Search Publications
A One-sided Ionization Cone in the Seyfert 2 Galaxy NGC 5643
Simpson, Chris; Krolik, J. H.; Wilson, A. S. +3 more
We present high-resolution (0.1") observations of the Seyfert 2 galaxy NGC 5643 taken with the WFPC2 on board the Hubble Space Telescope. Images taken in the light of [O III] λ5007 and Hα reveal a halo of emission centered on the nucleus and high-excitation extranuclear emission which extends eastward for at least 1.8 kpc. An excitation map of [O …
Detection of the Tip of the Red Giant Branch in NGC 3379 (M105) in the Leo I Group Using the Hubble Space Telescope
Madore, Barry F.; Freedman, Wendy L.; Lauer, Tod R. +3 more
We report the detection of individually resolved stars in the elliptical galaxy NGC 3379, a luminous member of the Leo I Group. The bright end of the stellar luminosity function has a logarithmic slope that is consistent with these stars being Population II red giants. An abrupt discontinuity in the apparent luminosity function at I = 26.30 +/- 0.…
Improved Parameters and New Lensed Features for Q0957+561 from WFPC2 Imaging
Tyson, J. Anthony; Fischer, Philippe; Bernstein, Gary +1 more
New Hubble Space Telescope WFPC2 observations of the lensed double QSO 0957+561 will allow stronger constraints on the lens mass distribution and hence will refine the derived value of H0. We first present improved optical positions and photometry for the known components of this lens. The optical separation between the A and B quasar i…
A Linear Relationship between the Latitude Gradient and 26 Day Recurrent Variation in the Fluxes of Galactic Cosmic Rays and Anomalous Nuclear Components. I. Observations
Zhang, Ming
We find that there exists a linear relationship between the magnitude of latitude gradient and the amplitude of 26 day recurrent variations in the fluxes of galactic cosmic rays and anomalous nuclear components. This result is based on energetic charged particle measurements from the University of Chicago High Energy Telescope (HET) in the Cosmic …
Interpretation of Ultraviolet Absorption Lines in SN 1006
Crenshaw, D. M.; Sarazin, C. L.; Wu, C. -C. +2 more
We present a theoretical interpretation of the broad silicon and iron ultraviolet absorption features observed with the Hubble Space Telescope (HST) in the spectrum of the Schweizer-Middleditch star behind the remnant of SN 1006. These features are caused by supernova ejecta in SN 1006.
We propose that the redshifted Si II 1260 Å feature cons…Eclipse Mapping of the Accretion Disk Wind in the Cataclysmic Variable UX Ursae Majoris
Drew, Janet E.; Knigge, Christian
We present the results of an effort to model recent HST eclipse observations of the C IV 1550 Å resonance line in the high-inclination nova-like cataclysmic variable UX UMa. Assuming this line to be predominantly wind-formed, we are able to roughly reproduce the shapes and strengths of the observed line profiles (both away from and during eclipse)…
Additional Observations and Analysis of the Lyman-α Absorption Lines toward the QSO Pair Q0107-025A,B
Morris, Simon L.; Weymann, Ray J.; Foltz, Craig B. +3 more
We present further analysis and discussion of the properties of the absorption lines in the QSO pair Q0107-025A,B (zem = 0.956, 0.952; angular separation 1.29 arcmin) based upon spectroscopy obtained with the Faint Object Spectrograph (FOS) of the Hubble Space Telescope (HST). We also present observations of the pair at shorter waveleng…
Evidence for Galaxy Interactions/Mergers from Medium Deep Survey WFPC2 Data
Im, M.; Griffiths, R. E.; Ratnatunga, K. U. +3 more
We examine the morphological and statistical properties of close galaxy pairs from two sets of 28 WFPC2 fields, acquired for the Medium Deep Survey (MDS) and the Groth-Westphal Survey (GWS) in F606W (V) and F814W (I) passbands. In the GWS sample all fields have uniform 95% completeness down to I <~ 24.3 mag, whereas in the MDS sample, fields ha…
The Distance to the Coma Cluster from Surface Brightness Fluctuations
Baum, William A.; Hammergren, Mark; Thomsen, Bjarne +1 more
We report on the first determination of the distance to the Coma Cluster from surface brightness fluctuation (SBF) measurements obtained from Hubble Space Telescope WFPC2 observations of the bright E0 galaxy NGC 4881 in the Coma Cluster and ground-based observations of the ``standard'' E1 galaxy NGC 3379 in the Leo-I group. Relative distances base…
The Discovery of Mg II λ4481 in the White Dwarf EG 102: Evidence for Ongoing Accretion
Barstow, M. A.; Holberg, J. B.; Green, Elizabeth M.
Recent optical spectra of the DA3 white dwarf EG 102 clearly show a feature due to Mg II λ4481. This is the first spectroscopic detection of Mg in a DA star at a temperature of 20,000 K. The presence of this ion in the stellar photosphere poses a severe dilemma for the theory of radiative levitation, which predicts a vanishingly small equilibrium …