65 research outputs found
Weak Gravitational Lensing Systematics from Image Combination
Extremely accurate shape measurements of galaxy images are needed to probe dark energy properties with weak gravitational lensing surveys. To increase survey area with a fixed observing time and pixel count, images from surveys such as the Wide Field Infrared Survey Telescope (WFIRST) or Euclid will necessarily be undersampled and therefore distorted by aliasing. Oversampled, unaliased images can be obtained by combining multiple, dithered exposures of the same source with a suitable reconstruction algorithm. Any such reconstruction must minimally distort the reconstructed images for weak lensing analyses to be unbiased. In this paper, we use the image combination (IMCOM) algorithm of Rowe, Hirata, and Rhodes to investigate the effect of image combination on shape measurements (size and ellipticity). We simulate dithered images of sources with varying amounts of ellipticity and undersampling, reconstruct oversampled output images from them using IMCOM, and measure shape distortions in the output. Our simulations show that IMCOM creates no significant distortions when the relative offsets between dithered images are precisely known. Distortions increase with the uncertainty in those offsets, but become problematic only with relatively poor astrometric precision; e.g., for images similar to those from the Astrophysics Focused Telescope Asset (AFTA) implementation of WFIRST, combining eight undersampled images (sampling ratio Q = 1) with highly pessimistic uncertainty in astrometric registration (σ_d ∼ 10^(-3) pixels) yields an rms shear error of O(10^(-4)). Our analysis pipeline is adapted from that of the Precision Projector Laboratory—a joint project between NASA Jet Propulsion Laboratory and Caltech that characterizes image sensors using laboratory emulations of astronomical data
Phase II of the Keck Planet Imager and characterizer: system-level laboratory characterization and preliminary on-sky commissioning
Observing Exoplanets with High-dispersion Coronagraphy. II. Demonstration of an Active Single-mode Fiber Injection Unit
Keck Planet Imager and Characterizer: concept and phased implementation
The Keck Planet Imager and Characterizer (KPIC) is a cost-effective upgrade path to the W.M. Keck observatory (WMKO) adaptive optics (AO) system, building on the lessons learned from first and second-generation extreme AO (ExAO) coronagraphs. KPIC will explore new scientific niches in exoplanet science, while maturing critical technologies and systems for future ground-based (TMT, EELT, GMT) and space-based planet imagers (HabEx, LUVOIR). The advent of fast low-noise IR cameras (IR-APD, MKIDS, electron injectors), the rapid maturing of efficient wavefront sensing (WFS) techniques (Pyramid, Zernike), small inner working angle (IWA) coronagraphs (e.g., vortex) and associated low-order wavefront sensors (LOWFS), as well as recent breakthroughs in high contrast high resolution spectroscopy, open new direct exoplanet exploration avenues that are complementary to planet imagers such as VLT-SPHERE and the Gemini Planet Imager (GPI). For instance, the search and detailed characterization of planetary systems on solar-system scales around late-type stars, mostly beyond SPHERE and GPI's reaches, can be initiated now at WMKO
The development of HISPEC for Keck and MODHIS for TMT: science cases and predicted sensitivities
HISPEC is a new, high-resolution near-infrared spectrograph being designed
for the W.M. Keck II telescope. By offering single-shot, R=100,000 between 0.98
- 2.5 um, HISPEC will enable spectroscopy of transiting and non-transiting
exoplanets in close orbits, direct high-contrast detection and spectroscopy of
spatially separated substellar companions, and exoplanet dynamical mass and
orbit measurements using precision radial velocity monitoring calibrated with a
suite of state-of-the-art absolute and relative wavelength references. MODHIS
is the counterpart to HISPEC for the Thirty Meter Telescope and is being
developed in parallel with similar scientific goals. In this proceeding, we
provide a brief overview of the current design of both instruments, and the
requirements for the two spectrographs as guided by the scientific goals for
each. We then outline the current science case for HISPEC and MODHIS, with
focuses on the science enabled for exoplanet discovery and characterization. We
also provide updated sensitivity curves for both instruments, in terms of both
signal-to-noise ratio and predicted radial velocity precision.Comment: 25 pages, 9 figures. To appear in the Proceedings of SPIE: Techniques
and Instrumentation for Detection of Exoplanets XI, vol. 12680 (2023
A Strategy to Locate Fixed Points and Global Perturbations of ODE’s: Mixing Topology with Metric Conditions
Identification of regulatory variants associated with genetic susceptibility to meningococcal disease.
Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes
Asymptotic Behavior of the Potential and Existence of a Periodic Solution for a Second Order Differential Equation
We establish the existence of a 2π-periodic solution for a second order semilinear equation in terms of the asymptotic behavior of the potential of the nonlinearity. Our condition includes the case in which the nonlinearity is asymptotically linear with slopes at infinity of the jumping nonlinearity between the positive axes and the first Fucik spectrum curve (see [S. Fucik (1976). Boundary value problems with jumping nonlinearities. Casopis Pest. Mat., 101, 69–87.]). Our results extend those of [L. Fernandez and F. Zanolin (1988). Periodic solutions of a second order differential equation with one-sided growth restriction on the restoning term. Arch. Math., 51, 151–163.]
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