260 research outputs found
Knot invariants in lens spaces
In this survey we summarize results regarding the Kauffman bracket, HOMFLYPT,
Kauffman 2-variable and Dubrovnik skein modules, and the Alexander polynomial
of links in lens spaces, which we represent as mixed link diagrams. These
invariants generalize the corresponding knot polynomials in the classical case.
We compare the invariants by means of the ability to distinguish between some
difficult cases of knots with certain symmetries
Thermodynamic Profiles of Galaxy Clusters from a Joint X-ray/SZ Analysis
We jointly analyze Bolocam Sunyaev-Zeldovich (SZ) effect and Chandra X-ray
data for a set of 45 clusters to derive gas density and temperature profiles
without using spectroscopic information. The sample spans the mass and redshift
range
and . We define cool-core (CC) and non-cool core (NCC)
subsamples based on the central X-ray luminosity, and 17/45 clusters are
classified as CC. In general, the profiles derived from our analysis are found
to be in good agreement with previous analyses, and profile constraints beyond
are obtained for 34/45 clusters. In approximately 30% of the CC
clusters our analysis shows a central temperature drop with a statistical
significance of ; this modest detection fraction is due mainly to a
combination of coarse angular resolution and modest S/N in the SZ data. Most
clusters are consistent with an isothermal profile at the largest radii near
, although 9/45 show a significant temperature decrease with
increasing radius. The sample mean density profile is in good agreement with
previous studies, and shows a minimum intrinsic scatter of approximately 10%
near . The sample mean temperature profile is consistent
with isothermal, and has an intrinsic scatter of approximately 50% independent
of radius. This scatter is significantly higher compared to earlier X-ray-only
studies, which find intrinsic scatters near 10%, likely due to a combination of
unaccounted for non-idealities in the SZ noise, projection effects, and sample
selection.Comment: 42 pages, 52 figure
An Evolving Entropy Floor in the Intracluster Gas?
Non-gravitational processes, such as feedback from galaxies and their active
nuclei, are believed to have injected excess entropy into the intracluster gas,
and therefore to have modified the density profiles in galaxy clusters during
their formation. Here we study a simple model for this so-called preheating
scenario, and ask (i) whether it can simultaneously explain both global X-ray
scaling relations and number counts of galaxy clusters, and (ii) whether the
amount of entropy required evolves with redshift. We adopt a baseline entropy
profile that fits recent hydrodynamic simulations, modify the hydrostatic
equilibrium condition for the gas by including approx. 20% non-thermal pressure
support, and add an entropy floor K_0 that is allowed to vary with redshift. We
find that the observed luminosity-temperature (L-T) relations of low-redshift
(z=0.05) HIFLUGCS clusters and high-redshift (z=0.8) WARPS clusters are best
simultaneously reproduced with an evolving entropy floor of
K_0(z)=341(1+z)^{-0.83}h^{-1/3} keV cm^2. If we restrict our analysis to the
subset of bright (kT > 3 keV) clusters, we find that the evolving entropy floor
can mimic a self-similar evolution in the L-T scaling relation. This degeneracy
with self-similar evolution is, however, broken when (0.5 < kT < 3 keV)
clusters are also included. The approx. 60% entropy increase we find from z=0.8
to z=0.05 is roughly consistent with that expected if the heating is provided
by the evolving global quasar population. Using the cosmological parameters
from the WMAP 3-year data with sigma_8=0.76, our best-fit model underpredicts
the number counts of the X-ray galaxy clusters compared to those derived from
the 158 deg^2 ROSAT PSPC survey. Treating sigma_8 as a free parameter, we find
a best-fit value of sigma_8=0.80+/- 0.02.Comment: 14 emulateapj pages with 9 figures, submitted to Ap
The Massive and Distant Clusters of WISE Survey: SZ effect Verification with the Atacama Compact Array -- Localization and Cluster Analysis
The Massive and Distant Clusters of WISE Survey (MaDCoWS) provides a catalog
of high-redshift () infrared-selected galaxy
clusters. However, the verification of the ionized intracluster medium,
indicative of a collapsed and nearly virialized system, is made challenging by
the high redshifts of the sample members. The main goal of this work is to test
the capabilities of the Atacama Compact Array (ACA; also known as the Morita
Array) Band 3 observations, centered at about 97.5 GHz, to provide robust
validation of cluster detections via the thermal Sunyaev-Zeldovich (SZ) effect.
Using a pilot sample that comprises ten MaDCoWS galaxy clusters, accessible to
ACA and representative of the median sample richness, we infer the masses of
the selected galaxy clusters and respective detection significance by means of
a Bayesian analysis of the interferometric data. Our test of the "Verification
with the ACA - Localization and Cluster Analysis" (VACA LoCA) program
demonstrates that the ACA can robustly confirm the presence of the virialized
intracluster medium in galaxy clusters previously identified in full-sky
surveys. In particular, we obtain a significant detection of the SZ effect for
seven out of the ten VACA LoCA clusters. We note that this result is
independent of the assumed pressure profile. However, the limited angular
dynamic range of the ACA in Band 3 alone, short observational integration
times, and possible contamination from unresolved sources limit the detailed
characterization of the cluster properties and the inference of the cluster
masses within scales appropriate for the robust calibration of mass-richness
scaling relations.Comment: 19 pages (including appendices), 14 figures, and 4 tables; accepted
for publication in A&
Grepafloxacin Versus Cefixime as Single-Dose Therapy for Uncomplicated Gonorrhea in Women
Objective: To compare the efficacy and tolerance of single-dose grepafloxacin with cefixime for treatment of uncomplicated gonorrhea in women
Sub-nanosecond, time-resolved, broadband infrared spectroscopy using synchrotron radiation
A facility for sub-nanosecond time-resolved (pump-probe) infrared
spectroscopy has been developed at the National Synchrotron Light Source of
Brookhaven National Laboratory. A mode-locked Ti:sapphire laser produces 2 ps
duration, tunable near-IR pump pulses synchronized to probe pulses from a
synchrotron storage ring. The facility is unique on account of the broadband
infrared from the synchrotron, which allows the entire spectral range from 2
cm-1 (0.25 meV) to 20,000 cm-1 (2.5 eV) to be probed. A temporal resolution of
200 ps, limited by the infrared synchrotron-pulse duration, is achieved. A
maximum time delay of 170 ns is available without gating the infrared detector.
To illustrate the performance of the facility, a measurement of electron-hole
recombination dynamics for an HgCdTe semiconductor film in the far- and mid
infrared range is presented.Comment: 11 pages with 9 figures include
A Titanium Nitride Absorber for Controlling Optical Crosstalk in Horn-Coupled Aluminum LEKID Arrays for Millimeter Wavelengths
We discuss the design and measured performance of a titanium nitride (TiN)
mesh absorber we are developing for controlling optical crosstalk in
horn-coupled lumped-element kinetic inductance detector arrays for
millimeter-wavelengths. This absorber was added to the fused silica
anti-reflection coating attached to previously-characterized, 20-element
prototype arrays of LEKIDs fabricated from thin-film aluminum on silicon
substrates. To test the TiN crosstalk absorber, we compared the measured
response and noise properties of LEKID arrays with and without the TiN mesh.
For this test, the LEKIDs were illuminated with an adjustable, incoherent
electronic millimeter-wave source. Our measurements show that the optical
crosstalk in the LEKID array with the TiN absorber is reduced by 66\% on
average, so the approach is effective and a viable candidate for future
kilo-pixel arrays.Comment: 7 pages, 5 figures, accepted for publication in the Journal of Low
Temperature Physic
Horn-Coupled, Commercially-Fabricated Aluminum Lumped-Element Kinetic Inductance Detectors for Millimeter Wavelengths
We discuss the design, fabrication, and testing of prototype horn-coupled,
lumped-element kinetic inductance detectors (LEKIDs) designed for cosmic
microwave background (CMB) studies. The LEKIDs are made from a thin aluminum
film deposited on a silicon wafer and patterned using standard
photolithographic techniques at STAR Cryoelectronics, a commercial device
foundry. We fabricated twenty-element arrays, optimized for a spectral band
centered on 150 GHz, to test the sensitivity and yield of the devices as well
as the multiplexing scheme. We characterized the detectors in two
configurations. First, the detectors were tested in a dark environment with the
horn apertures covered, and second, the horn apertures were pointed towards a
beam-filling cryogenic blackbody load. These tests show that the multiplexing
scheme is robust and scalable, the yield across multiple LEKID arrays is 91%,
and the noise-equivalent temperatures (NET) for a 4 K optical load are in the
range 26\thinspace\pm6 \thinspace \mu \mbox{K} \sqrt{\mbox{s}}
The Detector System for the Stratospheric Kinetic Inductance Polarimeter (SKIP)
The Stratospheric Kinetic Inductance Polarimeter (SKIP) is a proposed
balloon-borne experiment designed to study the cosmic microwave background, the
cosmic infrared background and Galactic dust emission by observing 1133 square
degrees of sky in the Northern Hemisphere with launches from Kiruna, Sweden.
The instrument contains 2317 single-polarization, horn-coupled, aluminum
lumped-element kinetic inductance detectors (LEKID). The LEKIDs will be
maintained at 100 mK with an adiabatic demagnetization refrigerator. The
polarimeter operates in two configurations, one sensitive to a spectral band
centered on 150 GHz and the other sensitive to 260 and 350 GHz bands. The
detector readout system is based on the ROACH-1 board, and the detectors will
be biased below 300 MHz. The detector array is fed by an F/2.4 crossed-Dragone
telescope with a 500 mm aperture yielding a 15 arcmin FWHM beam at 150 GHz. To
minimize detector loading and maximize sensitivity, the entire optical system
will be cooled to 1 K. Linearly polarized sky signals will be modulated with a
metal-mesh half-wave plate that is mounted at the telescope aperture and
rotated by a superconducting magnetic bearing. The observation program consists
of at least two, five-day flights beginning with the 150 GHz observations.Comment: J Low Temp Phys DOI 10.1007/s10909-013-1014-3 The final publication
is available at link.springer.co
Application of a Self-Similar Pressure Profile to Sunyaev-Zel'dovich Effect Data from Galaxy Clusters
We investigate the utility of a new, self-similar pressure profile for
fitting Sunyaev-Zel'dovich (SZ) effect observations of galaxy clusters. Current
SZ imaging instruments - such as the Sunyaev-Zel'dovich Array (SZA) - are
capable of probing clusters over a large range in physical scale. A model is
therefore required that can accurately describe a cluster's pressure profile
over a broad range of radii, from the core of the cluster out to a significant
fraction of the virial radius. In the analysis presented here, we fit a radial
pressure profile derived from simulations and detailed X-ray analysis of
relaxed clusters to SZA observations of three clusters with exceptionally high
quality X-ray data: A1835, A1914, and CL J1226.9+3332. From the joint analysis
of the SZ and X-ray data, we derive physical properties such as gas mass, total
mass, gas fraction and the intrinsic, integrated Compton y-parameter. We find
that parameters derived from the joint fit to the SZ and X-ray data agree well
with a detailed, independent X-ray-only analysis of the same clusters. In
particular, we find that, when combined with X-ray imaging data, this new
pressure profile yields an independent electron radial temperature profile that
is in good agreement with spectroscopic X-ray measurements.Comment: 28 pages, 6 figures, accepted by ApJ for publication (probably April
2009
- …