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The Evolution of the Global Star Formation History as Measured from the Hubble Deep Field
Dickinson, Mark; Connolly, A. J.; Szalay, A. S. +2 more
The Hubble Deep Field (HDF) is the deepest set of multicolor optical photometric observations ever undertaken, and it offers a valuable data set with which to study galaxy evolution. Combining the optical WFPC2 data with ground-based near-infrared photometry, we derive photometrically estimated redshifts for HDF galaxies with J < 23.5. We demon…
The Supermassive Black Hole of M87 and the Kinematics of Its Associated Gaseous Disk
Marconi, A.; Capetti, A.; Crane, P. +3 more
We have obtained long-slit observations of the circumnuclear region of M87 at three different locations, with a spatial sampling of 0.028" using the Faint Object Camera f/48 spectrograph on board HST. These data allow us to determine the rotation curve of the inner ~1" of the ionized gas disk in [O II] λ3727 to a distance as close as 0.07" (~=5 pc…
First Results from the SOHO Ultraviolet Coronagraph Spectrometer
Romoli, M.; Raymond, J. C.; Naletto, G. +23 more
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R⊙ from Sun center. Initial observations of polar coronal holes and equatorial streamers are described. The observations include measurements of spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å, Mgx 625 Å, Fexi…
Bi-directional plasma jets produced by magnetic reconnection on the Sun
Inhester, B.; Wilhelm, K.; Innes, D. E. +1 more
Magnetic reconnection, the process by which magnetic lines of force break and rejoin into a lower-energy configuration, is considered to be the fundamental process by which magnetic energy is converted into plasma kinetic energy1. The Sun has a large reservoir of magnetic energy, and the energy released by magnetic reconnection has been…
Ulysses electron distributions fitted with Kappa functions
Maksimovic, Milan; Riley, Pete; Pierrard, Viviane
We fit Kappa functions to 16,000 velocity distribution functions measured in the solar wind by the electron plasma instrument on board Ulysses. Statistically, the electron distributions are observed to have important high velocity tails in the fast solar wind but are closer to a Maxwellian in the slow wind. We also discuss how this result could su…
The Cluster Magnetic Field Investigation
Balogh, A.; Buchert, S.; Dunlop, M. W. +12 more
Cross-correlation characteristics of OB stars from IUE spectroscopy
Howarth, Ian D.; Prinja, Raman K.; Siebert, Kaj W. +1 more
We present a catalogue of homogeneous measures of the linewidth parameter, v_esin i, for 373 O-type stars and early B supergiants (including the separate components of 25 binary and three triple systems), produced by cross-correlating high-resolution, short-wavelength IUE spectra against a `template' spectrum of tauSco. We also tabulate terminal v…
LBDS 53W091: An Old, Red Galaxy at z = 1.552
Windhorst, Rogier; Dey, Arjun; Spinrad, Hyron +4 more
The weak radio source LBDS 53W091 is associated with a very faint (R ~ 24.5) red (R - K ~ 5.8) galaxy. Long spectroscopic integrations with the W. M. Keck telescope have provided an absorption-line redshift, z = 1.552 +/- 0.002. The galaxy has a rest frame ultraviolet spectrum very similar to that of an F6 V star, and a single-burst old stellar po…
Sustaining the Quiet Photospheric Network: The Balance of Flux Emergence, Fragmentation, Merging, and Cancellation
Shine, Richard A.; Title, Alan M.; Schrijver, Carolus J. +2 more
The magnetic field in the solar photosphere evolves as flux concentrations fragment in response to sheared flows, merge when they collide with others of equal polarity, or (partially) cancel against concentrations of opposite polarity. Newly emerging flux replaces the canceled flux. We present a quantitative statistical model that is consistent wi…
EIT Observations of the Extreme Ultraviolet Sun
Michels, D. J.; Gurman, J. B.; Berghmans, D. +32 more
The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrume…