Search Publications
The Excitation and Metallicity of Galactic H II Regions from Infrared Space Observatory SWS Observations of Mid-Infrared Fine-Structure Lines
Pauldrach, A. W. A.; Feuchtgruber, Helmut; Lutz, Dieter +2 more
We present mid-infrared Infrared Space Observatory Short-Wavelength Spectrometer (ISO-SWS) observations of the fine-structure emissions lines [Ne II] 12.8 µm, [Ne III] 15.6 µm, [Ne III] 36.0 µm, [Ar II] 6.99 µm, [Ar III] 8.99 µm, [S III] 18.7 µm, [S III] 33.5 µm, and [S IV] 10.5 µm and the recombinat…
Rapid Changes of Magnetic Fields Associated with Six X-Class Flares
Moon, Yong-Jae; Qiu, Jiong; Denker, Carsten +5 more
In this paper, we present the results of the study of six X-class flares. We found significant changes in the photospheric magnetic fields associated with all of the events. For the five events in 2001, when coronagraph data were available, all were associated with halo coronal mass ejections. Based on the analyses of the line-of-sight magnetogram…
The AGN contribution to mid-infrared surveys. X-ray counterparts of the mid-IR sources in the Lockman Hole and HDF-N
Altieri, B.; Elbaz, D.; Franceschini, A. +5 more
We provide constraints on the AGN contribution to the mid-IR extragalactic background light from a correlation analysis of deep X-ray and mid-IR observations in two regions centred on the Lockman Hole and Hubble Deep Field North (HDF-N). The Lockman region, of more than 200 square arcminutes, was observed by ISOCAM and XMM-Newton to a depth of 0.3…
Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator δ Cephei
McArthur, B. E.; Franz, O. G.; Bradley, A. J. +16 more
We present an absolute parallax and relative proper motion for the fundamental distance scale calibrator δ Cep. We obtain these with astrometric data from FGS 3, a white-light interferometer on the Hubble Space Telescope (HST). Utilizing spectrophotometric estimates of the absolute parallaxes of our astrometric reference stars and constraining δ C…
Compact Star Clusters in Nearby Dwarf Irregular Galaxies
Elmegreen, Bruce G.; Hunter, Deidre A.; Billett, Olivia H.
Nearby dwarf irregular galaxies were searched for compact star clusters by using data from the Hubble Space Telescope archives. Eight of the 22 galaxies in our sample were found to host compact clusters of some type. Three of these have populous clusters, with MV<-9.5 at a fiducial age of 10 Myr, and the same three also have super-st…
A Survey of Extended Radio Jets in Active Galactic Nuclei with Chandra and the Hubble Space Telescope: First Results
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +5 more
We present the first results from an X-ray and optical survey of a sample of radio jets in active galactic nuclei with Chandra and the Hubble Space Telescope (HST). We focus here on the first six sources observed in X-ray, in four of which a bright X-ray jet was detected for the first time. In three out of the four cases, optical emission from the…
Cosmic Shear and Power Spectrum Normalization with the Hubble Space Telescope
Refregier, Alexandre; Rhodes, Jason; Groth, Edward J.
Weak lensing by large-scale structure provides a direct measurement of matter fluctuations in the universe. We report a measurement of this ``cosmic shear'' based on 271 Wide Field Planetary Camera 2 archival images from the Hubble Space Telescope Medium Deep Survey. Our measurement method and treatment of systematic effects were discussed in an e…
Mass segregation in young compact star clusters in the Large Magellanic Cloud - II. Mass functions
Mackey, A. D.; de Grijs, R.; Gilmore, G. F. +1 more
We review the complications involved in the conversion of stellar luminosities into masses and apply a range of mass-to-luminosity relations to our Hubble Space Telescope observations of the young Large Magellanic Cloud (LMC) star clusters NGC 1805 and 1818.
Both the radial dependence of the mass function (MF) and the dependence of the cluste…The carrier of the ``30'' mu m emission feature in evolved stars. A simple model using magnesium sulfide
Waters, L. B. F. M.; Hony, S.; Tielens, A. G. G. M.
We present 2-45 mu m spectra of a large sample of carbon-rich evolved stars in order to study the ``30'' mu m feature. We find the ``30'' mu m feature in a wide range of sources: low mass loss carbon stars, extreme carbon-stars, post-AGB objects and planetary nebulae. We extract the profiles from the sources by using a simple systematic approach t…
Tightly Correlated X-Ray/Hα-emitting Filaments in the Superbubble and Large-Scale Superwind of NGC 3079
Veilleux, Sylvain; Bland-Hawthorn, Joss; Cecil, Gerald
Using Chandra and HST, we show that X-ray and Hα filaments that form the 1.3 kpc diameter superbubble of NGC 3079 have strikingly similar patterns at ~0.8" resolution. This tight optical line/X-ray match seems to arise from cool disk gas that has been driven by the wind, with X-rays being emitted from upstream, standoff bow shocks or by conductive…