Search Publications
Far-Infrared Detection of H2D+ toward Sgr B2
Cernicharo, J.; Goicoechea, J. R.; Polehampton, E.
We report on the first far-IR detection of H2D+, using the Infrared Space Observatory, in the line of sight toward Sgr B2 in the Galactic center. The transition at λ=126.853 µm connecting the ground level of o-H2D+, 11,1, with the 21,2 level at 113 K is observed in absorption …
Modeling Minor Ion Abundances in Quiescent Coronal Loops
Lie-Svendsen, Øystein; Killie, Mari Anne
We model minor element abundances in quiescent coronal loops anchored in the chromosphere, solving transport equations that give an improved description of thermal forces. Ionization, recombination, and radiative loss are included. The plasma consists of hydrogen and a minor element (oxygen, silicon, or iron), and we solve for all relevant charge …
Low Star Formation Rates for z = 1 Early-Type Galaxies in the Very Deep GOODS MIPS Imaging: Implications for Their Optical/Near-Infrared Spectral Energy Distributions
van der Wel, A.; Illingworth, G. D.; Franx, M. +1 more
We measure the obscured star formation in z~1 early-type galaxies. This constrains the influence of star formation on their optical/near-IR colors, which, we found, are redder than predicted by the model by Bruzual & Charlot. From deep ACS imaging we construct a sample of 95 morphologically selected early-type galaxies in the HDF-N and CDF-S w…
Does High Plasma-β Dynamics ``Load'' Active Regions?
McIntosh, Scott W.
Using long-duration observations in the He II 304 Å passband of SOHO EIT, we investigate the spatial and temporal appearance of impulsive intensity fluctuations in the pixel light curves. These passband intensity fluctuations come from plasma emitting in the chromosphere, in the transition region, and in the lowest portions of the corona. We see t…
Modeling the Accretion Disk X-Ray Continuum of Black Hole Candidates
Cui, Wei; Pszota, Gabor
We critically examine issues associated with determining the fundamental properties of the black hole and the surrounding accretion disk in an X-ray binary based on modeling the disk X-ray continuum of the source. We base our work mainly on two XMM-Newton observations of GX 339-4, because they provided high-quality data at low energies (below 1 ke…
Anticorrelation between Moving Magnetic Features and Coronal Loop Formation
Title, A.; Ryutova, M. P.; Hagenaar, H.
We study a possible connection of moving magnetic features (MMFs) and the overlying atmosphere using several sets of multiwavelength observations of sunspot areas from the photosphere to the corona. We find that as a collective phenomenon, very intense MMF formation anticorrelates with the presence of large-scale ``stable'' coronal loops: such loo…
A Possible Dearth of Hot Gas in Galaxy Groups at Intermediate Redshift
Paerels, Frits; Spiegel, David S.; Scharf, Caleb A.
We examine the X-ray luminosity of galaxy groups in the CNOC2 survey at redshifts 0.1<z<0.6. Previous work examining the gravitational lensing signal of the CNOC2 groups has shown that they are likely to be genuine, gravitationally bound objects. Of the 21 groups in the field of view of the EPIC pn camera on XMM-Newton, not one was visible i…
Solar Rossby Wave ``Hills'' Identified as Supergranules
Hathaway, D. H.; Cuntz, M.; Williams, P. E.
We explore the nature of ``hills'' observed on the solar surface that had previously been attributed to Rossby waves. We investigate the solar hills phenomenon by analyzing the output from a synthetic model based solely on the observed solar photospheric convection spectrum. We show that the characteristics of these hills can be explained by the c…
Morphological Study of Quiescent Streamers during Solar Minimum by Ultraviolet Emission Lines
Akinari, Nakagawa
We perform, by utilizing spectroscopic measurements made with SOHO/UVCS, a morphological characterization of the quiescent streamer during solar minimum, by means of both a comprehensive survey of daily synoptic observations over 33 weeks from 1996 April to November and detailed analysis of several specialized observations targeting quiescent stre…
Estimating the Structure and Geometry of Winds from Luminous Blue Variables via Fitting the Continuum Energy Distributions
Li, Y.; Guo, J. H.
By combining the UV spectra from IUE with photometric data in the optical band, we present a quantitative study on the continuum energy distributions of LBVs to determine the structure and geometry of LBV winds. It is shown that the shape of continuum energy distributions around the Balmer jump is sensitive to the velocity law of LBV winds. A simp…