In this paper, we describe the optical imaging data processing pipeline developed for the Subaru Telescope's Hyper Suprime-Cam (HSC) instrument. The HSC Pipeline builds on the prototype pipeline being developed by the Large Synoptic Survey Telescope's Data Management system, adding customizations for HSC, large-scale processing capabilities, and novel algorithms that have since been reincorporated into the LSST codebase. While designed primarily to reduce HSC Subaru Strategic Program (SSP) data, it is also the recommended pipeline for reducing general-observer HSC data. The HSC pipeline includes high level processing steps that generate coadded images and science-ready catalogs as well as low-level detrending and image characterizations.
We present and characterize the catalog of galaxy shape measurements that will be used for cosmological weak lensing measurements in the Wide layer of the first year of the Hyper Suprime-Cam (HSC) survey. The catalog covers an area of 136.9 deg 2 split into six fields, with a mean i-band seeing of 0.58 ′′ and 5σ point-source depth of i ∼ 26. Given conservative galaxy selection criteria for first year science, the depth and excellent image quality results in unweighted and weighted source number densities of 24.6 and 21.8 arcmin −2 , respectively. We define the requirements for cosmological weak lensing science with this catalog, then focus on characterizing potential systematics in the catalog using a series of internal null tests for problems with point-spread function (PSF) modeling, shear estimation, and other aspects of the image processing. We find that the PSF models narrowly meet requirements for weak lensing science with this catalog, with fractional PSF model size residuals of approximately 0.003 (requirement: 0.004) and the PSF model shape correlation function ρ 1 < 3 × 10 −7 (requirement:A variety of galaxy shape-related null tests are statistically consistent with zero, but star-galaxy shape correlations reveal additive systematics on on > 1• scales that are sufficiently large as to require mitigation in cosmic shear measurements. Finally, we discuss the dominant systematics and the planned algorithmic changes to reduce them in future data reductions.
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The observed UV continuum slope of star forming galaxies is strongly affected by the presence of dust. Its observation is then a potentially valuable diagnostic of dust attenuation, particularly at high-redshift where other diagnostics are currently inaccesible. Interpreting the observed UV continuum slope in the context of dust attenuation is often achieved assuming the empirically calibrated Meurer et al. (1999) relation. Implicit in this relation is the assumption of an intrinsic UV continuum slope (β = −2.23). However, results from numerical simulations suggest that the intrinsic UV continuum slopes of high-redshift star forming galaxies are bluer than this, and moreover vary with redshift. Using values of the intrinsic slope predicted by numerical models of galaxy formation combined with a Calzetti et al. (2000) reddening law we infer UV attenuations (A 1500 ) 0.35 − 0.5 mag (A V : 0.14 − 0.2 mag assuming Calzetti et al. 2000) greater than simply assuming the Meurer relation. This has significant implications for the inferred amount of dust attenuation at very-high (z ≈ 7) redshift given current observational constraints on β, combined with the Meurer relation, suggest dust attenuation to be virtually zero in all but the most luminous systems.
We explore the effect of massive neutrinos on the weak lensing shear bispectrum using the Cosmological Massive Neutrino Simulations [47]. We find that the primary effect of massive neutrinos is to suppress the amplitude of the bispectrum with limited effect on the bispectrum shape. The suppression of the bispectrum amplitude is a factor of two greater than the suppression of the small scale power-spectrum. For an LSST-like weak lensing survey that observes half of the sky with five tomographic redshift bins, we explore the constraining power of the bispectrum on three cosmological parameters: the sum of the neutrino mass m ν , the matter density Ω m and the amplitude of primordial fluctuations A s . Bispectrum measurements alone provide similar constraints to the power-spectrum measurements and combining the two probes leads to significant improvements than using the latter alone. We find that the joint constraints tighten the power spectrum 95% constraints by ∼ 32% for m ν , 13% for Ω m and 57% for A s . arXiv:1810.02374v1 [astro-ph.CO] 4 Oct 2018 6 The MassiveNuS data products, including galaxy and CMB lensing convergence maps, N-body snapshots, halo catalogues, and merger trees, are publicly available at http://ColumbiaLensing.org. 7 The neutrino patch kspace-neutrinos is publicly available at https://github.com/sbird/kspace-neutrinos 8 https://pypi.python.org/pypi/lenstools/
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