Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

The Deep Extragalactic VIsible Legacy Survey (DEVILS) is an ongoing high-completeness, deep spectroscopic survey of ∼60 000 galaxies to Y < 21.2 mag, over ∼6 deg2 in three well-studied deep extragalactic fields: D10 (COSMOS), D02 (XMMLSS), and D03 (ECDFS). Numerous DEVILS projects all require consistent, uniformly derived and state-of-the-art photometric data with which to measure galaxy properties. Existing photometric catalogues in these regions either use varied photometric measurement techniques for different facilities/wavelengths leading to inconsistencies, older imaging data and/or rely on source detection and photometry techniques with known problems. Here, we use the PROFOUND image analysis package and state-of-the-art imaging data sets (including Subaru-HSC, VST-VOICE, VISTA-VIDEO, and UltraVISTA-DR4) to derive matched-source photometry in 22 bands from the FUV to 500 μm. This photometry is found to be consistent, or better, in colour analysis to previous approaches using fixed-size apertures (which are specifically tuned to derive colours), but produces superior total source photometry, essential for the derivation of stellar masses, star formation rates, star formation histories, etc. Our photometric catalogue is described in detail and, after internal DEVILS team projects, will be publicly released for use by the broader scientific community.

Abstract:

<jats:p>We measured the cross-correlation between galaxy weak lensing data from the Kilo Degree Survey (KiDS-1000, DR4) and cosmic microwave background (CMB) lensing data from the Atacama Cosmology Telescope (ACT, DR4) and the <jats:italic>Planck</jats:italic> Legacy survey. We used two samples of source galaxies, selected with photometric redshifts, (0.1 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 1.2) and (1.2 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 2), which produce a combined detection significance of the CMB lensing and weak galaxy lensing cross-spectrum of 7.7<jats:italic>σ</jats:italic>. With the lower redshift galaxy sample, for which the cross-correlation was detected at a significance of 5.3<jats:italic>σ</jats:italic>, we present joint cosmological constraints on the matter density parameter, Ω<jats:sub>m</jats:sub>, and the matter fluctuation amplitude parameter, <jats:italic>σ</jats:italic><jats:sub>8</jats:sub>, marginalising over three nuisance parameters that model our uncertainty in the redshift and shear calibration as well as the intrinsic alignment of galaxies. We find our measurement to be consistent with the best-fitting flat ΛCDM cosmological models from both <jats:italic>Planck</jats:italic> and KiDS-1000. We demonstrate the capacity of CMB weak lensing cross-correlations to set constraints on either the redshift or shear calibration by analysing a previously unused high-redshift KiDS galaxy sample (1.2 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 2), with the cross-correlation detected at a significance of 7<jats:italic>σ</jats:italic>. This analysis provides an independent assessment for the accuracy of redshift measurements in a regime that is challenging to calibrate directly owing to known incompleteness in spectroscopic surveys.</jats:p>

Abstract:

<jats:p>We measured the cross-correlation between galaxy weak lensing data from the Kilo Degree Survey (KiDS-1000, DR4) and cosmic microwave background (CMB) lensing data from the Atacama Cosmology Telescope (ACT, DR4) and the <jats:italic>Planck</jats:italic> Legacy survey. We used two samples of source galaxies, selected with photometric redshifts, (0.1 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 1.2) and (1.2 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 2), which produce a combined detection significance of the CMB lensing and weak galaxy lensing cross-spectrum of 7.7<jats:italic>σ</jats:italic>. With the lower redshift galaxy sample, for which the cross-correlation was detected at a significance of 5.3<jats:italic>σ</jats:italic>, we present joint cosmological constraints on the matter density parameter, Ω<jats:sub>m</jats:sub>, and the matter fluctuation amplitude parameter, <jats:italic>σ</jats:italic><jats:sub>8</jats:sub>, marginalising over three nuisance parameters that model our uncertainty in the redshift and shear calibration as well as the intrinsic alignment of galaxies. We find our measurement to be consistent with the best-fitting flat ΛCDM cosmological models from both <jats:italic>Planck</jats:italic> and KiDS-1000. We demonstrate the capacity of CMB weak lensing cross-correlations to set constraints on either the redshift or shear calibration by analysing a previously unused high-redshift KiDS galaxy sample (1.2 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 2), with the cross-correlation detected at a significance of 7<jats:italic>σ</jats:italic>. This analysis provides an independent assessment for the accuracy of redshift measurements in a regime that is challenging to calibrate directly owing to known incompleteness in spectroscopic surveys.</jats:p>

Abstract:

Covariance matrices are among the most difficult pieces of end-to-end cosmological analyses. In principle, for two-point functions, each component involves a four-point function, and the resulting covariance often has hundreds of thousands of elements. We investigate various compression mechanisms capable of vastly reducing the size of the covariance matrix in the context of cosmic shear statistics. This helps identify which of its parts are most crucial to parameter estimation. We start with simple compression methods, by isolating and “removing” 200 modes associated with the lowest eigenvalues, then those with the lowest signal-to-noise ratio, before moving on to more sophisticated schemes like compression at the tomographic level and, finally, with the massively optimized parameter estimation and data compression (MOPED). We find that, while most of these approaches prove useful for a few parameters of interest, like Ωm, the simplest yield a loss of constraining power on the intrinsic alignment (IA) parameters as well as S8. For the case considered—cosmic shear from the first year of data from the Dark Energy Survey—only MOPED was able to replicate the original constraints in the 16-parameter space. Finally, we apply a tolerance test to the elements of the compressed covariance matrix obtained with MOPED and confirm that the IA parameter AIA is the most susceptible to inaccuracies in the covariance matrix.