Search Publications
Clues to Active Galactic Nucleus Growth from Optically Variable Objects in the Hubble Ultra Deep Field
Koekemoer, A. M.; Mobasher, B.; Hathi, N. P. +9 more
We present a photometric search for objects with point-source components that are optically variable on timescales of weeks to months in the Hubble Ultra Deep Field (HUDF) to i'AB=28.0 mag. The data are split into four substacks of approximately equal exposure times. Objects exhibiting the signature of optical variability are…
Supergranule Superrotation Identified as a Projection Effect
Hathaway, D. H.; Cuntz, M.; Williams, P. E.
Previous measurements of the rotation rate of the supergranule Doppler velocity pattern revealed surprising characteristics: (1) the pattern rotates faster than the plasma at the surface, and, at each latitude, it rotates faster than the plasma at any level below the surface (superrotation), (2) larger cells rotate more rapidly than smaller cells,…
Hubble Space Telescope NICMOS Polarization Measurements of OMC-1
Schultz, A. S. B.; Colgan, Sean W. J.; Burton, Michael G. +2 more
We present 2 µm polarization measurements of positions in the IRc2 and BN regions of the Orion Molecular Cloud (OMC-1) made with NICMOS Camera 2 (0.2" resolution) on the Hubble Space Telescope. Our results are as follows: BN is ~29% polarized by dichroic absorption and appears to be the illuminating source for most of the nebulosity to its n…
Spatially Resolved Narrow-Line Region Kinematics in Active Galactic Nuclei
Shields, Joseph C.; Greene, Jenny E.; Pogge, Richard W. +4 more
We have analyzed Hubble Space Telescope spectroscopy of 24 nearby active galactic nuclei (AGNs) to investigate spatially resolved gas kinematics in the narrow-line region (NLR). These observations effectively isolate the nuclear line profiles on less than 100 pc scales and are used to investigate the origin of the substantial scatter between the w…
ACS Photometry of the Remote M31 Globular Cluster B514
Bellazzini, M.; Galleti, S.; Federici, L. +2 more
We present deep F606W, F814W ACS photometry of the recently discovered globular cluster B514, the outermost known globular in the M31 galaxy. The cluster appears quite extended, and member stars are unequivocally identified out to ~200 pc from the center. The color-magnitude diagram reveals a steep red giant branch (RGB), and a horizontal branch e…
The Remarkable Be Star HD 110432 (BZ Crucis)
Smith, Myron A.; Balona, Luis
HD 110432 (B1e) has gained considerable recent attention because it is a hard, variable X-ray source with local absorption and also because its optical spectrum is affected by an extensive Be disk. From time-serial echelle data obtained over 2 weeks during 2005 January and February, we have discovered several remarkable characteristics in the star…
Electron Density and Turbulence Gradients within the Extended Atmosphere of the M Supergiant Betelgeuse (α Orionis)
Harper, Graham M.; Brown, Alexander
The extended atmosphere of the M supergiant Betelgeuse is complex with cool plasma dominating the structure by mass and small amounts of embedded hotter chromospheric plasma. A major challenge is to understand the interrelationship and juxtaposition of these different components, which in turn may provide clues to the nature of the process of nonr…
Dynamical Masses in Luminous Infrared Galaxies
Rieke, G. H.; Hinz, J. L.
We have studied the dynamics and masses of a sample of 10 nearby luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs, respectively) using 2.3 µm 12CO-absorption line spectroscopy and near-infrared H- and Ks-band imaging. By combining velocity dispersions derived from the spectroscopy, disk scale lengths obtai…
The Low-Mass Pre-Main-Sequence Population of the Stellar Association LH 52 in the Large Magellanic Cloud Discovered with Hubble Space Telescope WFPC2 Observations
Henning, Th.; Brandner, W.; Gouliermis, D.
We report on the serendipitous discovery of ~500 low-mass candidate pre-main-sequence (PMS) stars in the vicinity of the stellar association LH 52 in the Large Magellanic Cloud. We present evidence that the red faint sequence of these stars seen in the CMD of LH 52 from Hubble Space Telescope (HST) WFPC2 observations belongs only to the associatio…
Solar Wind Electric Fields in the Ion Cyclotron Frequency Range
Bale, S. D.; Horbury, T. S.; Reme, H. +2 more
Measurements of fluctuations of electric fields in the frequency range from a fraction of 1 to 12.5 Hz are presented and corrected for the Lorentz transformation of magnetic fluctuations to give the electric fields in the plasma frame. The electric fields are large enough to provide the dominant force on the ions of the solar wind in the region ne…