Search Publications
The ACS LCID Project. XI. On the Early Time Resolution of SFHs of Local Group Dwarf Galaxies: Comparing the Effects of Reionization in Models with Observations
Dolphin, Andrew; Skillman, Evan; Monelli, Matteo +10 more
The analysis of the early star formation history (SFH) of nearby galaxies, obtained from their resolved stellar populations, is relevant as a test for cosmological models. However, the early time resolution of observationally derived SFHs is limited by several factors. Thus, direct comparison of observationally derived SFHs with those derived from…
Cosmological Parameters from CMB Maps without Likelihood Approximation
Eriksen, H. K.; Wehus, I. K.; Racine, B. +1 more
We propose an efficient Bayesian Markov chain Monte Carlo (MCMC) algorithm for estimating cosmological parameters from cosmic microwave background (CMB) data without the use of likelihood approximations. It builds on a previously developed Gibbs sampling framework that allows for exploration of the joint CMB sky signal and power spectrum posterior…
Relaxation Processes within Flux Ropes in Solar Wind
Perri, S.; Bruno, R.; Carbone, V. +3 more
Flux ropes are localized structures in space plasma whose tube-like organized magnetic configuration can be well approximated by a force-free field model. Both numerical simulations and simple models suggest that the ideal magnetohydrodynamics (MHD) can relax toward a minimum energy state, where magnetic helicity is conserved, characterized by for…
Detection of a Dearth of Stars with Zero Angular Momentum in the Solar Neighborhood
Bovy, Jo; Hunt, Jason A. S.; Carlberg, Raymond G.
We report on the detection in the combined Gaia-DR1/RAVE data of a lack of disk stars in the solar neighborhood with velocities close to zero angular momentum. We propose that this may be caused by the scattering of stars with very low angular momentum onto chaotic, halo-type orbits when they pass through the Galactic nucleus. We model the effect …
Projection Effects in Coronal Dimmings and Associated EUV Wave Event
Magdalenić, J.; Temmer, M.; Veronig, A. M. +2 more
We investigate the high-speed (v > 1000 km s-1) extreme-ultraviolet (EUV) wave associated with an X1.2 flare and coronal mass ejection (CME) from NOAA active region 11283 on 2011 September 6 (SOL2011-09-06T22:12). This EUV wave features peculiar on-disk signatures in particular, we observe an intermittent “disappearance” of the front…
Solar Energetic Particle Event Onsets: Far Backside Solar Sources and the East-West Hemispheric Asymmetry
Kahler, S. W.
Prompt onsets and short rise times to peak intensities Ip have been noted in a few solar energetic (E > 10 MeV) particle (SEP) events from far behind (≥25°) the west limb. We discuss 15 archival and recent examples of these prompt events, giving their source longitudes, onset and rise times, and associated coronal mass ejection (CME) speeds. Th…
Multi-wavelength Lens Reconstruction of a Planck and Herschel-detected Star-bursting Galaxy
Baes, Maarten; Fu, Hai; Clements, David L. +21 more
We present a source-plane reconstruction of a Herschel and Planck-detected gravitationally lensed dusty star-forming galaxy (DSFG) at z = 1.68 using Hubble, Submillimeter Array (SMA), and Keck observations. The background submillimeter galaxy (SMG) is strongly lensed by a foreground galaxy cluster at z = 0.997 and appears as an arc with a length o…
SEEDS Direct Imaging of the RV-detected Companion to V450 Andromedae, and Characterization of the System
Kuzuhara, M.; Tamura, M.; Ishii, M. +49 more
We report the direct imaging detection of a low-mass companion to a young, moderately active star V450 And, that was previously identified with the radial velocity (RV) method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE …
Chandra View of Magnetically Confined Wind in HD191612: Theory Versus Observations
Zhekov, Svetozar A.; Nazé, Yaël; ud-Doula, Asif
High-resolution spectra of the magnetic star HD 191612 were acquired using the Chandra X-ray Observatory at both maximum and minimum emission phases. We confirm the flux and hardness variations previously reported with XMM-Newton, demonstrating the high repeatability of the behavior of HD 191612 over a decade. The line profiles appear typical for …
The ACS Fornax Cluster Survey. XII. Diffuse Star Clusters in Early-type Galaxies
Jordán, Andrés; Côté, Patrick; Peng, Eric W. +5 more
Diffuse star clusters (DSCs) are old and dynamically hot stellar systems that have lower surface brightness and more extended morphology than globular clusters (GCs). Using the images from Hubble Space Telescope (HST)/ACS Fornax Cluster Survey, we find that 12 out of 43 early-type galaxies (ETGs) in the Fornax Cluster host significant numbers of D…