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Deep HST V- and I-Band Observations of Two Globular Clusters in the Halo of M31.
Richer, Harvey B.; Fahlman, Gregory G.; Holland, Stephen
We present deep (V∼=27) V- and I-band stellar photometry of G302 and G312, two globular star clusters in the halo of M31. These data were obtained using the Hubble Space Telescope's Wide Field/Planetary Camera 2. We find iron abundances of [Fe/H]= -1.85±0.12 for G302 and [Fe/H]=-0.56±0.03 for G312, consistent with spectroscopic measurements. The c…
Association of Extreme-Ultraviolet Imaging Telescope (EIT) Polar Plumes with Mixed-Polarity Magnetic Network
Michels, D. J.; Gurman, J. B.; Delaboudinière, J. -P. +18 more
SOHO EIT spectroheliograms showing the polar coronal holes during the present sunspot minimum are compared with National Solar Observatory (Kitt Peak) magnetograms taken in Fe I λ8688 and Ca II λ8542. The chromospheric λ8542 magnetograms, obtained on a routine, near-daily basis since 1996 June, reveal the Sun's strong polar fields with remarkable …
The Nuclear Region of NGC 1068: High-Accuracy Alignment of the Optical and Radio Emission
Macchetto, F. D.; Capetti, A.; Lattanzi, M. G.
We present the results of a campaign to obtain an accurate registration of Hubble Space Telescope (HST) and MERLIN images of NGC 1068, the prototypical Seyfert 2 galaxy. The final registration is accurate to 100 mas.
A strong anticorrelation between radio and optical emission is revealed; in particular, the radio jet lies on a region of relat…Titan's North-South Asymmetry from HST and Voyager Imaging: Comparison with Models and Ground-Based Photometry
Karkoschka, Erich; Lorenz, Ralph D.; Lemmon, Mark T. +3 more
New measurements of Titan's hemispheric brightness asymmetry from HST images from 260 to 1040 nm show that the contrast is strongest near 450 nm (blue) and, with the opposite sign, at 889 nm (methane band). Comparison with a full Titan year of disk-integrated albedo data indicates that the seasonal cycle in asymmetry is smooth, but is insufficient…
The morphological segregation of galaxies in clusters. III. The distant cluster CL 0939+4713 (Abell 851).
Andreon, S.; Davoust, E.; Heim, T.
We have performed an isophotal analysis of galaxies in the distant (z=0.4) cluster Cl0939+4713 (Abell 851), using post-refurbished Hubble Space Telescope images. Morphological type estimates for the galaxies are given. A rigorous comparison of the properties of the types shows that early-type galaxies in Cl0939+4713 are, within the present statist…
Hot HB stars in globular clusters: physical parameters and consequences for theory III. NGC 6752 and its long blue vertical branch.
Heber, U.; Moehler, S.; Rupprecht, G.
We present spectroscopic analyses of 17 faint blue stars in the globular cluster NGC 6752, using optical and UV spectrophotometric data and intermediate resolution optical spectra. Effective temperatures, surface gravities, and helium abundances of the stars are determined and compared to theoretical predictions. All stars are helium deficient by …
A One-sided Ionization Cone in the Seyfert 2 Galaxy NGC 5643
Simpson, Chris; Krolik, J. H.; Wilson, A. S. +3 more
We present high-resolution (0.1") observations of the Seyfert 2 galaxy NGC 5643 taken with the WFPC2 on board the Hubble Space Telescope. Images taken in the light of [O III] λ5007 and Hα reveal a halo of emission centered on the nucleus and high-excitation extranuclear emission which extends eastward for at least 1.8 kpc. An excitation map of [O …
Detection of the Tip of the Red Giant Branch in NGC 3379 (M105) in the Leo I Group Using the Hubble Space Telescope
Madore, Barry F.; Freedman, Wendy L.; Lauer, Tod R. +3 more
We report the detection of individually resolved stars in the elliptical galaxy NGC 3379, a luminous member of the Leo I Group. The bright end of the stellar luminosity function has a logarithmic slope that is consistent with these stars being Population II red giants. An abrupt discontinuity in the apparent luminosity function at I = 26.30 +/- 0.…
Detection of [O I] 63µm in absorption toward SGR B2.
Prusti, T.; Liseau, R.; Burgdorf, M. +26 more
A high signal-to-noise 52-90µm spectrum is presented for the central part of the Sagittarius B2 complex. The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The [O I] 63µm line is detected in absorption even at the grating spectral resolution of 0.29µm. A lower limit for the…
SS 433 in the ultraviolet.
Dolan, J. F.; Boyd, P. T.; Fabrika, S. +8 more
The High Speed Photometer (HSP) on the Hubble Space Telescope observed SS 433 at 15 different epochs between 1993 May and November. Polarimetric observations were obtained in a 340Å FWHM bandpass centered at 2770Å; photometric observations were made in a bandpass extending between 1400 and 3000Å. The polarization in the UV is both large (
=13…