Search Publications
The Galaxy Luminosity Function at z ~= 1 in the HUDF: Probing the Dwarf Population
Panagia, N.; di Serego Alighieri, S.; Moustakas, L. A. +10 more
We present a catalog of spectrophotometric redshifts for 1308 galaxies from the Grism ACS Program for Extragalactic Science (GRAPES) observations with the Hubble Space Telescope. These low-resolution spectra between 6000 Å and 9500 Å are supplemented with U, J, H, and Ks data from various facilities, resulting in redshifts computed with…
New Physical Insight on the Changes in Magnetic Topology during Coronal Mass Ejections: Case Studies for the 2002 April 21 and August 24 Events
Lugaz, Noé; Roussev, Ilia I.; Sokolov, Igor V.
In order to investigate the dynamics of the coronal mass ejections on 2002 April 21 and August 24, we performed a series of numerical simulations with an ad hoc driver for the eruptions. The resulting evolution of the solar corona for each event was followed by means of three-dimensional MHD simulations. We used SOHO MDI data to set realistic boun…
Low-Mass X-Ray Binaries and Globular Clusters in Centaurus A
Sarazin, Craig L.; Jordán, Andrés; Raychaudhury, Somak +19 more
We present results of Hubble Space Telescope and Chandra X-Ray Observatory observations of globular clusters (GCs) and low-mass X-ray binaries (LMXBs) in the central regions of Centaurus A. Out of 440 GC candidates, we find 41 host X-ray point sources that are most likely LMXBs. We fit King models to our GC candidates in order to measure their str…
Color, Rotation, Age, and Chromospheric Activity Correlations in Late-Type Main-Sequence Stars
Cassatella, Angelo; Cardini, Daniela
A study of the rotation-activity-age relationships in a large sample of single late-type main-sequence stars is carried out, based on rotation period data from the literature, on our measurements of the Mg II k line chromospheric flux in IUE high-resolution spectra, and on Hipparcos parallaxes. The analysis of the rotation period data of open clus…
The Evolution of Galaxies in X-Ray-luminous Groups
Mulchaey, John S.; Fassnacht, Christopher D.; Lubin, Lori M. +1 more
We investigate the galaxy populations in seven X-ray-selected, intermediate-redshift groups (0.2<z<0.6). Overall, the galaxy populations in these systems are similar to those in clusters at the same redshift; they have large fractions of early-type galaxies (fe~70%) and small fractions of galaxies with significant star formation (…
The Spatio-Kinematical Structure and Distance of the Preplanetary Nebula IRAS 19134+2131
Sahai, Raghvendra; Morris, Mark; Imai, Hiroshi
Using the Very Long Baseline Array at six epochs, we have observed H2O maser emission in the preplanetary nebula IRAS 19134+2131 (I19134), in which the H2O maser spectrum has two groups of emission features separated in radial velocity by ~100 km s-1. We also obtained optical images of I19134 with the Hubble Space …
Spitzer Observations of Transient, Extended Dust in Two Elliptical Galaxies: New Evidence of Recent Feedback Energy Release in Galactic Cores
Brighenti, Fabrizio; Mathews, William G.; Temi, Pasquale
Spitzer observations of extended dust in two optically normal elliptical galaxies provide a new confirmation of buoyant feedback outflow in the hot gas atmospheres around these galaxies. AGN feedback energy is required to prevent wholesale cooling and star formation in these group-centered galaxies. In NGC 5044 we observe interstellar (presumably …
Born-Again Protoplanetary Disk around Mira B
Lloyd, J. P.; Tuthill, P. G.; Packham, C. +6 more
The Mira AB system is a nearby (~107 pc) example of a wind accreting binary star system. In this class of system, the wind from a mass-losing red giant star (Mira A) is accreted onto a companion (Mira B), as indicated by an accretion shock signature in spectra at ultraviolet and X-ray wavelengths. Using novel imaging techniques, we report the dete…
Probing the Large-Scale Plasma Structure of the Solar Corona with Faraday Rotation Measurements
Spangler, Steven R.; Ingleby, Laura D.; Whiting, Catherine A.
Faraday rotation measurements of the solar corona made with the VLA at frequencies of 1465 and 1665 MHz are reported. The measurements were made along 20 lines of sight to 19 extragalactic radio sources in 2005 March and April. The closest heliocentric distances of the lines of sight ranged from 5.6 to 9.7 Rsolar. Measured rotation meas…
Braiding-induced Interchange Reconnection of the Magnetic Field and the Width of Solar Coronal Loops
Schrijver, Carolus J.
The random walk of the footpoints of coronal loops in the rapidly evolving solar granulation is expected to cause braiding of the field, which in turn should lead to a multitude of coronal reconnection events. Consequently, plasma volumes in coronal loops should repeatedly be spliced onto parts of other such loop structures within their lifetime i…