Search Publications
How the X-ray spectrum of a narrow-line Seyfert 1 galaxy may be reflection-dominated
Merloni, A.; Iwasawa, K.; Vaughan, S. +3 more
A model for the inner regions of accretion flows is presented where, owing to disc instabilities, cold and dense material is clumped into deep sheets or rings. Surrounding these density enhancements is hot, tenuous gas where coronal dissipation processes occur. We expect this situation to be most relevant when the accretion rate is close to Edding…
Hubble Space Telescope Imaging of the Circumnuclear Environments of the CfA Seyfert Galaxies: Nuclear Spirals and Fueling
Pogge, Richard W.; Martini, Paul
We present archival Hubble Space Telescope (HST) images of the nuclear regions of 43 of the 46 Seyfert galaxies found in the volume-limited, spectroscopically complete CfA Redshift Survey sample. Using an improved method of image contrast enhancement, we create detailed high-quality ``structure maps'' that allow us to study the distributions of du…
Hubble Space Telescope Images of the HH 34 Jet and Bow Shock: Structure and Proper Motions
Bally, John; Morse, Jon; Reipurth, Bo +2 more
We present new, deep Hα and [S II] images of the HH 34 jet and bow shock obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST), which reveal the structure of this fine HH flow with unprecedented detail. Many of the knots in the jet appear to form small working surfaces with bright [S II] cores and thin Hα filame…
Spatially resolved X-ray spectroscopy of the core of the Centaurus cluster
Fabian, A. C.; Sanders, J. S.
We present Chandra data from a 31.7-ks observation of the Centaurus cluster, using the ACIS-S detector. Images of the X-ray emission show a plume-like feature at the centre of the cluster, of extent 60arcsec (20kpc in projection). The feature has the same metallicity as gas at a similar radius, but is cooler. Using adaptive binning, we generate te…
Optical and Ultraviolet Spectroscopy of SN 1995N: Evidence for Strong Circumstellar Interaction
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Fransson, Claes +9 more
Optical and ultraviolet observations of the Type IIn supernova SN 1995N at epochs between 321 and 1799 days after the explosion show three distinct velocity components. The narrow lines come from circumstellar gas and show both low and high ionization. This component has a low filling factor and is photoionized by X-rays from the shock. The interm…
Empirical Densities, Kinetic Temperatures, and Outflow Velocities in the Equatorial Streamer Belt at Solar Minimum
Biesecker, D. A.; Strachan, L.; Kohl, J. L. +2 more
We use combined Ultraviolet Coronagraph Spectrometer and Large Angle Spectroscopic Coronagraph data to determine the O5+ outflow velocities as a function of height along the axis of an equatorial streamer at solar minimum and as a function of latitude (at 2.3 Rsolar from Sun center). The results show that outflow increases ra…
Hubble Space Telescope WFPC2 Proper Motions in Two Bulge Fields: Kinematics and Stellar Population of the Galactic Bulge
Rich, R. Michael; Kuijken, Konrad
We report proper-motion dispersions for stars in the direction of two fields of the Galactic bulge, using Hubble Space Telescope Wide Field Planetary Camera 2 images taken 6 years apart. Our two fields are Baade's window [(l,b)=(1.13d,-3.77d)] and Sgr I [(l,b)=(1.25d,-2.65d)]. Our proper-motion dispersions are in good agreement with prior ground- …
Narrow Components within the Fe Kα Profile of NGC 3516: Evidence of the Importance of General Relativistic Effects?
Nandra, K.; Turner, T. J.; Kraemer, S. B. +6 more
We present results from a simultaneous Chandra High Energy Transmission Grating and XMM-Newton observation of NGC 3516. We find evidence of several narrow components of Fe Kα along with a broad line. We consider the possibility that the lines arise in a blob of material ejected from the nucleus with velocity ~0.25c. We also consider an origin in a…
Cold Dust in Late-Type Virgo Cluster Galaxies
Madore, Barry F.; Tuffs, Richard J.; Popescu, Cristina C. +2 more
We have statistically analyzed the spatially integrated far-infrared (FIR) emissions of the complete volume- and luminosity-limited sample of late-type (later than S0) Virgo Cluster galaxies measured using the Infrared Space Observatory by Tuffs and coworkers in bands centered on 60, 100, and 170 µm. Thirty of 38 galaxies detected at all thr…
The Luminosity Dependence of Ultraviolet Absorption in Active Galactic Nuclei
Brandt, W. N.; Laor, Ari
We describe the results of a survey of the UV absorption properties of the Boroson & Green sample of active galactic nuclei (AGNs), which extends from the Seyfert (MV~=-21) to the luminous quasar (MV~=-27) level. The survey is based mostly on Hubble Space Telescope archival data available for >~1/2 of the 87 sample obj…