrophysics Group | And 18 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

The Arcminute Microkelvin Imager (AMI) Galactic Plane Survey is a large-area survey of the outer Galactic plane to provide arcminute resolution images at milli-Jansky sensitivity in the centimetre-wave band. Here we present the first data release of the survey, consisting of 868 deg2 of the Galactic plane, covering the area 76° ≤ ℓ 170° between latitudes of |b| ≤ 5°, at a central frequency of 15.75 GHz (1.9 cm). We describe in detail the drift-scan observations which have been used to construct the maps, including the techniques used for observing, mapping and source extraction, and summarize the properties of the finalized data sets. These observations constitute the most sensitive Galactic plane survey of large extent at centimetre-wave frequencies greater than 1.4 GHz. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


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.


Schammel M.P.,Astrophysics Group | Feroz F.,Astrophysics Group | Grainge K.J.B.,Astrophysics Group | Grainge K.J.B.,Kavli Institute for Cosmology Cambridge | And 15 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present 16-GHz Sunyaev-Zel'dovich observations using the Arcminute Microkelvin Imager (AMI) and subsequent Bayesian analysis of six galaxy clusters at redshift z ≈ 1 chosen from an X-ray- and infrared-selected sample from Culverhouse et al. In the subsequent analysis, we use two cluster models, an isothermal β-model and a Dark Matter Generalised Navarro-Frenk-White (DM-GNFW) model in order to derive a formal detection probability and the cluster parameters. We detect two clusters (CL J1415+3612 and XMJ 0830+5241) and measure their total masses out to a radius of 200 times the critical density at the respective cluster's redshift. For CL J1415+3612, we find MT,200 = 7.3+1.8 -1.8 × 1014M (β-model) and MT,200 = 10.42.5 -2.4 × 1014M (DM-GNFW model) and for XMJ0830+5241, we find MT,200 = 3.6+1.1 -1.1 × 1014M, (β-model) and MT,200 = 4.7+1.4 -1.4 × 1014M (DM-GNFW model), which agree with each other for each cluster. We also present maps before and after source subtraction of the entire sample and provide 1D and 2D posterior marginalized probability distributions for each fitted cluster profile parameter of the detected clusters. Using simulations which take into account the measured source environment from the AMI Large Array (LA), source confusion noise, cosmic microwave background primordials, instrument noise, we estimate from small-radius (r2500) X-ray data from Culverhouse et al., the detectability of each cluster in the sample and compare it with the result from the Small Array (SA) data. Furthermore, we discuss the validity of the assumptions of isothermality and constant gas mass fraction. We comment on the bias that these small-radius estimates introduce to large-radius SZ predictions. In addition, we follow-up the two detections with deep, single-pointed LA observations. We find a 3σ tentative decrement towards CL J1415+3612 at high resolution and a 5σ high-resolution decrement towards XM J0830+5241. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


Soria R.,Curtin Institute of Radio Astronomy
Australian Physics | Year: 2010

The discovery of powerful jets from a nearby black hole has revealed new clues about the behavior of massive quasars in the early universe. While stars use nuclear fusion to extract energy from their gas, black holes extract gravitational energy from the infalling matter before it disappears into the hole - a process known as accretion. While it takes a lot of falling water to produce the same energy as we would get from nuclear fusion, this is only because the gravitational field of the Earth is so weak. One of the best things about black holes is that their fundamental physical properties are the same at all scales. Supermassive black holes in distant quasars work just like stellar-mass black holes in our galaxy apart from a simple rescaling in the equations. Powerful black-hole jets share a common structure. They drill through the surrounding gas until they lose enough energy or hit denser interstellar material.

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