Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

We present morphological classifications based on Galaxy Zoo analysis of 71,052 galaxies with imaging from the United Kingdom Infrared Telescope Infrared Deep Sky Survey (UKIDSS). Galaxies were selected out of the Galaxy Zoo 2 (GZ2) sample, so also have gri imaging from the Sloan Digital Sky Survey. An identical classification tree, and vote weighting/aggregation was applied to both UKIDSS and GZ2 classifications enabling direct comparisons. With this Research Note we provide a public release of the GZ:UKIDSS morphologies and discuss some initial comparisons with GZ2.

Abstract:

<jats:title>Abstract</jats:title><jats:p>We present a cosmological analysis of the combination of the DES-Y3, KiDS-1000 and HSC-DR1 weak lensing samples under a joint harmonic-space pipeline making use of angular scales down to ℓ<jats:sub>max</jats:sub>=4500, corresponding to significantly smaller scales (δθ ~ 2.4') than those commonly used in cosmological weak lensing studies. We are able to do so by accurately modelling non-linearities and the impact of baryonic effects using<jats:monospace>Baccoemu</jats:monospace>. We find<jats:italic>S</jats:italic><jats:sub>8</jats:sub>≡<jats:italic>σ</jats:italic><jats:sub>8</jats:sub>√(Ω<jats:sub>m</jats:sub>/0.3) = 0.795<jats:sup>+0.015</jats:sup><jats:sub>-0.017</jats:sub>, in relatively good agreement with CMB constraints from<jats:italic>Planck</jats:italic>(less than ~1.8<jats:italic>σ</jats:italic>tension), although we obtain a low value of Ω<jats:sub>m</jats:sub>=0.212<jats:sup>+0.017</jats:sup><jats:sub>-0.032</jats:sub>, in tension with<jats:italic>Planck</jats:italic>at the ~3σ level. We show that this can be recast as an H<jats:sub>0</jats:sub>tension if one parametrises the amplitude of fluctuations and matter abundance in terms of variables without hidden dependence on H<jats:sub>0</jats:sub>. Furthermore, we find that this tension reduces significantly after including a prior on the distance-redshift relationship from BAO data, without worsening the fit. In terms of baryonic effects, we show that failing to model and marginalise over them on scales<jats:italic>ℓ</jats:italic>≲ 2000 does not significantly affect the posterior constraints for DES-Y3 and KiDS-1000, but has a mild effect on deeper samples, such as HSC-DR1. This is in agreement with our ability to only mildly constrain the parameters of the Baryon Correction Model with these data.</jats:p>

Abstract:

We present a cosmological analysis of the combination of the DES-Y3, KiDS-1000 and HSC-DR1 weak lensing samples under a joint harmonic-space pipeline making use of angular scales down to ℓmax=4500, corresponding to significantly smaller scales (δθ ~ 2.4') than those commonly used in cosmological weak lensing studies. We are able to do so by accurately modelling non-linearities and the impact of baryonic effects using Baccoemu. We find S 8 ≡ σ 8√(Ωm/0.3) = 0.795+0.015 -0.017, in relatively good agreement with CMB constraints from Planck (less than ~1.8σ tension), although we obtain a low value of Ωm =0.212+0.017 -0.032, in tension with Planck at the ~3σ level. We show that this can be recast as an H0 tension if one parametrises the amplitude of fluctuations and matter abundance in terms of variables without hidden dependence on H0. Furthermore, we find that this tension reduces significantly after including a prior on the distance-redshift relationship from BAO data, without worsening the fit. In terms of baryonic effects, we show that failing to model and marginalise over them on scales ℓ ≲ 2000 does not significantly affect the posterior constraints for DES-Y3 and KiDS-1000, but has a mild effect on deeper samples, such as HSC-DR1. This is in agreement with our ability to only mildly constrain the parameters of the Baryon Correction Model with these data.

Abstract:

Patchy reionization generates kinematic Sunyaev–Zel’dovich (kSZ) anisotropies in the cosmic microwave background (CMB). Large-scale velocity perturbations along the line of sight modulate the small-scale kSZ power spectrum, leading to a trispectrum (or four-point function) in the CMB that depends on the physics of reionization. We investigate the challenges in detecting this trispectrum and use tools developed for CMB lensing, such as realization-dependent bias subtraction and cross-correlation based estimators, to counter uncertainties in the instrumental noise and assumed CMB power spectrum. We also find that both lensing and extragalactic foregrounds can impart larger trispectrum contributions than the reionization kSZ signal. We present a range of mitigation methods for both of these sources of contamination, validated on microwave-sky simulations. We use ACT DR6 and Planck data to calculate an upper limit on the reionization kSZ trispectrum from a measurement dominated by foregrounds. The upper limit is about 50 times the signal predicted from recent simulations.