Search Publications
Discovery of Extreme Asymmetry in the Debris Disk Surrounding HD 15115
Kalas, Paul; Fitzgerald, Michael P.; Graham, James R.
We report the first scattered light detection of a dusty debris disk surrounding the F2 V star HD 15115 using the Hubble Space Telescope in the optical and Keck adaptive optics in the near-infrared. The most remarkable property of the HD 15115 disk relative to other debris disks is its extreme length asymmetry. The east side of the disk is detecte…
Features and Properties of Coronal Mass Ejection/Flare Current Sheets
Raymond, J. C.; Ko, Y. -K.; Lin, J. +3 more
Solar eruptions occur when magnetic energy is suddenly converted into heat and kinetic energy by magnetic reconnection in a current sheet (CS). It is often assumed that CSs are too thin to be observable because the electric resistivity ηe in CSs is taken to be very small. In this work, we show the implications for the CS thickness d est…
Numerical Investigation of the Homologous Coronal Mass Ejection Events from Active Region 9236
Gombosi, T. I.; Tóth, G.; Lugaz, N. +2 more
We present a three-dimensional compressible magneto-hydrodynamics (MHD) simulation of the three coronal mass ejections (CMEs) of 2000 November 24, originating from NOAA active region 9236. These three ejections, with velocities around 1200 km s-1 and associated with X-class flares, erupted from the Sun in a period of about 16.5 hr. In o…
The Surface Density Profile of NGC 6388: A Good Candidate for Harboring an Intermediate-Mass Black Hole
Dalessandro, E.; Valenti, E.; Ferraro, F. R. +3 more
We have used a combination of HST high-resolution and ground-based wide-field observations of the Galactic globular cluster NGC 6388 to derive its center of gravity, projected density profile, and central surface brightness profile. While the overall projected profiles are well fit by a King model with an intermediate concentration (c=1.8) and a s…
A Panchromatic Study of the Globular Cluster NGC 1904. I. The Blue Straggler Population
Valenti, E.; Sanna, N.; Beccari, G. +6 more
By combining high-resolution (HST/WFPC2) and wide-field ground-based (2.2 m ESO/WFI) and space (GALEX) observations, we have collected a multiwavelength photometric database (ranging from the far-UV to the near infrared) of the galactic globular cluster NGC 1904 (M79). The sample covers the entire cluster extension, from the very central regions u…
X-Ray Spectral Variation of η Carinae through the 2003 X-Ray Minimum
Hamaguchi, Kenji; Corcoran, Michael F.; Hillier, D. John +7 more
We report the results of an observing campaign on η Car around the 2003 X-ray minimum, mainly using the XMM-Newton observatory. These are the first spatially resolved X-ray monitoring observations of the stellar X-ray spectrum during the minimum. The hard X-ray emission, associated with the wind-wind collision (WWC) in the binary system, varied st…
Where the Blue Stragglers Roam: Searching for a Link between Formation and Environment
Sills, Alison; Knigge, Christian; Leigh, Nathan
The formation of blue stragglers is still not completely understood, particularly the relationship between formation environment and mechanism. We use a large, homogeneous sample of blue stragglers in the cores of 57 globular clusters to investigate the relationships between blue straggler populations and their environments. We use a consistent de…
The Stellar Population of Lyα-emitting Galaxies at z ~ 5.7
Cowie, Lennox L.; Huang, Jia-Sheng; Hu, Esther M. +3 more
We present a study of three Lyα-emitting galaxies (LAEs), selected via a narrowband survey in the GOODS northern field and spectroscopically confirmed to have redshifts of z~5.65. Using HST ACS and Spitzer IRAC data, we constrain the rest-frame UV-to-optical spectral energy distributions (SEDs) of the galaxies. Fitting stellar population synthesis…
A More Fundamental Plane
Treu, Tommaso; Koopmans, Léon V. E.; Bolton, Adam S. +2 more
We combine strong-lensing masses with SDSS stellar velocity dispersions and HST ACS effective (half-light) radii for 36 lens galaxies from the Sloan Lens ACS (SLACS) Survey to study the mass dependence of mass-dynamical structure in early-type galaxies. We find that over a 180-390 km s-1 range in velocity dispersion, structure is indepe…
Old and Young Bulges in Late-Type Disk Galaxies
Carollo, C. M.; Scarlata, C.; Stiavelli, M. +2 more
We use HST ACS and NICMOS imaging to study the inner B-I and I-H colors of nine late-type spiral galaxies, which we interpret on the basis of different star formation histories. The colors and scale lengths of the bulges of these late-type systems are correlated with those of the disks in which they are embedded. We find that in about half of the …