Analyses of spectra obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, together with spectra from the Copernicus and IMAPS instruments, reveal an unexplained very wide range in the observed deuterium/hydrogen (D/H) ratios for interstellar gas in the Galactic disk beyond the Local Bubble. We argue that spatial variations in the depletion of deuterium onto dust grains can explain these local variations in the observed gas-phase D/H ratios. We present a variable deuterium depletion model that naturally explains the constant measured values of D/H inside the Local Bubble, the wide range of

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The Advanced Camera for Surveys (ACS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) have been used to obtain new Hubble Space Telescope images of NGC 4038/4039 ("The Antennae"). These new observations allow us to better differentiate compact star clusters from individual stars, based on both size and color. We use this ability to extend the cluster luminosity function by approximately two magnitudes over our previous WFPC2 results, and find that it continues as a single power law, dN/dL ∝ L α with α = −2.13 ± 0.07, down to the observational limit of M V ≈ −7. Similarly, the mass function is a single power law dN/dM ∝ M β with β = −2.10 ± 0.20 for -2clusters with ages < 3 × 10 8 yr, corresponding to lower mass limits that range from 10 4 to 10 5 M ⊙ , depending on the age range of the subsample. Hence the power law indices for the luminosity and mass functions are essentially the same. The luminosity function for intermediate-age clusters (i.e., ∼100-300 Myr old objects found in the loops, tails, and outer areas) shows no bend or turnover down to M V ≈ −6, consistent with relaxation-driven cluster disruption models which predict the turnover should not be observed until M V ≈ −4. An analysis of individual ∼0.5-kpc sized areas over diverse environments shows good agreement between values of α and β, similar to the results for the total population of clusters in the system. There is tentative evidence that the values of both α and β are flatter for the youngest clusters in some areas, but it is possible that this is caused by observational biases. Several of the areas studied show evidence for age gradients, with somewhat older clusters appearing to have triggered the formation of younger clusters. The area around Knot B is a particularly interesting example, with an ∼10-50 Myr old cluster of estimated mass ∼ 10 6 M ⊙ having apparently triggered the formation of several younger, more massive (up to 5 × 10 6 M ⊙ ) clusters along a dust lane. A comparison with new NICMOS observations reveals that only 16 ± 6% of the IR-bright clusters in the Antennae are still heavily obscured, with values of A V > 3 mag.

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We present Hubble Space T elescope (HST) Wide Field and Planetary Camera 2 images and Faint Object Spectrograph data of two young supernova remnants in the Magellanic Clouds, N132D (LMC) and 1E 0102.2[7219 (SMC). The spectra cover essentially the entire UV/optical range available to HST and provide the Ðrst true comparison of UV/optical line intensities from astrophysical shocks that do not depend on scalings from di †erent aperture sizes or instruments. For the spectra, we isolated speciÐc knots and Ðlaments that contain fast-moving debris of nuclear-processed material that are devoid of hydrogen and appear to have originated from the cores of the progenitor stars. In N132D we also observed a knot on the outer rim of the remnant that represents a shocked interstellar cloud. In the debris from both remnants, we identify only the elements O, Ne, C, and Mg. We Ðnd no evidence for oxygen-burning products, such as S, Ca, Ar, etc., which are seen in Cas A and are expected from models of Type II supernovae. We suggest that the progenitor stars of N132D and 1E 0102.2[7219 had large, oxygen-rich mantles (perhaps Wolf-Rayet stars) and may be the products of Type Ib supernovae. Shock modeling demonstrates systematic di †erences in the relative abundances in the O-rich debris, possibly pointing to di †erent progenitor masses for these two objects. The shocked interstellar knot in N132D shows that we are probably seeing a range of conditions within the D1A aperture and that no evidence is present for enrichment by a precursor star wind.

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The Far Ultraviolet Spectroscopic Explorer satellite observes light in the far-ultraviolet spectral region, 905 -1187 Å with high spectral resolution. The instrument consists of four coaligned prime-focus telescopes and Rowland spectrographs with microchannel plate detectors. Two of the telescope channels use Al:LiF coatings for optimum reflectivity from approximately 1000 to 1187 Å and the other two use SiC coatings for optimized throughput between 905 and 1105 Å. The gratings are holographically ruled to largely correct for astigmatism and to minimize scattered light. The microchannel plate detectors have KBr photocathodes and use photon counting to achieve good quantum efficiency with low background signal. The sensitivity is sufficient to examine reddened lines of sight within the Milky Way as well as active galactic nuclei and QSOs for absorption line studies of both Milky Way and extra-galactic gas clouds. This spectral region contains a number of key scientific diagnostics, including O VI, H I, D I and the strong electronic transitions of H 2 and HD.