Search Publications
The H II Regions of the Damped Lyα Absorber SBS 1543+593
Turnshek, David A.; Rao, Sandhya M.; Pettini, Max +3 more
We report new imaging and spectroscopic observations of the damped Lyα absorber (DLA) galaxy SBS 1543+593, a nearby dwarf galaxy whose stellar disk is intersected by the sight line to the bright background QSO HS 1543+5921. Hubble Space Telescope imaging observations with WFPC2 in the F450W and F702W bands are used to measure the DLA galaxy's prop…
The X-Ray Spectrum of the z=6.30 QSO SDSS J1030+0524
Farrah, D.; McMahon, R.; Priddey, R. +2 more
We present a deep XMM-Newton observation of the z=6.30 QSO SDSS J1030+0524, the second most distant quasar currently known. The data contain sufficient counts for spectral analysis, demonstrating the ability of XMM-Newton to measure X-ray spectral shapes of z~6 QSOs with integration times >~100 ks. The X-ray spectrum is well fitted by a power l…
A Bias in Optical Observations of High-Redshift Luminous Infrared Galaxies
Le Floc'h, E.; Charmandaris, V.; Mirabel, I. F.
We present evidence for the dramatically different morphology between the rest-frame UV and 7 µm mid-IR emission of VV 114 and Arp 299, two nearby (z~0) violently interacting luminous infrared galaxies (LIRGs). Nearly all LIRGs are interacting systems, and it is currently accepted that they dominate the IR emission at z>1. LIRGs located a…
Three-Dimensional Photoionization Structure and Distances of Planetary Nebulae. I. NGC 6369
Monteiro, Hektor; Heathcote, Steve; Schwarz, Hugo E. +1 more
We present the results of mapping the planetary nebula NGC 6369 by using multiple long-slit spectra taken with the Cerro Tololo Inter-American Observatory 1.5 m telescope. We create two-dimensional emission-line images from our spectra and use these to derive fluxes for 17 lines, the Hα/Hβ extinction map, the [S II ] line ratio density map, and th…
The Continued Spectral Evolution of the Neutron Star RX J0720.4-3125
Verbunt, Frank; Vink, Jacco; de Vries, Cor P. +1 more
We observed the isolated neutron star RX J0720.4-3125 with Chandra's Low Energy Transmission Grating Spectrometer, following the XMM-Newton discovery of the long-term spectral evolution of this source. The new observation shows that the spectrum of RX J0720.4-3125 has continued to change in the course of 5 months. It has remained hard, similar to …
Microlensing Candidates in M87 and the Virgo Cluster with the Hubble Space Telescope
Zurek, David R.; Zepf, Stephen E.; Lauer, Tod R. +4 more
The position of the giant elliptical galaxy M87 at the center of the Virgo Cluster means that the inferred column density of dark matter associated with both the cluster halo and the galaxy halo is quite large. This system is thus an important laboratory for studying massive dark objects in elliptical galaxies and galaxy clusters by gravitational …
Iron Kα Emission from the Low-Luminosity Active Galaxies M81 and NGC 4579
Schurch, N. J.; Dewangan, G. C.; Griffiths, R. E. +1 more
We report on the XMM-Newton spectroscopy of the low-luminosity active galaxies (LLAGNs) M81 and NGC 4579, both of which have known black hole masses and well-sampled spectral energy distributions (SEDs). The iron Kα line profiles from both LLAGNs can be described in terms of two components: a narrow line at 6.4 keV, and a moderately broad line (FW…
Models for Solar Magnetic Loops. III. Dynamic Models and Coronal Diagnostic Spectrometer Observations
Landini, M.; Landi, E.
In the present work SOHO Coronal Diagnostic Spectrometer (CDS) observations of a quiescent active region loop are compared to a steady state, dynamic loop model. Three different heating functions are adopted: uniform, concentrated at the top, and concentrated at the footpoints. Predicted temperature and density profiles of the selected loop are co…
Radio Observations of Rapid Acceleration in a Slow Filament Eruption/Fast Coronal Mass Ejection Event
Janardhan, P.; Kundu, M. R.; White, S. M. +4 more
We discuss a filament eruption/coronal mass ejection (CME) event associated with a flare of GOES class M2.8 that occurred on 2001 November 17. This event was observed by the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz. NoRH observed the filament during its eruption both as a dark feature against the solar disk and a bright feature above the …
On Collisionless Electron-Ion Temperature Equilibration in the Fast Solar Wind
Laming, J. Martin
We explore a mechanism, entirely new to the fast solar wind, of electron heating by lower hybrid waves to explain the shift to higher charge states observed in various elements in the fast wind at 1 AU relative to the original coronal hole plasma. This process is a variation on that previously discussed for two-temperature accretion flows by Begel…