Search Publications
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A 13 Year Study of Spectral Variability in NGC 5548
Filippenko, A. V.; Shapovalova, A. I.; Chavushyan, V. H. +38 more
We present the final installment of an intensive 13 year study of variations of the optical continuum and broad Hβ emission line in the Seyfert 1 galaxy NGC 5548. The database consists of 1530 optical continuum measurements and 1248 Hβ measurements. The Hβ variations follow the continuum variations closely, with a typical time delay of about 20 da…
The Dark Matter Density Profile of the Lensing Cluster MS 2137-23: A Test of the Cold Dark Matter Paradigm
Treu, Tommaso; Ellis, Richard S.; Sand, David J.
We present new spectroscopic observations of the gravitational arcs and the brightest cluster galaxy (BCG) in the cluster MS 2137-23 (z=0.313) obtained with the Echelle Spectrograph and Imager on the Keck II telescope. We find that the tangential and radial arcs arise from sources at almost identical redshifts (z=1.501, 1.502). We combine the meas…
High-Resolution Observations of the Elliptical Galaxy NGC 4636 with the Reflection Grating Spectrometer on Board XMM-Newton
Behar, E.; Kahn, S. M.; Mushotzky, R. F. +6 more
We present the first high spectral resolution X-ray observation of the giant elliptical galaxy NGC 4636, obtained with the reflection grating spectrometer on board the XMM-Newton Observatory. The resulting spectrum contains a wealth of emission lines from various charge states of oxygen, neon, magnesium, and iron. Examination of the cross-dispersi…
The Counterrotating Core and the Black Hole Mass of IC 1459
Carollo, C. M.; Illingworth, G. D.; Franx, M. +5 more
The E3 giant elliptical galaxy IC 1459 is the prototypical galaxy with a fast counterrotating stellar core. We obtained one Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) long-slit spectrum along the major axis of this galaxy and Cerro Tololo Inter-American Observatory (CTIO) spectra along five position angles. The signal…
The Far-Ultraviolet Spectrum of TW Hydrae. I. Observations of H2 Fluorescence
Herczeg, Gregory J.; Valenti, Jeff A.; Johns-Krull, Christopher M. +2 more
We observed the classical T Tauri star TW Hya with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST) using the E140M grating, from 1150 to 1700 Å, with the E230M grating, from 2200 to 2900 Å, and with the Far Ultraviolet Spectroscopic Explorer from 900 to 1180 Å. Emission in 146 Lyman-band H2 lines, repr…
The Kinematic Connection between absorbing Gas toward QSOs and Galaxies at Intermediate Redshift
Dickinson, Mark; Pettini, Max; Shapley, Alice E. +3 more
We present complementary data on five intermediate-redshift (0.44<=z<=0.66) Mg II-absorbing galaxies, combining high spatial resolution imaging from the Hubble Space Telescope, high-resolution quasi-stellar object (QSO) spectroscopy from the Keck High Resolution Echelle Spectrometer, and galaxy kinematics from intermediate-resolution spectro…
Are the Narrow-Line Regions in Active Galaxies Dusty and Radiation Pressure Dominated?
Dopita, Michael A.; Sutherland, Ralph S.; Binette, Luc +2 more
The remarkable similarity between emission spectra of narrow-line regions (NLRs) in Seyfert galaxies has long presented a mystery. In photoionization models, this similarity implies that the ionization parameter is nearly always the same, about U~0.01. Here we present dusty, radiation pressure-dominated photoionization models that can provide natu…
Time-Distance Helioseismology: The Forward Problem for Random Distributed Sources
Birch, A. C.; Gizon, L.
The forward problem of time-distance helioseismology is computing travel-time perturbations that result from perturbations to a solar model. We present a new and physically motivated general framework for calculations of the sensitivity of travel times to small local perturbations to solar properties, taking into account the fact that the sources …
Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-Newton/EPIC-pn Spectrum of XTE J1650-500
Wijnands, R.; Fabian, A. C.; Miller, J. M. +7 more
We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the ``very high'' state. We find a broad, skewed Fe Kα emission line that suggests the primary in this system may be a Ker…
Detection of a Supernova Signature Associated with GRB 011121
Piro, L.; Axelrod, T. S.; Frontera, F. +20 more
Using observations from an extensive monitoring campaign with the Hubble Space Telescope, we present the detection of an intermediate-time flux excess that is redder in color relative to the afterglow of GRB 011121, currently distinguished as the gamma-ray burst with the lowest known redshift. The red ``bump,'' which exhibits a spectral rollover a…