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Galaxy Morphology without Classification: Self-organizing Maps
Griffiths, Richard E.; Ratnatunga, Kavan U.; Naim, Avi
We examine a general framework for visualizing data sets of high (greater than 2) dimensionality and demonstrate the framework by taking the morphology of galaxies at moderate redshifts as an example. The distributions of various populations of such galaxies are examined in a space spanned by four purely morphological parameters. Galaxy images are…
Hubble Space Telescope Wide Field Planetary Camera 2 Imaging of the Crab Nebula. I. Observational Overview
Blair, William P.; Davidson, Kris; Henry, Richard B. C. +3 more
We present Hubble Space Telescope WFPC2 images of a portion of the Crab Nebula supernova remnant obtained using narrow passband filters. These images show a wide range of filament morphologies including small individual isolated knots, long smooth arcs, and chaotic filament complexes, with evidence that some filament cores are far denser and coole…
Gamma-Ray Burst Arrival Time Localizations: Simultaneous Observations by Mars Observer, Compton Gamma Ray Observatory, and ULYSSES
Hurley, K. C.; Fishman, G. J.; Kouveliotou, C. +12 more
Between 1992 October 4 and 1993 August 1, concurrent coverage by the Compton Gamma Ray Observatory (CGRO), Mars Observer (MO), and Ulysses spacecraft was obtained for 78 gamma-ray bursts (GRBs). Although most of these were below the MO and Ulysses thresholds, nine were positively detected by all three spacecraft, with data quality adequate for qua…
The Spectrum of the Planetary Nebula NGC 6884
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H.
The bright, compact, moderately high-excitation planetary nebula, NGC 6884 (Perek-Kohoutek 82 +07°1) has a rich spectrum promising good diagnostics and offering a good target for the Hamilton Echelle Spectrograph at Lick Observatory. We combine International Ultraviolet Explorer (IUE), near-UV, visual, and IR data to obtain N(ion)/N(H+)…
Infrared Photometry of 487 Sources in the Inner Regions of NGC 5128 (Centaurus A)
Minniti, Dante; Alonso, M. Victoria
We study the sources present in the inner 3 kpc region of NGC 5128 (Cen A), most of which are star clusters of different ages. Photometry of archival Hubble Space Telescope WFPC images (F675W filter) is complemented with IR photometry (JHK' filters) obtained with the IRAC2B infrared array camera at the ESO/MPI 2.2 m telescope. From IR color maps w…
The IUE Spectrum of the ``O VI Sequence'' Planetary Nebula IC 2003
Feibelman, Walter A.
We present archival low- and high-dispersion, as well as new SWP high-dispersion, IUE data of the ``O VI sequence'' planetary nebula IC 2003 that has not been studied extensively in the UV. Contrary to earlier UV studies, IC 2003 shows a rich spectrum of stellar and nebular emission lines. Nearly 60 new emission line fluxes are presented for He II…
The Greatly Expanded IUE Spectrum of the Planetary Nebula NGC 2371-2 and Its Central Star
Feibelman, Walter A.
Early IUE low-dispersion SWP and LWR spectra have been reexamined by means of refined current data reduction routines. These spectra contain much more information than was reported in 1981. A high-dispersion SWP spectrum was obtained in 1994 from which more than 80 emission and absorption features were identified, and log Ne = 3.0 +/- 0…
The Morphologies of Distant Galaxies. II. Classifications from the Hubble Space Telescope Medium Deep Survey
Glazebrook, Karl; Ellis, Richard S.; Abraham, Roberto G. +4 more
The morphological properties of high-redshift galaxies are investigated using a sample of 507 objects (I < 22.0 mag) from the Hubble Space Telescope (HST) Medium Deep Survey. Independent visual morphological classifications for each galaxy are used to quantify the statistical uncertainties in the galaxy classifications. Visual classifications a…
Comparative Analysis of the High- and Low-Ionization Lines in the Broad-Line Region of Active Galactic Nuclei
Marziani, P.; Moles, M.; Sulentic, J. W. +2 more
We present the first comparative study of high- and low-ionization lines in a large sample of active galactic nuclei (AGNs). We report measurements of C IV λ1549, HeII λ1640, and O III] λ1663 paired to measurements of Hβ, HeII λ4686, and Fe II_opt_ in 52 low-redshift AGNs (z <~0.8). Ultraviolet archival spectra covering the region of C IV λ1549…
HST Snapshot Survey of 3CR Radio Source Counterparts. I. Intermediate Redshifts
Baum, Stefi A.; Sparks, William B.; Miley, George K. +5 more
We have obtained images of 267 3CR radio galaxies and quasars by conducting a snapshot survey with HST's WFPC2 through a broadband red (F702W) filter. This is the first in a series of papers resulting from this survey, describing and presenting the basic data. Here we focus on the 77 radio galaxies within the redshift range 0.1 <z < 0.5 (91%…