1,619 research outputs found
Cross-Correlation Detection of Point Sources in WMAP First Year Data
We apply a Cross-correlation (CC) method developed previously for detecting
gamma-ray point sources to the WMAP first year data by using the Point-Spread
Function of WMAP and obtain a full sky CC coefficient map. Analyzing this map,
we find that the CC method is a powerful tool to examine the WMAP foreground
residuals which can be further cleaned accordingly. Evident foreground signals
are found in WMAP foreground cleaned maps and Tegmark cleaned map. In this
process 101 point-sources are detected, and 26 of them are new sources besides
the originally listed WMAP 208 sources. We estimate the flux of these new
sources and verify them by another method. As a result, a revised mask file
based on the WMAP first year data is produced by including these new sources.Comment: 14 pages, 10 figures; accepted for publication by ChJA
Rigid Chiral Membranes
Statistical ensembles of flexible two-dimensional fluid membranes arise
naturally in the description of many physical systems. Typically one encounters
such systems in a regime of low tension but high stiffness against bending,
which is just the opposite of the regime described by the Polyakov string. We
study a class of couplings between membrane shape and in-plane order which
break 3-space parity invariance. Remarkably there is only {\it one} such
allowed coupling (up to boundary terms); this term will be present for any
lipid bilayer composed of tilted chiral molecules. We calculate the
renormalization-group behavior of this relevant coupling in a simplified model
and show how thermal fluctuations effectively reduce it in the infrared.Comment: 11 pages, UPR-518T (This replaced version has fonts not used
removed.
Filling in the Gaps in the 4.85 GHz Sky
We describe a 4.85 GHz survey of bright, flat-spectrum radio sources
conducted with the Effelsberg 100 m telescope in an attempt to improve the
completeness of existing surveys, such as CRATES. We report the results of
these observations and of follow-up 8.4 GHz observations with the VLA of a
subset of the sample. We comment on the connection to the WMAP point source
catalog and on the survey's effectiveness at supplementing the CRATES sky
coverage.Comment: 13 pages, 3 figures, 2 tables. Accepted for publication in the
Astronomical Journal. Tables available in electronic form:
http://astro.stanford.edu/gaps
Faraday Rotation as a diagnostic of Galactic foreground contamination of CMB maps
The contribution from the residuals of the foreground can have a significant
impact on the temperature maps of the Cosmic Microwave Background (CMB).
Mostly, the focus has been on the galactic plane, when foreground cleaning has
taken place. However, in this paper, we will investigate the possible
foreground contamination, from sources outside the galactic plane in the CMB
maps. We will analyze the correlation between the Faraday rotation map and the
CMB temperature map. The Faraday rotation map is dependent on the galactic
magnetic field, as well as the thermal electron density, and both may
contribute to the CMB temperature. We find that the standard deviation for the
mean cross correlation deviate from that of simulations at the 99.9% level.
Additionally, a comparison between the CMB temperature extrema and the extremum
points of the Faraday rotation is also performed, showing a general overlap
between the two. Also we find that the CMB Cold Spot is located at an area of
strong negative cross correlation, meaning that it may be explained by a
galactic origin. Further, we investigate nearby supernova remnants in the
galaxy, traced by the galactic radio loops. These super nova remnants are
located at high and low galactic latitude, and thus well outside the galactic
plane. We find some correlation between the Faraday Rotation and the CMB
temperature, at select radio loops. This indicate, that the galactic
foregrounds may affect the CMB, at high galactic latitudesComment: 13 pages, 22 figures, 6 table
The MAP Satellite Feed Horns
We present the design, manufacturing methods, and characterization of 20
microwave feed horns currently in use on the Microwave Anisotropy Probe (MAP)
satellite. The nature of the cosmic microwave background (CMB) anisotropy
requires a detailed understanding of the properties of every optical component
of a microwave telescope. In particular, the properties of the feeds must be
known so that the forward gain and sidelobe response of the telescope can be
modeled and so that potential systematic effects may be computed. MAP requires
low emissivity, azimuthally symmetric, low-sidelobe feeds in five microwave
bands (K, Ka, Q, V, and W) that fit within a constrained geometry. The beam
pattern of each feed is modeled and compared with measurements; the agreement
is generally excellent to the -60 dB level (80 degrees from the beam peak).
This agreement verifies the beam-predicting software and the manufacturing
process. The feeds also affect the properties and modeling of the microwave
receivers. To this end, we show that the reflection from the feeds is less than
-25 dB over most of each band and that their emissivity is acceptable. The
feeds meet their multiple requirements.Comment: 9 pages with 7 figures, of which 2 are in low-resolution versions;
paper is available with higher quality figures at
http://map.gsfc.nasa.gov/m_mm/tp_links.htm
An Evaluative History of Bisphosphonate Drugs: Dual Physiologic Effects of Pyrophosphate as Inspiration for a Novel Pharmaceutical Class
The documented history of the development of the bisphosphonate drugs is reviewed in sufficient detail to permit independent evaluation of the consistency of the conclusions reached from the available data. The evidence developed during the early interval of these studies 1960–1975 was sufficient to establish that pyrophosphate shares the subsequently established dual bisphosphonate characteristics of bone resorption inhibition and prevention of tissue mineralization
Theory of Chiral Modulations and Fluctuations in Smectic-A Liquid Crystals Under an Electric Field
Chiral liquid crystals often exhibit periodic modulations in the molecular
director; in particular, thin films of the smectic-C* phase show a chiral
striped texture. Here, we investigate whether similar chiral modulations can
occur in the induced molecular tilt of the smectic-A phase under an applied
electric field. Using both continuum elastic theory and lattice simulations, we
find that the state of uniform induced tilt can become unstable when the system
approaches the smectic-A--smectic-C* transition, or when a high electric field
is applied. Beyond that instability point, the system develops chiral stripes
in the tilt, which induce corresponding ripples in the smectic layers. The
modulation persists up to an upper critical electric field and then disappears.
Furthermore, even in the uniform state, the system shows chiral fluctuations,
including both incipient chiral stripes and localized chiral vortices. We
compare these predictions with observed chiral modulations and fluctuations in
smectic-A liquid crystals.Comment: 11 pages, including 9 postscript figures, uses REVTeX 3.0 and
epsf.st
The galaxy cluster Ysz-Lx and Ysz-M relations from the WMAP 5-yr data
We use multifrequency matched filters to estimate, in the WMAP 5-year data,
the Sunyaev-Zel'dovich (SZ) fluxes of 893 ROSAT NORAS/REFLEX clusters spanning
the luminosity range Lx,[0.1-2.4]keV = 2 10^{41} - 3.5 10^{45} erg s^{-1}. The
filters are spatially optimised by using the universal pressure profile
recently obtained from combining XMM-Newton observations of the REXCESS sample
and numerical simulations. Although the clusters are individually only
marginally detected, we are able to firmly measure the SZ signal (>10 sigma)
when averaging the data in luminosity/mass bins. The comparison between the
bin-averaged SZ signal versus luminosity and X-ray model predictions shows
excellent agreement, implying that there is no deficit in SZ signal strength
relative to expectations from the X-ray properties of clusters. Using the
individual cluster SZ flux measurements, we directly constrain the Y500-Lx and
Y500-M500 relations, where Y500 is the Compton y-parameter integrated over a
sphere of radius r500. The Y500-M500 relation, derived for the first time in
such a wide mass range, has a normalisation Y*500=[1.60 pm 0.19] 10^{-3}
arcmin^2 at M500=3 10^{14} h^{1} Msun, in excellent agreement with the X-ray
prediction of 1.54 10^{-3} arcmin^2, and a mass exponent of alpha=1.79 pm 0.17,
consistent with the self-similar expectation of 5/3. Constraints on the
redshift exponent are weak due to the limited redshift range of the sample,
although they are compatible with self-similar evolution.Comment: Version accepted for publication in Astronomy and Astrophysic
Simulated SKA maps from Galactic 3D-emission models
(Abridged) We present maps for various Galactic longitudes and latitudes at
1.4 GHz, which is the frequency where deep SKA surveys are proposed. The maps
are about 1.5 deg in size and have an angular resolution of about 1.6 arcsec.
We analyse the maps in terms of their probability density functions (PDFs) and
structure functions. Total intensity emission is more smooth in the plane than
at high latitudes due to the different contributions from the regular and
random magnetic field. The high latitude fields show more extended polarized
emission and RM structures than those in the plane, where patchy emission
structures on very small scales dominate. The RM PDFs in the plane are close to
Gaussians, but clearly deviate from that at high latitudes. The RM structure
functions show smaller amplitudes and steeper slopes towards high latitudes.
These results emerge from the fact that much more turbulent cells are passed
through by the line-of-sights in the plane. Although the simulated random
magnetic field components distribute in 3D, the magnetic field spectrum
extracted from the structure functions of RMs conforms to 2D in the plane and
approaches 3D at high latitudes. This is partly related to the outer scale of
the turbulent magnetic field, but mainly to the different lengths of the
line-of-sights.Comment: 19 pages, 15 figures, accepted for publication in Astronomy and
Astrophysics. The sizes of figures have been significantly reduced. For the
version with full resolution, see
ftp://ftp.mpifr-bonn.mpg.de/outgoing/p098wre/sun-reich.pd
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