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An Eccentric-Disk Model for the Nucleus of M31
Tremaine, Scott
The nucleus of M31 may be a thick eccentric disk, composed of stars traveling on nearly Keplerian orbits around a black hole or other dark compact object. This hypothesis reproduces most of the features seen in HST photometry of the center of M31; in particular the bright off-center source P1 is the apoapsis region of the disk. An eccentric disk c…
The Morphological Mix of Field Galaxies to M I = 24.25 mag (b J approximately 26 mag) from a Deep Hubble Space Telescope WFPC2 Image
Keel, William C.; Driver, Simon P.; Windhorst, Rogier A. +3 more
We determine the morphological mix of field galaxies down to mI ~= 24.25 mag (mB ~ 26.0 mag) from a single ultradeep Hubble Space Telescope wide field planetary camera (WFPC2) image in both the V606 and the I814 filters. In total, we find 227 objects with mI <= 24.5 mag and classify these into three types: ellipticals (16%), early-type spirals …
Hubble Space Telescope Observations of the SN 1987A Triple Ring Nebula
Casertano, Stefano; Ballester, Gilda E.; Crisp, David +16 more
We have observed SN 1987A with the optically corrected WFPC2 on the Hubble Space Telescope both in emission lines and in the UV and optical continuum. The previously observed outer nebular structure is shown to be part of two closed unresolved loops. These loops were flash-ionized by the supernova itself. They are not caused by limb brightening of…
Hubble Space Telescope Imaging of Super Star Clusters in M82
O'Connell, Robert W.; Gallagher, John S., III; Hunter, Deidre A. +1 more
We describe high resolution V- and I-band images obtained with the HST Planetary Camera of the center of the prototype starburst galaxy M82. The deconvolved images reveal a remarkable complex of over 100 compact, luminous "super" star clusters, concentrated to the inner few 100 pcs of the galaxy. These clusters typically have half-peak intensity s…
Hubble Space Telescope Observations of Globular Clusters in M87 and an Estimate of H 0
Lucas, Ray A.; Whitmore, Bradley C.; Sparks, William B. +2 more
Hubble Space Telescope observations of over 1000 globular clusters in the central region of M87 have been made using the Wide Field and Planetary Camera 2. The limiting magnitude in V is 26 mag, more than 2 mag beyond the turnover of the luminosity function. The distribution is well fitted by a Gaussian profile with a mean of <m0
Ulysses Solar Wind Plasma Observations at High Southerly Latitudes
McComas, D. J.; Goldstein, B. E.; Bame, S. J. +7 more
Solar wind plasma observations made by the Ulysses spacecraft through -80.2^circ solar latitude and continuing equatorward to -40.1^circ are summarized. Recurrent high-speed streams and corotating interaction regions dominated at middle latitudes. The speed of the solar wind was typically 700 to 800 kilometers per second poleward of -35^circ. Coro…
The Contribution of Late-Type/Irregulars to the Faint Galaxy Counts from Hubble Space Telescope Medium-Deep Survey Images
Driver, Simon P.; Windhorst, Rogier A.; Griffiths, Richard E.
We present a complete morphologically classified sample of 144 faint field galaxies from the HST Medium Deep Survey with 20.0 ≤ mI <22.0 mag. We compare the global properties of the ellipticals and early- and late-type spirals and find a nonnegligible fraction (13/144) of compact blue [(V - I) ≤ 1.0 mag] systems with r1/4 …
Multiwavelength Observations of Markarian 421 During a TeV/X-Ray Flare
Kafatos, M.; Takahashi, T.; Kondo, Y. +38 more
A TeV flare from the BL Lac object Mrk 421 was detected in May of 1994 by the Whipple Observatory air Cherenkov experiment during which the flux above 250 GeV increased by nearly an order of magnitude over a 2-day period. Contemporaneous observations by ASCA showed the X-ray flux to be in a very high state. We present these results, combined with …
Ultraviolet to Near-Infrared Spectral Distributions of Star-forming and Seyfert 2 Galaxies
Storchi-Bergmann, Thaisa; Challis, Peter; Kinney, Anne L.
Combined UV, optical and near-IR spectral distributions of a sample of 48 southern star-forming and Seyfert 2 galaxies are presented. The optical and near-IR spectra were obtained using apertures matching those of the UV observations (10" X 20") and in most cases correspond to the bulk of the gas and stellar population contribution from the whole …
Determination of the Hubble constant from observations of Cepheid variables in the galaxy M96
Ferguson, H. C.; Tanvir, N. R.; Shanks, T. +1 more
New Hubble Space Telescope observations of Cepheid variable stars in the nearby galaxy M96 give a distance to the host galaxy group, Leo I, of 11.6 +/- 0.8 Mpc. This value, used in conjunction with several reliable secondary indicators of relative distance, constrains the distances to more remote galaxy clusters, and yields a value of the Hubble c…