7,160 research outputs found
Wavelength Dependent PSFs and their impact on Weak Lensing Measurements
We measure and model the wavelength dependence of the PSF in the Hyper
Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey. We find that PSF
chromaticity is present in that redder stars appear smaller than bluer stars in
the and -bands at the 1-2 per cent level and in the and
-bands at the 0.1-0.2 per cent level. From the color dependence of the PSF,
we fit a model between the monochromatic PSF trace radius, , and wavelength
of the form . We find values of between -0.2
and -0.5, depending on the epoch and filter. This is consistent with the
expectations of a turbulent atmosphere with an outer scale length of m, indicating that the atmosphere is dominating the chromaticity. We
find evidence in the best seeing data that the optical system and detector also
contribute some wavelength dependence. Meyers and Burchat (2015) showed that
must be measured to an accuracy of not to dominate the
systematic error budget of the Large Synoptic Survey Telescope (LSST) weak
lensing (WL) survey. Using simple image simulations, we find that can be
inferred with this accuracy in the and -bands for all positions in the
LSST field of view, assuming a stellar density of 1 star arcmin and that
the optical PSF can be accurately modeled. Therefore, it is possible to correct
for most, if not all, of the bias that the wavelength-dependent PSF will
introduce into an LSST-like WL survey.Comment: 14 pages, 10 figures. Submitted to MNRAS. Comments welcom
Non-quasiparticle states in CoMnSi evidenced through magnetic tunnel junction spectroscopy measurements
We investigate the effects of electronic correlations in the full-Heusler
CoMnSi, by combining a theoretical analysis of the spin-resolved density of
states with tunneling-conductance spectroscopy measurements using CoMnSi as
electrode. Both experimental and theoretical results confirm the existence of
so-called non-quasiparticle states and their crucial contribution to the
finite-temperature spin polarisation in this material.Comment: Repalced Fig. 1. of PRL, 100, 086402 (2008), better k-space
resolution for DOS around Fermi energ
Fermi arc in doped high-Tc cuprates
We propose a -density wave induced by the spin-orbit coupling in the CuO
plane. The spectral function of high-temperature superconductors in the under
doped and lightly doped regions is calculated in order to explain the Fermi arc
spectra observed recently by angle-resolved photoemission spectroscopy. We take
into account the tilting of CuO octahedra as well as the on-site
Coulombrepulsive interaction; the tilted octahedra induce the staggered
transfer integral between orbitals and Cu orbitals, and
bring about nontrivial effects of spin-orbit coupling for the electrons in
the CuO plane. The spectral weight shows a peak at around (,) for
light doping and extends around this point forming an arc as the carrier
density increases, where the spectra for light doping grow continuously to be
the spectra in the optimally doped region. This behavior significantly agrees
with that of the angle-resolved photoemissionspectroscopy spectra. Furthermore,
the spin-orbit term and staggered transfer effectively induce a flux state, a
pseudo-gap with time-reversal symmetry breaking. We have a nodal metallic state
in the light-doping case since the pseudogap has a symmetry.Comment: 5 pages, 7 figure
Electronic inhomogeneity in EuO: Possibility of magnetic polaron states
We have observed the spatial inhomogeneity of the electronic structure of a
single-crystalline electron-doped EuO thin film with ferromagnetic ordering by
employing infrared magneto-optical imaging with synchrotron radiation. The
uniform paramagnetic electronic structure changes to a uniform ferromagnetic
structure via an inhomogeneous state with decreasing temperature and increasing
magnetic field slightly above the ordering temperature. One possibility of the
origin of the inhomogeneity is the appearance of magnetic polaron states.Comment: 4 pages, 3 figure
The Stellar Population of the M31 Spiral Arm Around OB Association A24
A study of the stellar population of the M31 spiral arm around OB association
A24 was carried out based on the photometric data obtained from deep V and JHK
imaging. The luminosity function was obtained for -7 <~ Mbol <~ -3.5 by
applying the extinction correction corresponding to Av=1 and the bolometric
correction BC(K) as an empirical function of (J-K)o. In comparing the observed
color-luminosity diagrams with semitheoretical isochrones modified for the
dust-shell effects, we found the young population of t <~ 30 Myr with
supergiants of Mbol <~ -5, the bulk of the intermediate-age population of t ~
0.2 - 2.5 Gyr with bright asymptotic giant branch (AGB) stars of -5 <~ Mbol <~
-4, and old populations of t ~> 3 Gyr with AGB and red giant branch (RGB) stars
of Mbol ~> -4. The average star formation rate was estimated to be ~1.8x10^4
M_o/Myr and ~0.7x10^4 M_o/Myr per deprojected disk area of 1 kpc^2 from the
number density of B0 V stars around Mv=-4.0 (age ~10 Myr) and the number
density of bright AGB stars around Mbol = -4.3 (age ~1 Gyr), respectively. A
study of the local variation in the V and the J and H luminosity functions
revealed a kind of anticorrelation between the population of the young
component and that of the intermediate-age component when subdomains of ~100 pc
scales were concerned. This finding suggests that the disk domain around the
A24 area experienced a series of star formation episodes alternatively among
different subdomains with a timescale of a few spiral passage periods. Brief
discussions are given about the interstellar extinction and about the lifetimes
of bright AGB stars and the highly red objects (HROs) in the same area.Comment: 27 pages, 11 figures, accepted: ApJ, July 1, 199
A wide area survey for high-redshift massive galaxies. I. Number counts and clustering of BzKs and EROs
We have combined deep BRIz' imaging over 2x940 arcmin^2 fields obtained with
the Suprime-Cam on the Subaru telescope with JKs imaging with the SOFI camera
at the New Technology Telescope to search for high-redshift massive galaxies.
K-band selected galaxies have been identified over an area of ~920 arcmin^2 to
K_Vega=19.2, of which 320 arcmin^2 are complete to K_Vega=20. The BzK selection
technique was used to obtain complete samples of ~500 candidate massive
star-forming galaxies (sBzKs) and ~160 candidate massive, passively-evolving
galaxies (pBzKs), both at 1.4 5 criterion we also
identified ~850 extremely red objects (EROs). The surface density of sBzKs and
pBzKs is found to 1.20+/-0.05 arcmin^{-2} and 0.38+/-0.03 arcmin^{-2},
respectively. Both sBzKs and pBzKs are strongly clustered, at a level at least
comparable to that of EROs, with pBzKs appearing more clustered than sBzKs. We
estimate the reddening, star formation rates (SFRs) and stellar masses (M_*) of
the sBzKs, confirming that to K_Vega~20 median values are M_*~10^{11}M_sun, SFR
190M_sun yr^{-1}, and E(B-V)~0.44. The most massive sBzKs are also the most
actively star-forming, an effect which can be seen as a manifestation of
downsizing at early epochs. The space density of massive pBzKs at z~1.4-2 is
20%+/-7% that of similarly massive early-type galaxies at z~0, and similar to
that of sBzKs of the same mass. We argue that star formation quenching in these
sBzKs will result in nearly doubling the space density of massive early-type
galaxies, thus matching their local density.Comment: 19 pages, 13 figures, accepted by ApJ. While checking the proofs we
became aware of a material mistake of non-trivial scientific relevance. In
the original it was reported that the comoving volume density of passive
BzK-selected galaxies with =1.7 and more massive than 10^{11}M_sun was
45%+/-15% of the local number density of similarly massive early-type
galaxies. This fraction actually turns out to be 20%+/-7%. Section 6.4, point
5 in section 7, and the abstract have been modified accordingl
Glasslike Arrest in Spinodal Decomposition as a Route to Colloidal Gelation
Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich
and colloid-poor regions. Gelation results when interconnected colloid-rich
regions solidify. We show that this occurs when these regions undergo a glass
transition, leading to dynamic arrest of the spinodal decomposition. The
characteristic length scale of the gel decreases with increasing quench depth,
and the nonergodicity parameter exhibits a pronounced dependence on scattering
vector. Mode coupling theory gives a good description of the dynamics, provided
we use the full static structure as input.Comment: 14 pages, 4 figures; replaced with published versio
The Clustering of Extragalactic Extremely Red Objects
We have measured the angular and spatial clustering of 671 K5
Extremely Red Objects (EROs) from a 0.98 square degree sub-region of the NOAO
Deep Wide-Field Survey (NDWFS). Our study covers nearly 5 times the area and
has twice the sample size of any previous ERO clustering study. The wide field
of view and BwRIK passbands of the NDWFS allow us to place improved constraints
on the clustering of z=1 EROs. We find the angular clustering of EROs is
slightly weaker than in previous measurements, and w(1')=0.25+/-0.05 for
K<18.40 EROs. We find no significant correlation of ERO spatial clustering with
redshift, apparent color or absolute magnitude, although given the
uncertainties, such correlations remain plausible. We find the spatial
clustering of K5 EROs is well approximated by a power-law, with
r_0=9.7+/-1.1 Mpc/h in comoving coordinates. This is comparable to the
clustering of 4L* early-type galaxies at z<1, and is consistent with the
brightest EROs being the progenitors of the most massive ellipticals. There is
evidence of the angular clustering of EROs decreasing with increasing apparent
magnitude, when NDWFS measurements of ERO clustering are combined with those
from the literature. Unless the redshift distribution of K>20 EROs is very
broad, the spatial clustering of EROs decreases from r_0=9.7+/-1.1 Mpc/h for
K20 EROs.Comment: Accepted for publication in the ApJ. 29 pages with 10 figures. The
NOAO Deep Wide-Field Survey Bootes data release is available online at
http://www.noao.edu/noao/noaodeep
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