1,099 research outputs found
The evolution of the cluster X-ray scaling relations in the WARPS sample at 0.6<z<1.0
The X-ray properties of a sample of 11 high-redshift (0.6<z<1.0) clusters
observed with Chandra and/or XMM are used to investigate the evolution of the
cluster scaling relations. The observed evolution of the L-T and M-L relations
is consistent with simple self-similar predictions, in which the properties of
clusters reflect the properties of the universe at their redshift of
observation. When the systematic effect of assuming isothermality on the
derived masses of the high-redshift clusters is taken into account, the
high-redshift M-T and Mgas-T relations are also consistent with self-similar
evolution. Under the assumption that the model of self-similar evolution is
correct and that the local systems formed via a single spherical collapse, the
high-redshift L-T relation is consistent with the high-z clusters having formed
at a significantly higher redshift than the local systems. The data are also
consistent with the more realistic scenario of clusters forming via the
continuous accretion of material. The slope of the L-T relation at
high-redshift (B=3.29+/-0.38) is consistent with the local relation, and
significantly steeper then the self-similar prediction of B=2. This suggests
that the non-gravitational processes causing the steepening occurred at z>1 or
in the early stages of the clusters' formation, prior to their observation. The
properties of the intra-cluster medium at high-redshift are found to be similar
to those in the local universe. The mean surface-brightness profile slope for
the sample is 0.66+/-0.05, the mean gas mass fractions within R2500 and R200
are 0.073+/-0.010 and 0.12+/-0.02 respectively, and the mean metallicity of the
sample is 0.28+/-0.16 solar.Comment: 23 pages, 17 figures. Accepted for publication in MNRAS. Revised to
match accepted version: reanalysed data with latest calibrations, several
minor changes. Conclusions unchange
The WARPS Survey. VIII. Evolution of the Galaxy Cluster X-ray Luminosity Function
We present measurements of the galaxy cluster X-ray Luminosity Function (XLF)
from the Wide Angle ROSAT Pointed Survey (WARPS) and quantify its evolution.
WARPS is a serendipitous survey of the central region of ROSAT pointed
observations and was carried out in two phases (WARPS-I and WARPS-II). The
results here are based on a final sample of 124 clusters, complete above a flux
limit of 6.5 10E-15 erg/s/cm2, with members out to redshift z ~ 1.05, and a sky
coverage of 70.9 deg2. We find significant evidence for negative evolution of
the XLF, which complements the majority of X-ray cluster surveys. To quantify
the suggested evolution, we perform a maximum likelihood analysis and conclude
that the evolution is driven by a decreasing number density of high luminosity
clusters with redshift, while the bulk of the cluster population remains nearly
unchanged out to redshift z ~ 1.1, as expected in a low density Universe. The
results are found to be insensitive to a variety of sources of systematic
uncertainty that affect the measurement of the XLF and determination of the
survey selection function. We perform a Bayesian analysis of the XLF to fully
account for uncertainties in the local XLF on the measured evolution, and find
that the detected evolution remains significant at the 95% level. We observe a
significant excess of clusters in the WARPS at 0.1 < z < 0.3 and LX ~ 2 10E42
erg/s compared with the reference low-redshift XLF, or our Bayesian fit to the
WARPS data. We find that the excess cannot be explained by sample variance, or
Eddington bias, and is unlikely to be due to problems with the survey selection
function.Comment: 13 pages, 12 figures, accepted for publication in MNRA
A computational technique for simulating ionization energy deposition by energetic ions in complex targets
An ion transport code was developed for simulating ionization energy deposition by energetic ions in sensitive volumes of complex structures. The code was used to simulate recent microdosimetry measurements performed with silicon-on-insulator (SOI) microdosimeters in Fast Neutron Therapy (FNT)
Associations between diurnal preference, sleep quality and externalizing behaviours: a behavioural genetic analysis
Background - Certain aspects of sleep co-occur with externalizing behaviours in youth, yet little is known about these associations in adults. The present study: (1) examines the associations between diurnal preference (morningness versus eveningness), sleep quality and externalizing behaviours; (2) explores the extent to which genetic and environmental influences are shared between or are unique to these phenotypes; (3) examines the extent to which genetic and environmental influences account for these associations.
Method - Questionnaires assessing diurnal preference, sleep quality and externalizing behaviours were completed by 1556 young adult twins and siblings.
Results - A preference for eveningness and poor sleep quality were associated with greater externalizing symptoms [r=0.28 (95% CI 0.23–0.33) and 0.34 (95% CI 0.28–0.39), respectively]. A total of 18% of the genetic influences on externalizing behaviours were shared with diurnal preference and sleep quality and an additional 14% were shared with sleep quality alone. Non-shared environmental influences common to the phenotypes were small (2%). The association between diurnal preference and externalizing behaviours was mostly explained by genetic influences [additive genetic influence (A)=80% (95% CI 0.56–1.01)], as was the association between sleep quality and externalizing behaviours [A=81% (95% CI 0.62–0.99)]. Non-shared environmental (E) influences accounted for the remaining variance for both associations [E=20% (95% CI −0.01 to 0.44) and 19% (95% CI 0.01–0.38), respectively].
Conclusions - A preference for eveningness and poor sleep quality are moderately associated with externalizing behaviours in young adults. There is a moderate amount of shared genetic influences between the phenotypes and genetic influences account for a large proportion of the association between sleep and externalizing behaviours. Further research could focus on identifying specific genetic polymorphisms common to both sleep and externalizing behaviours
A phase II study of capecitabine and oxalplatin combination chemotherapy in patients with inoperable adenocarcinoma of the gall bladder or biliary tract
Background: Advanced biliary tract carcinomas are associated with a poor prognosis, and palliative chemotherapy has only modest benefit. This multi-centre phase II study was conducted to determine the efficacy of capecitabine in combination with oxaliplatin in patients with inoperable gall bladder or biliary tract cancer. Methods: This was a Phase II, non-randomised, two-stage Simon design, multi-centre study. Ethics approval was sought and obtained by the North West MREC, and then locally by the West Glasgow Hospitals Research Ethics Com mittee. Eligible patients with inoperable locally advanced or metastatic adenocarcinoma of the gall bladder or biliary tract and with adequate performance status, haematologic, renal, and hepatic function were treated with capecit abine (1000 mg/m2 po, twice daily, days 1–14) and oxaliplatin (130 mg/m2 i.v., day 1) every 3 weeks for up to six cycles. The primary objective of the study was to determine the objective tumour response rates (complete and partial). The secondary objectives included assessment of toxicity, progression-free survival, and overall survival. Results: Forty-three patients were recruited between July 2003 and December 2005. The regimen was well tolerated with no grade 3/4 neutropenia or thrombocytopenia. Grade 3/4 sensory neuropathy was observed in six patients. Two-thirds of patients received their chemotherapy without any dose delays. Overall response rate was 23.8 % (95 % CI 12.05–39.5 %). Stable disease was observed in a further 13 patients (31 %) and progressive disease observed in 12 (28.6 %) of patients. The median progression-free survival was 4.6 months (95 % CI 2.8–6.4 months; Fig. 1) and the median overall survival 7.9 months (95 % CI 5.3–10.4 months; Fig. 2). Conclusion: Capecitabine combined with oxaliplatin has a lower disease control and shorter overall survival than the combination of cisplatin with gemcitabine which has subsequently become the standard of care in this disease. How ever, capecitabine in combination with oxaliplatin does have modest activity in this disease, and can be considered as an alternative treatment option for patients in whom cisplatin and/or gemcitabine are contra-indicated
X-MAS2: Study Systematics on the ICM Metallicity Measurements
(Abridged)The X-ray measurements of the ICM metallicity are becoming more
frequent due to the availability of powerful X-ray telescope with excellent
spatial and spectral resolutions. The information which can be extracted from
the measurements of the alpha-elements, like Oxygen, Magnesium and Silicon with
respect to the Iron abundance is extremely important to better understand the
stellar formation and its evolutionary history. In this paper we investigate
possible source of bias connected to the plasma physics when recovering metal
abundances from X-ray spectra. To do this we analyze 6 simulated galaxy
clusters processed through the new version of our X-ray MAp Simulator, which
allows to create mock XMM-Newton EPIC MOS1 and MOS2 observations. By comparing
the spectroscopic results to the input values we find that: i) Fe is recovered
with high accuracy for both hot (T>3 keV) and cold (T<2 keV) systems; at
intermediate temperatures, however, we find a systematic overestimate which
depends on the number counts; ii) O is well recovered in cold clusters, while
in hot systems its measure may overestimate by a factor up to 2-3; iii) Being a
weak line, the measurement of Mg is always difficult; despite of this, for cold
systems (T<2 keV) we do not find any systematic behavior, while for very hot
systems (T>5 keV) the spectroscopic measurement may be strongly overestimated
up to a factor of 4; iv) Si is well recovered for all the clusters in our
sample. We investigate in detail the nature of the systematic effects and
biases found. We conclude that they are mainly connected with the
multi-temperature nature of the projected observed spectra and to the intrinsic
limitation of the XMM-Newton EPIC spectral resolution that does not always
allow to disentangle among the emission lines produced by different elements.Comment: (e.g.: 17 pages, 8 figures, accepted for publication in the
Astrophysical Journal, updated discussion to match published version-new
section:6.3
Deep XMM and Chandra observations of ClJ1226.9+3332: A detailed X-ray mass analysis of a z=0.89 galaxy cluster
Deep XMM and Chandra observations of ClJ1226.9+3332 at z=0.89 have enabled
the most detailed X-ray mass analysis of any such high-redshift galaxy cluster.
The XMM temperature profile of the system shows no sign of central cooling,
with a hot core and a radially declining profile. A temperature map shows
asymmetry with a hot region that appears to be associated with a subclump of
galaxies at the cluster redshift, but is not visible in the X-ray surface
brightness. This is likely to be result of a merger event in the cluster, but
does not appear to significantly affect the overall temperature profile. The
XMM temperature profile, and combined Chandra and XMM emissivity profile
allowed precise measurements of the global properties of ClJ1226.9+3332; we
find kT=10.4+/-0.6keV, Z=0.16+/-0.05\Zsol, and M=5.2^{+1.0}_{-0.8}x10^{14}Msol.
We obtain profiles of the metallicity, entropy, cooling time and gas fraction,
and find a high concentration parameter for the total density profile of the
system. The global properties are compared with the local LT and MT relations,
and we are able to make the first observational test of the predicted evolution
of the YM relation. We find that departures from these scaling relations are
most likely caused by an underestimate of the total mass by ~30% in the X-ray
hydrostatic mass analysis due to the apparent recent or ongoing merger
activity.Comment: 14 pages, 19 figures. To be submitted to Ap
An XMM-Newton observation of the massive, relaxed galaxy cluster ClJ1226.9+3332 at z=0.89
A detailed X-ray analysis of an XMM-Newton observation of the high-redshift
(z=0.89) galaxy cluster ClJ1226.9+3332 is presented. The X-ray temperature is
found to be 11.5{+1.1}{-0.9}keV, the highest X-ray temperature of any cluster
at z>0.6. In contrast to MS1054-0321, the only other very hot cluster currently
known at z>0.8, ClJ1226.9+3332 features a relaxed X-ray morphology, and its
high overall gas temperature is not caused by one or several hot spots. The
system thus constitutes a unique example of a high redshift, high temperature,
relaxed cluster, for which the usual hydrostatic equilibrium assumption, and
the X-ray mass is most reliable. A temperature profile is constructed (for the
first time at this redshift) and is consistent with the cluster being
isothermal out to 45% of the virial radius. Within the virial radius
(corresponding to a measured overdensity of a factor of 200), a total mass of
(1.4+/-0.5)*10^15 M_solar is derived, with a gas mass fraction of 12+/-5%. The
bolometric X-ray luminosity is (5.3+/-0.2)*10^45 erg/s. The probabilities of
finding a cluster of this mass within the volume of the discovery X-ray survey
are 8*10^{-5} for Omega_M=1 and 0.64 for Omega_M=0.3, making Omega_M=1 highly
unlikely. The entropy profile suggests that entropy evolution is being
observed. The metal abundance (of Z=0.33{+0.14}{-0.10} Z_solar), gas mass
fraction, and gas distribution are consistent with those of local clusters;
thus the bulk of the metals were in place by z=0.89.Comment: 13 pages, 8 figures. Accepted for publication in MNRA
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