1,114 research outputs found

    The extended ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II) IV. X-ray Luminosity Function and First Constraints on Cosmological Parameters

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    The X-ray luminosity function is an important statistic of the census of galaxy clusters and an important means to probe the cosmological model of our Universe. Based on our recently completed REFLEX II cluster sample we construct the X-ray luminosity function of galaxy clusters for several redshift slices from z=0z = 0 to z=0.4z = 0.4 and discuss its implications. We find no significant signature of redshift evolution of the luminosity function in the redshift interval. We provide the results of fits of a parameterized Schechter function and extensions of it which provide a reasonable characterization of the data. Using a model for structure formation and galaxy cluster evolution we compare the observed X-ray luminosity function with predictions for different cosmological models. For the most interesting constraints for the cosmological parameters Ωm\Omega_m and σ8\sigma_8 we obatain Ωm∼0.27±0.03\Omega_m \sim 0.27 \pm 0.03 and σ8∼0.80±0.03\sigma_8 \sim 0.80 \pm 0.03 based on the statistical uncertainty alone. Marginalizing over the most important uncertainties, the normalisation and slope of the LX−ML_X - M scaling relation, we find Ωm∼0.29±0.04\Omega_m \sim 0.29 \pm 0.04 and σ8∼0.77±0.07\sigma_8 \sim 0.77 \pm 0.07 (1σ1\sigma confidence limits). We compare our results with those of the SZ-cluster survey provided by the PLANCK mission and we find very good agreement with the results using PLANCK clusters as cosmological probes, but we have some tension with PLANCK cosmological results from the microwave background anisotropies. We also make a comparison with other cluster surveys. We find good agreement with these previous results and show that the REFLEX II survey provides a significant reduction in the uncertainties compared to earlier measurements.Comment: Submitted for publication to Astronomy and Astrophysics, 15 pages, 17 figure

    Abell 3627: A Nearby, X-ray Bright, and Massive Galaxy Cluster

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    The cluster A3627 was recently recognized to be a very massive, nearby cluster in a galaxy survey close to the galactic plane. We are reporting on ROSAT PSPC observations of this object which confirm that the cluster is indeed very massive. The X-ray emission detected from the cluster extends over almost 1 degree in radius. The X-ray image is not spherically symmetric and shows indications of an ongoing cluster merger. Due to the strong interstellar absorption the spectral analysis and the gas temperature determination are difficult. The data are consistent with an overall gas temperature in the range 5 to 10 keV. There are signs of temperature variations in the merger region. A mass estimate based on the X-ray data yields values of 0.4−2.2⋅10150.4 - 2.2 \cdot 10^{15} \msu \ if extrapolated to the virial radius of 3h50−13 h_{50}^{-1} Mpc. In the ROSAT energy band (0.1 - 2.4 keV) the cluster emission yields a flux of about 2⋅10−102 \cdot 10^{-10} erg s−1^{-1} cm−2^{-2} which makes A3627 the 6th^{th} brightest cluster in the ROSAT All Sky Survey. The cluster was missed in earlier X-ray surveys because it was confused with a neighbouring X-ray bright, galactic X-ray binary (1H1556-605). The large X-ray flux makes A3627 an important target for future studies.Comment: 14 pages, Latex file, including aaspp.sty, 9 postscript figures and 1 table, accepted for publication by the Astrophysical Journa

    The REFLEX Galaxy Cluster Survey VII: Omega_m and sigma_8 from cluster abundance and large-scale clustering

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    For the first time the large-scale clustering and the mean abundance of galaxy clusters are analysed simultaneously to get precise constraints on the normalized cosmic matter density Ωm\Omega_m and the linear theory RMS fluctuations in mass σ8\sigma_8. A self-consistent likelihood analysis is described which combines, in a natural and optimal manner, a battery of sensitive cosmological tests where observational data are represented by the (Karhunen-Lo\'{e}ve) eigenvectors of the sample correlation matrix. This method breaks the degeneracy between Ωm\Omega_m and σ8\sigma_8. The cosmological tests are performed with the ROSAT ESO Flux-Limited X-ray (REFLEX) cluster sample. The computations assume cosmologically flat geometries and a non-evolving cluster population mainly over the redshift range 0<z<0.30<z<0.3. The REFLEX sample gives the cosmological constraints and their 1σ1\sigma random errors of Ωm=0.341−0.029+0.031\Omega_m = 0.341 ^{+0.031}_{-0.029} and σ8=0.711−0.031+0.039\sigma_8 = 0.711 ^{+0.039}_{-0.031}. Possible systematic errors are evaluated by estimating the effects of uncertainties in the value of the Hubble constant, the baryon density, the spectral slope of the initial scalar fluctuations, the mass/X-ray luminosity relation and its intrinsic scatter, the biasing scheme, and the cluster mass density profile. All these contributions sum up to total systematic errors of σΩm=−0.071+0.087\sigma_{\Omega_m}=^{+0.087}_{-0.071} and σσ8=−0.162+0.120\sigma_{\sigma_8}=^{+0.120}_{-0.162}.Comment: 10 pages, 7 figures, accepted for publication in Astronomy and Astrophysic

    Central galaxy growth and feedback in the most massive nearby cool core cluster

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    We present multi-wavelength observations of the centre of RXCJ1504.1-0248 - the galaxy cluster with the most luminous and relatively nearby cool core at z~0.2. Although there are several galaxies within 100 kpc of the cluster core, only the brightest cluster galaxy (BCG), which lies at the peak of the X-ray emission, has blue colours and strong line-emission. Approximately 80 Msun/yr of intracluster gas is cooling below X-ray emitting temperatures, similar to the observed UV star formation rate of ~140 Msun/yr. Most star formation occurs in the core of the BCG and in a 42 kpc long filament of blue continuum, line emission, and X-ray emission, that extends southwest of the galaxy. The surrounding filamentary nebula is the most luminous around any observed BCG. The number of ionizing stars in the BCG is barely sufficient to ionize and heat the nebula, and the line ratios indicate an additional heat source is needed. This heat source can contribute to the H\alpha-deduced star formation rates (SFRs) in BCGs and therefore the derived SFRs should only be considered upper limits. AGN feedback can slow down the cooling flow to the observed mass deposition rate if the black hole accretion rate is of the order of 0.5 Msun/yr at 10% energy output efficiency. The average turbulent velocity of the nebula is vturb ~325 km/s which, if shared by the hot gas, limits the ratio of turbulent to thermal energy of the intracluster medium to less than 6%.Comment: 15 pages, 11 figures, MNRAS in press. Corrected typo in abstract

    Efficiency and Equity Implications of Alternative Instruments to Reduce Carbon Leakage

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    The cost-effectiveness of unilateral emission abatement can be seriously hampered by emission leakage. We assess three widely-discussed proposals for leakage reduction targeted at energy-intensive and trade-exposed industries: border tax adjustments, output-based allocation and industry exemptions. We find that none of these measures amounts to a "magic bullet" when both efficiency and equity criteria matter. Border tax adjustments reduce leakage and provide global cost savings but exacerbate regional inequality. Exemptions produce very little leakage reduction and run the risk of increasing efficiency cost of climate policy. Output-based allocation does no harm but also does relatively little good by our outcome measures

    The Strategic Value of Carbon Tariffs

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    Unilateral carbon policies are inefficient due to the fact that they generally involve emission reductions in countries with high marginal abatement costs and because they are subject to carbon leakage. In this paper, we ask whether the use of carbon tariffstariffs on the carbon embodied in imported goodsmight lower the cost of achieving a given reduction in world emissions. Specifically, we explore the role tariffs might play as an inducement to unregulated countries adopting emission controls of their own. We use an applied general equilibrium model to generate the payoffs of a policy game. In the game, a coalition of countries regulates its own emissions and chooses whether or not to employ carbon tariffs against unregulated countries. Unregulated countries may respond by adopting emission regulations of their own, retaliating against the carbon tariffs by engaging in a trade war, or by pursuing no policy at all. In the unique Nash equilibrium produced by this game, the use of carbon tariffs by coalition countries is credible. China and Russia respond by adopting binding abatement targets to avoid being subjected to them. Other unregulated countries retaliate. Cooperation by China and Russia lowers the global welfare cost of achieving a 10% reduction in global emissions by half relative to the case where coalition countries undertake all of this abatement on their own

    Who bears the burden of greening electricity?

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    Faced with the threat of climate change many countries are promoting renewable energies to decarbonize their energy system. A common policy to foster electricity from renewable energy sources are feed-in tariffs which are financed by surcharges on electricity prices. Higher electricity prices in turn raise concerns on regressive distributional impacts. In this paper, we investigate the distributional impacts of three alternative policies to subsidize renewable energy production in Spain: (i) exemptions from the electricity surcharge for residential consumers, (ii) an increase in mineral oil taxes, and (iii) an increase in value-added taxes. We find that all three options can attenuate the regressive distributional effects compared to feed-in tariffs. For our quantitative impact assessment, we couple a microsimulation model with a computable general equilibrium model to capture the incidence on heterogeneous households in an economy-wide framework.This research is supported by the Basque Government through the BERC 2018-2021 program and by the Spanish Ministry of Economy and Competitiveness MINECO through BC3 María de Maeztu excellence accreditation MDM-2017-0714. In addition, this study received funding from the Ministry of Science, Innovation and Universities of Spain ( RTI2018-093352-B-I00 ) and from the European Unio

    The X-ray Luminosity - Velocity Dispersion relation in the REFLEX Cluster Survey

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    We present an estimate of the bolometric X-ray luminosity - velocity dispersion L_x - sigma_v relation measured from a new, large and homogeneous sample of 171 low redshift, X-ray selected galaxy clusters. The linear fitting of log(L_x) - log(sigma_v) gives L_x = 10^{32.72 \pm 0.08} sigma^{4.1 \pm 0.3}_v erg s^{-1} h^{-2}_{50}. Furthermore, a study of 54 clusters, for which the X-ray temperature of the intracluster medium T is available, allows us to explore two other scaling relations, L_x -T and sigma_v -T. From this sample we obtain L_x \propto T^{3.1 \pm 0.2} and sigma_v \propto T^{1.00 \pm 0.16}, which are fully consistent with the above result for the L_x-sigma_v. The slopes of L_x -T and sigma_v -T are incompatible with the values predicted by self-similarity (L_x \propto T^{2} \propto \sigma_v^4), thus suggesting the presence of non-gravitational energy sources heating up the intracluster medium, in addition to the gravitational collapse, in the early stages of cluster formation. On the other hand, the result on log(L_x) - log(sigma_v) supports the self-similar model.Comment: 9 pages, accepted for publication in MNRA

    The XMM/2dF survey III: Comparison between optical and X-ray cluster detection methods

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    We directly compare X-ray and optical techniques of cluster detection by combining SDSS photometric data with a wide-field (∼1.8\sim 1.8 deg2^{2}) XMM-{\em Newton} survey in the North Galactic Pole region. The optical cluster detection procedure is based on merging two independent selection methods - a smoothing+percolation technique, and a Matched Filter Algorithm. The X-ray cluster detection is based on a wavelet-based algorithm, incorporated in the SAS v.5.2 package. The final optical sample counts 9 candidate clusters with richness of more than 20 galaxies, corresponding roughly to APM richness class. Three, of our optically detected clusters are also detected in our X-ray survey. The most probable cause of the small number of optical cluster candidates detected in our X-ray survey is that they are relatively poor clusters, fainter than the X-ray flux limit (for extended sources) of our survey fx(0.3−2keV)≃2×10−14ergcm−2s−1f_{x}(0.3-2 {\rm keV}) \simeq 2 \times 10^{-14} erg cm^{-2} s^{-1}.Comment: 9 pages, 5 figures, MNRAS accepte
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