6 Search Results

Line intensity mapping using atomic hydrogen (H I) has the potential to efficiently map large volumes of the Universe if the signal can be successfully separated from overwhelmingly bright radio foreground emission. This motivates cross correlations, to ascertain the cosmological nature of measured H I fluctuations, and to study their connections with galaxies and the underlying matter density field. However, these same foregrounds render the cross correlation with projected fields such as the lensing of the cosmic microwave background (CMB) difficult. Indeed, the correlated Fourier modes vary slowly along the line of sight and are thus most contaminated by themore » smooth-spectrum radio continuum foregrounds. In this paper, we implement a method that avoids this issue by attempting to measure the nonlinear gravitational coupling of the small-scale 21 cm power from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) with large-scale Planck CMB lensing. This measurement is a position-dependent power spectrum, i.e., a squeezed integrated bispectrum. Using 94 nights of CHIME data between 1.0 < z < 1.3 and aggressive foreground filtering, we find that the expected signal is 5 times smaller than the current noise. We forecast that incorporating the additional nights of CHIME data already collected would enable a signal-to-noise ratio of 3, without any further improvements in filtering for foreground cleaning.« less

We present a detection of 21 cm emission from large-scale structure (LSS) between redshift 0.78 and 1.43 made with the Canadian Hydrogen Intensity Mapping Experiment. Radio observations acquired over 102 nights are used to construct maps that are foreground filtered and stacked on the angular and spectral locations of luminous red galaxies (LRGs), emission-line galaxies (ELGs), and quasars (QSOs) from the eBOSS clustering catalogs. We find decisive evidence for a detection when stacking on all three tracers of LSS, with the logarithm of the Bayes factor equal to 18.9 (LRG), 10.8 (ELG), and 56.3 (QSO). An alternative frequentist interpretation, basedmore » on the likelihood ratio test, yields a detection significance of 7.1σ (LRG), 5.7σ (ELG), and 11.1σ (QSO). These are the first 21 cm intensity mapping measurements made with an interferometer. We constrain the effective clustering amplitude of neutral hydrogen (H I), defined as $${{ \mathcal A }}_{{\rm{H}}\,{\rm\small{I}}}\equiv {10}^{3}\,{{\rm{\Omega }}}_{{\rm{H}}\,{\rm\small{I}}}\left({b}_{{\rm{H}}\,{\rm\small{I}}}+\langle \,f{\mu }^{2}\rangle \right)$$, where Ω_{H I} is the cosmic abundance of H I, b_{H I} is the linear bias of H I, and $$\langle$$fμ²$$\rangle$$ = 0.552 encodes the effect of redshift-space distortions at linear order. We find $${{ \mathcal A }}_{{\rm{H}}\,{\rm\small{I}}}={1.51}_{-0.97}^{+3.60}$$ for LRGs (z = 0.84), $${{ \mathcal A }}_{{\rm{H}}\,{\rm\small{I}}}={6.76}_{-3.79}^{+9.04}$$ for ELGs (z = 0.96), and $${{ \mathcal A }}_{{\rm{H}}\,{\rm\small{I}}}={1.68}_{-0.67}^{+1.10}$$ for QSOs (z = 1.20), with constraints limited by modeling uncertainties at nonlinear scales. We are also sensitive to bias in the spectroscopic redshifts of each tracer, and we find a nonzero bias Δ v = - 66 ± 20 km s^-1 for the QSOs. We split the QSO catalog into three redshift bins and have a decisive detection in each, with the upper bin at z = 1.30 producing the highest-redshift 21 cm intensity mapping measurement thus far.« less

Abstract We search the Planck data for a thermal Sunyaev–Zel’dovich (tSZ) signal due to gas filaments between pairs of Luminous Red Galaxies (LRGs) taken from the Sloan Digital Sky Survey Data Release 12 (SDSS/DR12). We identify ∼260 000 LRG pairs in the DR12 catalogue that lie within 6–10 $$h^{-1} \, \mathrm{Mpc}$$ of each other in tangential direction and within 6 $$h^{-1} \, \mathrm{Mpc}$$ in radial direction. We stack pairs by rotating and scaling the angular positions of each LRG so they lie on a common reference frame, then we subtract a circularly symmetric halo from each member of the pair tomore » search for a residual signal between the pair members. We find a statistically significant (5.3σ) signal between LRG pairs in the stacked data with a magnitude Δy = (1.31 ± 0.25) × 10−8. The uncertainty is estimated from two Monte Carlo null tests which also establish the reliability of our analysis. Assuming a simple, isothermal, cylindrical filament model of electron overdensity with a radial density profile proportional to rc/r (as determined from simulations), where r is the perpendicular distance from the cylinder axis and rc is the core radius of the density profile, we constrain the product of overdensity and filament temperature to be $$\delta _\mathrm{ c} \times (T_{\rm e}/10^7 \, {\rm K}) \times (r_\mathrm{ c}/0.5h^{-1} \, {\rm Mpc}) = 2.7 \pm 0.5$$. To our knowledge, this is the first detection of filamentary gas at overdensities typical of cosmological large-scale structure. We compare our result to the BAHAMAS suite of cosmological hydrodynamic simulations (McCarthy et al. 2017) and find a slightly lower, but marginally consistent Comptonization excess, Δy = (0.84 ± 0.24) × 10−8.« less

ABSTRACT We construct the mean thermal Sunyaev–Zel’dovich (tSZ) Comptonization y-profile around luminous red galaxies (LRGs) in the redshift range 0.16 < z < 0.47 from the Sloan Digital Sky Survey Data Release 7 using the Planck y-map. We detect a significant tSZ signal out to ∼30 arcmin, which is well beyond the 10 arcmin angular resolution of the y-map and well beyond the virial radii of the LRGs. We compare the measured profile with predictions from the cosmo-OWLS suite of cosmological hydrodynamical simulations. The best agreement is obtained for models that include efficient feedback from active galactic nuclei, over and abovemore » feedback associated with star formation. We also compare our results with predictions based on the halo model with a universal pressure profile giving the y-signal. The predicted profile is consistent with the data when using stacked weak lensing measurements to estimate the halo masses of the LRGs, but only if we account for the clustering of neighbouring haloes via a two-halo term.« less

The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial configuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordialmore » perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping ≈ 10% of the sky to a white noise level of 2 μK-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of σ(r)=0.003. The large aperture telescope will map ≈ 40% of the sky at arcminute angular resolution to an expected white noise level of 6 μK-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. In conclusion, the survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.« less

Here, we analyze simulated maps of the Cosmology Large Angular Scale Surveyor (CLASS) experiment and recover a nearly cosmic variance limited estimate of the reionization optical depth τ. We use a power spectrum-based likelihood to simultaneously clean foregrounds and estimate cosmological parameters in multipole space. Using software specifically designed to constrain τ, the amplitude of scalar fluctuations A _s, and the tensor-to-scalar ratio r, we demonstrate that the CLASS experiment will be able to estimate τ within a factor of two of the cosmic variance limit allowed by full-sky cosmic microwave background polarization measurements. Additionally, we discuss the role ofmore » CLASS's τ constraint in conjunction with gravitational lensing of the CMB on obtaining a ≳4σ measurement of the sum of the neutrino masses.« less