220 research outputs found
Sunyaev-Zel'dovich Cluster Profiles Measured with the South Pole Telescope
We present Sunyaev-Zel'dovich measurements of 15 massive X-ray selected
galaxy clusters obtained with the South Pole Telescope. The Sunyaev-Zel'dovich
(SZ) cluster signals are measured at 150 GHz, and concurrent 220 GHz data are
used to reduce astrophysical contamination. Radial profiles are computed using
a technique that takes into account the effects of the beams and filtering. In
several clusters, significant SZ decrements are detected out to a substantial
fraction of the virial radius. The profiles are fit to the beta model and to a
generalized NFW pressure profile, and are scaled and stacked to probe their
average behavior. We find model parameters that are consistent with previous
studies: beta=0.86 and r_core/r_500 = 0.20 for the beta model, and (alpha,
beta, gamma, c_500)=(1.0,5.5,0.5,1.0) for the generalized NFW model. Both
models fit the SPT data comparably well, and both are consistent with the
average SZ profile out to the virial radius. The integrated Compton-y parameter
Y_SZ is computed for each cluster using both model-dependent and
model-independent techniques, and the results are compared to X-ray estimates
of cluster parameters. We find that Y_SZ scales with Y_X and gas mass with low
scatter. Since these observables have been found to scale with total mass, our
results point to a tight mass-observable relation for the SPT cluster survey.Comment: 21 pages, 24 figures, updated to published versio
Measurements of Secondary Cosmic Microwave Background Anisotropies with the South Pole Telescope
We report cosmic microwave background (CMB) power spectrum measurements from
the first 100 sq. deg. field observed by the South Pole Telescope (SPT) at 150
and 220 GHz. On angular scales where the primary CMB anisotropy is dominant,
ell ~< 3000, the SPT power spectrum is consistent with the standard LambdaCDM
cosmology. On smaller scales, we see strong evidence for a point source
contribution, consistent with a population of dusty, star-forming galaxies.
After we mask bright point sources, anisotropy power on angular scales of 3000
50 at both frequencies. We
combine the 150 and 220 GHz data to remove the majority of the point source
power, and use the point source subtracted spectrum to detect
Sunyaev-Zel'dovich (SZ) power at 2.6 sigma. At ell=3000, the SZ power in the
subtracted bandpowers is 4.2 +/- 1.5 uK^2, which is significantly lower than
the power predicted by a fiducial model using WMAP5 cosmological parameters.
This discrepancy may suggest that contemporary galaxy cluster models
overestimate the thermal pressure of intracluster gas. Alternatively, this
result can be interpreted as evidence for lower values of sigma8. When combined
with an estimate of the kinetic SZ contribution, the measured SZ amplitude
shifts sigma8 from the primary CMB anisotropy derived constraint of 0.794 +/-
0.028 down to 0.773 +/- 0.025. The uncertainty in the constraint on sigma8 from
this analysis is dominated by uncertainties in the theoretical modeling
required to predict the amplitude of the SZ power spectrum for a given set of
cosmological parameters.Comment: 28 pages, 11 figures, submitted to Ap
Extragalactic millimeter-wave sources in South Pole Telescope survey data: source counts, catalog, and statistics for an 87 square-degree field
We report the results of an 87 square-degree point-source survey centered at
R.A. 5h30m, decl. -55 deg. taken with the South Pole Telescope (SPT) at 1.4 and
2.0 mm wavelengths with arc-minute resolution and milli-Jansky depth. Based on
the ratio of flux in the two bands, we separate the detected sources into two
populations, one consistent with synchrotron emission from active galactic
nuclei (AGN) and one consistent with thermal emission from dust. We present
source counts for each population from 11 to 640 mJy at 1.4 mm and from 4.4 to
800 mJy at 2.0 mm. The 2.0 mm counts are dominated by synchrotron-dominated
sources across our reported flux range; the 1.4 mm counts are dominated by
synchroton-dominated sources above ~15 mJy and by dust-dominated sources below
that flux level. We detect 141 synchrotron-dominated sources and 47
dust-dominated sources at S/N > 4.5 in at least one band. All of the most
significantly detected members of the synchrotron-dominated population are
associated with sources in previously published radio catalogs. Some of the
dust-dominated sources are associated with nearby (z << 1) galaxies whose dust
emission is also detected by the Infrared Astronomy Satellite (IRAS). However,
most of the bright, dust-dominated sources have no counterparts in any existing
catalogs. We argue that these sources represent the rarest and brightest
members of the population commonly referred to as sub-millimeter galaxies
(SMGs). Because these sources are selected at longer wavelengths than in
typical SMG surveys, they are expected to have a higher mean redshift
distribution and may provide a new window on galaxy formation in the early
universe.Comment: 35 emulateapj pages, 12 figures, 5 table
Galaxy Clusters Selected with the Sunyaev-Zel'dovich Effect from 2008 South Pole Telescope Observations
We present a detection-significance-limited catalog of 21 Sunyaev-Zel'dovich
selected galaxy clusters. These clusters, along with 1 unconfirmed candidate,
were identified in 178 deg^2 of sky surveyed in 2008 by the South Pole
Telescope to a depth of 18 uK-arcmin at 150 GHz. Optical imaging from the
Blanco Cosmology Survey (BCS) and Magellan telescopes provided photometric (and
in some cases spectroscopic) redshift estimates, with catalog redshifts ranging
from z=0.15 to z>1, with a median z = 0.74. Of the 21 confirmed galaxy
clusters, three were previously identified as Abell clusters, three were
presented as SPT discoveries in Staniszewski et al, 2009, and three were first
identified in a recent analysis of BCS data by Menanteau et al, 2010; the
remaining 12 clusters are presented for the first time in this work. Simulated
observations of the SPT fields predict the sample to be nearly 100% complete
above a mass threshold of M_200 ~ 5x10^14 M_sun/h at z = 0.6. This completeness
threshold pushes to lower mass with increasing redshift, dropping to ~4x10^14
M_sun/h at z=1. The size and redshift distribution of this catalog are in good
agreement with expectations based on our current understanding of galaxy
clusters and cosmology. In combination with other cosmological probes, we use
the cluster catalog to improve estimates of cosmological parameters. Assuming a
standard spatially flat wCDM cosmological model, the addition of our catalog to
the WMAP 7-year analysis yields sigma_8 = 0.81 +- 0.09 and w = -1.07 +- 0.29, a
~50% improvement in precision on both parameters over WMAP7 alone.Comment: 19 pages, 9 figures, 4 appendice
Angular Power Spectra of the Millimeter Wavelength Background Light from Dusty Star-forming Galaxies with the South Pole Telescope
We use data from the first 100 square-degree field observed by the South Pole
Telescope (SPT) in 2008 to measure the angular power spectrum of temperature
anisotropies contributed by the background of dusty star-forming galaxies
(DSFGs) at millimeter wavelengths. From the auto and cross-correlation of 150
and 220 GHz SPT maps, we significantly detect both Poisson distributed and, for
the first time at millimeter wavelengths, clustered components of power from a
background of DSFGs. The spectral indices between 150 and 220 GHz of the
Poisson and clustered components are found to be 3.86 +- 0.23 and 3.8 +- 1.3
respectively, implying a steep scaling of the dust emissivity index beta ~ 2.
The Poisson and clustered power detected in SPT, BLAST (at 600, 860, and 1200
GHz), and Spitzer (1900 GHz) data can be understood in the context of a simple
model in which all galaxies have the same graybody spectrum with dust
emissivity index of beta = 2 and dust temperature T_d = 34 K. In this model,
half of the 150 GHz background light comes from redshifts greater than 3.2. We
also use the SPT data to place an upper limit on the amplitude of the kinetic
Sunyaev-Zel'dovich power spectrum at l = 3000 of 13 uK^2 at 95% confidence.Comment: 18 pages, 9 figure
Conserved quantities in Lemaitre-Tolman-Bondi cosmology
We study linear perturbations to a Lema{\^\i}tre-Tolman-Bondi (LTB)
background spacetime. Studying the transformation behaviour of the
perturbations under gauge transformations, we construct gauge invariant
quantities. We show, using the perturbed energy conservation equation, that
there are conserved quantities in LTB, in particular a spatial metric trace
perturbation, \zeta_{SMTP}, which is conserved on all scales. We then briefly
extend our discussion to the Lema{\^\i}tre spacetime, and construct
gauge-invariant perturbations in this extension of LTB spacetime.Comment: 16 pages, 0 figures, revtex4; v5: minor changes, additional 2+2
formalism appendix added, references added, version accepted by CQ
The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectra
We present cosmological parameters derived from the angular power spectrum of
the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz
over 296 deg^2 with the Atacama Cosmology Telescope (ACT) during its 2008
season. ACT measures fluctuations at scales 500<l<10000. We fit a model for the
lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz
and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from
radio and infrared point sources, and clustered power from infrared point
sources. The power from thermal and kinetic SZ at 148 GHz is estimated to be
B_3000 = 6.8+-2.9 uK^2, where B_l=l(l+1)C_l/2pi. We estimate primary
cosmological parameters from the 148 GHz spectrum, marginalizing over SZ and
source power. The LCDM cosmological model is a good fit to the data, and LCDM
parameters estimated from ACT+WMAP are consistent with the 7-year WMAP limits,
with scale invariant n_s = 1 excluded at 99.7% CL (3sigma). A model with no CMB
lensing is disfavored at 2.8sigma. By measuring the third to seventh acoustic
peaks, and probing the Silk damping regime, the ACT data improve limits on
cosmological parameters that affect the small-scale CMB power. The ACT data
combined with WMAP give a 6sigma detection of primordial helium, with Y_P =
0.313+-0.044, and a 4sigma detection of relativistic species, assumed to be
neutrinos, with Neff = 5.3+-1.3 (4.6+-0.8 with BAO+H0 data). From the CMB alone
the running of the spectral index is constrained to be dn/dlnk = -0.034 +-
0.018, the limit on the tensor-to-scalar ratio is r<0.25 (95% CL), and the
possible contribution of Nambu cosmic strings to the power spectrum is
constrained to string tension Gmu<1.6 \times 10^-7 (95% CL).Comment: 20 pages, 13 figures. Submitted to ApJ. This paper is a companion to
Hajian et al. (2010) and Das et al. (2010
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