No abstract

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea in Hawaii. A team of scientists from Japan, Taiwan and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg 2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg 2 in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg 2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.

We constrain the abundance of primordial black holes (PBH) using 2622 microlensing events obtained from 5-years observations of stars in the Galactic bulge by the Optical Gravitational Lensing Experiment (OGLE). The majority of microlensing events display a single or at least continuous population that has a peak around the light curve timescale tE 20 days and a wide distribution over the range tE [1, 300] days, while the data also indicates a second population of 6 ultrashorttimescale events in tE [0.1, 0.3] days, which are advocated to be due to free-floating planets. We confirm that the main population of OGLE events can be well modeled by microlensing due to brown dwarfs, main sequence stars and stellar remnants (white dwarfs and neutron stars) in the standard Galactic bulge and disk models for their spatial and velocity distributions. Using the dark matter (DM) model for the Milky Way (MW) halo relative to the Galactic bulge/disk models, we obtain the tightest upper bound on the PBH abundance in the mass range MPBH [10 −6 , 10 −3 ]M (Earth-Jupiter mass range), if we employ "null hypothesis" that the OGLE data does not contain any PBH microlensing event. More interestingly, we also show that Earth-mass PBHs can well reproduce the 6 ultrashort-timescale events, without the need of free-floating planets, if the mass fraction of PBH to DM is at a per cent level, which is consistent with other constraints such as the microlensing search for Andromeda galaxy (M31) and the longer timescale OGLE events. Our result gives a hint of PBH existence, and can be confirmed or falsified by microlensing search for stars in M31, because M31 is towards the MW halo direction and should therefore contain a much less number of free-floating planets, even if exist, than the direction to the MW center. * niikura@hep.phys.s.u-tokyo.ac.jp † masahiro.takada@ipmu.jp producing PBHs with a target mass scale and a target abundance. Furthermore, there is a renewed interest in PBH scenario because of recent claims [12][13][14][15][16] [also see 17] that PBHs can be progenitors of binary black holes whose gravitational wave events have been detected by the LIGO/Virgo experiments [18,19].There are various attempts at constraining PBHs over almost twenty orders of magnitudes in their mass scales; gamma-ray background from PBH evaporation [20], femtolensing of gamma-ray bursts [21] (although Ref. [22] recently pointed out that a finite-source size effect of the gamma-ray burst progenitor significantly relaxes or even removes the constraint), supernovae of white dwarfs triggered by PBH [23], PBH capture by neutron stars [24,25], microlensing constraints [26][27][28][29], caustics-network lensing in the galaxy cluster region [30][31][32], X-ray background from gas accretion on PBH [33], and the effect of PBH gas accretion on the cosmic microwave background optical depth [34] (see Refs. [35,36] for the revisited calculations), the effect of PBH on pulsar timing array observation [37] and the effect on type-Ia supernova observation [38]. Except fo...

The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered imaging survey aimed at addressing some of the most important outstanding questions in astronomy today, including the nature of dark matter and dark energy. The survey has been awarded 300 nights of observing time at the Subaru Telescope, and it started in 2014 March. This paper presents the first public data release of HSC-SSP. This release includes data taken in the first 1.7 yr of observations (61.5 nights), and each of the Wide, Deep, and UltraDeep layers covers about 108, 26, and 4 square degrees down to depths of i ∼ 26.4, ∼26.5, and ∼27.0 mag, respectively (5 σ for point sources). All the layers are observed in five broad bands (grizy), and the Deep and UltraDeep layers are observed in narrow bands as well. We achieve an impressive image quality of 0${^{\prime\prime}_{.}}$6 in the i band in the Wide layer. We show that we achieve 1%–2% point spread function (PSF) photometry (root mean square) both internally and externally (against Pan-STARRS1), and ∼10 mas and 40 mas internal and external astrometric accuracy, respectively. Both the calibrated images and catalogs are made available to the community through dedicated user interfaces and database servers. In addition to the pipeline products, we also provide value-added products such as photometric redshifts and a collection of public spectroscopic redshifts. Detailed descriptions of all the data can be found online. The data release website is https://hsc-release.mtk.nao.ac.jp.

We develop a novel method of measuring the lensing distortion profiles of clusters with stacking the "scaled" amplitudes of background galaxy ellipticities as a function of the "scaled" centric radius according to the Navarro-Frenk-White (NFW) prediction of each cluster, based on the assumption that the different clusters in a sample follow the universal NFW profile. First we demonstrate the feasibility of this method using both the analytical NFW model and simulated halos in a suite of high-resolution N-body simulations. We then apply, as a proof of concept, this method to the Subaru weak lensing data and the XMM/Chandra X-ray observables for a sample of 50 massive clusters in the redshift range 0.15 ≤ z ≤ 0.3, where their halo masses differ from each other by up to a factor of 10. To estimate the NFW parameters of each cluster, we use the halo mass proxy relation of X-ray observables, based on either the hydrostatic equilibrium or the gas mass, and then infer the halo concentration from the model scaling relation of halo concentration with halo mass. We evaluate a performance of the NFW scaling analysis by measuring the scatters of 50 cluster lensing profiles relative to the NFW predictions over a range of radii, 0.14 ≤ R/[h −1 Mpc] ≤ 2.8. We found a 4 -6σ level evidence of the universal NFW profile in 50 clusters, for both the X-ray halo mass proxy relations, although the gas mass appears to be a better proxy of the underlying true mass. By comparing the measurements with the simulations of cluster lensing profiles taking into account the statistical errors of intrinsic galaxy shapes in the Subaru data, we argue that additional halo mass errors or intrinsic scatters of σ(M 500c )/M 500c ∼ 0.2 -0.3 could reconcile a difference between the measurements and the simulations. This method allows us to some extent to preserve characteristics of individual clusters in the statistical weak lensing analysis, thereby yielding a new means of exploiting the underlying genuine form of the halo mass profile and the halo mass proxy relations via weak lensing information, under the assumption of the existence of the universal profile.