326,651 research outputs found
Enumerating Regular Objects associated with Suzuki Groups
We use the M\"obius function of the simple Suzuki group Sz(q) to enumerate
regular objects such as maps, hypermaps, dessins d'enfants and surface
coverings with automorphism groups isomorphic to Sz(q).Comment: 20 page
Simulations of the Microwave Sky
We create realistic, full-sky, half-arcminute resolution simulations of the
microwave sky matched to the most recent astrophysical observations. The
primary purpose of these simulations is to test the data reduction pipeline for
the Atacama Cosmology Telescope (ACT) experiment; however, we have widened the
frequency coverage beyond the ACT bands to make these simulations applicable to
other microwave background experiments. Some of the novel features of these
simulations are that the radio and infrared galaxy populations are correlated
with the galaxy cluster populations, the CMB is lensed by the dark matter
structure in the simulation via a ray-tracing code, the contribution to the
thermal and kinetic Sunyaev-Zel'dovich (SZ) signals from galaxy clusters,
groups, and the IGM has been included, and the gas prescription to model the SZ
signals matches the most recent X-ray observations. Regarding the contamination
of cluster SZ flux by radio galaxies, we find for 148 GHz (90 GHz) only 3% (4%)
of halos have their SZ decrements contaminated at a level of 20% or more. We
find the contamination levels higher for infrared galaxies. However, at 90 GHz,
less than 20% of clusters with M_{200} > 2.5 x 10^{14} Msun and z<1.2 have
their SZ decrements filled in at a level of 20% or more. At 148 GHz, less than
20% of clusters with M_{200} > 2.5 x 10^{14} Msun and z<0.8 have their SZ
decrements filled in at a level of 50% or larger. Our models also suggest that
a population of very high flux infrared galaxies, which are likely lensed
sources, contribute most to the SZ contamination of very massive clusters at 90
and 148 GHz. These simulations are publicly available and should serve as a
useful tool for microwave surveys to cross-check SZ cluster detection, power
spectrum, and cross-correlation analyses.Comment: Sims are now public at
http://lambda.gsfc.nasa.gov/toolbox/tb_cmbsim_ov.cfm; Expanded discussion of
N-body sim and IGM; Version accepted by Ap
The Sunyaev Zel'dovich effect: simulation and observation
The Sunyaev Zel'dovich effect (SZ effect) is a complete probe of ionized
baryons, the majority of which are likely hiding in the intergalactic medium.
We ran a CDM simulation using a moving mesh hydro code to
compute the statistics of the thermal and kinetic SZ effect such as the power
spectra and measures of non-Gaussianity. The thermal SZ power spectrum has a
very broad peak at multipole with temperature fluctuations
K. The power spectrum is consistent with available
observations and suggests a high and a possible role of
non-gravitational heating. The non-Gaussianity is significant and increases the
cosmic variance of the power spectrum by a factor of for .
We explore optimal driftscan survey strategies for the AMIBA CMB
interferometer and their dependence on cosmology. For SZ power spectrum
estimation, we find that the optimal sky coverage for a 1000 hours of
integration time is several hundred square degrees. One achieves an accuracy
better than 40% in the SZ measurement of power spectrum and an accuracy better
than 20% in the cross correlation with Sloan galaxies for . For
cluster searches, the optimal scan rate is around 280 hours per square degree
with a cluster detection rate 1 every 7 hours, allowing for a false positive
rate of 20% and better than 30% accuracy in the cluster SZ distribution
function measurement.Comment: 34 pages, 20 figures. Submitted to ApJ. Simulation maps have been
replaced by high resolution images. For higher resolution color images,
please download from http://www.cita.utoronto.ca/~zhangpj/research/SZ/ We
corrected a bug in our analysis. the SZ power spectrum decreases 50% and y
parameter decrease 25
Detection Feasibility of Cluster-Induced CMB Polarization
Galaxy clusters can potentially induce sub-K polarization signals in the
CMB with characteristic scales of a few arcminutes in nearby clusters. We
explore four such polarization signals induced in a rich nearby cluster and
calculate the likelihood for their detection by the currently operational
SPTpol, advanced ACTpol, and the upcoming Simons Array. In our feasibility
analysis we include instrumental noise, primordial CMB anisotropy, statistical
thermal SZ cluster signal, and point source confusion, assuming a few percent
of the nominal telescope observation time of each of the three projects. Our
analysis indicates that the thermal SZ intensity can be easily mapped in rich
nearby clusters, and that the kinematic SZ intensity can be measured with high
statistical significance toward a fast moving nearby cluster. The detection of
polarized SZ signals will be quite challenging, but could still be feasible
towards several very rich nearby clusters with exceptionally high SZ intensity.
The polarized SZ signal from a sample of clusters can be
statistically detected at , if observed for several months.Comment: 9 pages, 6 figures, submitted to MNRA
Further Sunyaev-Zel'dovich observations of two Planck ERCSC clusters with the Arcminute Microkelvin Imager
We present follow-up observations of two galaxy clusters detected blindly via
the Sunyaev-Zel'dovich (SZ) effect and released in the Planck Early Release
Compact Source Catalogue. We use the Arcminute Microkelvin Imager, a dual-array
14-18 GHz radio interferometer. After radio source subtraction, we find a SZ
decrement of integrated flux density -1.08+/-0.10 mJy toward PLCKESZ
G121.11+57.01, and improve the position measurement of the cluster, finding the
centre to be RA 12 59 36.4, Dec +60 04 46.8, to an accuracy of 20 arcseconds.
The region of PLCKESZ G115.71+17.52 contains strong extended emission, so we
are unable to confirm the presence of this cluster via the SZ effect.Comment: 4 tables, 3 figures, revised after referee's comments and resubmitted
to MNRA
Contamination of Cluster Radio Sources in the Measurement of the Thermal Sunyaev-Zel'dovich Angular Power Spectrum
We present a quantitative estimate of the confusion of cluster radio halos
and galaxies in the measurement of the angular power spectrum of the thermal
Sunyaev-Zel'dovich (SZ) effect. To achieve the goal, we use a purely analytic
approach to both radio sources and dark matter of clusters by incorporating
empirical models and observational facts together with some theoretical
considerations. It is shown that the correction of cluster radio halos and
galaxies to the measurement of the thermal SZ angular power spectrum is no more
than 20% at for observing frequencies GHz. This eliminates
the concern that the SZ measurement may be seriously contaminated by the
existence of cluster radio sources.Comment: 15 pages, 3 figures, accepted for publication in Ap
Real-time dynamics in spin-1/2 chains with adaptive time-dependent DMRG
We investigate the influence of different interaction strengths and
dimerizations on the magnetization transport in antiferromagnetic spin-1/2
XXZ-chains. We focus on the real-time evolution of the inhomogeneous initial
state with all spins pointing up along the z axis in the left half and down in
the right half of the chain, using the adaptive time-dependent density-matrix
renormalization group (adaptive t-DMRG). We find on time-scales accessible to
us ballistic magnetization transport for small Sz-Sz-interaction and arbitrary
dimerization, but almost no transport for stronger Sz-Sz-interaction, with a
sharp crossover at Jz=1. At Jz=1 results indicate superdiffusive transport.
Additionally, we perform a detailed analysis of the error made by the adaptive
time-dependent DMRG using the fact that the evolution in the XX-model is known
exactly. We find that the error at small times is dominated by the error made
by the Trotter decomposition, whereas for longer times the DMRG truncation
error becomes the most important, with a very sharp crossover at some "runaway"
time.Comment: 13 pages, 20 figure
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