Search Publications
The timing of martian valley network activity: Constraints from buffered crater counting
Head, James W.; Fassett, Caleb I.
Valley networks, concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity, have been cited as indicators that the climate of Mars differed significantly in the past from the present hyperarid cold desert conditions. Some researchers suggest that the change in climate was abrupt, while others favor a much more…
Size Evolution of the Most Massive Galaxies at 1.7 < z < 3 from GOODS NICMOS Survey Imaging
Dickinson, Mark; Conselice, Christopher J.; Bouwens, Rychard J. +3 more
We measure the sizes of 82 massive (M >= 1011 M⊙) galaxies at 1.7 <= z <= 3 utilizing deep HST NICMOS data taken in the GOODS North and South fields. Our sample is almost an order of magnitude larger than previous studies at these redshifts, providing the first statistical study of massive galaxy sizes at z > 2, c…
Galaxy merger morphologies and time-scales from simulations of equal-mass gas-rich disc mergers
Lotz, Jennifer M.; Primack, Joel R.; Jonsson, Patrik +1 more
A key obstacle to understanding the galaxy merger rate and its role in galaxy evolution is the difficulty in constraining the merger properties and time-scales from instantaneous snapshots of the real Universe. The most common way to identify galaxy mergers is by morphology, yet current theoretical calculations of the time-scales for galaxy distur…
Review of modeling of losses and sources of relativistic electrons in the outer radiation belt II: Local acceleration and loss
Meredith, Nigel P.; Shprits, Yuri Y.; Subbotin, Dmitriy A. +1 more
This paper focuses on the modeling of local acceleration and loss processes in the outer radiation belt. We begin by reviewing the statistical properties of waves that violate the first and second adiabatic invariants, leading to the loss and acceleration of high energy electrons in the outer radiation belt. After a brief description of the most c…
Evolution of the Bar Fraction in COSMOS: Quantifying the Assembly of the Hubble Sequence
Mobasher, Bahram; Schinnerer, Eva; Ellis, Richard S. +13 more
We have analyzed the redshift-dependent fraction of galactic bars over 0.2 < z < 0.84 in 2157 luminous face-on spiral galaxies from the COSMOS 2 deg2 field. Our sample is an order of magnitude larger than that used in any previous investigation, and is based on substantially deeper imaging data than that available from earlier wid…
The Solar Optical Telescope of Solar-B ( Hinode): The Optical Telescope Assembly
Kubo, M.; Ichimoto, K.; Tsuneta, S. +18 more
The Solar Optical Telescope (SOT) aboard the Solar-B satellite (Hinode) is designed to perform high-precision photometric and polarimetric observations of the Sun in visible light spectra (388 - 668 nm) with a spatial resolution of 0.2 - 0.3 arcsec. The SOT consists of two optically separable components: the Optical Telescope Assembly (OTA), consi…
Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology
Head, James W.; Fassett, Caleb I.
A new catalog of 210 open-basin lakes (lakes with outlet valleys) fed by valley networks shows that they are widely distributed in the Noachian uplands of Mars. In order for an outlet valley to form, water must have ponded in the basin to at least the level of the outlet. We use this relationship and the present topography to directly estimate the…
The Acs Survey of Globular Clusters. V. Generating a Comprehensive Star Catalog for each Cluster
Milone, Antonino P.; Anderson, Jay; Majewski, Steven R. +10 more
The ACS Survey of Globular Clusters has used Hubble Space Telescope's Wide-Field Channel to obtain uniform imaging of 65 of the nearest globular clusters to provide an extensive homogeneous data set for a broad range of scientific investigations. The survey goals required not only a uniform observing strategy, but also a uniform reduction strategy…
Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies
Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Bournaud, Frédéric
Gas-rich disks in the early universe are highly turbulent and have giant star-forming clumps. Models suggest that the clumps form by gravitational instabilities, and if they resist disruption by star formation, then they interact, lose angular momentum, and migrate to the center to form a bulge. Here we study the properties of the bulges formed by…
Polarization Calibration of the Solar Optical Telescope onboard Hinode
Ichimoto, K.; Tsuneta, S.; Suematsu, Y. +17 more
The Solar Optical Telescope (SOT) onboard Hinode aims to obtain vector magnetic fields on the Sun through precise spectropolarimetry of solar spectral lines with a spatial resolution of 0.2 - 0.3 arcsec. A photometric accuracy of 10−3 is achieved and, after the polarization calibration, any artificial polarization from crosstalk among S…