39 research outputs found
Deep CFHT Y-band imaging of VVDS-F22 field: I. data products and photometric redshifts
We present our deep -band imaging data of a two square degree field within
the F22 region of the VIMOS VLT Deep Survey. The observations were conducted
using the WIRCam instrument mounted at the Canada--France--Hawaii Telescope
(CFHT). The total on-sky time was 9 hours, distributed uniformly over 18 tiles.
The scientific goals of the project are to select faint quasar candidates at
redshift , and constrain the photometric redshifts for quasars and
galaxies. In this paper, we present the observation and the image reduction, as
well as the photometric redshifts that we derived by combining our -band
data with the CFHTLenS optical data and UKIDSS DXS
near-infrared data. With -band image as reference total 80,000
galaxies are detected in the final mosaic down to -band point
source limiting depth of 22.86 mag. Compared with the 3500 spectroscopic
redshifts, our photometric redshifts for galaxies with and
mag have a small systematic offset of
, 1 scatter ,
and less than 4.0% of catastrophic failures. We also compare to the CFHTLenS
photometric redshifts, and find that ours are more reliable at
because of the inclusion of the near-infrared bands. In particular, including
the -band data can improve the accuracy at because the
location of the 4000\AA-break is better constrained. The -band images, the
multi-band photometry catalog and the photometric redshifts are released at
\url{http://astro.pku.edu.cn/astro/data/DYI.html}.Comment: 16 pages, 12 figures, 4 tables. AJ accepted. Updated access to the
data: https://zenodo.org/record/140003
Observational constraints on cosmic neutrinos and dark energy revisited
Using several cosmological observations, i.e. the cosmic microwave background
anisotropies (WMAP), the weak gravitational lensing (CFHTLS), the measurements
of baryon acoustic oscillations (SDSS+WiggleZ), the most recent observational
Hubble parameter data, the Union2.1 compilation of type Ia supernovae, and the
HST prior, we impose constraints on the sum of neutrino masses (\mnu), the
effective number of neutrino species (\neff) and dark energy equation of
state (), individually and collectively. We find that a tight upper limit on
\mnu can be extracted from the full data combination, if \neff and are
fixed. However this upper bound is severely weakened if \neff and are
allowed to vary. This result naturally raises questions on the robustness of
previous strict upper bounds on \mnu, ever reported in the literature. The
best-fit values from our most generalized constraint read
\mnu=0.556^{+0.231}_{-0.288}\rm eV, \neff=3.839\pm0.452, and
at 68% confidence level, which shows a firm lower limit on
total neutrino mass, favors an extra light degree of freedom, and supports the
cosmological constant model. The current weak lensing data are already helpful
in constraining cosmological model parameters for fixed . The dataset of
Hubble parameter gains numerous advantages over supernovae when ,
particularly its illuminating power in constraining \neff. As long as is
included as a free parameter, it is still the standardizable candles of type Ia
supernovae that play the most dominant role in the parameter constraints.Comment: 39 pages, 15 figures, 7 tables, accepted to JCA
Characterization of a fatal feline panleukopenia virus derived from giant panda with broad cell tropism and zoonotic potential
Represented by feline panleukopenia virus (FPV) and canine parvovirus (CPV), the species carnivore protoparvovirus 1 has a worldwide distribution through continuous ci13rculation in companion animals such as cats and dogs. Subsequently, both FPV and CPV had engaged in host-to-host transfer to other wild animal hosts of the order Carnivora. In the present study, we emphasized the significance of cross-species transmission of parvoviruses with the isolation and characterization of an FPV from giant panda displaying severe and fatal symptoms. The isolated virus, designated pFPV-sc, displayed similar morphology as FPV, while phylogenetic analysis indicated that the nucleotide sequence of pFPV-sc clades with Chinese FPV isolates. Despite pFPV-sc is seemingly an outcome of a spillover infection event from domestic cats to giant pandas, our study also provided serological evidence that FPV or other parvoviruses closely related to FPV could be already prevalent in giant pandas in 2011. Initiation of host transfer of pFPV-sc is likely with association to giant panda transferrin receptor (TfR), as TfR of giant panda shares high homology with feline TfR. Strikingly, our data also indicate that pFPV-sc can infect cell lines of other mammal species, including humans. To sum up, observations from this study shall promote future research of cross-host transmission and antiviral intervention of Carnivore protoparvovirus 1, and necessitate surveillance studies in thus far unacknowledged potential reservoirs
Upconversion NaYF 4
Upconversion nanoparticles (UCNPs) based on NaYF4 nanocrystals with strong upconversion luminescence are synthesized by the solvothermal method. The emission color of these NaYF4 upconversion nanoparticles can be easily modulated by the doping. These NaYF4 upconversion nanocrystals can be employed as fluorescence donors to pump fluorescent organic molecules. For example, the efficient luminescence resonant energy transfer (LRET) can be achieved by controlling the distance between NaYF4:Yb3+/Er3+ UCNPs and Rhodamine B (RB). NaYF4:Yb3+/Er3+ UCNPs can emit green light at the wavelength of ~540 nm while RB can efficiently absorb the green light of ~540 nm to emit red light of 610 nm. The LRET efficiency is highly dependent on the concentration of NaYF4 upconversion fluorescent donors. For the fixed concentration of 3.2 µg/mL RB, the optimal concentration of NaYF4:Yb3+/Er3+ UCNPs is equal to 4 mg/mL which generates the highest LRET signal ratio. In addition, it is addressed that the upconversion nanoparticles with diameter of 200 nm are suitable for imaging the cells larger than 10 µm with clear differentiation between cell walls and cytoplasm
KiDS-1000: cross-correlation with Planck cosmic microwave background lensing and intrinsic alignment removal with self-calibration
Galaxy shear - cosmic microwave background (CMB) lensing convergence
cross-correlations contain additional information on cosmology to
auto-correlations. While being immune to certain systematic effects, they are
affected by the galaxy intrinsic alignments (IA). This may be responsible for
the reported low lensing amplitude of the galaxy shear CMB convergence
cross-correlations, compared to the standard Planck CDM (cosmological
constant and cold dark matter) cosmology prediction. In this work, we
investigate how IA affects the Kilo-Degree Survey (KiDS) galaxy lensing shear -
Planck CMB lensing convergence cross-correlation and compare it to previous
treatments with or without IA taken into consideration. More specifically, we
compare marginalization over IA parameters and the IA self-calibration (SC)
method (with additional observables defined only from the source galaxies) and
prove that SC can efficiently break the degeneracy between the CMB lensing
amplitude and the IA amplitude . We further
investigate how different systematics affect the resulting and
, and validate our results with the MICE2 simulation. We find
that by including the SC method to constrain IA, the information loss due to
the degeneracy between CMB lensing and IA is strongly reduced. The best-fit
values are and , while different angular scale cuts can affect
by . We show that appropriate treatment of the boost
factor, cosmic magnification, and photometric redshift modeling is important
for obtaining the correct IA and cosmological results.Comment: match version accepted by A&
Probing galaxy bias and intergalactic gas pressure with KiDS Galaxies-tSZ-CMB lensing cross-correlations
We constrain the redshift dependence of gas pressure bias (bias-weighted average electron pressure), which
characterises the thermodynamics of intergalactic gas, through a combination of
cross-correlations between galaxy positions and the thermal Sunyaev-Zeldovich
(tSZ) effect, as well as galaxy positions and the gravitational lensing of the
cosmic microwave background (CMB). The galaxy sample is from the fourth data
release of the Kilo-Degree Survey (KiDS). The tSZ map and the CMB lensing
map are from the {\textit{Planck}} 2015 and 2018 data releases, respectively.
The measurements are performed in five redshift bins with . With
these measurements, combining galaxy-tSZ and galaxy-CMB lensing
cross-correlations allows us to break the degeneracy between galaxy bias and
gas pressure bias, and hence constrain them simultaneously. In all redshift
bins, the best-fit values of \bpe are at a level of and increase slightly with redshift. The galaxy bias is
consistent with unity in all the redshift bins. Our results are not sensitive
to the non-linear details of the cross-correlation, which are smoothed out by
the {\textit{Planck}} beam. Our measurements are in agreement with previous
measurements as well as with theoretical predictions. We also show that our
conclusions are not changed when CMB lensing is replaced by galaxy lensing,
which shows the consistency of the two lensing signals despite their radically
different redshift ranges. This study demonstrates the feasibility of using CMB
lensing to calibrate the galaxy distribution such that the galaxy distribution
can be used as a mass proxy without relying on the precise knowledge of the
matter distribution.Comment: 20 pages, 14 figures, 3 tables, accepted for publication on Astronomy
& Astrophysic
Science from an Ultra-Deep, High-Resolution Millimeter-Wave Survey
Opening up a new window of millimeter-wave observations that span frequency
bands in the range of 30 to 500 GHz, survey half the sky, and are both an order
of magnitude deeper (about 0.5 uK-arcmin) and of higher-resolution (about 10
arcseconds) than currently funded surveys would yield an enormous gain in
understanding of both fundamental physics and astrophysics. In particular, such
a survey would allow for major advances in measuring the distribution of dark
matter and gas on small-scales, and yield needed insight on 1.) dark matter
particle properties, 2.) the evolution of gas and galaxies, 3.) new light
particle species, 4.) the epoch of inflation, and 5.) the census of bodies
orbiting in the outer Solar System.Comment: 5 pages + references; Submitted to the Astro2020 call for science
white paper