arXiv subjects

Masato Shirasaki

Publications and source records attributed to Masato Shirasaki.

At least 73 records · Page 4Linked to original sources

arXiv2019

The Pseudo Evolution of Galaxy-Cluster Masses and Its Connection to Mass Density Profile

A mass of dark matter halo is commonly defined as the spherical over-density (SO) mass with respect to a reference density, whereas the time evolution of an SO mass can be affected by the redshift evolution of the reference density as well as the physical mass accretion around halos. In this study, we directly measure the amount of pseudo evolution of the SO masses of cluster-sized halos by the changes in the reference density from a time series of $N$-body simulations for the first time. We find that the $52\pm19\%$ difference in the virial SO masses between $z=0$ and $1$ can be accounted for by the pseudo evolution of clusters with a virial mass of $10^{14}\, h^{-1}M_{\odot}$ at $z=0$. The amount of pseudo evolution is found to be correlated with the age and density environment of a galaxy cluster. The stacked mass density profiles of cluster-sized halos with a greater amount of pseudo evolution in the SO mass shows the higher concentration ${\it and}$ greater linear bias parameter that is a counter-example of the known secondary halo bias due to concentration on the scale of clusters. We discuss how more concentrated clusters can show larger clustering amplitudes than their less concentrated counterparts and argue that the presence of rich filamentary structures plays a critical role in determining the linear halo bias of galaxy clusters.

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arXiv2019

Denoising Weak Lensing Mass Maps with Deep Learning

Weak gravitational lensing is a powerful probe of the large-scale cosmic matter distribution. Wide-field galaxy surveys allow us to generate the so-called weak lensing maps, but actual observations suffer from noise due to imperfect measurement of galaxy shape distortions and to the limited number density of the source galaxies. In this paper, we explore a deep-learning approach to reduce the noise. We develop an image-to-image translation method with conditional adversarial networks (CANs), which learn efficient mapping from an input noisy weak lensing map to the underlying noise field. We train the CANs using $30000$ image pairs obtained from $1000$ ray-tracing simulations of weak gravitational lensing. We show that the trained CANs reproduce the true one-point probability distribution function (PDF) of the noiseless lensing map with a bias less than $1σ$ on average, where $σ$ is the statistical error. We perform a Fisher analysis to make forecast for cosmological parameter inference with the one-point lensing PDF. By our denoising method using CANs, the first derivative of the PDF with respect to the cosmic mean matter density and the amplitude of the primordial curvature perturbations becomes larger by $\sim50\%$. This allows us to improve the cosmological constraints by $\sim30-40\%$ with using observational data from ongoing and upcoming galaxy imaging surveys.

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arXiv2019

The mass-richness relation of optically-selected clusters from weak gravitational lensing and abundance with Subaru HSC first-year data

Constraining the relation between the richness $N$ and the halo mass $M$ over a wide redshift range for optically-selected clusters is a key ingredient for cluster-related science in optical surveys, including the Subaru Hyper Suprime-Cam (HSC) survey. We measure stacked weak lensing profiles around 1747 HSC CAMIRA clusters over a redshift range of $0.1\leq z_{\rm cl}\leq 1.0$ with $N\geq 15$ using the HSC first-year shear catalog covering $\sim$$140$ ${\rm deg^2}$. The exquisite depth and image quality of the HSC survey allow us to measure lensing signals around the high-redshift clusters at $0.7\leq z_{\rm cl}\leq 1.0$ with a signal-to-noise ratio of 19 in the comoving radius range $0.5\lesssim R\lesssim 15 h^{-1}{\rm Mpc}$. We constrain richness-mass relations $P(\ln N|M,z)$ of the HSC CAMIRA clusters assuming a log-normal distribution without informative priors on model parameters, by jointly fitting to the lensing profiles and abundance measurements under both Planck and WMAP cosmological models. We show that our model gives acceptable $p$-values when we add redshift dependent terms which are proportional to $\ln (1+z)$ and $[\ln (1+z)]^{2}$ into the mean and scatter relations of $P(\ln N|M,z)$. Such terms presumably originate from the variation of photometric redshift errors as a function of the redshift. We show that the constraints on the mean relation $\langle M|N \rangle$ are consistent between the Planck and WMAP models, whereas the scatter values $σ_{\ln M|N}$ for the Planck model are systematically larger than those for the WMAP model. We also show that the scatter values for the Planck model increase toward lower richness values, whereas those for the WMAP model are consistent with constant values as a function of richness. This result highlights the importance of the scatter in the mass-richness relation for cluster cosmology.

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arXiv2019

Dark Quest. I. Fast and Accurate Emulation of Halo Clustering Statistics and Its Application to Galaxy Clustering

We perform an ensemble of $N$-body simulations with $2048^3$ particles for 101 flat $w$CDM cosmological models sampled based on a maximin-distance Sliced Latin Hypercube Design. By using the halo catalogs extracted at multiple redshifts in the range of $z=[0,1.48]$, we develop Dark Emulator, which enables fast and accurate computations of the halo mass function, halo-matter cross-correlation, and halo auto-correlation as a function of halo masses, redshift, separations and cosmological models, based on the Principal Component Analysis and the Gaussian Process Regression for the large-dimensional input and output data vector. We assess the performance of the emulator using a validation set of $N$-body simulations that are not used in training the emulator. We show that, for typical halos hosting CMASS galaxies in the Sloan Digital Sky Survey, the emulator predicts the halo-matter cross correlation, relevant for galaxy-galaxy weak lensing, with an accuracy better than $2\%$ and the halo auto-correlation, relevant for galaxy clustering correlation, with an accuracy better than $4\%$. We give several demonstrations of the emulator. It can be used to study properties of halo mass density profiles such as the mass-concentration relation and splashback radius for different cosmologies. The emulator outputs can be combined with an analytical prescription of halo-galaxy connection such as the halo occupation distribution at the equation level, instead of using the mock catalogs, to make accurate predictions of galaxy clustering statistics such as the galaxy-galaxy weak lensing and the projected correlation function for any model within the $w$CDM cosmologies, in a few CPU seconds.

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arXiv2019

Weak Lensing Measurement of Filamentary Structure with the SDSS BOSS and Subaru Hyper Suprime-Cam Data

We report the weak lensing measurement of filaments between Sloan Digital Sky Survey (SDSS) III/Baryon Oscillation Spectroscopic Survey (BOSS) CMASS galaxy pairs at $z\sim0.55$, using the Subaru Hyper Suprime-Cam (HSC) first-year galaxy shape catalogue. Despite of the small overlap of $140$ deg$^2$ between these surveys we detect the filament lensing signal at 3.9$σ$ significance, which is the highest signal-to-noise lensing measurement of filaments between galaxy-scale halos at this redshift range. We derive a theoretical prediction and covariance using mock catalogues based on full-sky ray-tracing simulations. We find that the intrinsic scatter of filament properties and the fluctuations in large scale structure along the line-of-sight are the primary component of the covariance and the intrinsic shape noise from source galaxies no longer limits our lensing measurement. This fact demonstrates the statistical power of the HSC survey due to its deep observations and high number density of source galaxies. Our result is consistent with the theoretical prediction and supports the "thick" filament model. As the HSC survey area increases, we will be able to study detailed filament properties such as the dark matter distributions and redshift evolution of filaments.

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arXiv2019

Mock galaxy shape catalogs in the Subaru Hyper Suprime-Cam Survey

We use the full-sky ray-tracing weak lensing simulations to generate 2268 mock catalogues for the Subaru Hyper Suprime-Cam (HSC) survey first-year shear catalogue. Our mock catalogues take into account various effects as in the real data: the survey footprints, inhomogeneous angular distribution of source galaxies, statistical uncertainties in photometric redshift (photo-$z$) estimate, variations in the lensing weight, and the statistical noise in galaxy shape measurements including both intrinsic shapes and the measurement errors. We then utilize our mock catalogues to evaluate statistical uncertainties expected in measurements of cosmic shear two-point correlations $ξ_{\pm}$ with tomographic redshift information for the HSC survey. We develop a quasi-analytical formula for the Gaussian sample variance properly taking into account the number of source pairs in the survey footprints. The standard Gaussian formula significantly overestimates or underestimates the mock results by $50\%$ level. We also show that different photo-$z$ catalogues or the six disconnected fields, rather than a consecutive geometry, cause variations in the covariance by $\sim 5\%$. The mock catalogues enable us to study the chi-square distribution for $ξ_{\pm}$. We find the wider distribution than that naively expected for the distribution with the degrees-of-freedom of data vector used. Finally, we propose a method to include non-zero multiplicative bias in mock shape catalogue and show the non-zero multiplicative bias can change the effective shape noise in cosmic shear analyses. Our results suggest an importance of estimating an accurate form of the likelihood function (and therefore the covariance) for robust cosmological parameter inference from the precise measurements.

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arXiv2019

Measurement of redshift dependent cross correlation of HSC clusters and Fermi $γ$ rays

The cross-correlation study of the unresolved $γ$-ray background (UGRB) with galaxy clusters has a potential to reveal the nature of the UGRB. In this paper, we perform a cross-correlation analysis between $γ$-ray data by the Fermi Large Area Telescope (Fermi-LAT) and a galaxy cluster catalogue from the Subaru Hyper Suprime-Cam (HSC) survey. The Subaru HSC cluster catalogue provides a wide and homogeneous large-scale structure distribution out to the high redshift at $z=1.1$, which has not been accessible in previous cross-correlation studies. We conduct the cross-correlation analysis not only for clusters in the all redshift range ($0.1 < z < 1.1$) of the survey, but also for subsamples of clusters divided into redshift bins, the low redshift bin ($0.1 < z < 0.6$) and the high redshift bin ($0.6 < z < 1.1$), to utilize the wide redshift coverage of the cluster catalogue. We find the evidence of the cross-correlation signals with the significance of 2.0-2.3$σ$ for all redshift and low-redshift cluster samples. On the other hand, for high-redshift clusters, we find the signal with weaker significance level (1.6-1.9$σ$). We also compare the observed cross-correlation functions with predictions of a theoretical model in which the UGRB originates from $γ$-ray emitters such as blazars, star-forming galaxies and radio galaxies. We find that the detected signal is consistent with the model prediction.

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arXiv2019

Cosmology from cosmic shear power spectra with Subaru Hyper Suprime-Cam first-year data

We measure cosmic weak lensing shear power spectra with the Subaru Hyper Suprime-Cam (HSC) survey first-year shear catalog covering 137deg$^2$ of the sky. Thanks to the high effective galaxy number density of $\sim$17 arcmin$^{-2}$ even after conservative cuts such as magnitude cut of $i<24.5$ and photometric redshift cut of $0.3\leq z \leq 1.5$, we obtain a high significance measurement of the cosmic shear power spectra in 4 tomographic redshift bins, achieving a total signal-to-noise ratio of 16 in the multipole range $300 \leq \ell \leq 1900$. We carefully account for various uncertainties in our analysis including the intrinsic alignment of galaxies, scatters and biases in photometric redshifts, residual uncertainties in the shear measurement, and modeling of the matter power spectrum. The accuracy of our power spectrum measurement method as well as our analytic model of the covariance matrix are tested against realistic mock shear catalogs. For a flat $Λ$ cold dark matter ($Λ$CDM) model, we find $S_8\equiv σ_8(Ω_{\rm m}/0.3)^α=0.800^{+0.029}_{-0.028}$ for $α=0.45$ ($S_8=0.780^{+0.030}_{-0.033}$ for $α=0.5$) from our HSC tomographic cosmic shear analysis alone. In comparison with Planck cosmic microwave background constraints, our results prefer slightly lower values of $S_8$, although metrics such as the Bayesian evidence ratio test do not show significant evidence for discordance between these results. We study the effect of possible additional systematic errors that are unaccounted in our fiducial cosmic shear analysis, and find that they can shift the best-fit values of $S_8$ by up to $\sim 0.6σ$ in both directions. The full HSC survey data will contain several times more area, and will lead to significantly improved cosmological constraints.

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arXiv2018

Impact of radio sources and cosmic infrared background on thermal Sunyaev-Zel'dovich - gravitational lensing cross correlation

Cross correlation with thermal Sunyaev-Zel'dovich (tSZ) effect in cosmic microwave background observation and weak gravitational lensing effect in galaxy imaging survey opens a new window on constraining matter contents in the Universe at redshift less than 1. In this paper, we study the impact of radio sources and cosmic infrared background (CIB) on observed tSZ-lensing correlation. Assuming the best-fit model of CIB by the Planck satellite, we estimate that the residual correlation of CIB with large-scale structures will be of an order of $2\%$ of expected tSZ-lensing correlation from intracluster medium in current lensing surveys. On the other hand, despite large model uncertainties, we find that correlation of lensing and radio sources can induce a negative correction for the observed tSZ-lensing correlation with a $\sim10-30\%$ level. This is originated from positive cross correlation with radio sources and lensing at $\sim100\, {\rm GHz}$ frequency, whereas tSZ-lensing correlation should show a negative value in temperature fluctuations at that frequency. We also show that the negative correction by radio-lensing correlation can solve the tension between recent measurements of tSZ-lensing correlation and an expected signal from "universal" gas pressure profile of nearby galaxy clusters, when the radio sources with flat-spectral index are assumed to populate massive cluster-sized dark matte halos. Our results indicate that minor source population in radio bands can play an important role in determining observed tSZ-lensing correlation at $<10$ arcmin.

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arXiv2018

Covariances for cosmic shear and galaxy-galaxy lensing in the response approach

In this study, we measure the response of matter and halo projected power spectra $P^{\rm 2D}_{\rm XY}(k)$ (X, Y are matter and/or halos), to a large-scale density contrast, $δ_{\rm b}$, using separate universe simulations. We show that the fractional response functions, i.e., $\mathrm{d}\ln P^{\rm 2D}_{\rm XY}(k)/\mathrm{d}δ_{\rm b}$, are identical to their respective three-dimensional power spectra within simulation measurement errors. Then, using various $N$-body simulation combinations (small-box simulations with periodic boundary conditions and sub-volumes of large-box simulations) to construct {mock observations of projected fields}, we study how super-survey modes, in both parallel and perpendicular directions to the projection direction, affect the covariance matrix of $P^{\rm 2D}_{\rm XY}(k)$, known as super-sample covariance (SSC). Our results indicate that the SSC term provides dominant contributions to the covariances of matter-matter and matter-halo spectra at small scales but does not provide significant contributions in the halo-halo spectrum. We observe that the large-scale density contrast in each redshift shell causes most of the SSC effect, and we did not observe a SSC signature arising from large-scale tidal field within the levels of measurement accuracy. We also develop a response approach to calibrate the SSC term for cosmic shear correlation function and galaxy--galaxy weak lensing, and validate the method by comparison with the light-cone ray-tracing simulations. Our method provides a reasonably accurate, albeit computationally inexpensive, way to calibrate the covariance matrix for clustering observables available from wide-area galaxy surveys.

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arXiv2018

The correlation of extragalactic $γ$-rays with cosmic matter density distributions from weak-gravitational lensing

The extragalactic $γ$-ray background (EGB) arises from the accumulation of $γ$-ray emissions from resolved and unresolved extragalactic sources as well as diffuse processes. It is important to study the statistical properties of the EGB in the context of cosmological structure formation. Known astrophysical $γ$-ray sources such as blazars, star-forming galaxies, and radio galaxies are expected to trace the underlying cosmic matter density distribution. We explore the correlation of the EGB from Fermi-LAT data with the large-scale matter density distribution from the Subaru Hyper Suprime-Cam (HSC) SSP survey. We reconstruct an unbiased surface matter density distribution $κ$ at $z<1$ by applying weak-gravitational lensing analysis to the first-year HSC data. We then calculate the $γ- κ$ cross-correlation. Our measurements are consistent with a null detection, but a weak correlation is found at angular scales of 30-60 arcmin, especially when distant source galaxies at $z > 1$ are used for the lensing $κ$ reconstruction. The large-scale correlation suggests strong clustering of high-redshift $γ$-ray sources such as blazars. However, the inferred bias factor of $4-5$ is larger by about a factor of two than results from other clustering analyses. The final HSC data covering 1,400 squared degrees will play an essential role to determine accurately the blazar bias at $z > 0.5$.

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arXiv2018

Stacked lensing estimators and their covariance matrices: Excess surface mass density vs. Lensing shear

Stacked lensing is a powerful means of measuring the average mass distribution around large-scale structure tracers. There are two stacked lensing estimators used in the literature, denoted as $ΔΣ$ and $γ_+$, which are related as $ΔΣ=Σ_{\rm cr}γ_+$, where $Σ_{\rm cr}(z_l,z_s)$ is the critical surface mass density for each lens-source pair ($z_l$ and $z_s$ are lens and source redshifts, respectively). In this paper we derive a formula for the covariance matrix of $ΔΣ$-estimator focusing on `weight' function to improve the signal-to-noise ($S/N$). We assume that the lensing fields and the distribution of lensing objects obey the Gaussian statistics. With this formula, we show that, if background galaxy shapes are weighted by an amount of $Σ_{\rm cr}^{-2}(z_l,z_s)$, the $ΔΣ$-estimator maximizes the $S/N$ in the shot noise limited regime. We also show that the $ΔΣ$-estimator with the weight $Σ_{\rm cr}^{-2}$ gives a greater $(S/N)^2$ than that of the $γ_+$-estimator by about 5--25\% for lensing objects at redshifts comparable with or higher than the median of source galaxy redshifts for hypothetical Subaru HSC and DES surveys. However, for low-redshift lenses such as $z_l<0.3$, the $γ_+$-estimator has higher $(S/N)^2$ than $ΔΣ$. We also discuss that the $(S/N)^2$ for $ΔΣ$ at large separations in the sample variance limited regime can be boosted, by up to a factor of 1.5, if one adopts a weight of $Σ_{\rm cr}^{-α}$ with $α>2$. Our formula allows one to explore how the combination of the different estimators can approach an optimal estimator in all regimes of redshifts and separation scales.

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arXiv2018

Weak-Lensing Mass Calibration of ACTPol Sunyaev-Zel'dovich Clusters with the Hyper Suprime-Cam Survey

We present weak-lensing measurements using the first-year data from the Hyper Suprime-Cam Strategic Survey Program on the Subaru telescope for eight galaxy clusters selected through their thermal Sunyaev-Zel'dovich (SZ) signal measured at 148 GHz with the Atacama Cosmology Telescope Polarimeter experiment. The overlap between the two surveys in this work is 33.8 square degrees, before masking bright stars. The signal-to-noise ratio of individual cluster lensing measurements ranges from 2.2 to 8.7, with a total of 11.1 for the stacked cluster weak-lensing signal. We fit for an average weak-lensing mass distribution using three different profiles, a Navarro-Frenk-White profile, a dark-matter-only emulated profile, and a full cosmological hydrodynamic emulated profile. We interpret the differences among the masses inferred by these models as a systematic error of 10\%, which is currently smaller than the statistical error. We obtain the ratio of the SZ-estimated mass to the lensing-estimated mass (the so-called hydrostatic mass bias $1-b$) of $0.74^{+0.13}_{-0.12}$, which is comparable to previous SZ-selected clusters from the Atacama Cosmology Telescope and from the {\sl Planck} Satellite. We conclude with a discussion of the implications for cosmological parameters inferred from cluster abundances compared to cosmic microwave background primary anisotropy measurements.

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arXiv2018

Modelling Baryonic Effects on Galaxy Cluster Mass Profiles

Gravitational lensing is a powerful probe of the mass distribution of galaxy clusters and cosmology. However, accurate measurements of the cluster mass profiles are limited by uncertainties in cluster astrophysics. In this work, we present a physically motivated model of baryonic effects on the cluster mass profiles, which self-consistently takes into account the impact of baryons on the concentration as well as mass accretion histories of galaxy clusters. We calibrate this model using the Omega500 hydrodynamical cosmological simulations of galaxy clusters with varying baryonic physics. Our model will enable us to simultaneously constrain cluster mass, concentration, and cosmological parameters using stacked weak lensing measurements from upcoming optical cluster surveys.

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arXiv2018

A large sample of shear selected clusters from the Hyper Suprime-Cam Subaru Strategic Program S16A wide field mass maps

We present the result of searching for clusters of galaxies based on weak gravitational lensing analysis of the $\sim 160$~deg$^2$ area surveyed by Hyper Suprime-Cam (HSC) as a Subaru Strategic Program. HSC is a new prime focus optical imager with a 1.5 diameter field of view on the 8.2-meter Subaru telescope. The superb median seeing on the HSC $i$-band images of $0.56$ arcsec allows the reconstruction of high angular resolution mass maps via weak lensing, which is crucial for the weak lensing cluster search. We identify 65 mass map peaks with signal-to-noise (SN) ratio larger than 4.7, and carefully examine their properties by cross-matching the clusters with optical and X-ray cluster catalogs. We find that all the 39 peaks with SN$>5.1$ have counterparts in the optical cluster catalogs, and only 2 out of the 65 peaks are probably false positives. The upper limits of X-ray luminosities from ROSAT All Sky Survey (RASS) imply the existence of an X-ray under-luminous cluster population. We show that the X-rays from the shear selected clusters can be statistically detected by stacking the RASS images. The inferred average X-ray luminosity is about half that of the X-ray selected clusters of the same mass. The radial profile of the dark matter distribution derived from the stacking analysis is well modeled by the Navarro-Frenk-White profile with a small concentration parameter value of $c_{500}\sim 2.5$, which suggests that the selection bias on the orientation or the internal structure for our shear selected cluster sample is not strong.

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arXiv2018

Investigating Cluster Astrophysics and Cosmology with Cross-Correlation of the Thermal Sunyaev-Zel'dovich Effect and Weak Lensing

Recent detections of the cross-correlation of the thermal Sunyaev-Zel'dovich (tSZ) effect and weak gravitational lensing (WL) enable unique studies of cluster astrophysics and cosmology. In this work, we present constraints on the amplitude of the non-thermal pressure fraction in galaxy clusters, $α_0$, and the amplitude of the matter power spectrum, $σ_8$, using measurements of the tSZ power spectrum from Planck, and the tSZ-WL cross-correlation from Planck and the Red Cluster Sequence Lensing Survey. We fit the data to a semi-analytic model with the covariance matrix using $N$-body simulations. We find that the tSZ power spectrum alone prefers $σ_8 \sim 0.85$ and a large fraction of non-thermal pressure ($α_0 \sim 0.2$-$0.3$). The tSZ-WL cross-correlation on the other hand prefers a significantly lower $σ_8 \sim 0.6$, and low $α_0 \sim 0.05$. We show that this tension can be mitigated by allowing for a steep slope in the stellar-mass-halo-mass relation, which would cause a reduction of the gas in low-mass halos. In such a model, the combined data prefer $σ_8 \sim 0.7$ and $α_0 \sim 0.2$, consistent with predictions from hydrodynamical simulations.

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arXiv2018

Constraints on the mass-richness relation from the abundance and weak lensing of SDSS clusters

We constrain the scaling relation between optical richness ($λ$) and halo mass ($M$) for a sample of SDSS redMaPPer galaxy clusters within the context of the {\it Planck} cosmological model. We use a forward modeling approach where we model the probability distribution of optical richness for a given mass, $P(\ln λ| M)$. To model the abundance and the stacked lensing profiles, we use an emulator specifically built to interpolate the halo mass function and the stacked lensing profile for an arbitrary set of halo mass and redshift, which is calibrated based on a suite of high-resolution $N$-body simulations. We apply our method to 8,312 SDSS redMaPPer clusters with $20\le λ\le 100$ and $0.10\le z_λ\le0.33$, and show that the log-normal distribution model for $P(λ|M)$, with four free parameters, well reproduces the measured abundances and lensing profiles simultaneously. The constraints are characterized by the mean relation, $\left\langle \lnλ\right\rangle(M)=A+B\ln(M/M_{\rm pivot})$, with $A=3.207^{+0.044}_{-0.046}$ and $B=0.993^{+0.041}_{-0.055}$ (68\%~CL), where the pivot mass scale $M_{\rm pivot}=3\times 10^{14} h^{-1}M_\odot$, and the scatter $σ_{\mathrm{\lnλ}|M}=σ_0+q\ln(M/M_{\rm pivot})$ with $σ_0=0.456^{+0.047}_{-0.039}$ and $q=-0.169^{+0.035}_{-0.026}$. We find that a large scatter in halo masses is required at the lowest richness bins ($20\le λ\lesssim 30$) in order to reproduce the measurements. Without such a large scatter, the model prediction for the lensing profiles tends to overestimate the measured amplitudes. This might imply a possible contamination of intrinsically low-richness clusters due to the projection effects. Such a low-mass halo contribution is significantly reduced when applying our method to the sample of $30\le λ\le 100$.

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arXiv2017

The first-year shear catalog of the Subaru Hyper Suprime-Cam SSP Survey

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 $0.58$ arcsec and $5σ$ point-source depth of $i\sim 26$. 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 $ρ_1<3\times 10^{-7}$ (requirement: $4\times 10^{-7}$) at 0.5$^\circ$ scales. A variety of galaxy shape-related null tests are statistically consistent with zero, but star-galaxy shape correlations reveal additive systematics on $>1^\circ$ 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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