RXTE and ASCA Constraints on Non-thermal Emission from the A2256 Galaxy Cluster

An 8.3 hour observation of the Abell 2256 galaxy cluster using the Rossi X-ray Timing Explorer proportional counter array produced a high quality spectrum in the 2 - 30 keV range. Joint fitting with the 0.7 - 11 keV spectrum obtained with the Advanced Satellite for Astrophysics and Cosmology gas imaging spectrometer gives an upperlimit of 2.3x10^-7 photons/cm^2/sec/keV for non-thermal emission at 30 keV. This yields a lower limit to the mean magnetic field of 0.36 micro Gauss (uG) and an upperlimit of 1.8x10^-13 ergs/cm^3 for the cosmic-ray electron energy density. The resulting lower limit to the central magnetic field is ~1 - 3 uG While a magnetic field of ~0.1 - 0.2 uG can be created by galaxy wakes, a magnetic field of several uG is usually associated with a cooling flow or, as in the case of the Coma cluster, a subcluster merger. However, for A2256, the evidence for a merger is weak and the main cluster shows no evidence of a cooling flow. Thus, there is presently no satisfactory hypothesis for the origin of an average cluster magnetic field as high as >0.36 uG in the A2256 cluster.Comment: 8 pages, Astrophysical Journal (in press

Combining Supernovae and LSS Information with the CMB

Observations of the Cosmic Microwave Background (CMB), large scale structure (LSS) and standard candles such as Type 1a Supernovae (SN) each place different constraints on the values of cosmological parameters. We assume an inflationary Cold Dark Matter model with a cosmological constant, in which the initial density perturbations in the universe are adiabatic. We discuss the parameter degeneracies inherent in interpreting CMB or SN data, and derive their orthogonal nature. We then present our preliminary results of combining CMB and SN likelihood functions. The results of combining the CMB and IRAS 1.2 Jy survey information are given, with marginalised confidence regions in the H_0, Omega_m, b_IRAS and Q_rms-ps directions assuming n=1, Omega_Lambda+Omega_m=1 and Omega_b h^2=0.024. Finally we combine all three likelihood functions and find that the three data sets are consistent and suitably orthogonal, leading to tight constraints on H_0, Omega_m, b_IRAS and Q_rms-ps, given our assumptions.Comment: 7 pages, 4 figures, submitted to ``The CMB and the Planck Mission'', proceedings of the workshop held in Santander, Spain, June 199

Combining cosmological datasets: hyperparameters and Bayesian evidence

A method is presented for performing joint analyses of cosmological datasets, in which the weight assigned to each dataset is determined directly by it own statistical properties. The weights are considered in a Bayesian context as a set of hyperparameters, which are then marginalised over in order to recover the posterior distribution as a function only of the cosmological parameters of interest. In the case of a Gaussian likelihood function, this marginalisation may be performed analytically. Calculation of the Bayesian evidence for the data, with and without the introduction of hyperparameters, enables a direct determination of whether the data warrant the introduction of weights into the analysis; this generalises the standard likelihood ratio approach to model comparison. The method is illustrated by application to the classic toy problem of fitting a straight line to a set of data. A cosmological illustration of the technique is also presented, in which the latest measurements of the cosmic microwave background power spectrum are used to infer constraints on cosmological parameters.Comment: 12 pages, 6 figures, submitted to MNRA

Radio jet refraction in galactic atmospheres with static pressure gradients

A theory of double radio sources which have a 'Z' or 'S' morphology is proposed, based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy. The model describes a collimated jet of supersonic material bending self-consistently under the influence of external static pressure gradients. Gravity and magnetic fields are neglected in the simplest case except insofar as they determine the static pressure distribution. The calculation is a straightforward extension of a method used to calculate a ram-pressure model for twin radio trails ('C' morphology). It may also be described as a continuous-jet version of a buoyancy model proposed in 1973. The model has the added virtue of invoking a galactic atmosphere similar to those already indicated by X-ray measurements of some other radio galaxies and by models for the collimation of other radio jets

Precision Cosmology? Not Just Yet

The recent announcement from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite experiment combined with other recent advances in observational cosmology verifies key components of the standard cosmological model. However, we argue that there remain some significant open issues regarding the basic history and composition of the Universe and uncertainties in some of the most important parameters.Comment: 2 pages, 2 figures. Online journal version http://www.sciencemag.org/cgi/content/full/299/5612/153

The effect of processing and other factors on the colour characteristics of some red wines

Red wines were made from the same batch of Cascade grapes (Seibel 13.053) at Long Ashton by three different processing methods (a) extraction on the skins, (b) thermovinification and (c) carbonic maceration and were analysed at intervals. The wine made by thermovinification was much more coloured than that fermented on its skins, but it contained less anthocyanin and more polymeric pigment. The wine made by carbonic maceration was the least coloured, despite containing anthocyanins similar in amount to those in the thermovinified wine, and it appeared more brown. The red colour differences were attributed to variations in the physicochemical state of the anthocyanins and were expressed numerically in terms of their degrees of ionisation. There was a remarkably exact linear relationship between wine colour density and the degree of ionisation of the anthocyanins in the three wines.Factors affecting anthocyanin ionisation were studied in the Long Ashton wines and in some commercial young Beaujolais wines. Exposure to air augmented colour, increased anthocyanin polymerisation and, in some of the commercial wines, actually increased the amount of anthocyanins, presumably by oxidation of unknown colourless forms. The effects of adding acetaldehyde were even more striking. Large increases in the degree of ionisation of the anthocyanins occurred concurrently with losses of anthocyanins by further transformations into polymeric pigments. Of the Long Ashton wines, that made by thermovinification contained an excess of acetaldehyde over bisulphite, which was probably a factor augmenting its colour.lt was concluded that these fermentation and storage factors were superimposed upon the main effects which were attributed to the different mechanisms of anthocyanin-phenolic interactions operative under the various extraction procedures.Der Einfluß der Weinbereitung und anderer Faktoren auf die Farbmerkmale von RotweinenIn Long Ashton wurden aus demselben Lesegut von Cascade-Trauben (Seibel 13.053) Rotweine nach drei verschiedenen Verfahren - (a) Vergärung auf der Maische, (b) Maischeerhitzung, (c) Kohlensäuremazeration - hergestellt und in bestimmten zeitlichen Abständen analysiert. Der Wein nach (b) war viel intensiver gefärbt als derjenige nach (a); er enthielt jedoch weniger Anthocyan- und mehr polymere Farbstoffe. Der Wein nach (c) war am schwächsten gefärbt, obgleich er einen ähnlichen Anthocyangehalt aufwies wie nach (b) hergestellter Wein; außerdem war er stärker braun getönt. Die Unterschiede in der Rotfärbung wurden auf Schwankungen im physiko-chemischen Zustand der Anthocyane zurückgeführt und zahlenmäßig durch den Ionisationsgrad ausgedrückt. Zwischen der optischen Dichte der Rotweine und dem Ionisationsgrad ihrer Anthocyane bestand eine auffällig genaue lineare Beziehung. Bei den Weinen aus Long Ashton und einigen jungen Beaujolais-Weinen aus dem Handel wurden die Faktoren untersucht, welche die Ionisierung der Anthocyane beeinflussen. Einwirkung von Luft verstärkte die Färbung, steigerte die Polymerisation der Anthocyane und erhöhte bei einigen kommerziellen Weinen, wohl durch Oxidation unbekannter farbloser Vorstufen, den tatsächlichen Anthocyangehalt. Ein Zusatz von Acetaldehyd war noch wirkungsvoller: Ein beträchtlicher Zuwachs ionisierter Anthocyane war begleitet von Anthocyanverlusten durch verstärkte Umwandlung in polymere Farbstoffe. Bei den Weinen aus Long Ashton überwog in den nach (b) hergestellten das Acetaldehyd gegenüber dem Bisulfit, wodurch wahrscheinlich die Färbung vertieft wurde.Die unterschiedliche Ausprägung der Rotweinfärbung ist in erster Linie durch das angewandte Extraktionsverfahren bedingt, wobei Anthocyane und Phenole in verschiedener Weise miteinander reagieren. Im Verlauf der Gärung und Lagerung wird der Farbcharakter durch weitere Faktoren abgewandelt

Asymmetry of jets, lobe size and spectral index in radio galaxies and quasars

We investigate the correlations between spectral index, jet side and extent of the radio lobes for a sample of nearby FRII radio galaxies. In Dennett-Thorpe et al. (1997) we studied a sample of quasars and found that the high surface brightness regions had flatter spectra on the jet side (explicable as a result of Doppler beaming) whilst the extended regions had spectral asymmetries dependent on lobe length. Unified schemes predict that asymmetries due to beaming will be much smaller in narrow-line radio galaxies than in quasars: we therefore investigate in a similar manner, a sample of radio galaxies with detected jets. We find that spectral asymmetries in these objects are uncorrelated with jet sidedness at all brightness levels, but depend on relative lobe volume. Our results are not in conflict with unified schemes, but suggest that the differences between the two samples are due primarily to power or redshift, rather than to orientation. We also show directly that hotspot spectra steepen as a function of radio power or redshift. Whilst a shift in observed frequency due to the redshift may account for some of the steepening, it cannot account for all of it, and a dependence on radio power is required.Comment: accepted for publication in MNRAS, 10 pages; typos/minor correctio

Bayesian `Hyper-Parameters' Approach to Joint Estimation: The Hubble Constant from CMB Measurements

Recently several studies have jointly analysed data from different cosmological probes with the motivation of estimating cosmological parameters. Here we generalise this procedure to take into account the relative weights of various probes. This is done by including in the joint \chi^2 function a set of `Hyper-Parameters', which are dealt with using Bayesian considerations. The resulting algorithm (in the case of uniform priors on the log of the Hyper-Parameters) is very simple: instead of minimising \sum \chi_j^2 (where \chi_j^2 is per data set j) we propose to minimise \sum N_j \ln (\chi_j^2) (where N_j is the number of data points per data set j). We illustrate the method by estimating the Hubble constant H_0 from different sets of recent CMB experiments (including Saskatoon, Python V, MSAM1, TOCO and Boomerang).Comment: submitted to MNRAS, 6 pages, Latex, with 3 figures embedde

Model wine solutions: Colour and composition changes during ageing

The interaction between malvidin 3-glucoside, the main anthocyanin in red wine made from Vitis vinifera grapes, and (+)-catechin and the effect on this interaction of ferric ions and acetaldehyde was examined. In the models not containing acetaldehyde losses of malvidin 3-glucoside were observed, but there were only negligible losses of catechin; no new compounds were observed. In the presence of acetaldehyde the formation of new compounds was determined by high performance liquid chromatography; this formation coincided with rapid losses in the concentrations of malvidin 3-glucoside and catechin. A molecular ion at m/z 809 was determined by FAB MS, corresponding to a dimer consisting of malvidin 3-glucoside linked to catechin by an acetaldehyde bridge, according to a mechanism previously suggested by TIMBER-LAKE and BRIDLE (1976). Concurrent with the losses in anthocyanins, qualitative and quantitative changes in visible colour were also observed, consisting of changes in the wavelength of maximum absorbance (λmax) and in maximum absorbance intensity (Amax). Models containing malvidin 3-glucoside plus catechin or catechin plus ferric ions showed a marked decrease in their λmax from 525 nm to 440 nm; there was little net effect of the ferric ions on these changes. The model containing acetaldehyde showed a large increase in Amax while the λmax showed a bathochromic shift from 524 nm to 557 nm; colour decreased after achieving a maximum and the λmax decreased slightly. Changes in colour monitored by measuring hue angle, chroma and L* value are also reported

Model wine solutions: Effect of sulphur dioxide on colour and composition during ageing

The effect of sulphur dioxide and acetaldehyde on the interaction between malvidin 3-glucoside, the main anthocyanin in red wine made from Vitis vinifera grapes, and (+)-catechin was examined. In all model wines the molar losses of malvidin 3-glucoside were significantly greater than the losses of catechin. The concentration of malvidin 3-glucoside decreased fastest in the presence of acetaldehyde while the most rapid loss of catechin occurred in the model containing malvidin 3-glucoside and catechin only. In the presence of sulphur dioxide, these losses still occurred, but much more slowly, indicating that condensation reactions may take place even in the presence of sulphur dioxide. Polymerisation was most prominent in the model containing malvidin 3-glucoside, catechin and acetaldehyde. Concurrent with the losses in anthocyanin and catechin, qualitative and quantitative changes in visible colour were also observed. Changes in colour monitored by measuring hue angle and chroma are also reported