20 research outputs found
Cosmological constraints from Subaru weak lensing cluster counts
We present results of weak lensing cluster counts obtained from 11 sq.deg
SuprimeCam data. Although the area is much smaller than previous work dealing
with weak lensing peak statistics, the number density of galaxies usable for
weak lensing analysis is about twice as large as those. The higher galaxy
number density reduces the noise in the weak lensing mass maps, and thus
increases the signal-to-noise ratio of peaks of the lensing signal due to
massive clusters. This enables us to construct a weak lensing selected cluster
sample by adopting a high threshold S/N, such that the contamination rate due
to false signals is small. We find 6 peaks with S/N>5. For all the peaks,
previously identified clusters of galaxies are matched within a separation of 1
arcmin, demonstrating good correspondence between the peaks and clusters of
galaxies. We evaluate the statistical error using mock weak lensing data, and
find Npeak=6+/-3.1 in an effective area of 9.0 sq.deg. We compare the measured
weak lensing cluster counts with the theoretical model prediction based on halo
models and place the constraint on Omega_m-sigma_8 plane which is found to be
consistent with currently standard LCDM models. It is demonstrated that the
weak lensing cluster counts can place a unique constraint on sigma_8-c_0 plane,
where c_0 is the normalization of the dark matter halo mass-concentration
relationship. Finally we discuss prospects for ongoing/future wide field
optical galaxy surveys.Comment: 15 pages, 11 figures, submitted to PASJ, comments welcom
GALAXY CRUISE: Deep Insights into Interacting Galaxies in the Local Universe
We present the first results from GALAXY CRUISE, a community (or citizen)
science project based on data from the Hyper Suprime-Cam Subaru Strategic
Program (HSC-SSP). The current paradigm of galaxy evolution suggests that
galaxies grow hierarchically via mergers, but our observational understanding
of the role of mergers is still limited. The data from HSC-SSP are ideally
suited to improve our understanding with improved identifications of
interacting galaxies thanks to the superb depth and image quality of HSC-SSP.
We have launched a community science project, GALAXY CRUISE, in 2019 and
collected over 2 million independent classifications of 20,686 galaxies at z <
0.2. We first characterize the accuracy of the participants' classifications
and demonstrate that it surpasses previous studies based on shallower imaging
data. We then investigate various aspects of interacting galaxies in detail. We
show that there is a clear sign of enhanced activities of super massive black
holes and star formation in interacting galaxies compared to those in isolated
galaxies. The enhancement seems particularly strong for galaxies undergoing
violent merger. We also show that the mass growth rate inferred from our
results is roughly consistent with the observed evolution of the stellar mass
function. The 2nd season of GALAXY CRUISE is currently under way and we
conclude with future prospects. We make the morphological classification
catalog used in this paper publicly available at the GALAXY CRUISE website,
which will be particularly useful for machine-learning applications.Comment: 23 pages, 22 figures, PASJ in press. Data available at
https://galaxycruise.mtk.nao.ac.jp/en/for_researchers.htm
The Hyper Suprime-Cam Software Pipeline
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.Comment: 39 pages, 21 figures, 2 tables. Submitted to Publications of the
Astronomical Society of Japa
First Data Release of the Hyper Suprime-Cam Subaru Strategic Program
The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered
imaging survey aimed at addressing some of the most 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 March 2014. This paper presents the first public data release
of HSC-SSP. This release includes data taken in the first 1.7 years 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 (5sigma 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 0.6 arcsec in
the i-band in the Wide layer. We show that we achieve 1-2 per cent PSF
photometry (rms) 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/.Comment: 34 pages, 20 figures, 7 tables, moderate revision, accepted for
publication in PAS
The Hyper Suprime-Cam SSP survey: Overview and survey design
Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2-m Subaru telescope on the summit of Mauna Kea 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 deg2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg2 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 deg2). 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