Search Publications
GREAT3 results - I. Systematic errors in shear estimation and the impact of real galaxy morphology
Zhang, Jun; Hogg, David W.; Gavazzi, Raphaël +40 more
We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included simulated space- and …
The VLT-FLAMES Tarantula Survey. XXII. Multiplicity properties of the B-type stars
Howarth, I. D.; Dufton, P. L.; Simón-Díaz, S. +7 more
We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal absorption lines for each of our targets. Object…
Growth of cosmic structure: Probing dark energy beyond expansion
Mandelbaum, Rachel; Sehgal, Neelima; Connolly, Andrew +18 more
The quantity and quality of cosmic structure observations have greatly accelerated in recent years, and further leaps forward will be facilitated by imminent projects. These will enable us to map the evolution of dark and baryonic matter density fluctuations over cosmic history. The way that these fluctuations vary over space and time is sensitive…
Full-Sun observations for identifying the source of the slow solar wind
Warren, Harry P.; Ugarte-Urra, Ignacio; Brooks, David H.
Fast (>700 km s-1) and slow (~400 km s-1) winds stream from the Sun, permeate the heliosphere and influence the near-Earth environment. While the fast wind is known to emanate primarily from polar coronal holes, the source of the slow wind remains unknown. Here we identify possible sites of origin using a slow solar wind s…
Gravitational Lens Modeling with Basis Sets
Amara, Adam; Refregier, Alexandre; Birrer, Simon
We present a strong lensing modeling technique based on versatile basis sets for the lens and source planes. Our method uses high performance Monte Carlo algorithms, allows for an adaptive build up of complexity, and bridges the gap between parametric and pixel based reconstruction methods. We apply our method to a Hubble Space Telescope image of …
A statistical study of EMIC waves observed by Cluster: 1. Wave properties
André, M.; Klecker, B.; Kistler, L. M. +6 more
Electromagnetic ion cyclotron (EMIC) waves are an important mechanism for particle energization and losses inside the magnetosphere. In order to better understand the effects of these waves on particle dynamics, detailed information about the occurrence rate, wave power, ellipticity, normal angle, energy propagation angle distributions, and local …
A Massive, Distant Proto-cluster at z = 2.47 Caught in a Phase of Rapid Formation?
Sanders, D. B.; Treister, E.; Cooray, A. +6 more
Numerical simulations of cosmological structure formation show that the universe’s most massive clusters, and the galaxies living in those clusters, assemble rapidly at early times (2.5\lt z\lt 4). While more than 20 proto-clusters have been observed at z≳ 2 based on associations of 5-40 galaxies around rare sources, the observational evidence for…
Widespread surface weathering on early Mars: A case for a warmer and wetter climate
Mangold, Nicolas; Bibring, Jean-Pierre; Poulet, François +2 more
Early Mars (>3 Ga) underwent aqueous alteration as evidenced by fluvial/lacustrine morphologies and the recent discovery of widespread hydrous clays. Despite compelling evidence for diverse and localized aqueous environments, the possibility for sustained liquid water globally on the martian surface and over geological timescales is still highl…
Noise-based Detection and Segmentation of Nebulous Objects
Ichikawa, Takashi; Akhlaghi, Mohammad
A noise-based non-parametric technique for detecting nebulous objects, for example, irregular or clumpy galaxies, and their structure in noise is introduced. “Noise-based” and “non-parametric” imply that this technique imposes negligible constraints on the properties of the targets and that it employs no regression analysis or fittings. The sub-sk…
Planck data reconsidered
Spergel, David N.; Hložek, Renée; Flauger, Raphael
The tension between the best fit parameters derived by the Planck team and a number of other astronomical measurements suggests either systematics in the astronomical measurements, systematics in the Planck data, the need for new physics, or a combination thereof. We reanalyze the Planck data and find that the 217 GHz ×217 GHz detector set spectru…