86 research outputs found
Tentative Appraisal of Compatibility of Small-Scale CMB Anisotropy Detections in the Context of COBE-DMR-Normalized Open and Flat CDM Cosmogonies
Goodness-of-fit statistics are used to quantitatively establish the
compatibility of CMB anisotropy predictions in a wide range of DMR-normalized,
open and spatially-flat , CDM cosmogonies with the set of all
presently available small-scale CMB anisotropy detection data. Conclusions
regarding model viability depend sensitively on the prescription used to
account for the 1 uncertainty in the assumed value of the DMR
normalization, except for low-density, -- 0.4, open models
which are compatible with the data for all prescriptions used. While large
baryon-density (\Omega_B \gap 0.0175 h^{-2}), old (t_0 \gap 15 -- 16 Gyr),
low-density ( -- 0.4), flat- models might be
incompatible, no model is incompatible with the data for all prescriptions. In
fact, some open models seem to fit the data better than should be expected, and
this might be an indication that some error bars are mildly overconservative.Comment: 15 page PostScript file, including 6 included figures. Also available
via anonymous ftp from ftp://astro.caltech.edu/users/kmg/chi.p
The Amplitude and Spectral Index of the Large Angular Scale Anisotropy in the Cosmic Microwave Background Radiation
In many cosmological models, the large angular scale anisotropy in the cosmic
microwave background is parameterized by a spectral index, , and a
quadrupolar amplitude, . For a Peebles-Harrison-Zel'dovich spectrum, .
Using data from the Far Infra-Red Survey (FIRS) and a new statistical measure,
a contour plot of the likelihood for cosmological models for which
and is obtained. We find that the likelihood is
maximum at . For constant the likelihood falls to
half its maximum at and and for constant the
likelihood falls to half its maximum at and . Regardless
of , the likelihood is always less than half its maximum for and
for , as it is for .Comment: Ten Page
First Detection of Cosmic Microwave Background Lensing and Lyman-{\alpha} Forest Bispectrum
We present the first detection of a correlation between the Lyman-
forest and cosmic microwave background (CMB) lensing. For each Lyman-
forest in SDSS-III/BOSS DR12, we correlate the one-dimensional power spectrum
with the CMB lensing convergence on the same line of sight from Planck. This
measurement constitutes a position-dependent power spectrum, or a squeezed
bispectrum, and quantifies the non-linear response of the Lyman- forest
power spectrum to a large-scale overdensity. The signal is measured at
5~ and is consistent with the CDM expectation. We measure the
linear bias of the Lyman- forest with respect to the dark matter
distribution, and constrain a combination of non-linear terms including the
non-linear bias. This new observable provides a consistency check for the
Lyman- forest as a large-scale structure probe and tests our
understanding of the relation between intergalactic gas and dark matter. In the
future, it could be used to test hydrodynamical simulations and calibrate the
relation between the Lyman- forest and dark matter.Comment: 8 pages, 7 figures; accepted for publication in Phys. Rev.
The quasi-optical design of the QUaD Telescope
QUaD is a ground-based high-resolution (up to l â 2500) instrument designed to map the polarisation of the Cosmic Microwave Background and to measure its E-mode and B-mode polarisation power spectra. QUaD comprises a bolometric array receiver (100 and 150 GHz) and re-imaging optics on a 2.6-m Cassegrain telescope 2. It will operate for two years and begin observations in 2005. CMB polarisation measurements will require not only a significant increase in sensitivity over earlier experiments but also a better understanding and control of systematic effects particularly those that contribute to the polarised signal. To this end we have undertaken a comprehensive quasi-optical analysis of the QUaD telescope. In particular we have modelled the effects of diffraction on beam propagation through the system. The corrugated feeds that couple radiation from the telescope to phase-sensitive bolometers need to have good beam symmetry and low sidelobe levels over the required bandwidth. It is especially important that the feed horns preserve the polarisation orientation of the incoming fields. We have used an accurate mode-matching model to design such feed horns. In this paper we present the diffraction analysis of the QUaD front-end optics as well as the electromagnetic design and testing of the QUaD corrugated feeds
Galactic Foreground Constraints from the Python V Cosmic Microwave Background Anisotropy Data
We constrain Galactic foreground contamination of the Python V cosmic
microwave background anisotropy data by cross correlating it with foreground
contaminant emission templates. To model foreground emission we use 100 and 12
m dust emission templates and two point source templates based on the PMN
survey. The analysis takes account of inter-modulation correlations in 8
modulations of the data that are sensitive to a large range of angular scales
and also densely sample a large area of sky. As a consequence the analysis here
is highly constraining. We find little evidence for foreground contamination in
an analysis of the whole data set. However, there is indication that
foregrounds are present in the data from the larger-angular-scale modulations
of those Python V fields that overlap the region scanned earlier by the UCSB
South Pole 1994 experiment. This is an independent consistency cross-check of
findings from the South Pole 1994 data.Comment: 15 pages, 1 figure, ApJ accepted versio
An Analysis Package for Bolometer Ground Testing
ESA's Herschel Space Observatory, to be launched in 2007, will be sensitive to far infrared wavelengths beyond 60 ÎŒm. The longer wavelength interval between 200 and 670 ÎŒm will be covered by SPIRE, a combination of broad band camera and Fourier transform spectrometer. SPIRE will use exclusively spiderweb bolometers as detectors, which are manufactured and tested at JPL. We describe a data analysis package developed at the NASA Herschel Science Center at IPAC in support of the testing activity, which expects to cover 12 detector arrays with between 24 and 144 channels each. The package consists of a widget based viewer allowing immediate display and limited processing of the 193 recorded data channels in the lab and a suite of subroutines and scripts, allowing fast and flexible pipeline data reduction
Python I, II, and III CMB Anisotropy Measurement Constraints on Open and Flat-Lambda CDM Cosmogonies
We use Python I, II, and III cosmic microwave background anisotropy data to
constrain cosmogonies. We account for the Python beamwidth and calibration
uncertainties. We consider open and spatially-flat-Lambda cold dark matter
cosmogonies, with nonrelativistic-mass density parameter Omega_0 in the range
0.1--1, baryonic-mass density parameter Omega_B in the range (0.005--0.029)
h^{-2}, and age of the universe t_0 in the range (10--20) Gyr. Marginalizing
over all parameters but Omega_0, the combined Python data favors an open
(spatially-flat-Lambda) model with Omega_0 simeq 0.2 (0.1). At the 2 sigma
confidence level model normalizations deduced from the combined Python data are
mostly consistent with those drawn from the DMR, UCSB South Pole 1994, ARGO,
MAX 4 and 5, White Dish, and SuZIE data sets.Comment: 20 pages, 7 figures, accepted by Ap
CMB Anisotropy Constraints on Flat-Lambda and Open CDM Cosmogonies from DMR, UCSB South Pole, Python, ARGO, MAX, White Dish, OVRO, and SuZIE Data
We use joint likelihood analyses of combinations of fifteen cosmic microwave
background (CMB) anisotropy data sets from the DMR, UCSB South Pole 1994,
Python I--III, ARGO, MAX 4 and 5, White Dish, OVRO, and SuZIE experiments to
constrain cosmogonies. We consider open and spatially-flat-Lambda cold dark
matter cosmogonies, with nonrelativistic-mass density parameter Omega_0 in the
range 0.1--1, baryonic-mass density parameter Omega_B in the range
(0.005--0.029) h^{-2}, and age of the universe t_0 in the range (10--20) Gyr.
Marginalizing over all parameters but Omega_0, the data favor Omega_0 \simeq
0.9--1 (0.4--0.6) flat-Lambda (open) models. The range in deduced Omega_0
values is partially a consequence of the different combinations of
smaller-angular-scale CMB anisotropy data sets used in the analyses, but more
significantly a consequence of whether the DMR quadrupole moment is accounted
for or ignored in the analysis. For both flat-Lambda and open models, after
marginalizing over all other parameters, a lower Omega_B h^2 \simeq
0.005--0.009 is favored. This is also marginally at odds with estimates from
more recent CMB anisotropy data and some estimates from standard
nucleosynthesis theory and observed light element abundances. For both sets of
models a younger universe with t_0 \simeq 12--15 Gyr is favored, consistent
with other recent non-CMB indicators. We emphasize that since we consider only
a small number of data sets, these results are tentative. More importantly, the
analyses here do not rule out the currently favored flat-Lambda model with
Omega_0 \sim 0.3, nor the larger Omega_B h^2 values favored by some other data.Comment: 25 pages, 10 figures, submitted to ApJ; the abstract here is slightly
abridge
Using White Dish CMB Anisotropy Data to Probe Open and Flat-Lambda CDM Cosmogonies
We use data from the White Dish experiment to set limits on cosmic microwave
background radiation anisotropies in open and spatially-flat-Lambda cold dark
matter cosmogonies. We account for the White Dish calibration uncertainty, and
marginalize over the offset and gradient removed from the data. Our 2-sigma
upper limits are larger than those derived previously. These upper limits are
consistent with those derived from the -DMR data for all models tested.Comment: 17 pages of latex. Uses aasms4.sty. 4 figures included. Submitted to
ApJ
MAX 4 and MAX 5 CMB anisotropy measurement constraints on open and flat-Lambda CDM cosmogonies
We account for experimental and observational uncertainties in likelihood
analyses of cosmic microwave background (CMB) anisotropy data from the MAX 4
and MAX 5 experiments. These analyses use CMB anisotropy spectra predicted in
open and spatially-flat Lambda cold dark matter cosmogonies. Amongst the models
considered, the combined MAX data set is most consistent with the CMB
anisotropy shape in Omega_0 ~ 0.1-0.2 open models and less so with that in old
(t_0 >~ 15 - 16 Gyr, i.e., low h), high baryon density (Omega_B >~ 0.0175/h^2),
low density (Omega_0 ~ 0.2 - 0.4), flat-Lambda models. The MAX data alone do
not rule out any of the models we consider at the 2-sigma level.
Model normalizations deduced from the combined MAX data are consistent with
those drawn from the UCSB South Pole 1994 data, except for the flat bandpower
model where MAX favours a higher normalization. The combined MAX data
normalization for open models with Omega_0 ~ 0.1-0.2 is higher than the upper
2-sigma value of the DMR normalization. The combined MAX data normalization for
old (low h), high baryon density, low-density flat-Lambda models is below the
lower 2-sigma value of the DMR normalization. Open models with Omega_0 ~
0.4-0.5 are not far from the shape most favoured by the MAX data, and for these
models the MAX and DMR normalizations overlap. The MAX and DMR normalizations
also overlap for Omega_0 = 1 and some higher h, lower Omega_B, low-density
flat-Lambda models.Comment: Latex, 37 pages, uses aasms4 styl
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