537 research outputs found
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Evolution of the Quasar Luminosity Function: Implications for EoR-21cm
AbstractWe present predictions for the spatial distribution of 21 cm brightness temperature fluctuations from high-dynamic-range simulations for AGN-dominated reionization histories that have been tested against available Lyα and CMB data. We model AGN by extrapolating the observed Mbh–σ relation to high redshifts and assign them ionizing emissivities consistent with recent UV luminosity function measurements. AGN-dominated reionization histories increase the variance of the 21 cm emission by a factor of up to ten compared to similar reionization histories dominated by faint galaxies, to values close to 100 mK2 at scales accessible to experiments (k ≲ 1 cMpc−1h). This is lower than the sensitivity reached by ongoing experiments by only a factor of about two or less. AGN dominated reionization should be easily detectable by LOFAR (and later HERA and SKA1) at their design sensitivity.</jats:p
Lyman α emitters gone missing: Evidence for late reionization?
We combine high resolution hydrodynamical simulations with an intermediate
resolution, dark matter only simulation and an analytical model for the growth
of ionized regions to estimate the large scale distribution and redshift
evolution of the visibility of Lyman-alpha emission in 6<=z<=8 galaxies. The
inhomogeneous distribution of neutral hydrogen during the reionization process
results in significant fluctuations in the Lyman-alpha transmissivity on large
scales. The transmissivity depends not only on the ionized fraction of the
intergalactic medium by volume and the amplitude of the local ionizing
background, but is also rather sensitive to the evolution of the relative
velocity shift of the Lyman-alpha emission line due to resonant scattering. We
reproduce a decline in the space density of Lyman-alpha emitting galaxies as
rapid as observed with a rather rapidly evolving neutral fraction between
z=6-8, and a typical Lyman-alpha line velocity offset of 100 km/s redward of
systemic at z=6 which decreases toward higher redshift. The new (02/2015)
Planck results indicate such a recent end to reionization is no longer
disfavoured by constraints from the cosmic microwave background
Large 21 cm signals from AGN-dominated reionization
We present predictions for the spatial distribution of 21-cm brightness temperature fluctuations from high-dynamic-range simulations for active galactic nucleus (AGN)-dominated reionization histories that have been tested against available Ly and cosmic microwave background (CMB) data. We model AGNs by extrapolating the observed − σ relation to high redshifts and assign them ionizing emissivities consistent with recent UV luminosity function measurements. We assess the observability of the predicted spatial 21-cm fluctuations in the late stages of reionization in the limit in which the hydrogen 21-cm spin temperature is significantly larger than the CMB temperature. Our AGN-dominated reionization histories increase the variance of the 21-cm emission by a factor of up to 10 compared to similar reionization histories dominated by faint galaxies, to values close to 100 mK at scales accessible to experiments ( 1 cMpc ). This is lower than the sensitivity reached by ongoing experiments only by a factor of about 2 or less. When reionization is dominated by AGNs, the 21-cm power spectrum is enhanced on all scales due to the enhanced bias of the clustering of the more massive haloes and the peak in the large scale 21-cm power is strongly enhanced and moved to larger scales due to bigger characteristic bubble sizes. AGN-dominated reionization should be easily detectable by Low Frequency Array (and later Hydrogen Epoch of Reionization Array and Phase 1 of the Square Kilometre Array) at their design sensitivity, assuming successful foreground subtraction and instrument calibration. Conversely, these could become the first non-trivial reionization scenarios to be ruled out by 21-cm experiments, thereby constraining the contribution of AGNs to reionization.Support by ERC Advanced grant 320596 ‘The Emergence of Structure During the Epoch of Reionization’ is gratefully acknowledged. EP gratefully acknowledges support by the Kavli Foundation. We acknowledge PRACE for awarding us access to the Curie supercomputer, based in France at the Tres Grand Centre de Calcul ´ (TGCC). This work used the DiRAC Data Centric system at Durham University, operated by the Institute for Computational Cosmology on behalf of the STFC DiRAC HPC Facility (www.dirac.ac.uk). This equipment was funded by BIS National E-infrastructure capital grant ST/K00042X/1, STFC capital grants ST/H008519/1 and ST/K00087X/1, STFC DiRAC Operations grant ST/K003267/1 and Durham University. DiRAC is part of the National E-Infrastructure. This research was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence ‘Origin and Structure of the Universe’
Lyman-α emitters gone missing: The different evolution of the bright and faint populations
We model the transmission of the Lyman-alpha line through the circum- and
intergalactic media around dark matter haloes expected to host Lyman-alpha
emitters (LAEs) at z > 5.7, using the high-dynamic-range Sherwood simulations.
We find very different CGM environments around more massive haloes (~10^11
M_sun) compared to less massive haloes (~10^9 M_sun) at these redshifts, which
can contribute to a different evolution of the Lyman-alpha transmission from
LAEs within these haloes. Additionally we confirm that part of the differential
evolution could result from bright LAEs being more likely to reside in larger
ionized regions. We conclude that a combination of the CGM environment and the
IGM ionization structure is likely to be responsible for the differential
evolution of the bright and faint ends of the LAE luminosity function at z > 6.
More generally, we confirm the suggestion that the self-shielded neutral gas in
the outskirts of the host halo can strongly attenuate the Lyman-alpha emission
from high redshift galaxies. We find that this has a stronger effect on the
more massive haloes hosting brighter LAEs. The faint-end of the LAE luminosity
function is thus a more reliable probe of the average ionization state of the
IGM. Comparing our model for LAEs with a range of observational data we find
that the favoured reionization histories are our previously advocated `Late'
and `Very Late' reionization histories, in which reionization finishes rather
rapidly at around z ~ 6
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A consistent and robust measurement of the thermal state of the IGM at 2 ≤ z ≤ 4 from a large sample of Ly α forest spectra: Evidence for late and rapid He ii reionization
We characterise the thermal state of the intergalactic medium (IGM) in ten
redshift bins in the redshift range with a sample of 103 high
resolution, high S/N Ly forest spectra using four different flux
distribution statistics. Our measurements are calibrated with mock spectra from
a large suite of hydrodynamical simulations post-processed with our thermal IGM
evolution code CITE, finely sampling amplitude and slope of the expected
temperature-density relation. The thermal parameters inferred from our
measurements of the flux power spectrum, Doppler parameter distribution, as
well as wavelet and curvature statistics agree well within their respective
errors and all clearly show the peak in temperature and minimum in slope of the
temperature density relation expected from HeII reionization. Combining our
measurements from the different flux statistics gives K
for the peak temperature at mean density and a corresponding minimum slope
. The peak in the temperature evolution occurs at , in agreement with previous measurements that had suggested the
presence of such a peak, albeit with a large scatter. Using CITE, we also
calculate the thermal state of the IGM predicted by five widely used (spatially
homogeneous) UV-background models. The rather rapid thermal evolution inferred
by our measurements is well reproduced by two of the models, if we assume
(physically well motivated) non-equilibrium evolution with photo-heating rates
that are reduced by a moderate factor of . The other three models
predict HeII reionization to be more extended with a somewhat earlier as well
as higher temperature peak than our measurements suggest
Sexual Size Dimorphism and Body Condition in the Australasian Gannet
Funding: The research was financially supported by the Holsworth Wildlife Research Endowment. Acknowledgments We thank the Victorian Marine Science Consortium, Sea All Dolphin Swim, Parks Victoria, and the Point Danger Management Committee for logistical support. We are grateful for the assistance of the many field volunteers involved in the study.Peer reviewedPublisher PD
Non-homologous end-joining pathway associated with occurrence of myocardial infarction: gene set analysis of genome-wide association study data
<p>Purpose: DNA repair deficiencies have been postulated to play a role in the development and progression of cardiovascular disease (CVD). The hypothesis is that DNA damage accumulating with age may induce cell death, which promotes formation of unstable plaques. Defects in DNA repair mechanisms may therefore increase the risk of CVD events. We examined whether the joints effect of common genetic variants in 5 DNA repair pathways may influence the risk of CVD events.</p>
<p>Methods: The PLINK set-based test was used to examine the association to myocardial infarction (MI) of the DNA repair pathway in GWAS data of 866 subjects of the GENetic DEterminants of Restenosis (GENDER) study and 5,244 subjects of the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) study. We included the main DNA repair pathways (base excision repair, nucleotide excision repair, mismatch repair, homologous recombination and non-homologous end-joining (NHEJ)) in the analysis.</p>
<p>Results: The NHEJ pathway was associated with the occurrence of MI in both GENDER (P = 0.0083) and PROSPER (P = 0.014). This association was mainly driven by genetic variation in the MRE11A gene (PGENDER = 0.0001 and PPROSPER = 0.002). The homologous recombination pathway was associated with MI in GENDER only (P = 0.011), for the other pathways no associations were observed.</p>
<p>Conclusion: This is the first study analyzing the joint effect of common genetic variation in DNA repair pathways and the risk of CVD events, demonstrating an association between the NHEJ pathway and MI in 2 different cohorts.</p>
Cancer mortality in ethnic South Asian migrants in England and Wales (1993–2003): patterns in the overall population and in first and subsequent generations
BACKGROUND: Cancer mortality has been examined among ethnic South Asian migrants in England and Wales, but not by generation of migration. METHODS: Using South Asian mortality records, identified by a name-recognition algorithm, and census information, age-standardised rates among South Asians, and South Asian vs non-South Asian rate ratios, were calculated. RESULTS AND CONCLUSIONS: All-cancer rates in ethnic South Asians were half of those in non-South Asians in first-generation (all-cancer-standardised mortality ratio (SMR) in males 0.51 and in females 0.56) and subsequent-generation South Asians (SMR in males 0.43 and in females 0.36). The higher mortality in first-generation South Asians for liver (both sexes), oral cavity and gallbladder cancer (females), particularly marked among Bangladeshis, was reduced in subsequent generations
Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC
We present the first results of meson production in the K^+K^- decay channel
from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by
the PHENIX detector at RHIC. Precision resonance centroid and width values are
extracted as a function of collision centrality. No significant variation from
the PDG accepted values is observed. The transverse mass spectra are fitted
with a linear exponential function for which the derived inverse slope
parameter is seen to be constant as a function of centrality. These data are
also fitted by a hydrodynamic model with the result that the freeze-out
temperature and the expansion velocity values are consistent with the values
previously derived from fitting single hadron inclusive data. As a function of
transverse momentum the collisions scaled peripheral.to.central yield ratio RCP
for the is comparable to that of pions rather than that of protons. This result
lends support to theoretical models which distinguish between baryons and
mesons instead of particle mass for explaining the anomalous proton yield.Comment: 326 authors, 24 pages text, 23 figures, 6 tables, RevTeX 4. To be
submitted to Physical Review C as a regular article. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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