Search Publications
The Origin of a Chemically Enriched Lyα Absorption System at Z = 0.167
Chen, Hsiao-Wen; Prochaska, Jason X.
We present the first detailed analysis of the chemical abundances, ionization state, and origin of a partial Lyman limit system [N(H I)~1016 cm-2] at low redshift (z=0.167 toward PKS 0405-1219). Two galaxies at an ~70 h-1 kpc projected distance to the QSO have been identified at the absorber redshift. We analyze an…
Silicate Emission in T Tauri Stars: Evidence for Disk Atmospheres?
Meyer, Michael R.; Beckwith, Steven V. W.; Natta, Antonella
We present low-resolution mid-infrared spectra of nine classical T Tauri stars associated with the Chamaeleon I dark cloud. The data were obtained with the PHOT-S instrument on board the Infrared Space Observatory (ISO) in the two wavelength ranges 2.5-4.9 and 5.9-11.7 µm. All nine stars show evidence of silicate emission at 10 µm, whi…
The Very Red Afterglow of GRB 000418: Further Evidence for Dust Extinction in a Gamma-Ray Burst Host Galaxy
Pian, E.; Palazzi, E.; Greiner, J. +36 more
We report near-infrared and optical follow-up observations of the afterglow of the GRB 000418 starting 2.5 days after the occurrence of the burst and extending over nearly 7 weeks. GRB 000418 represents the second case for which the afterglow was initially identified by observations in the near-infrared. During the first 10 days its R-band aftergl…
Discovery of a Nuclear Gas Bar Feeding the Active Nucleus in Circinus
Maiolino, R.; Rieke, G. H.; Alonso-Herrero, A. +4 more
We report the discovery of gas inflow motions toward the active nucleus of the Circinus galaxy caused by the nonaxisymmetric potential of a nuclear gas bar. Evidence for dust associated with the bar comes from the HST/NICMOS H-K color map, whereas the streaming motions along the gas bar are seen in the velocity field of the H2 S(1) (1-0…
Detection of Extended Thermal Infrared Emission around the Vega-like Source HD 141569
Telesco, C. M.; Fisher, R. S.; Piña, R. K. +2 more
We report the detection of extended IR emission at 10.8 and 18.2 µm around the Vega-like source HD 141569. Mid-IR imaging with OSCIR on Keck II shows emission from dust extending out to 100 AU from the B9.5 Ve star. Our modeling of the dust places an upper limit of ~2 µm on the diameter of the mid-IR-emitting particles if they are Mie …
Empirical Verification of the Fe II Oscillator Strengths in the FUSE Bandpass
Sembach, Kenneth R.; Roth, Katherine C.; Howk, J. Christopher +1 more
We report empirical determinations of atomic oscillator strengths, or f-values, for 11 ground-state transitions of Fe II in the wavelength range 1050<~λ<~1150 Å. We use ultraviolet absorption-line observations of interstellar material toward stars in the Galaxy and the Magellanic Clouds taken with Copernicus, the Goddard High Resolution Spec…
Evidence of a North-South Asymmetry in the Heliosphere Associated with a Southward Displacement of the Heliospheric Current Sheet
Smith, E. J.; Szabo, A.; Lepping, R. P. +2 more
Evidence of a north-south asymmetry in the global heliosphere, first inferred from Ulysses cosmic-ray observations, is investigated using simultaneous Ulysses and Wind magnetic field observations. Such an asymmetry, presumably associated with a southward displacement of the heliospheric current sheet (HCS), is expected to produce significantly dif…
A High Signal-to-Noise Ultraviolet Spectrum of NGC 7469: New Support for Reprocessing of Continuum Radiation
Peterson, Bradley M.; Kriss, Gerard A.; Zheng, Wei +1 more
From 1996 June 10 to 1996 July 29, the International AGN Watch monitored the Seyfert 1 galaxy NGC 7469 using the International Ultraviolet Explorer, the Rossi X-Ray Timing Explorer, and a network of ground-based observatories. On 1996 June 18, in the midst of this intensive monitoring period, we obtained a high signal-to-noise snapshot of the UV s…
Galaxy Morphologies in the Cluster Cl 1358+62 at z=0.33
Franx, Marijn; van Dokkum, Pieter; Fabricant, Daniel
We describe the morphological composition of a sample of 518 galaxies in the field of Cl 1358+62 at z=0.33, drawn from a large Hubble Space Telescope mosaic covering 53 square arcminutes. The sample is complete to I=22, corresponding to MV=-18.5 in the rest frame. The galaxy morphologies have been independently classified by the authors…
Infrared Spectroscopy of NGC 1068: Probing the Obscured Ionizing AGN Continuum
Lutz, Dieter; Netzer, Hagai; Alexander, Tal +3 more
The ISO-SWS4 2.5-45 µm infrared spectroscopic observations of the nucleus of the Seyfert 2 galaxy NGC 1068 (see companion paper) are combined with a compilation of UV to IR narrow emission line data to determine the spectral energy distribution (SED) of the obscured extreme-UV continuum that photoionizes the narrow-line-emitting gas in the a…