Further evidence for a merger in Abell 2218 from an XMM-Newton observation

(Abridged) The galaxy cluster Abell 2218, at z=0.171, is well-known for the discrepancy between mass estimates derived from X-ray and strong lensing analyses. With the present XMM observation, we trace the gas density and temperature profiles out to a radius of ~ 1400 h_70^-1 kpc (approximately the virial radius of the cluster). The surface brightness profile is well fitted over three orders of magnitude with a beta model, with a core radius of 0.'95 and \beta=0.63. The projected temperature profile declines steeply with radius (by ~50%), and is well described by a polytrope with parameters t_0=8.09 keV and \gamma=1.15. The temperature map shows a pronounced peak in the central arcminute, with an increase of a factor of two (from ~5 to ~10 keV). The mass profile, calculated assuming hydrostatic equilibrium and spherical symmetry, is best fitted with a King approximation to an isothermal sphere, implying a dark matter distribution with a central core, in contrast with the cusped cores found in more obviously relaxed clusters. The X-ray mass is two times less than the strong lensing mass at r ~ 80 h_50^-1 kpc, although the agreement between X-ray and weak lensing mass measurements at larger radius (r ~ 400 h_50^-1 kpc) is slightly better. While the X-ray total mass estimates can vary by 30% depending on the mass model, all measurements are lower than the corresponding total mass from optical measurements. Given the X-ray results indicating disturbance of the intracluster gas, leading to a likely violation of the assumption of hydrostatic equilibrium, and the observed substructure in the optical, suggesting a line-of-sight merger, it is unlikely that the different mass estimates of this cluster can be reconciled, at least with standard modelling assumptions.Comment: 9 pages, 7 figures; to appear in A&

Relationships between internal and external handcycle training load in people with spinal cord injury training for the handbikebattle

Objective: To establish the relationship between internal and external handcycling training load for monitoring training in people with paraplegia. Design: Observational study. Subjects: Ten people with paraplegia. Methods: All participants performed a graded peak exercise test. Power output and heart rate (HR) were measured and the session rating of perceived exertion (sRPE) was determined during a 12-week training period. Training Stress Score (TSS) was calculated from power output data, and TRaining IMPuls (TRIMP) was determined, based on HR, HRzones and sRPE. Partial correlations (for all training sessions of all participants) and Pearson’s correlations (for all training sessions of an individual participant) were performed to determine the relationship between external (TSS) and internal (TRIMPHR, TRIMPHRzones and TRIMPsRPE) training loads. Results: Partial correlations between measures of internal and external loads (r = 0.81–0.85) and correlations between TRIMPsRPE and TRIMP scores based on HR (r = 0.77–0.78) were very large. At the individual level, Pearson’s correlations varied from moderate (r=0.48) to nearly perfect (r = 0.99). Conclusion: TRIMPsRPE and TRIMPHR showed very large correlations with external training load, and thus appear appropriate for use in monitoring handcycling training load in people with paraplegia. However, it is recommended that both measures are used in combination, when possible, since some individuals showed weaker relationships

Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts

We present constraints on cosmological parameters using number counts as a function of redshift for a sub-sample of 189 galaxy clusters from the Planck SZ (PSZ) catalogue. The PSZ is selected through the signature of the Sunyaev--Zeldovich (SZ) effect, and the sub-sample used here has a signal-to-noise threshold of seven, with each object confirmed as a cluster and all but one with a redshift estimate. We discuss the completeness of the sample and our construction of a likelihood analysis. Using a relation between mass $M$ and SZ signal $Y$ calibrated to X-ray measurements, we derive constraints on the power spectrum amplitude $\sigma_8$ and matter density parameter $\Omega_{\mathrm{m}}$ in a flat $\Lambda$CDM model. We test the robustness of our estimates and find that possible biases in the $Y$--$M$ relation and the halo mass function are larger than the statistical uncertainties from the cluster sample. Assuming the X-ray determined mass to be biased low relative to the true mass by between zero and 30%, motivated by comparison of the observed mass scaling relations to those from a set of numerical simulations, we find that $\sigma_8=0.75\pm 0.03$, $\Omega_{\mathrm{m}}=0.29\pm 0.02$, and $\sigma_8(\Omega_{\mathrm{m}}/0.27)^{0.3} = 0.764 \pm 0.025$. The value of $\sigma_8$ is degenerate with the mass bias; if the latter is fixed to a value of 20% we find $\sigma_8(\Omega_{\mathrm{m}}/0.27)^{0.3}=0.78\pm 0.01$ and a tighter one-dimensional range $\sigma_8=0.77\pm 0.02$. We find that the larger values of $\sigma_8$ and $\Omega_{\mathrm{m}}$ preferred by Planck's measurements of the primary CMB anisotropies can be accommodated by a mass bias of about 40%. Alternatively, consistency with the primary CMB constraints can be achieved by inclusion of processes that suppress power on small scales relative to the $\Lambda$CDM model, such as a component of massive neutrinos (abridged).Comment: 20 pages, accepted for publication by A&

The influence of protocol design on the identification of ventilatory thresholds and the attainment of peak physiological responses during synchronous arm crank ergometry in able-bodied participants

Purpose To examine the effects of stage duration on power output (PO), oxygen uptake (VO2), and heart rate (HR) at peak level and ventilatory thresholds during synchronous arm crank ergometry. Methods Nineteen healthy participants completed a ramp, 1-min stepwise, and 3-min stepwise graded arm crank exercise test. PO, VO2, and HR at the first and second ventilatory threshold (VT1, VT2) and peak level were compared among the protocols: a repeated measures analysis of variance was performed to test for systematic differences, while intraclass correlation coefficients (ICC) and Bland-Altman plots were calculated to determine relative and absolute agreement. Results Systematic differences among the protocols were found for PO at VT1, VT2, and peak level. At peak level, PO differed significantly among all protocols (ramp: 115 +/- 37 W; 1-min stepwise: 108 +/- 34 W; 3-min stepwise: 94 +/- 31 W, p Conclusions PO at VTs and peak level was significantly higher in short-stage protocols compared with the 3-min stepwise protocol, whereas HR and VO2 showed no differences. Therefore, training zones based on PO determined in short-stage protocols might give an overestimation. Moreover, due to large random error in HR at VTs between the protocols, it is recommended that different protocols should not be used interchangeably within individuals

Relationship between internal and external handcycle training load in people with spinal cord injury training for the handbikebattle

Objective: To establish the relationship between internal and external handcycling training load for monitoring training in people with paraplegia. Design: Observational study. Subjects: Ten people with paraplegia. Methods: All participants performed a graded peak exercise test. Power output and heart rate (HR) were measured and the session rating of perceived exertion (sRPE) was determined during a 12-week training period. Training Stress Score (TSS) was calculated from power output data, and TRaining IMPuls (TRIMP) was determined, based on HR, HRzones and sRPE. Partial correlations (for all training sessions of all participants) and Pearson's correlations (for all training sessions of an individual participant) were performed to determine the relationship between external (TSS) and internal (TRIMPHR, TRIMPHRzones and TRIMPsRPE) training loads. Results: Partial correlations between measures of internal and external loads (r=0.81-0.85) and correlations between TRIMPsRPE and TRIMP scores based on HR (r=0.77-0.78) were very large. At the Individual level, Pearson's correlations varied from moderate (r=0.48) to nearly perfect (r=0.99). Conclusion: TRIMP(sRPE )and TRIMPHR showed very large correlations with external training load, and thus appear appropriate for use in monitoring handcycling training load in people with paraplegia. However, it is recommended that both measures are used in combination, when possible, since some individuals showed weaker relationships

The mass profile of A1413 observed with XMM-Newton: implications for the M-T relation

We present an XMM-Newton observation of A1413, a hot (kT = 6.5 keV) galaxy cluster at z=0.143. We construct gas and temperature profiles up to ~1700 kpc, equivalent to ~0.7 r_200. The gas distribution is well described by a beta model in the outer regions, but is more concentrated in the inner ~250 kpc. We introduce a new parameterisation for the inner regions, allowing a steeper gas density distribution. The projected radial temperature profile declines gradually towards the outer regions, by ~20% between 0.1 r_200 and 0.5 r_200, and is well described by a polytropic model with gamma = 1.07+/-0.01. We find that neither projection nor PSF effects change substantially the form of the temperature profile. Assuming hydrostatic equilibrium (HE) and spherical symmetry, we use the observed temperature profile and the new parametric form for the gas density profile to produce the total mass distribution. The mass profile is remarkably well fitted with the Moore et al. (1999) parameterisation with a concentration parameter in the range expected from numerical simulations. There are several indications that beyond a density contrast delta \~600, the gas may no longer be in HE. There is an offset with respect to adiabatic numerical simulations in the virialised part of the cluster, in that the predicted mass for the cluster temperature is ~40% too high. The gas distribution is peaked in the centre primarily as a result of the cusp in the dark matter profile. The X-ray gas to total mass ratio rises with increasing radius to f_gas ~ 0.2. These data strongly support the validity of the current approach for the modelling of the dark matter collapse, but confirm that understanding the gas specific physics is essential. (Abridged)Comment: To appear in A&