Search Publications
Longitudinal Magnetic Field Changes Accompanying Solar Flares
Harvey, J. W.; Sudol, J. J.
We have used Global Oscillation Network Group (GONG) magnetograms to characterize the changes in the photospheric longitudinal magnetic field during 15 X-class solar flares. An abrupt, significant, and persistent change in the magnetic field occurred in at least one location within the flaring active region during each event. We have identified a …
Evolution since z = 1 of the Morphology-Density Relation for Galaxies
Smith, Graham P.; Treu, Tommaso; Ellis, Richard S. +2 more
We measure the morphology-density relation of galaxies at z=1 across the full 3 orders of magnitude in projected galaxy density available in low-redshift studies. Our study adopts techniques that are comparable with those applied at lower redshifts, allowing a direct investigation of how the morphological segregation of galaxies has evolved over t…
A Deep Chandra Survey of the Globular Cluster 47 Tucanae: Catalog of Point Sources
Heinke, C. O.; Cohn, H. N.; Lugger, P. M. +5 more
We have detected 300 X-ray sources within the half-mass radius (2.79 arcmin) of the globular cluster 47 Tucanae in a deep (281 ks) Chandra exposure. We perform photometry and simple spectral fitting for our detected sources and construct luminosity functions, X-ray color-magnitude, and color-color diagrams. Eighty-seven X-ray sources show variabil…
Discovery of an X-Ray-luminous Galaxy Cluster at z=1.4
Böhringer, H.; Rosati, P.; Schwope, A. +4 more
We report the discovery of a massive, X-ray-luminous cluster of galaxies at z=1.393, the most distant X-ray-selected cluster found to date. XMMU J2235.3-2557 was serendipitously detected as an extended X-ray source in an archival XMM-Newton observation of NGC 7314. VLT FORS2 R- and z-band snapshot imaging reveals an overdensity of red galaxies in …
Super-Helium-rich Populations and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters
Joo, Seok-Joo; Han, Sang-Il; Ree, Chang H. +7 more
Recent observations for the color-magnitude diagrams (CMDs) of the massive globular cluster ω Centauri have shown that it has a striking double main sequence (MS), with a minority population of bluer and fainter MS stars well separated from a majority population of MS stars. Here we confirm, with the most up-to-date Y2 isochrones, that …
Keck Spectroscopy of Distant GOODS Spheroidal Galaxies: Downsizing in a Hierarchical Universe
Treu, Tommaso; van Dokkum, Pieter G.; Ellis, Richard S. +1 more
We analyze the evolution of the fundamental plane for 141 field spheroidal galaxies in the redshift range 0.2<z<1.2, selected morphologically to a magnitude limit F850LP=22.43 in the northern field of the Great Observatories Origins Deep Survey. For massive galaxies, we find that the bulk of the star formation was completed prior to z=2. How…
A Full View of EIT Waves
Chen, P. F.; Shibata, K.; Fang, C.
Early observations by the EUV Imaging Telescope (EIT) on the Solar and Heliospheric Observatory indicated that propagating diffuse wave fronts, now conventionally referred to as ``EIT waves,'' can often be seen on the solar disk with a propagation velocity several times smaller than that of Hα Moreton waves. They are almost always associated with …
AGN Host Galaxies at z~0.4-1.3: Bulge-dominated and Lacking Merger-AGN Connection
Jogee, S.; Hornschemeier, A. E.; Alexander, D. M. +13 more
We investigate morphological structure parameters and local environments of distant moderate-luminosity active galactic nucleus (AGN) host galaxies in the overlap between the HST/ACS observations of the Great Observatories Origins Deep Survey (GOODS) and the two Chandra Deep Fields. We compute near-neighbor counts and BViz asymmetry (A) and concen…
Eruption of a Kink-unstable Filament in NOAA Active Region 10696
van Driel-Gesztelyi, Lidia; Démoulin, Pascal; Török, Tibor +2 more
We present rapid-cadence Transition Region and Coronal Explorer (TRACE) observations that show evidence of a filament eruption from NOAA active region 10696, accompanied by an X2.5 flare, on 2004 November 10. The eruptive filament, which manifests as a fast coronal mass ejection some minutes later, rises as a kinking structure with an apparently e…
An Overabundance of Transient X-Ray Binaries within 1 Parsec of the Galactic Center
Brandt, W. N.; Muno, M. P.; Baganoff, F. K. +4 more
During 5 years of Chandra observations, we have identified seven X-ray transients located within 23 pc of Sgr A*. These sources each vary in luminosity by more than a factor of 10 and have peak X-ray luminosities greater than 5×1033 ergs s-1, which strongly suggests that they are accreting black holes or neutron stars. The pe…