Search Publications
The Extended Star Formation History of the Andromeda Spheroid at 21 kpc on the Minor Axis
Ferguson, Henry C.; Brown, Thomas M.; Gilbert, Karoline M. +8 more
Using the Hubble Space Telescope Advanced Camera for Surveys, we have obtained deep optical images of a southeast minor-axis field in the Andromeda galaxy, 21 kpc from the nucleus. In both star counts and metallicity, this field represents a transition zone between the metal-rich, highly disturbed inner spheroid that dominates within 15 kpc and th…
A Statistical Study of Shear Motion of the Footpoints in Two-Ribbon Flares
Golub, Leon; Su, Yingna; Van Ballegooijen, Adriaan A.
We present a statistical investigation of shear motion of the ultraviolet (UV) or extreme-ultraviolet (EUV) footpoints in two-ribbon flares, using the high spatial resolution data obtained in 1998-2005 by TRACE. To do this study, we have selected 50 well-observed X and M class two-ribbon flares as our sample. All 50 of these flares are classified …
The Radio-Coronal Mass Ejection Event on 2001 April 15
Maia, Dalmiro Jorge Filipe; Gama, Ricardo; Mercier, Claude +3 more
On 2001 April 15, the Nançay radioheliograph observed fast-moving, expanding loops in images taken in the wavelength range between 164 and 432 MHz. We were able to follow the progression of the radio loops, starting from a few tenths to more than 1 Rsolar above the solar limb, with a time cadence of order seconds. The loops seen in radi…
Hubble Space Telescope Survey of Interstellar 12CO/13CO in the Solar Neighborhood
Gredel, R.; Lambert, D. L.; Federman, S. R. +2 more
We examine 20 diffuse and translucent Galactic sight lines and extract the column densities of the 12CO and 13CO isotopologues from their ultraviolet A-X absorption bands detected in archival Space Telescope Imaging Spectrograph data with λ/Δλ>=46,000. Five more targets with Goddard High-Resolution Spectrograph data are ad…
Gravitational Shear, Flexion, and Strong Lensing in Abell 1689
Massey, Richard; Goldberg, David M.; Leonard, Adrienne +1 more
We present a gravitational lensing analysis of the galaxy cluster Abell 1689, incorporating measurements of the weak shear, flexion, and strong lensing induced in background galaxies. This is the first time that a shapelet technique has been used to reconstruct the distribution of mass in this cluster and the first time that a flexion signal has b…
Spectroscopy of z ~ 6 i-Dropout Galaxies: Frequency of Lyα Emission and the Sizes of Lyα-emitting Galaxies1,
Rosati, P.; van der Wel, A.; Bouwens, R. J. +8 more
We report on deep spectroscopy, using LRIS on Keck I and FORS2 on the VLT, of a sample of 22 candidate z~6 Lyman break galaxies (LBGs) selected by the i775-z850>1.3 dropout criterion. Redshifts could be measured for eight objects. These redshifts are all in the range z=5.5-6.1, confirming the efficiency of the i775
Cosmological Effects of Powerful AGN Outbursts in Galaxy Clusters: Insights from an XMM-Newton Observation of MS 0735+7421
McNamara, B. R.; Nulsen, P. E. J.; Gitti, M. +1 more
We report on the results of an analysis of XMM-Newton observations of MS 0735+7421, the galaxy cluster that hosts the most energetic AGN outburst currently known. The previous Chandra image shows twin giant X-ray cavities (~200 kpc diameter) filled with radio emission and surrounded by a weak shock front. XMM data are consistent with these finding…
Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf
Luhman, K. L.; McLeod, Kim K.; Hartmann, Lee +7 more
We present observations of a circumstellar disk that is inclined close to edge-on around a young brown dwarf in the Taurus star-forming region. Using data obtained with SpeX at the NASA Infrared Telescope Facility, we find that the slope of the 0.8-2.5 µm spectrum of the brown dwarf 2MASS J04381486+2611399 cannot be reproduced with a photosp…
Constraints on the Cosmic Near-Infrared Background Excess from NICMOS Deep Field Observations
Fan, Xiaohui; Kennicutt, Robert C.; Rieke, Marcia +2 more
NICMOS observations of the resolved object fluxes in the Hubble Deep Field-North and the Hubble Ultra Deep Field are significantly below the fluxes attributed to a 1.4-1.8 µm near-infrared background excess (NIRBE) from previous low spatial resolution NIRS measurements. Tests placing sources in the NICMOS image with fluxes sufficient to acco…
The Distance to the Isolated Neutron Star RX J0720.4-3125
van Kerkwijk, M. H.; Anderson, J.; Kaplan, D. L.
We have used a set of dedicated astrometric data from the Hubble Space Telescope to measure the parallax and proper motion of the nearby neutron star RX J0720.4-3125. At each of eight epochs over 2 years, we used the High Resolution Camera of the Advanced Camera for Surveys to measure the position of the B=26.6 target to a precision of ~2 mas (~0.…