Search Publications
X-Ray Absorption by the Low-Redshift Intergalactic Medium: A Numerical Study of the Λ Cold Dark Matter Model
Davé, Romeel; Weinberg, David H.; Chen, Xuelei +1 more
Using a hydrodynamic simulation of a cold dark matter universe with a cosmological constant, we investigate the ``X-ray forest'' absorption imprinted on the spectra of background quasars by the intervening intergalactic medium (IGM), at redshift z~0. In agreement with previous studies, we find that O VII and O VIII produce the strongest absorption…
The Contribution of Polar Plumes to the Fast Solar Wind
Lemaire, P.; Gabriel, A. H.; Bely-Dubau, F.
The Doppler dimming technique is used for the first time to study ultraviolet polar plumes in the height range of 1.05-1.35 Rsolar, using observations from the spectrometer SUMER on the Solar and Heliospheric Observatory. It is found that, contrary to a number of published suggestions, outflow velocities in the plumes exceed those in th…
The Internal Ultraviolet-Optical Color Dispersion: Quantifying the Morphological K-Correction
Papovich, Casey; Dickinson, Mark; Ferguson, Henry C. +2 more
We present a quantitative measure of the internal color dispersion within galaxies, which quantifies differences in galaxy morphology as a function of observed wavelength. We apply this statistic to a sample of local galaxies with archival images at 1500 and 2500 Å from the Ultraviolet Imaging Telescope and ground-based B-band observations in orde…
Physical Conditions and Star Formation Activity in the Intragroup Medium of Stephan's Quintet
Lu, N.; Xu, C. K.; Tuffs, R. J. +2 more
New multiband observations of the famous compact group of galaxies Stephan's Quintet (SQ) are presented and analyzed. These include far-infrared (FIR) images at 60 and 100 µm (ISOPHOT C100 camera), radio continuum images at 1.4 GHz (VLA B configuration) and 4.86 GHz (VLA C configuration), and long-slit optical spectrographs (Palomar 200" tel…
A Compact X-Ray Source and Possible X-Ray Jets within the Planetary Nebula Menzel 3
Soker, Noam; Frank, Adam; Balick, Bruce +4 more
We report the discovery, by the Chandra X-Ray Observatory, of X-ray emission from the bipolar planetary nebula Menzel 3. In Chandra CCD imaging, Mz 3 displays hot [~(3-6)×106 K] gas within its twin, coaxial bubbles of optical nebulosity as well as a compact X-ray source at the position of its central star(s). The brightest diffuse X-ray…
Modeling the Ne IX Triplet Spectral Region of Capella with the Chandra and XMM-Newton Gratings
Drake, Jeremy J.; Ness, Jan-Uwe; Huenemoerder, David P. +1 more
High-resolution X-ray spectroscopy with the diffraction gratings of Chandra and XMM-Newton offers new chances to study a large variety of stellar coronal phenomena. A popular X-ray calibration target is Capella, which has been observed with all gratings with significant exposure times. We gathered together all available data of the High Energy Tra…
Keck Spectroscopy and Hubble Space Telescope Imaging of GRB 000926: Probing a Host Galaxy at z = 2.038
Harrison, F. A.; Galama, T. J.; Bloom, J. S. +4 more
We present early-time Keck spectroscopic observations and late-time Hubble Space Telescope (HST) imaging of GRB 000926. The HST images show a small offset between the optical transient and a bright, compact knot in the host galaxy. Combined with the large equivalent widths measured for metallic absorption lines by the Keck Echellette Spectrograph …
Space Telescope Imaging Spectrograph Slitless Observations of Small Magellanic Cloud Planetary Nebulae: A Study on Morphology, Emission-Line Intensity, and Evolution
Mutchler, Max; Villaver, Eva; Blades, J. Chris +3 more
A sample of 27 planetary nebulae (PNs) in the Small Magellanic Cloud (SMC) have been observed with the Hubble Space Telescope Imaging Spectrograph (HST/STIS) to determine their morphology, size, and the spatial variation of the ratios of bright emission lines. The morphologies of SMC PNs are similar to those of LMC and Galactic PNs. However, only …
Discovery of Two Distant Type Ia Supernovae in the Hubble Deep Field-North with the Advanced Camera for Surveys
White, Richard L.; Broadhurst, Tom; Franx, Marijn +30 more
We present observations of the first two supernovae discovered with the recently installed Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). The supernovae were found in Wide Field Camera images of the Hubble Deep Field-North taken with the F775W, F850LP, and G800L optical elements as part of the ACS guaranteed time observatio…
The Phase Coherence of Light from Extragalactic Sources: Direct Evidence against First-Order Planck-Scale Fluctuations in Time and Space
Lieu, Richard; Hillman, Lloyd W.
We present a method of directly testing whether time continues to have its usual meaning on scales of <=tP=(ℏG/c5)1/2~5.4×10-44 s, the Planck time. According to quantum gravity, the time t of an event cannot be determined more accurately than a standard deviation of the form σt/t=a0