Search Publications
The Dynamical Generation of Current Sheets in Astrophysical Plasma Turbulence
Howes, Gregory G.
Turbulence profoundly affects particle transport and plasma heating in many astrophysical plasma environments, from galaxy clusters to the solar corona and solar wind to Earth's magnetosphere. Both fluid and kinetic simulations of plasma turbulence ubiquitously generate coherent structures, in the form of current sheets, at small scales, and the l…
Neptune's Dynamic Atmosphere from Kepler K2 Observations: Implications for Brown Dwarf Light Curve Analyses
Fortney, Jonathan J.; Wong, Michael H.; Morales-Juberias, Raul +9 more
Observations of Neptune with the Kepler Space Telescope yield a 49 day light curve with 98% coverage at a 1 minute cadence. A significant signature in the light curve comes from discrete cloud features. We compare results extracted from the light curve data with contemporaneous disk-resolved imaging of Neptune from the Keck 10-m telescope at 1.65 …
Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. IV. Kinematic Profiles and Average Masses of Blue Straggler Stars
Anderson, J.; van der Marel, R. P.; Bellini, A. +3 more
We make use of the Hubble Space Telescope proper-motion catalogs derived by Bellini et al. to produce the first radial velocity dispersion profiles σ (R) for blue straggler stars (BSSs) in Galactic globular clusters (GCs), as well as the first dynamical estimates for the average mass of the entire BSS population. We show that BSSs typically have l…
Evidence for the Rapid Formation of Low-mass Early-type Galaxies in Dense Environments
Jordán, Andrés; Côté, Patrick; Peng, Eric W. +6 more
We explore the environmental dependence of star formation timescales in low-mass galaxies using the [α/Fe] abundance ratio as an evolutionary clock. We present integrated [α/Fe] measurements for 11 low-mass ({M}\star ∼ {10}9 {M}⊙ ) early-type galaxies (ETGs) with a large range of cluster-centric distance in the Vir…
Reconnection Properties of Large-scale Current Sheets During Coronal Mass Ejection Eruptions
Lynch, B. J.; Guidoni, S. E.; Edmondson, J. K. +1 more
We present a detailed analysis of the properties of magnetic reconnection at large-scale current sheets (CSs) in a high cadence version of the Lynch & Edmondson 2.5D MHD simulation of sympathetic magnetic breakout eruptions from a pseudostreamer source region. We examine the resistive tearing and break-up of the three main CSs into chains of X…
Imaging Prominence Eruptions out to 1 AU
Howard, Russell A.; Linton, Mark G.; Wood, Brian E.
Views of two bright prominence eruptions trackable all the way to 1 AU are here presented, using the heliospheric imagers on the Solar TErrestrial RElations Observatory (STEREO) spacecraft. The two events first erupted from the Sun on 2011 June 7 and 2012 August 31, respectively. Only these two examples of clear prominence eruptions observable thi…
Luminosity Dependence and Redshift Evolution of Strong Emission-Line Diagnostics in Star-Forming Galaxies
Barger, A. J.; Cowie, L. L.; Songaila, A.
We examine the redshift evolution of standard strong emission-line diagnostics for Hβ-selected star-forming galaxies using the local SDSS sample and a new z=0.2{--}2.3 sample obtained from Hubble Space Telescope WFC3 grism and Keck DEIMOS and MOSFIRE data. We use the SDSS galaxies to show that there is a systematic dependence of the strong emissio…
Constraints on Photoionization Feedback from Number Counts of Ultra-faint High-redshift Galaxies in the Frontier Fields
Castellano, M.; Santini, P.; Merlin, E. +11 more
We exploit a sample of ultra-faint high-redshift galaxies (demagnified Hubble Space Telescope, HST, H 160 magnitude > 30) in the Frontier Fields clusters A2744 and M0416 to constrain a theoretical model for the UV luminosity function in the presence of photoionization feedback. The objects have been selected on the basis of accurate …
Discovery of an Inner Disk Component around HD 141569 A
Stark, Christopher C.; Weinberger, Alycia J.; Nesvold, Erika R. +20 more
We report the discovery of a scattering component around the HD 141569 A circumstellar debris system, interior to the previously known inner ring. The discovered inner disk component, obtained in broadband optical light with Hubble Space Telescope/Space Telescope Imaging Spectrograph coronagraphy, was imaged with an inner working angle of 0.″25, a…
The Mysterious Case of the Solar Argon Abundance near Sunspots in Flares
Doschek, G. A.; Warren, H. P.
Recently we discussed an enhancement of the abundance of Ar xiv relative to Ca xiv near a sunspot during a flare, observed in spectra recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. The observed Ar xiv/Ca xiv ratio yields an argon/calcium abundance ratio seven times greater than expected from the photospher…