- S. M. L. Vogt, et al., — Constraints on $f(R)$ gravity from tSZE-selected SPT galaxy clusters and
weak lensing mass calibration from DES and HST
- We present constraints on the $f(R)$ gravity model using a sample of 1,005
galaxy clusters in the redshift range $0.25 - 1.78$ that have been selected
through the thermal Sunyaev-Zel'dovich effect (tSZE) from South Pole Telescope
(SPT) data and subjected to optical and near-infrared confirmation with the
Multi-component Matched Filter (MCMF) algorithm. We employ weak gravitational
lensing mass calibration from the Dark Energy Survey (DES) Year 3 data for 688
clusters at $z < 0.95$ and from the Hubble Space Telescope (HST) for 39
clusters with $0.6 < z < 1.7$. Our cluster sample is a powerful probe of $f(R)$
gravity, because this model predicts a scale-dependent enhancement in the
growth of structure, which impacts the halo mass function (HMF) at cluster mass
scales. To account for these modified gravity effects on the HMF, our analysis
employs a semi-analytical approach calibrated with numerical simulations.
Combining calibrated cluster counts with primary cosmic microwave background
(CMB) temperature and polarization anisotropy measurements from the Planck2018
release, we derive robust constraints on the $f(R)$ parameter $f_{R0}$. Our
results, $\log_{10} |f_{R0}| < -5.32$ at the 95 % credible level, are the
tightest current constraints on $f(R)$ gravity from cosmological scales. This
upper limit rules out $f(R)$-like deviations from general relativity that
result in more than a $\sim$20 % enhancement of the cluster population on mass
scales $M_\mathrm{200c}>3\times10^{14}M_\odot$.
- A. Coerver, et al., — Measurement and Modeling of Polarized Atmosphere at the South Pole with
SPT-3G
- We present the detection and characterization of fluctuations in linearly
polarized emission from the atmosphere above the South Pole. These measurements
make use of Austral winter survey data from the SPT-3G receiver on the South
Pole Telescope in three frequency bands centered at 95, 150, and 220 GHz. We
use the cross-correlation between detectors to produce an unbiased estimate of
the power in Stokes I, Q, and U parameters on large angular scales. Our results
are consistent with the polarized signal being produced by the combination of
Rayleigh scattering of thermal radiation from the ground and thermal emission
from a population of horizontally aligned ice crystals with an anisotropic
distribution described by Kolmogorov turbulence. The signal is most significant
at large angular scales, high observing frequency, and low elevation angle.
Polarized atmospheric emission has the potential to significantly impact
observations on the large angular scales being targeted by searches for
inflationary B-mode CMB polarization. We present the distribution of measured
angular power spectrum amplitudes in Stokes Q and I for 4 years of winter
observations, which can be used to simulate the impact of atmospheric
polarization and intensity fluctuations at the South Pole on a specified
experiment and observation strategy. For the SPT-3G data, downweighting the
small fraction of significantly contaminated observations is an effective
mitigation strategy. In addition, we present a strategy for further improving
sensitivity on large angular scales where maps made in the 220 GHz band are
used to measure and subtract the polarized atmosphere signal from the 150 GHz
band maps. In observations with the SPT-3G instrument at the South Pole, the
polarized atmospheric signal is a well-understood and sub-dominant contribution
to the measured noise after implementing the mitigation strategies described
here.
- Charles E. Romero, et al., — Surface Brightness Fluctuations in Two SPT clusters: a Pilot Study
- Studies of surface brightness fluctuations in the intracluster medium (ICM)
present an indirect probe of turbulent properties such as the turbulent
velocities, injection scales, and the slope of the power spectrum of
fluctuations towards smaller scales. With the advancement of Sunyaev-Zel'dovich
(SZ) studies and surveys relative to X-ray observations, we seek to investigate
surface brightness fluctuations in a sample of SPT-SZ clusters which also have
archival \textit{XMM-Newton} data. Here we present a pilot study of two typical
clusters in that sample: SPT-CLJ0232-4421 and SPT-CLJ0638-5358. We infer
injection scales larger than 500 kpc in both clusters and Mach numbers $\approx
0.5$ in SPT-CLJ0232-4421 and Mach numbers $\approx 0.6 - 1.6$ in
SPT-CLJ0638-5358, which has a known shock. We find hydrostatic bias values for
$M_{500}$ less than 0.2 for SPT-CLJ0232-4421 and less than 0.1 for
SPT-CLJ0638-5358. These results show the importance to assess its quantitative
values via a detailed multiwavelength approach and suggest that the drivers of
turbulence may occur at quite larger scales.