ABSTRACT
We estimate the intracluster light (ICL) component within a sample of 18 clusters detected in the XMM Cluster Survey (XCS) data using the deep (∼26.8 mag) Hyper Suprime-Cam Subaru Strategic ...Programme data release 1 i-band data. We apply a rest-frame μB = 25 mag arcsec−2 isophotal threshold to our clusters, below which we define light as the ICL within an aperture of RX,500 (X-ray estimate of R500) centred on the brightest cluster galaxy (BCG). After applying careful masking and corrections for flux losses from background subtraction, we recover ∼20 per cent of the ICL flux, approximately four times our estimate of the typical background at the same isophotal level (${\sim}5{{\ \rm per\ cent}}$). We find that the ICL makes up about ${\sim}24{{\ \rm per\ cent}}$ of the total cluster stellar mass on average (∼41 per cent including the flux contained in the BCG within 50 kpc); this value is well matched with other observational studies and semi-analytic/numerical simulations, but is significantly smaller than results from recent hydrodynamical simulations (even when measured in an observationally consistent way). We find no evidence for any links between the amount of ICL flux with cluster mass, but find a growth rate of 2–4 for the ICL between 0.1 < z < 0.5. We conclude that the ICL is the dominant evolutionary component of stellar mass in clusters from z ∼ 1. Our work highlights the need for a consistent approach when measuring ICL alongside the need for deeper imaging, in order to unambiguously measure the ICL across as broad a redshift range as possible (e.g. 10-yr stacked imaging from the Vera C. Rubin Observatory).
The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas ...filling the potential wells of galaxy clusters. However, it would not influence the clusters weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, z = 0.02). Here we apply the technique to the stacked profiles of 58 clusters at higher redshifts (0.1 < z < 1.2), including 12 new to the literature, using X-ray data from the XMM Cluster Survey and weak lensing data from the Canada–France–Hawaii–Telescope Lensing Survey. Using a multiparameter Markov chain Monte Carlo analysis, we constrain the two chameleon gravity parameters (β and ϕ∞). Our fits are consistent with general relativity, not requiring a fifth force. In the special case of f(R) gravity (where
$\beta = \sqrt{1/6}$
), we set an upper limit on the background field amplitude today of |f
R0| < 6 × 10−5 (95 per cent CL). This is one of the strongest constraints to date on |f
R0| on cosmological scales. We hope to improve this constraint in future by extending the study to hundreds of clusters using data from the Dark Energy Survey.
Galaxy clusters are very useful astronomical tools; they are used as a means to study galaxy formation and evolution, large scale structure, but also as probes to constrain cosmological parameters. ...This work aims to explore some of the uses of galaxy clusters in cosmology by constructing an optically confirmed X-ray selected galaxy cluster catalogue and studying various aspects of galaxy clusters and their effect on cosmology. I introduce the theoretical background of this work, describing the current cosmological model, the properties, dynamics and use of galaxy clusters. I describe the main tools that were used to create the XMM Cluster Survey (XCS) DR2 cluster catalogue in the SDSS region and proceed with a thorough outline of the construction and properties of the clusters in the catalogue. The properties of these clusters, along with clusters from optical catalogues and clusters from simulations were studied further as a function of their environment. Possible differences in the properties, mass functions and luminosity-temperature relation of clusters in different environments show the influence of the latter on the formation and growth of galaxy clusters. Moreover, those differences can affect the results of cosmological studies that do not take into account this environmental selection effect. Finally, I study the rotation of the constituents of the galaxy clusters. Rotating cluster galaxy members can change the result of the calculation of the virial mass of the galaxy clusters that is used in many types of studies, amongst which is cosmology. A comparison of the rotation of the different constituents of the clusters give insight on their formation and the processes happening during their lifetime. I close with the conclusions of the studies of galaxy clusters and the future prospects of this work.
Galaxy clusters are widely used to constrain cosmological parameters through their properties, such as masses, luminosity and temperature distributions. One should take into account all kind of ...biases that could affect these analyses in order to obtain reliable constraints. In this work, we study the difference in the properties of clusters residing in different large scale environments, defined by their position within or outside of voids, and the density of their surrounding space. We use both observational and simulation cluster and void catalogues, i.e. XCS and redMaPPer clusters, BOSS voids, and Magneticum simulations. We devise two different environmental proxies for the clusters and study their redshift, richness, mass, X-ray luminosity and temperature distributions as well as some properties of their galaxy populations. We use the Kolmogorov-Smirnov two-sample test to discover that richer and more massive clusters are more prevalent in overdense regions and outside of voids. We also find that clusters of matched richness and mass in overdense regions and outside voids tend to have higher X-ray luminosities and temperatures. These differences could have important implications for precision cosmology with clusters of galaxies, since cluster mass calibrations can vary with environment.
We estimate the Intracluster Light (ICL) component within a sample of 18
clusters detected in XMM Cluster Survey (XCS) data using deep ($\sim$ 26.8 mag)
Hyper Suprime Cam Subaru Strategic Program DR1 ...(HSC-SSP DR1) $i$-band data. We
apply a rest-frame ${\mu}_{B} = 25 \ \mathrm{mag/arcsec^{2}}$ isophotal
threshold to our clusters, below which we define light as the ICL within an
aperture of $R_{X,500}$ (X-ray estimate of $R_{500}$) centered on the Brightest
Cluster Galaxy (BCG). After applying careful masking and corrections for flux
losses from background subtraction, we recover $\sim$20% of the ICL flux,
approximately four times our estimate of the typical background at the same
isophotal level ($\sim$ 5%). We find that the ICL makes up about $\sim$ 24% of
the total cluster stellar mass on average ($\sim$ 41% including the flux
contained in the BCG within 50 kpc); this value is well-matched with other
observational studies and semi-analytic/numerical simulations, but is
significantly smaller than results from recent hydrodynamical simulations (even
when measured in an observationally consistent way). We find no evidence for
any links between the amount of ICL flux with cluster mass, but find a growth
rate of $2-4$ for the ICL between $0.1 < z < 0.5$. We conclude that the ICL is
the dominant evolutionary component of stellar mass in clusters from $z \sim
1$. Our work highlights the need for a consistent approach when measuring ICL
alongside the need for deeper imaging, in order to unambiguously measure the
ICL across as broad a redshift range as possible (e.g. 10-year stacked imaging
from the Vera C. Rubin Observatory).
Twenty patients suffering from malignancy received furosemide, twenty patients were examined by FDG-PET without diuretics. Urine volume and radioactivity were measured before and after acquisition. ...Bladder activity was evaluated qualitatively and quantitatively.
Radioactivity in the bladder was lower and the image quality higher in the furosemide group. SUV values showed a median of 3.0 in the furosemide and 6.0 in the control group. With furosemide, a larger excreted volume was seen compared to the control group. The furosemide group showed a significantly higher ratio of excreted/ injected radioactivity early after injection. However, the totally excreted radioactivity was not significantly different (p = 0.93).
Diuretics cause a higher urine volume with a diluted FDG concentration leading to an improved image quality. Furosemide accelerates early renal FDG elimination, reducing radiation exposure.
We characterize the X-ray luminosity--temperature ($L_{\rm X}-T$) relation
using a sample of 353 clusters and groups of galaxies with temperatures in
excess of 1 keV, spanning the redshift range $0.1 ...< z < 0.6$, the largest ever
assembled for this purpose. All systems are part of the ${\it XMM-Newton}$
Cluster Survey (XCS), and have also been independently identified in Sloan
Digital Sky Survey (SDSS) data using the redMaPPer algorithm. We allow for
redshift evolution of the normalisation and intrinsic scatter of the $L_{\rm
X}-T$ relation, as well as, for the first time, the possibility of a
temperature-dependent change-point in the exponent of such relation. However,
we do not find strong statistical support for deviations from the usual
modelling of the $L_{\rm X}-T$ relation as a single power-law, where the
normalisation evolves self-similarly and the scatter remains constant with
time. Nevertheless, assuming {\it a priori} the existence of the type of
deviations considered, then faster evolution than the self-similar expectation
for the normalisation of the $L_{\rm X}-T$ relation is favoured, as well as a
decrease with redshift in the scatter about the $L_{\rm X}-T$ relation.
Further, the preferred location for a change-point is then close to 2 keV,
possibly marking the transition between the group and cluster regimes. Our
results also indicate an increase in the power-law exponent of the $L_{\rm
X}-T$ relation when moving from the group to the cluster regime, and faster
evolution in the former with respect to the later, driving the
temperature-dependent change-point towards higher values with redshift.
We estimate the Intracluster Light (ICL) component within a sample of 18 clusters detected in XMM Cluster Survey (XCS) data using deep (\(\sim\) 26.8 mag) Hyper Suprime Cam Subaru Strategic Program ...DR1 (HSC-SSP DR1) \(i\)-band data. We apply a rest-frame \({\mu}_{B} = 25 \ \mathrm{mag/arcsec^{2}}\) isophotal threshold to our clusters, below which we define light as the ICL within an aperture of \(R_{X,500}\) (X-ray estimate of \(R_{500}\)) centered on the Brightest Cluster Galaxy (BCG). After applying careful masking and corrections for flux losses from background subtraction, we recover \(\sim\)20% of the ICL flux, approximately four times our estimate of the typical background at the same isophotal level (\(\sim\) 5%). We find that the ICL makes up about \(\sim\) 24% of the total cluster stellar mass on average (\(\sim\) 41% including the flux contained in the BCG within 50 kpc); this value is well-matched with other observational studies and semi-analytic/numerical simulations, but is significantly smaller than results from recent hydrodynamical simulations (even when measured in an observationally consistent way). We find no evidence for any links between the amount of ICL flux with cluster mass, but find a growth rate of \(2-4\) for the ICL between \(0.1 < z < 0.5\). We conclude that the ICL is the dominant evolutionary component of stellar mass in clusters from \(z \sim 1\). Our work highlights the need for a consistent approach when measuring ICL alongside the need for deeper imaging, in order to unambiguously measure the ICL across as broad a redshift range as possible (e.g. 10-year stacked imaging from the Vera C. Rubin Observatory).
The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas ...filling the potential wells of galaxy clusters. However, it would not influence the clusters' weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, \(z=0.02\)). Here we apply the technique to the stacked profiles of 58 clusters at higher redshifts (\(0.1<z<1.2\)), including 12 new to the literature, using X-ray data from the XMM Cluster Survey (XCS) and weak lensing data from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Using a multi-parameter MCMC analysis, we constrain the two chameleon gravity parameters (\(\beta\) and \(\phi_{\infty}\)). Our fits are consistent with general relativity, not requiring a fifth force. In the special case of \(f(R)\) gravity (where \(\beta = \sqrt{1/6}\)), we set an upper limit on the background field amplitude today of \(|f_{\rm{R0}}| < 6 \times 10^{-5}\) (95% CL). This is one of the strongest constraints to date on \(|f_{\rm{R0}}|\) on cosmological scales. We hope to improve this constraint in future by extending the study to hundreds of clusters using data from the Dark Energy Survey.
We characterize the X-ray luminosity--temperature (\(L_{\rm X}-T\)) relation using a sample of 353 clusters and groups of galaxies with temperatures in excess of 1 keV, spanning the redshift range ...\(0.1 < z < 0.6\), the largest ever assembled for this purpose. All systems are part of the \({\it XMM-Newton}\) Cluster Survey (XCS), and have also been independently identified in Sloan Digital Sky Survey (SDSS) data using the redMaPPer algorithm. We allow for redshift evolution of the normalisation and intrinsic scatter of the \(L_{\rm X}-T\) relation, as well as, for the first time, the possibility of a temperature-dependent change-point in the exponent of such relation. However, we do not find strong statistical support for deviations from the usual modelling of the \(L_{\rm X}-T\) relation as a single power-law, where the normalisation evolves self-similarly and the scatter remains constant with time. Nevertheless, assuming {\it a priori} the existence of the type of deviations considered, then faster evolution than the self-similar expectation for the normalisation of the \(L_{\rm X}-T\) relation is favoured, as well as a decrease with redshift in the scatter about the \(L_{\rm X}-T\) relation. Further, the preferred location for a change-point is then close to 2 keV, possibly marking the transition between the group and cluster regimes. Our results also indicate an increase in the power-law exponent of the \(L_{\rm X}-T\) relation when moving from the group to the cluster regime, and faster evolution in the former with respect to the later, driving the temperature-dependent change-point towards higher values with redshift.
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