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Hubble Space Telescope Space Telescope Imaging Spectrograph Imaging of the Host Galaxy of GRB 980425/SN 1998BW
Tanvir, N.; Hjorth, J.; Björnsson, G. +6 more
We present Hubble Space Telescope Space Telescope Imaging Spectrograph observations of ESO 184-G82, the host galaxy of the gamma-ray burst GRB 980425 associated with the peculiar Type Ic supernova SN 1998bw. ESO 184-G82 is found to be an actively star-forming SBc subluminous galaxy. We detect an object consistent with being a point source within t…
RX J0911+05: A Massive Cluster Lens at z=0.769
Kneib, Jean-Paul; Hjorth, Jens; Cohen, Judith G.
We report the detection of a massive high-redshift cluster of galaxies near the quadruple quasar RX J0911+05, using the Low-Resolution Imaging Spectrograph instrument on the Keck II telescope. The cluster is found to have a mean redshift of z=0.7689+/-0.002 and a velocity dispersion of σ=836+180-200 km s-1, based o…
Signatures of the Rise of Cycle 23
Kosovichev, A. G.; Schou, J.; Dziembowski, W. A. +1 more
During the rise of Cycle 23, we have found a sizable, systematic evolution of the Solar and Heliospheric Observatory/Michelson Doppler Imager solar oscillation frequencies implying significant changes in the spherically symmetric structure of the Sun's outer layers as well as in its asphericity up to a P18 Legendre distortion. We conduc…
Seeing Galaxies through Thick and Thin. I. Optical Opacity Measures in Overlapping Galaxies
Conselice, Christopher J.; White, Raymond E., III; Keel, William C.
We describe the use of partially overlapping galaxies to provide direct measurements of the effective absorption in galaxy disks, independent of assumptions about internal disk structure. The nonoverlapping parts of the galaxies and symmetry considerations are used to reconstruct, via differential photometry, how much background galaxy light is lo…
HST/WFPC2 and VLT/ISAAC Observations of Proplyds in the Giant H II Region NGC 3603
Grebel, Eva K.; Brandner, Wolfgang; Chu, You-Hua +6 more
We report the discovery of three proplyd-like structures in the giant H II region NGC 3603. The emission nebulae are clearly resolved in narrowband and broadband HST/WFPC2 observations in the optical and broadband VLT/ISAAC observations in the near-infrared. All three nebulae are tadpole shaped, with the bright ionization front at the head facing …
The first VLT FORS1 spectra of Lyman-break candidates in the HDF-S and AXAF Deep Field
Aragón-Salamanca, A.; Cristiani, S.; Arnouts, S. +9 more
We report on low-resolution multi-object spectroscopy of 30 faint targets (R =~ 24-25) in the HDF-S and AXAF deep field obtained with the VLT Focal Reducer/low dispersion Spectrograph (FORS1). Eight high-redshift galaxies with 2.75< z < 4 have been identified. The spectroscopic redshifts are in good agreement with the photometric ones with a…
On the Emergence and Discovery of Hot Spots in SNR 1987A
Crotts, Arlin P. S.; Lawrence, Stephen S.; Heathcote, Steve +3 more
We present the discovery of several new regions of interaction between the ejecta and equatorial circumstellar ring of SN 1987A, an interaction leading to a much-expanded development of the supernova remnant. We also trace the development of the first such ``hot spot,'' discovered in 1997, back to 1995. Later hot spots seem to have emerged by earl…
A Recalibration of IUE NEWSIPS Low-Dispersion Data
Fitzpatrick, E. L.; Massa, D.
While the low-dispersion IUE New Spectroscopic Image Processing System (NEWSIPS) data products represent a significant improvement over original IUE Spectroscopic Image Processing System (SIPS) data, they still contain serious systematic effects which compromise their utility for certain applications. We show that NEWSIPS low-resolution data are i…
On the Helium Content of Galactic Globular Clusters via the R-Parameter
Djorgovski, S. G.; Zoccali, M.; Rich, R. M. +3 more
We estimate the empirical R-parameter in 26 Galactic globular clusters covering a wide metallicity range, imaged by Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The improved spatial resolution permits a large fraction of evolved stars to be measured and permits accurate assessment of radial population gradients and completene…
Multi-component structure of solar and stellar transition regions
Peter, H.
Emission lines from the solar transition region between the chromosphere and the corona often show a two Gaussian component profile with a core and a broad second component contributing up to 25% to the total intensity. For the first time a systematic study of the broadening and Doppler shift of the second weaker components is performed using SUME…