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Reddening and Star Formation in Starburst Galaxies

Calzetti, Daniela

The reddening properties and the star formation history of a sample of 19 starburst galaxies are investigated using multiwavelength spectroscopy and infrared broad band photometry. New photometric data in the J, H, and K bands of the central starburst regions are supplemented with previously published spectra, covering the wavelength range 0.12-2.…

Peace: a Plasma Electron and Current Experiment

Coates, A. J.; Winningham, J. D.; Grande, M. +13 more

Keck Spectroscopy of Redshift z ~ 3 Galaxies in the Hubble Deep Field

Illingworth, Garth D.; Faber, S. M.; Gronwall, Caryl +6 more

We have obtained spectra with the 10 m Keck telescope of a sample of 24 galaxies having colors consistent with star-forming galaxies at redshifts 2 <~ z <~ 4.5 in the Hubble deep field (HDF). Eleven of these galaxies are confirmed to be at high redshift (z_med = 3.0), one is at z = 0.5, and the other 12 have uncertain redshifts but…

The Cepheid period-luminosity zero-point from HIPPARCOS trigonometrical parallaxes

Catchpole, R. M.; Feast, M. W.

Hipparcos trigonometrical parallaxes of Cepheid variables are used to derive a zero-point for the period-luminosity (PL) relation. Adopting a slope from the Large Magellanic Cloud (LMC), the relation is found to be <M_V>=-2.81 log P-1.43. The standard error of the zero-point is 0.10 mag. Together with metallicity corrections this corresponds…

The Homogeneity of Spheroidal Populations in Distant Clusters

Smail, Ian; Ellis, Richard S.; Dressler, Alan +4 more

The small scatter observed for the (U-V) colors of spheroidal galaxies in nearby clusters of galaxies provides a powerful constraint on the history of star formation in dense environments. However, with local data alone, it is not possible to separate models where galaxies assembled synchronously over redshifts 0 < z < 1 from ones where gala…

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…