| 1. |
- Hilton, Matt, et al.
(författare)
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The XMM Cluster Survey : evidence for energy injection at high redshift from evolution of the X-ray luminosity-temperature relation
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 424:3, s. 2086-2096
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Tidskriftsartikel (refereegranskat)abstract
- We measure the evolution of the X-ray luminositytemperature (LX - T) relation since z similar to 1.5 using a sample of 211 serendipitously detected galaxy clusters with spectroscopic redshifts drawn from the XMM Cluster Survey first data release (XCS-DR1). This is the first study spanning this redshift range using a single, large, homogeneous cluster sample. Using an orthogonal regression technique, we find no evidence for evolution in the slope or intrinsic scatter of the relation since z similar to 1.5, finding both to be consistent with previous measurements at z similar to 0.1. However, the normalization is seen to evolve negatively with respect to the self-similar expectation: we find E-1(z)?LX = 1044.67 +/- 0.09(T/5)3.04 +/- 0.16(1 + z)-1.5 +/- 0.5, which is within 2 sigma of the zero evolution case. We see milder, but still negative, evolution with respect to self-similar when using a bisector regression technique. We compare our results to numerical simulations, where we fit simulated cluster samples using the same methods used on the XCS data. Our data favour models in which the majority of the excess entropy required to explain the slope of the LX - T relation is injected at high redshift. Simulations in which active galactic nucleus feedback is implemented using prescriptions from current semi-analytic galaxy formation models predict the positive evolution of the normalization, and differ from our data at more than 5 sigma. This suggests that more efficient feedback at high redshift may be needed in these models.
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| 2. |
- Mehrtens, Nicola, et al.
(författare)
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The XMM Cluster Survey : optical analysis methodology and the first data release
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 423:2, s. 1024-1052
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Tidskriftsartikel (refereegranskat)abstract
- The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMMNewton Science Archive. Its main aims are to measure cosmological parameters and trace the evolution of X-ray scaling relations. In this paper we present the first data release from the XMM Cluster Survey (XCS-DR1). This consists of 503 optically confirmed, serendipitously detected, X-ray clusters. Of these clusters, 256 are new to the literature and 357 are new X-ray discoveries. We present 463 clusters with a redshift estimate (0.06 < z < 1.46), including 261 clusters with spectroscopic redshifts. The remainder have photometric redshifts. In addition, we have measured X-ray temperatures (TX) for 401 clusters (0.4 < TX < 14.7 keV). We highlight seven interesting subsamples of XCS-DR1 clusters: (i) 10 clusters at high redshift (z > 1.0, including a new spectroscopically confirmed cluster at z= 1.01); (ii) 66 clusters with high TX (>5 keV); (iii) 130 clusters/groups with low TX (<2 keV); (iv) 27 clusters with measured TX values in the Sloan Digital Sky Survey (SDSS) Stripe 82 co-add region; (v) 77 clusters with measured TX values in the Dark Energy Survey region; (vi) 40 clusters detected with sufficient counts to permit mass measurements (under the assumption of hydrostatic equilibrium); (vii) 104 clusters that can be used for applications such as the derivation of cosmological parameters and the measurement of cluster scaling relations. The X-ray analysis methodology used to construct and analyse the XCS-DR1 cluster sample has been presented in a companion paper, Lloyd-Davies et al.
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| 3. |
- Viana, P. T. P., et al.
(författare)
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The XMM Cluster Survey : Present status and latest results
- 2013
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Ingår i: Astronomical Notes - Astronomische Nachrichten. - : Wiley. - 0004-6337 .- 1521-3994. ; 334:4-5, s. 462-465
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Tidskriftsartikel (refereegranskat)abstract
- The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM-Newton Science Archive. Our recent first data release (XCS-DR1) contains 503 optically confirmed groups and clusters, among which 256 new to the literature and 357 whose X-ray emission was detected for the first time. We discuss their properties and provide an update on the work being done. As examples of the applications of XCS-DR1, we mention the 17 fossil groups/clusters identified with the help of the Sloan Digital Sky Survey. Their brightest galaxies have stellar populations and star-formation histories which are similar to normal brightest cluster galaxies, but their stellar masses are significantly larger and correspond to a much bigger fraction of the total group/cluster optical luminosity. We also highlight the 15 clusters expected to be also detected by the Planck satellite, and characterize the expected overlap between the final XCS and Planck cluster catalogues.
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| 4. |
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| 5. |
- Mayers, Joshua, 1988, et al.
(författare)
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Influence of the N: P supply ratio on biomass productivity and time-resolved changes in elemental and bulk biochemical composition of Nannochloropsis sp.
- 2014
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 169, s. 588-595
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Tidskriftsartikel (refereegranskat)abstract
- This work reports for the first time the detailed impacts of dual nitrogen (N) and phosphorus (P) stress on growth dynamics and biochemical composition in the Eustigmatophyte Nannochloropsis sp. P-stress concurrent with N-stress had subtle effects on culture bulk biochemical composition, but negatively influenced biomass productivity. However, the N:P supply ratio can be raised to at least 32:1 without compromising productivity (yielding a maximum lipid content of 52% of dry weight and volumetric lipid concentration of 233mgL-1). The maximum biomass and lipid yields per unit of cell-P were 1.2kgDW (gP)-1 and 0.54kglipid (gP)-1. The P concentration of many common media is thus in surplus for optimal Nannochloropsis sp. biomass and lipid production, offering potential for significant savings in P usage and improving the sustainability of algal cultivation. © 2014 Elsevier Ltd.
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| 6. |
- Mayers, Joshua, 1988, et al.
(författare)
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Rapid determination of bulk microalgal biochemical composition by Fourier-Transform Infrared spectroscopy
- 2013
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 148, s. 215-220
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of bulk biochemical composition is a key in fundamental and applied studies of microalgae and is essential to understanding responses to different cultivation scenarios. Traditional biochemical methods for the quantification of lipids, carbohydrates and proteins are often time-consuming, often involve hazardous reagents, require significant amounts of biomass and are highly dependent on practitioner proficiency. This study presents a rapid and non-destructive method, utilising Fourier-Transform Infrared (FTIR) spectroscopy for the simultaneous determination of lipid, protein and carbohydrate content in microalgal biomass. A simple univariate regression was applied to sets of reference microalgal spectra of known composition and recognised IR peak integrals. A robust single-species model was constructed, with coefficients of determination r2>0.95, high predictive accuracy and relative errors below 5%. The applicability of this methodology is demonstrated by monitoring the time-resolved changes in biochemical composition of the marine alga Nannochloropsis sp. grown to nitrogen starvation. © 2013 Elsevier Ltd.
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| 7. |
- Viana, Pedro T. P., et al.
(författare)
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The XMM Cluster Survey : predicted overlap with the Planck Cluster Catalogue
- 2012
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 422:2, s. 1007-1013
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Tidskriftsartikel (refereegranskat)abstract
- We present a list of 15 clusters of galaxies, serendipitously detected by the XMM Cluster Survey (XCS), that have a high probability of detection by the Planck satellite. Three of them already appear in the Planck Early Sunyaev-Zel'dovich (ESZ) catalogue. The estimation of the Planck detection probability assumes the flat Lambda cold dark matter (Lambda CDM) cosmology most compatible with 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) data. It takes into account the XCS selection function and Planck sensitivity, as well as the covariance of the cluster X-ray luminosity, temperature and integrated Comptonization parameter, as a function of cluster mass and redshift, determined by the Millennium gas simulations. We also characterize the properties of the galaxy clusters in the final data release of the XCS that we expect Planck will have detected by the end of its extended mission. Finally, we briefly discuss possible joint applications of the XCS and Planck data.
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