Search Publications
Annealing a Follow-up Program: Improvement of the Dark Energy Figure of Merit for Optical Galaxy Cluster Surveys
Wu, Hao-Yi; Wechsler, Risa H.; Rozo, Eduardo
The precision of cosmological parameters derived from galaxy cluster surveys is limited by uncertainty in relating observable signals to cluster mass. We demonstrate that a small mass-calibration follow-up program can significantly reduce this uncertainty and improve parameter constraints, particularly when the follow-up targets are judiciously ch…
Time Evolution of Coronal Magnetic Helicity in the Flaring Active Region NOAA 10930
Jing, Ju; Wang, Haimin; Chae, Jongchul +2 more
To study the three-dimensional (3D) magnetic field topology and its long-term evolution associated with the X3.4 flare of 2006 December 13, we investigate the coronal relative magnetic helicity in the flaring active region (AR) NOAA 10930 during the time period of December 8-14. The coronal helicity is calculated based on the 3D nonlinear force-fr…
Brightest Cluster Galaxies and Core Gas Density in REXCESS Clusters
Donahue, Megan; Voit, G. Mark; Pierini, Daniele +7 more
We investigate the relationship between brightest cluster galaxies (BCGs) and their host clusters using a sample of nearby galaxy clusters from the Representative XMM-Newton Cluster Structure Survey. The sample was imaged with the Southern Observatory for Astrophysical Research in R band to investigate the mass of the old stellar population. Using…
SHELS: Testing Weak-Lensing Maps with Redshift Surveys
Geller, Margaret J.; Kurtz, Michael J.; Dell'Antonio, Ian P. +2 more
Weak-lensing surveys are emerging as an important tool for the construction of "mass-selected" clusters of galaxies. We evaluate both the efficiency and completeness of a weak-lensing selection by combining a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), with a weak-lensing map from the Deep Lens Survey (DLS). …
Unveiling the σ-Discrepancy in Infrared-Luminous Mergers. I. Dust and Dynamics
Rothberg, Barry; Fischer, Jacqueline
Mergers in the local universe present a unique opportunity for studying the transformations of galaxies in detail. Presented here are recent results, based on multi-wavelength, high-resolution imaging and medium resolution spectroscopy, which demonstrate how star formation and the presence of red supergiants and/or asymptotic giant branch stars ha…
Evidence of Explosive Evaporation in a Microflare Observed by Hinode/EIS
Ding, M. D.; Chen, F.
We present a detailed study of explosive chromospheric evaporation during a microflare which occurred on 2007 December 7 as observed with the Extreme-ultraviolet Imaging Spectrometer on board Hinode. We find temperature-dependent upflows for lines formed from 1.0 to 2.5 MK and downflows for lines formed from 0.05 to 0.63 MK in the impulsive phase …
Evidence for Spatially Compact Lyα Emission in z = 3.1 Lyα-emitting Galaxies
Gronwall, Caryl; Gawiser, Eric; Ciardullo, Robin +3 more
We present the results of a high spatial resolution study of the line emission in a sample of z = 3.1 Lyα-emitting galaxies (LAEs) in the Extended Chandra Deep Field-South. Of the eight objects with coverage in our HST/WFPC2 narrowband imaging, two have clear detections and two are barely detected (~2 σ). The clear detections are within ~0.5 kpc o…
Radius-expansion Burst Spectra from 4U 1728-34: An Ultracompact Binary?
Marshall, Herman; Galloway, Duncan K.; Yao, Yangsen +2 more
Recent theoretical and observational studies have shown that ashes from thermonuclear burning may be ejected during radius-expansion bursts, giving rise to photoionization edges in the X-ray spectra. We report a search for such features in Chandra spectra observed from the low-mass X-ray binary 4U 1728-34. We analyzed the spectra from four radius-…
Seismic Constraints on Interior Solar Convection
DeRosa, Marc L.; Duvall, Thomas L., Jr.; Hanasoge, Shravan M.
We constrain the velocity spectral distribution of global-scale solar convective cells at depth using techniques of local helioseismology. We calibrate the sensitivity of helioseismic waves to large-scale convective cells in the interior by analyzing simulations of waves propagating through a velocity snapshot of global solar convection via method…
Star Formation Histories in a Cluster Environment at z ~ 0.84
Ford, H. C.; Demarco, R.; Lidman, C. +8 more
We present a spectrophotometric analysis of galaxies belonging to the dynamically young, massive cluster RX J0152.7-1357 at z ~ 0.84, aimed at understanding the effects of the cluster environment on the star formation history (SFH) of cluster galaxies and the assembly of the red sequence (RS). We use VLT/FORS spectroscopy, ACS/WFC optical, and NTT…