Search Publications
ISOGAL-DENIS detection of red giants with weak mass loss in the Galactic bulge
Price, S. D.; Alard, C.; Blommaert, J. A. D. L. +21 more
The ISOGAL project is a survey of the stellar populations, structure, and recent star formation history of the inner disk and bulge of the Galaxy. ISOGAL combines 15 mu m and 7 mu m ISOCAM observations with DENIS IJK_s data to determine the nature of a source and the interstellar extinction. In this paper we report an ISOGAL study of a small field…
The Photometry of Undersampled Point-Spread Functions
Lauer, Tod R.
An undersampled point-spread function (PSF) may interact with the microstructure of a solid-state detector such that the total flux detected can depend sensitively on where the PSF center falls within a pixel. Such intrapixel sensitivity variations will not be corrected by flat-field calibration and may limit the accuracy of stellar photometry con…
Filtration of interstellar hydrogen in the two-shock heliospheric interface: Inferences on the local interstellar cloud electron density
Gloeckler, George; Geiss, Johannes; Lallement, Rosine +3 more
The solar system is moving through the partially ionized local interstellar cloud (LIC). The ionized matter of the LIC interacts with the expanding solar wind forming the heliospheric interface. The neutral component (interstellar atoms) penetrates through the heliospheric interface into the heliosphere, where it is measured directly ``in situ'' a…
NICMOS Imaging of the Dusty Microjansky Radio Source VLA J123642+621331 at z = 4.424
Stern, D.; Spinrad, H.; Windhorst, R. A. +3 more
We present the discovery of a radio galaxy at a likely redshift of z=4.424 in one of the flanking fields of the Hubble Deep Field (HDF). Radio observations with the Very Large Array and MERLIN centered on the HDF yielded a complete sample of microjansky radio sources, of which about 20% have no optical counterpart to I<=25 mag. In this Letter, …
A Bayesian classifier for photometric redshifts: identification of high-redshift clusters
Bell, Eric F.; Kodama, Tadayuki; Bower, Richard G.
Photometric redshift classifiers provide a means of estimating galaxy redshifts from observations using a small number of broad-band filters. However, the accuracy with which redshifts can be determined is sensitive to the star formation history of the galaxy, for example the effects of age, metallicity and ongoing star formation. We present a pho…
Homogeneous photometry and metal abundances for a large sample of Hipparcos metal-poor stars*
Clementini, G.; Sneden, C.; Carretta, E. +1 more
Homogeneous photometric data (Johnson V, B-V, V-K, Cousins V-I and Strömgren b-y), radial velocities, and abundances of Fe, O, Mg, Si, Ca, Ti, Cr and Ni are presented for 99 stars with high-precision parallaxes measured by the Hipparcos satellite. These data have been previously used to assist the derivation of accurate distances and ages of Galac…
Does Magnetic Flux Submerge at Flux Cancelation Sites?
Schrijver, Carolus J.; Harvey, Karen L.; Jones, Harrison P. +1 more
Simultaneous measurements of the magnetic fields in the photosphere and chromosphere were used to investigate if magnetic flux is submerging at sites between adjacent opposite polarity magnetic network elements in which the flux is observed to decrease or `cancel'. These data were compared with chromospheric and coronal intensity images to establi…
The ``Water-Fountain Nebula'' IRAS 16342-3814: Hubble Space Telescope/Very Large Array Study of a Bipolar Protoplanetary Nebula
Sahai, Raghvendra; Morris, Mark; Zijlstra, Albert +2 more
We present Hubble Space Telescope (HST) Wide-Field and Planetary Camera 2 images and VLA OH maser emission-line maps of the cold infrared object IRAS 16342-3814, believed to be a protoplanetary nebula. The HST images show an asymmetrical bipolar nebula, with the lobes separated by a dark equatorial waist. The two bright lobes and the dark waist ar…
Carbon dioxide-methanol intermolecular complexes in interstellar grain mantles
Ehrenfreund, P.; Dartois, E.; Demyk, K. +1 more
We present new laboratory data to interpret the Infrared Space Observatory (ISO) spectra of protostellar objects, and particularly RAFGL7009S. Our experimental results show that solid methanol and carbon dioxide exhibit specific intermolecular interactions. We propose the formation of a Lewis acid-base complex between carbon dioxide and methanol m…
An Unusual Brightening Of Eta Carinae
Gull, Theodore R.; Humphreys, Roberta M.; Davidson, Kris +7 more
HST/Space Telescope Imaging Spectrograph data show that the apparent near-UV, visual-wavelength, and near-IR brightness of η Car increased by a factor of two during 1998. Meanwhile its Homunculus ejecta nebula brightened by about 30%, the largest fluctuation of this type in the past 40 years. These developments were quite unexpected and are not ea…