Search Publications
A Revised Cepheid Distance to NGC 4258 and a Test of the Distance Scale
Zepf, Stephen E.; Davis, Marc; Madore, Barry F. +5 more
In a previous paper we reported a Hubble Space Telescope (HST) Cepheid distance to the galaxy NGC 4258 obtained using the calibrations and methods then standard for the Key Project. Here we reevaluate the Cepheid distance using the recently revised Key Project procedures. These revisions alter the zero points and slopes of the Cepheid period-lumin…
The complex iron line of NGC 5506
Piro, L.; Perola, G. C.; Fiore, F. +4 more
The bright Narrow Emission Line Galaxy, NGC 5506, has been observed simultaneously by XMM-Newton and BeppoSAX. The iron line is complex, with at least two components: one narrow and corresponding to neutral iron, the second one broad and corresponding to ionized iron. The latter line is equally well fitted by a truly broad line or by a blend of He…
A Near-Infrared Stellar Census of Blue Compact Dwarf Galaxies: The Wolf-Rayet Galaxy I Zw 36
Greggio, Laura; Hopp, Ulrich; Schulte-Ladbeck, Regina E. +2 more
We report the results of near-IR imaging in J and H, of I Zw 36 (~Zsolar/14) with the Hubble Space Telescope. Whereas imaging with the pre-COSTAR Faint Object Camera (FOC) previously resolved hot and massive stars in the near-UV, the NICMOS data furnish a census of the cool, intermediate- and low-mass stars. There clearly was star forma…
The Interaction between the Interstellar Medium and Star Formation in the Dwarf Starburst Galaxy NGC 4214
Scoville, Nick; Walter, Fabian; Taylor, Christopher L. +2 more
We present the first interferometric study of the molecular gas in the metal-poor dwarf starburst galaxy NGC 4214. Our map of the 12CO (1-0) emission, obtained at the Owens Valley Radio Observatory's millimeter array, reveals an unexpected structural wealth. We detected three regions of molecular emission in the northwest, southeast, an…
Morphology and Evolution of the Large Magellanic Cloud Planetary Nebulae
Mutchler, Max; Blades, J. Chris; Balick, Bruce +2 more
The LMC is ideal for studying the coevolution of planetary nebulae (PNs) and their central stars in that the debilitating uncertainties of the Galactic PN distance scale and selection biases from attenuation by interstellar dust do not apply. We present images and analyze slitless spectra that were obtained in a survey of Large Magellanic Cloud PN…
The Jet and the Supernova in GRB 990712
Christensen, L.; Hjorth, J.; Jakobsson, P. +2 more
The optical light curve of the afterglow following the gamma-ray burst GRB 990712 is reexamined. Recently published polarization measurements of that source require a collimated outflow geometry that in turn predicts a break in the light curve. We show that the V-band light curve is consistent with such a break and that the postbreak light-curve e…
Generation mechanism for magnetic holes in the solar wind
Tsurutani, B. T.; Goldstein, B. E.; Neugebauer, M. +1 more
A new mechanism for generation of magnetic holes in the solar wind is presented. In the high speed solar wind, large-amplitude right-hand polarized Alfvénic wave packets propagating at large angles to the ambient magnetic field are shown to generate magnetic holes (MHs). Characteristics of these holes crucially depend on plasma β (β being the rati…
The Rich Ultraviolet Spectrum of Vibrationally Excited Interstellar H2 toward HD 37903
Sofia, Ulysses J.; Meyer, David M.; Draine, B. T. +2 more
Based on recent high-resolution Hubble Space Telescope Space Telescope Imaging Spectrograph observations over the 1160-1360 Å wavelength region, we have discovered that HD 37903 (the illuminating star of the bright reflection nebula NGC 2023 in Orion) exhibits a rich spectrum of vibrationally excited interstellar H2 absorption. We have …
Far-infrared mapping of the starburst galaxy NGC 253 with ISOPHOT
Lemke, D.; Radovich, M.; Kahanpää, J.
A 180 mu m map and strip maps at 120 and 180 mu m were obtained for the edge-on starburst galaxy
Kinematics from spectroscopy with a wide slit: detecting black holes in galaxy centres
Binney, James; Maciejewski, Witold
We consider long-slit emission-line spectra of galactic nuclei when the slit is wider than the instrumental point spread function, and the target has large velocity gradients. The finite width of the slit generates complex distributions of brightness at a given spatial point in the measured spectrum, which can be misinterpreted as coming from addi…