The Birmingham-CfA cluster scaling project - II. Mass composition and distribution

We investigate the spatial distribution of the baryonic and non-baryonic mass components in a sample of 66 virialized systems. We have used X-ray measurements to determine the deprojected temperature and density structure of the intergalactic medium and have employed these to map the underlying gravitational potential. In addition, we have measured the deprojected spatial distribution of galaxy luminosity for a subset of this sample, spanning over 2 decades in mass. With this combined X-ray/optical study we examine the scaling properties of the baryons and address the issue of mass-to-light (M/L) ratio in groups and clusters of galaxies. We measure a median mass-to-light ratio of 224 h70 M/L (solar) in the rest frame B_j band, in good agreement with other measurements based on X-ray determined masses. There is no trend in M/L with X-ray temperature and no significant trend for mass to increase faster than luminosity: M \propto \L_{B,j}^{1.08 +/- 0.12}. This implied lack of significant variation in star formation efficiency suggests that gas cooling cannot be greatly enhanced in groups, unless it drops out to form baryonic dark matter. Correspondingly, our results indicate that non-gravitational heating must have played a significant role in establishing the observed departure from self-similarity in low mass systems. The median baryon fraction for our sample is 0.162 h70^{-3/2}, which allows us to place an upper limit on the cosmological matter density, Omega_m <= 0.27 h70^{-1}, in good agreement with the latest results from WMAP. We find evidence of a systematic trend towards higher central density concentration in the coolest haloes, indicative of an early formation epoch and consistent with hierarchical formation models.Comment: 14 pages, 11 figures; published in MNRAS. Corrected mistake in photometric conversion (equation 2): Bj luminosities increased for A2218, N2563 & N5846. Conclusions unchange

The Birmingham-CfA cluster scaling project - III: entropy and similarity in galaxy systems

We examine profiles and scaling properties of the entropy of the intergalactic gas in a sample of 66 virialized systems, ranging in mass from single elliptical galaxies to rich clusters, for which we have resolved X-ray temperature profiles. Some of the properties we derive appear to be inconsistent with any of the models put forward to explain the breaking of self-similarity in the baryon content of clusters. In particular, the entropy profiles, scaled to the virial radius, are broadly similar in form across the sample, apart from a normalization factor which differs from the simple self-similar scaling with temperature. Low mass systems do not show the large isentropic cores predicted by preheating models, and the high entropy excesses reported at large radii in groups by Finoguenov et al (2002) are confirmed, and found to extend even to moderately rich clusters. We discuss the implications of these results for the evolutionary history of the hot gas in clusters, and suggest that preheating may affect the entropy of intracluster gas primarily by reducing the density of material accreting into groups and clusters along cosmic filaments.Comment: 13 pages, 8 figures - accepted for publication in MNRA

The Birmingham-CfA cluster scaling project - I: gas fraction and the M-T relation

We have assembled a large sample of virialized systems, comprising 66 galaxy clusters, groups and elliptical galaxies with high quality X-ray data. To each system we have fitted analytical profiles describing the gas density and temperature variation with radius, corrected for the effects of central gas cooling. We present an analysis of the scaling properties of these systems and focus in this paper on the gas distribution and M-T relation. In addition to clusters and groups, our sample includes two early-type galaxies, carefully selected to avoid contamination from group or cluster X-ray emission. We compare the properties of these objects with those of more massive systems and find evidence for a systematic difference between galaxy-sized haloes and groups of a similar temperature. We derive a mean logarithmic slope of the M-T relation within R_200 of 1.84+/-0.06, although there is some evidence of a gradual steepening in the M-T relation, with decreasing mass. We recover a similar slope using two additional methods of calculating the mean temperature. Repeating the analysis with the assumption of isothermality, we find the slope changes only slightly, to 1.89+/-0.04, but the normalization is increased by 30%. Correspondingly, the mean gas fraction within R_200 changes from (0.13+/-0.01)h70^-1.5 to (0.11+/-0.01)h70^-1.5, for the isothermal case, with the smaller fractional change reflecting different behaviour between hot and cool systems. There is a strong correlation between the gas fraction within 0.3*R_200 and temperature. This reflects the strong (5.8 sigma) trend between the gas density slope parameter, beta, and temperature, which has been found in previous work. (abridged)Comment: 27 pages, accepted for publication in MNRAS; uses longtable.sty & lscape.st

Challenges to evaluation of multilingual geographic information retrieval in GeoCLEF

This is the third year of the evaluation of geographic information retrieval (GeoCLEF) within the Cross-Language Evaluation Forum (CLEF). GeoCLEF 2006 presented topics and documents in four languages (English, German, Portuguese and Spanish). After two years of evaluation we are beginning to understand the challenges to both Geographic Information Retrieval from text and of evaluation of the results of geographic information retrieval. This poster enumerates some of these challenges to evaluation and comments on the limitations encountered in the first two evaluations

Wetting to Non-wetting Transition in Sodium-Coated C_60

Based on ab initi and density-functional theory calculations, an empirical potential is proposed to model the interaction between a fullerene molecule and many sodium atoms. This model predicts homogeneous coverage of C_60 below 8 Na atoms, and a progressive droplet formation above this size. The effects of ionization, temperature, and external electric field indicate that the various, and apparently contradictory, experimental results can indeed be put into agreement.Comment: 4 pages, 4 postscript figure

LoCuSS: The steady decline and slow quenching of star formation in cluster galaxies over the last four billion years

We present an analysis of the levels and evolution of star formation activity in a representative sample of 30 massive galaxy clusters at 0.15<z<0.30 from the Local Cluster Substructure Survey (LoCuSS), combining wide-field Spitzer 24um data with extensive spectroscopy of cluster members. The specific-SFRs of massive (M>10^10 M_sun) star-forming cluster galaxies within r200 are found to be systematically 28% lower than their counterparts in the field at fixed stellar mass and redshift, a difference significant at the 8.7-sigma level. This is the unambiguous signature of star formation in most (and possibly all) massive star-forming galaxies being slowly quenched upon accretion into massive clusters, their SFRs declining exponentially on quenching time-scales in the range 0.7-2.0 Gyr. We measure the mid-infrared Butcher-Oemler effect over the redshift range 0.0-0.4, finding rapid evolution in the fraction (f_SF) of massive (M_K3M_sun/yr, of the form f_SF (1+z)^7.6. We dissect the origins of the Butcher-Oemler effect, revealing it to be due to the combination of a ~3x decline in the mean specific-SFRs of star-forming cluster galaxies since z~0.3 with a ~1.5x decrease in number density. Two-thirds of this reduction in the specific-SFRs of star-forming cluster galaxies is due to the steady cosmic decline in the specific-SFRs among those field galaxies accreted into the clusters. The remaining one-third reflects an accelerated decline in the star formation activity of galaxies within clusters. The slow quenching of star-formation in cluster galaxies is consistent with a gradual shut down of star formation in infalling spiral galaxies as they interact with the intra-cluster medium via ram-pressure stripping or starvation mechanisms. We find no evidence for the build-up of cluster S0 bulges via major nuclear star-burst episodes.Comment: 24 pages, 12 figures. Accepted for publication in Ap

Quantum theory of large amplitude collective motion and the Born-Oppenheimer method

We study the quantum foundations of a theory of large amplitude collective motion for a Hamiltonian expressed in terms of canonical variables. In previous work the separation into slow and fast (collective and non-collective) variables was carried out without the explicit intervention of the Born Oppenheimer approach. The addition of the Born Oppenheimer assumption not only provides support for the results found previously in leading approximation, but also facilitates an extension of the theory to include an approximate description of the fast variables and their interaction with the slow ones. Among other corrections, one encounters the Berry vector and scalar potential. The formalism is illustrated with the aid of some simple examples, where the potentials in question are actually evaluated and where the accuracy of the Born Oppenheimer approximation is tested. Variational formulations of both Hamiltonian and Lagrangian type are described for the equations of motion for the slow variables.Comment: 29 pages, 1 postscript figure, preprint no UPR-0085NT. Latex + epsf styl

In the Interests of clients or commerce? Legal aid, supply, demand, and 'ethical indeterminacy' in criminal defence work

As a professional, a lawyer's first duty is to serve the client's best interests, before simple monetary gain. In criminal defence work, this duty has been questioned in the debate about the causes of growth in legal aid spending: is it driven by lawyers (suppliers) inducing unnecessary demand for their services or are they merely responding to increased demand? Research reported here found clear evidence of a change in the handling of cases in response to new payment structures, though in ways unexpected by the policy's proponents. The paper develops the concept of 'ethical indeterminacy' as a way of understanding how defence lawyers seek to reconcile the interests of commerce and clients. Ethical indeterminacy suggests that where different courses of action could each be said to benefit the client, the lawyer will tend to advise the client to decide in the lawyer's own interests. Ethical indeterminacy is mediated by a range of competing conceptions of 'quality' and 'need'. The paper goes on to question the very distinction between 'supply' and 'demand' in the provision of legal services

Scale-Up Effect on Heat Transfer in a Fluidized Bed Near the Onset of Turbulent Fluidization

Heat transfer coefficients were measured in 0.29 m ID and 1.56 m ID fluidization columns with the same heater tube, identical alumina particles and geometrically scaled distributors. The maximum coefficients occurred in the turbulent fluidization flow regime. The Froude number based on superficial velocity and column diameter captures the scale-up effect well, so long as the heater is located in a region of similar flow structure