1,241 research outputs found
Constraints on the Optical Depth of Galaxy Groups and Clusters
Future data from galaxy redshift surveys, combined with high-resolutions maps of the cosmic microwave background, will enable measurements of the pairwise kinematic SunyaevâZel'dovich (kSZ) signal with unprecedented statistical significance. This signal probes the matter-velocity correlation function, scaled by the average optical depth (Ï) of the galaxy groups and clusters in the sample, and is thus of fundamental importance for cosmology. However, in order to translate pairwise kSZ measurements into cosmological constraints, external constraints on Ï are necessary. In this work, we present a new model for the intracluster medium, which takes into account star formation, feedback, non-thermal pressure, and gas cooling. Our semi-analytic model is computationally efficient and can reproduce results of recent hydrodynamical simulations of galaxy cluster formation. We calibrate the free parameters in the model using recent X-ray measurements of gas density profiles of clusters, and gas masses of groups and clusters. Our observationally calibrated model predicts the average Ïâ
ââ (i.e., the integrated Ï within a disk of size R â
ââ) to better than 6% modeling uncertainty (at 95% confidence level). If the remaining uncertainties associated with other astrophysical uncertainties and X-ray selection effects can be better understood, our model for the optical depth should break the degeneracy between optical depth and cluster velocity in the analysis of future pairwise kSZ measurements and improve cosmological constraints with the combination of upcoming galaxy and CMB surveys, including the nature of dark energy, modified gravity, and neutrino mass.National Science Foundation (U.S.) (AST-1412768)United States. National Aeronautics and Space Administration (GO4-15122A)United States. National Aeronautics and Space Administration (contract GO5-16141X
2005-2006 Master Class - Yoshikazu Nagai (Piano)
Piano Recital - Yoshikazu Nagai (October 15, 2005) - Programhttps://spiral.lynn.edu/conservatory_masterclasses/1140/thumbnail.jp
Flavour Breaking Effects of Wilson twisted mass fermions
We study the flavour breaking effects appearing in the Wilson twisted mass
formulation of lattice QCD. In this quenched study, we focus on the mass
splitting between the neutral and the charged pion, determining the neutral
pion mass with a stochastic noise method to evaluate the disconnected
contributions. We find that these disconnected contributions are significant.
Using the Osterwalder-Seiler interpretation of the connected piece of the
neutral pion correlator, we compute the corresponding neutral pion mass to
study with more precision the scaling behaviour of the mass splitting.Comment: 15 pages, 2 figure
Optimal transport distances for directed, weighted graphs: a case study with cell-cell communication networks
Comparing graphs by means of optimal transport has recently gained
significant attention, as the distances induced by optimal transport provide
both a principled metric between graphs as well as an interpretable description
of the associated changes between graphs in terms of a transport plan. As the
lack of symmetry introduces challenges in the typically considered
formulations, optimal transport distances for graphs have mostly been developed
for undirected graphs. Here, we propose two distance measures to compare
directed graphs based on variants of optimal transport: (i) an earth movers
distance (Wasserstein) and (ii) a Gromov-Wasserstein (GW) distance. We evaluate
these two distances and discuss their relative performance for both simulated
graph data and real-world directed cell-cell communication graphs, inferred
from single-cell RNA-seq data.Comment: 5 pages, 1 figur
Internal Knowledge Sharing by Infrastructure Maintenance Engineers in Small and Medium Size Construction Companies in Japan
It is necessary to increase the capability of engineers to carry out maintenance management for keeping infrastructure safe and serviceable. Many regional training programs have been established to develop engineers into âmaintenance experts.â While small and medium size construction companies and engineering consultants play an active role in infrastructure maintenance, they have limited human and economic resources for joining the training programs, so the sharing of knowledge acquired from the programs becomes important for improving the capability of the company as a whole. The objective of this research is to investigate how engineers who participated in regional training programs shared their knowledge inside their organization using an online questionnaire survey. It was found that leadership is an important factor for driving knowledge sharing activities, particularly for adapting the knowledge acquired from the training program to the companyâs environment. However, the lack of experience serves as a barrier to the deeper transfer of knowledge, such as on-the-job training or seminars, as these methods of knowledge sharing require expert knowledge. For organizations to improve their knowledge sharing practices, it is necessary to consider the type of knowledge to be shared and the appropriate method for sharing, along with the improvement of the leadership for knowledge sharing in the organization
Imaging the Thermal and Kinematic Sunyaev-Zel'dovich Effect Signals in a Sample of Ten Massive Galaxy Clusters: Constraints on Internal Velocity Structures and Bulk Velocities
We have imaged the Sunyaev-Zel'dovich (SZ) effect signals at 140 and 270 GHz
towards ten galaxy clusters with Bolocam and AzTEC/ASTE. We also used Planck
data to constrain the signal at large angular scales, Herschel-SPIRE images to
subtract the brightest galaxies that comprise the cosmic infrared background
(CIB), Chandra imaging to map the electron temperature of the
intra-cluster medium (ICM), and HST imaging to derive models of each galaxy
cluster's mass density. The galaxy clusters gravitationally lens the background
CIB, which produced an on-average reduction in brightness towards the galaxy
clusters' centers after the brightest galaxies were subtracted. We corrected
for this deficit, which was between 5-25% of the 270 GHz SZ effect signal
within . Using the SZ effect measurements, along with the X-ray
constraint on , we measured each galaxy cluster's average line of sight
(LOS) velocity within , with a median per-cluster uncertainty
of +-700 km/s. We found an ensemble-mean of 430+-210 km/s, and an
intrinsic cluster-to-cluster scatter of 470+-340 km/s. We also
obtained maps of over each galaxy cluster's face with an angular
resolution of 70". All four galaxy clusters previously identified as having a
merger oriented along the LOS showed an excess variance in these maps at a
significance of 2-4, indicating an internal rms of 1000
km/s. None of the six galaxy clusters previously identified as relaxed or plane
of sky mergers showed any such excess variance.Comment: Accepted for publication in Ap
Twisted mass fermions: neutral pion masses from disconnected contributions
Twisted mass fermions allow light quarks to be explored but with the
consequence that there are mass splittings, such as between the neutral and
charged pion. Using a direct calculation of the connected neutral pion
correlator and stochastic methods to evaluate the disconnected correlations, we
determine the neutral pion mass. We explore the dependence on lattice spacing
and quark mass in quenched QCD. For dynamical QCD, we determine the sign of the
splitting which is linked, via chiral PT, to the nature of the phase transition
at small quark mass.Comment: 6 pages, poster (hadron spectrum and quark masses) at Lattice
2005,Dublin, July 25-3
Hydrodynamical Simulations of Galaxy Clusters with Galcons
We present our recently developed {\em galcon} approach to hydrodynamical
cosmological simulations of galaxy clusters - a subgrid model added to the {\em
Enzo} adaptive mesh refinement code - which is capable of tracking galaxies
within the cluster potential and following the feedback of their main baryonic
processes. Galcons are physically extended galactic constructs within which
baryonic processes are modeled analytically. By identifying galaxy halos and
initializing galcons at high redshift (, well before most clusters
virialize), we are able to follow the evolution of star formation, galactic
winds, and ram-pressure stripping of interstellar media, along with their
associated mass, metals and energy feedback into intracluster (IC) gas, which
are deposited through a well-resolved spherical interface layer. Our approach
is fully described and all results from initial simulations with the enhanced
{\em Enzo-Galcon} code are presented. With a galactic star formation rate
derived from the observed cosmic star formation density, our galcon simulation
better reproduces the observed properties of IC gas, including the density,
temperature, metallicity, and entropy profiles. By following the impact of a
large number of galaxies on IC gas we explicitly demonstrate the advantages of
this approach in producing a lower stellar fraction, a larger gas core radius,
an isothermal temperature profile in the central cluster region, and a flatter
metallicity gradient than in a standard simulation
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