256 research outputs found
Separating intrinsic alignment and galaxy-galaxy lensing
The coherent physical alignment of galaxies is an important systematic for
gravitational lensing studies as well as a probe of the physical mechanisms
involved in galaxy formation and evolution. We develop a formalism for treating
this intrinsic alignment (IA) in the context of galaxy-galaxy lensing and
present an improved method for measuring IA contamination, which can arise when
sources physically associated with the lens are placed behind the lens due to
photometric redshift scatter. We apply the technique to recent Sloan Digital
Sky Survey (SDSS) measurements of Luminous Red Galaxy lenses and typical (L*)
source galaxies with photometric redshifts selected from the SDSS imaging data.
Compared to previous measurements, this method has the advantage of being fully
self-consistent in its treatment of the IA and lensing signals, solving for the
two simultaneously. We find an IA signal consistent with zero, placing tight
constraints on both the magnitude of the IA effect and its potential
contamination to the lensing signal. While these constraints depend on source
selection and redshift quality, the method can be applied to any measurement
that uses photometric redshifts. We obtain a model-independent upper-limit of
roughly 10% IA contamination for projected separations of approximately 0.1-100
Mpc/h. With more stringent photo-z cuts and reasonable assumptions about the
physics of intrinsic alignments, this upper limit is reduced to 1-2%. These
limits are well below the statistical error of the current lensing
measurements. Our results suggest that IA will not present intractable
challenges to the next generation of galaxy-galaxy lensing experiments, and the
methods presented here should continue to aid in our understanding of alignment
processes and in the removal of IA from the lensing signal.Comment: 31 pages, 8 Figures. Minor changes to reflect published versio
Shear Recovery Accuracy in Weak Lensing Analysis with Elliptical Gauss-Laguerre Method
We implement the Elliptical Gauss-Laguerre (EGL) galaxy-shape measurement
method proposed by Bernstein & Jarvis (2002) and quantify the shear recovery
accuracy in weak lensing analysis. This method uses a deconvolution fitting
scheme to remove the effects of the point-spread function (PSF). The test
simulates >10^7 noisy galaxy images convolved with anisotropic PSFs, and
attempts to recover an input shear. The tests are designed to be immune to
shape noise, selection biases, and crowding. The systematic error in shear
recovery is divided into two classes, calibration (multiplicative) and
additive, with the latter arising from PSF anisotropy. At S/N > 50, the
deconvolution method measures the galaxy shape and input shear to ~ 1%
multiplicative accuracy, and suppresses > 99% of the PSF anisotropy. These
systematic errors increase to ~ 4% for the worst conditions, with poorly
resolved galaxies at S/N ~ 20. The EGL weak lensing analysis has the best
demonstrated accuracy to date, sufficient for the next generation of weak
lensing surveys.Comment: 22 pages, 14 figures, submitted to Astronomical Journa
Weak-lensing shear measurement with machine learning: teaching artificial neural networks about feature noise
Cosmic shear is a primary cosmological probe for several present and upcoming
surveys investigating dark matter and dark energy, such as Euclid or WFIRST.
The probe requires an extremely accurate measurement of the shapes of millions
of galaxies based on imaging data. Crucially, the shear measurement must
address and compensate for a range of interwoven nuisance effects related to
the instrument optics and detector, noise, unknown galaxy morphologies, colors,
blending of sources, and selection effects. This paper explores the use of
supervised machine learning (ML) as a tool to solve this inverse problem. We
present a simple architecture that learns to regress shear point estimates and
weights via shallow artificial neural networks. The networks are trained on
simulations of the forward observing process, and take combinations of moments
of the galaxy images as inputs. A challenging peculiarity of this ML
application is the combination of the noisiness of the input features and the
requirements on the accuracy of the inverse regression. To address this issue,
the proposed training algorithm minimizes bias over multiple realizations of
individual source galaxies, reducing the sensitivity to properties of the
overall sample of source galaxies. Importantly, an observational selection
function of these source galaxies can be straightforwardly taken into account
via the weights. We first introduce key aspects of our approach using toy-model
simulations, and then demonstrate its potential on images mimicking Euclid
data. Finally, we analyze images from the GREAT3 challenge, obtaining
competitively low shear biases despite the use of a simple training set. We
conclude that the further development of ML approaches is of high interest to
meet the stringent requirements on the shear measurement in current and future
surveys. A demonstration implementation of our technique is publicly available.Comment: 31 pages, 26 figures, minor changes to match the version published in
A&A, code available at https://astro.uni-bonn.de/~mtewes/ml-shear-meas
Acute- or Subacute-Onset Lung Complications in Treating Patients With Rheumatoid Arthritis
AbstractRheumatoid arthritis (RA) is a common systemic disease that manifests as inflammatory arthritis of multiple joints and produces a wide variety of intrathoracic lesions, including pleural diseases, diffuse interstitial pneumonia, rheumatoid nodules, and airway disease. Patients treated for RA can have associated lung disease that commonly manifests as diffuse interstitial pneumonia, drug-induced lung injury, and infection. The purpose of this pictorial review is to illustrate the radiographic and clinical features of lung complications of acute or subacute onset in patients treated for RA and to show the computed tomography features of these complications
Optical-to-virial velocity ratios of local disk galaxies from combined kinematics and galaxy-galaxy lensing
In this paper, we measure the optical-to-virial velocity ratios Vopt/V200c of
disk galaxies in the Sloan Digital Sky Survey (SDSS) at a mean redshift of
= 0.07 and with stellar masses 10^9 M_sun < M_* < 10^11 M_sun. Vopt/V200c, the
ratio of the circular velocity measured at the virial radius of the dark matter
halo (\sim150 kpc) to that at the optical radius of the disk (\sim10 kpc), is a
powerful observational constraint on disk galaxy formation. It links galaxies
to their dark matter haloes dynamically and constrains the total mass profile
of disk galaxies over an order of magnitude in length scale. For this
measurement, we combine Vopt derived from the Tully-Fisher relation (TFR) from
Reyes et al. with V200c derived from halo masses measured with galaxy-galaxy
lensing. In anticipation of this combination, we use similarly-selected galaxy
samples for both the lensing and TFR analysis. For three M_* bins with
lensing-weighted mean stellar masses of 0.6, 2.7, and 6.5 x 10^10 M_sun, we
find halo-to-stellar mass ratios M_vir/M_* = 41, 23, and 26, with 1-sigma
statistical uncertainties of around 0.1 dex, and Vopt/V200c = 1.27\pm0.08,
1.39\pm0.06, 1.27\pm0.08 (1{\sigma}). Our results suggest that the dark matter
and baryonic contributions to the mass within the optical radius are
comparable, if the dark matter halo profile has not been significantly modified
by baryons. The results obtained in this work will serve as inputs to and
constraints on disk galaxy formation models, which will be explored in future
work. Finally, we note that this paper presents a new and improved galaxy shape
catalogue for weak lensing that covers the full SDSS DR7 footprint.Comment: Matches accepted version in MNRAS; added subsection on Sec. 6.3 and
expanded Table 4; 38 pages, 19 figure
Perfluorooctane Sulfonate (PFOS) and Related Perfluorinated Compounds in Human Maternal and Cord Blood Samples: Assessment of PFOS Exposure in a Susceptible Population during Pregnancy
Fluorinated organic compounds (FOCs), such as perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorooctane sulfonylamide (PFOSA), are widely used in the manufacture of plastic, electronics, textile, and construction material in the apparel, leather, and upholstery industries. FOCs have been detected in human blood samples. Studies have indicated that FOCs may be detrimental to rodent development possibly by affecting thyroid hormone levels. In the present study, we determined the concentrations of FOCs in maternal and cord blood samples. Pregnant women 17–37 years of age were enrolled as subjects. FOCs in 15 pairs of maternal and cord blood samples were analyzed by liquid chromatography–electrospray mass spectrometry coupled with online extraction. The limits of quantification of PFOS, PFOA, and PFOSA in human plasma or serum were 0.5, 0.5, and 1.0 ng/mL, respectively. The method enables the precise determination of FOCs and can be applied to the detection of FOCs in human blood samples for monitoring human exposure. PFOS concentrations in maternal samples ranged from 4.9 to 17.6 ng/mL, whereas those in fetal samples ranged from 1.6 to 5.3 ng/mL. In contrast, PFOSA was not detected in fetal or maternal samples, whereas PFOA was detected only in maternal samples (range, < 0.5 to 2.3 ng/mL, 4 of 15). Our results revealed a high correlation between PFOS concentrations in maternal and cord blood (r(2) = 0.876). However, we did not find any significant correlations between PFOS concentration in maternal and cord blood samples and age bracket, birth weight, or levels of thyroid-stimulating hormone or free thyroxine. Our study revealed that human fetuses in Japan may be exposed to relatively high levels of FOCs. Further investigation is required to determine the postnatal effects of fetal exposure to FOCs
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