165 research outputs found
Building a Morally Respectable Nation: Examining Japanese Foreign Policy through Ebara Soroku; 1913-1922
Mock Observatory: two thousand lightcone mock catalogues of luminous red galaxies from the Hyper Suprime-Cam Survey for the cosmological large-scale analysis
Estimating a reliable covariance matrix for correlation functions of galaxies
is a crucial task to obtain accurate cosmological constraints from galaxy
surveys. We generate 2,000 independent lightcone mock luminous red galaxy
(LRGs) catalogues at , designed to cover CAMIRA LRGs
observed by the Subaru Hyper Suprime-Cam Subaru Strategic Programme (HSC SSP).
We first produce full-sky lightcone halo catalogues using a COmoving Lagrangian
Acceleration (COLA) technique, and then trim them to match the footprints of
the HSC SSP S20A Wide layers. The mock LRGs are subsequently populated onto the
trimmed halo catalogues according to the halo occupation distribution model
constrained by the observed CAMIRA LRGs. The stellar mass () is
assigned to each LRG by the subhalo abundance-matching technique using the
observed stellar-mass functions of CAMIRA LRGs. We evaluate photometric
redshifts (photo-) of mock LRGs by incorporating the photo- scatter,
which is derived from the observed --photo--scatter relations of
the CAMIRA LRGs. We validate the constructed full-sky halo and lightcone LRG
mock catalogues by comparing their angular clustering statistics (i.e., power
spectra and correlation functions) with those measured from the halo catalogues
of full -body simulations and the CAMIRA LRG catalogues from the HSC SSP,
respectively. We detect clear signatures of baryon acoustic oscillations (BAOs)
from our mock LRGs, whose angular scales are well consistent with theoretical
predictions. These results demonstrate that our mock LRGs can be used to
evaluate covariance matrices at large scales and provide predictions for the
BAO detectability and cosmological constraints.Comment: 13 pages, 11 figures, submitted to MNRA
Galaxy-dark matter connection of photometric galaxies from the HSC-SSP Survey: Galaxy-galaxy lensing and the halo model
We infer the connection between the stellar mass of galaxies from the Subaru
Hyper Suprime-Cam (HSC) survey, and their dark matter halo masses and its
evolution in two bins of redshifts between . We use the
measurements of the weak lensing signal of galaxies using background sources
from the Year 1 shape catalog from the HSC survey. We bin galaxies in stellar
mass with varying thresholds ranging from and use stringent cuts in the selection of source
galaxies to measure the weak lensing signal. We model these measurements of the
weak lensing signal together with the abundance of galaxies in the halo
occupation distribution framework. We obtain constraints on the halo occupation
parameters of central galaxies and , which
correspond to the halo mass at which central galaxies for each threshold sample
reach half occupancy, and its scatter, respectively, along with parameters that
describe the occupation of the satellite galaxies. The measurements of
abundance and weak lensing individually constrain different degeneracy
directions in the and plane, thus breaking the
degeneracy in these parameters. We demonstrate that the weak lensing
measurements are best able to constrain the average central halo masses,
. We compare our measurements to those obtained
using the abundance and clustering of these galaxies as well as the subhalo
abundance matching measurements and demonstrate qualitative agreement. We find
that the galaxy-dark matter connection does not vary significantly between
redshift bins we explore in this study. Uncertainties in the photometric
redshift of the lens galaxies imply that more efforts are required to
understand the true underlying stellar mass-halo mass relation of galaxies and
its evolution over cosmic epoch
The Subaru high-z quasar survey: discovery of faint z~6 quasars
We present the discovery of one or two extremely faint z~6 quasars in 6.5
deg^2 utilizing a unique capability of the wide-field imaging of the
Subaru/Suprime-Cam. The quasar selection was made in (i'-z_B) and (z_B-z_R)
colors, where z_B and z_R are bandpasses with central wavelengths of 8842A and
9841A, respectively. The color selection can effectively isolate quasars at z~6
from M/L/T dwarfs without the J-band photometry down to z_R<24.0, which is 3.5
mag. deeper than SDSS. We have selected 17 promising quasar candidates. The
follow-up spectroscopy for seven targets identified one apparent quasar at
z=6.156 with M_1450=-23.10. We also identified one possible quasar at z=6.041
with a faint continuum of M_1450=-22.58 and a narrow Lyman-alpha emission with
HWHM=427 km/s, which cannot be distinguished from Lyman-alpha emitters. We
derive the quasar luminosity function at z~6 by combining our faint quasar
sample with the bright quasar samples by SDSS and CFHQS. Including our data
points invokes a higher number density in the faintest bin of the quasar
luminosity function than the previous estimate employed. This suggests a
steeper faint-end slope than lower-z, though it is yet uncertain based on a
small number of spectroscopically identified faint quasars and several quasar
candidates are still remain to be diagnosed. The steepening of the quasar
luminosity function at the faint-end does increase the expected emission rate
of the ionizing photon, however, it only changes by a factor of ~2-6. This was
found to be still insufficient for the required photon budget of reionization
at z~6.Comment: 10 pages, 8 figures. Accepted for publication in Ap
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