Search Publications
Fe II/Mg II Emission-Line Ratios of QSOs within 0 < z < 5.3
Doi, Mamoru; Yoshii, Yuzuru; Motohara, Kentaro +3 more
Near-infrared spectra of 13 QSOs located between 4.4<z<5.3 were obtained by the OH-airglow suppression spectrograph mounted on the Subaru telescope. The Fe II/Mg II emission-line ratios of the QSOs at various redshifts were examined by applying the same fitting algorithm to the present data together with published or archived spectra. We fou…
Is There a Metallicity-Luminosity Relationship in Active Galactic Nuclei? The Case of Narrow-Line Seyfert 1 Galaxies
Netzer, Hagai; Shemmer, Ohad
The well-known relationship between metallicity and luminosity in active galactic nuclei (AGNs) is addressed by introducing new metallicity measurements (based on the method of Hamann & Ferland, hereafter HF) for a sample of narrow-line Seyfert 1 galaxies (NLS1s). Our new results, based on a sample of 162 AGNs, including nine NLS1s, indicate t…
Mass Loss and Jet Outflow in the Orion Nebula Proplyd LV 2
O'Dell, C. R.; Henney, W. J.; Meaburn, J. +2 more
We have obtained Hubble Space Telescope (HST) Space Telescope Imaging Spectrometer high-resolution spectra of the Orion proplyd LV 2 in the C III doublet at 1906.68 and 1908.73 Å. New images at the 6 cm wavelength with MERLIN complement earlier HST images at a similar spatial resolution. This object is one of the closest proplyds to θ1 …
Quiescent and Flaring Structure in RS Canum Venaticorum Stars
Sanz-Forcada, J.; Dupree, A. K.; Brickhouse, N. S.
Four of the most active RS CVn stars (V711 Tau, II Peg, σ Gem, and UX Ari) have been observed for a total of 3 Ms with the Extreme Ultraviolet Explorer satellite (EUVE) between 1992 and 2000 January. Flaring and quiescent states of extreme ultraviolet spectra (λλ70-740) and light curves (λλ75-175) have been analyzed to provide emission measure dis…
Gasdynamics in NGC 5248: Fueling a Circumnuclear Starburst Ring of Super-Star Clusters
Wilson, Christine D.; Scoville, Nick; Laine, Seppo +4 more
Through observations and modeling, we demonstrate how the recently discovered large-scale bar in NGC 5248 generates spiral structure that extends from 10 kpc down to 100 pc, fuels star formation on progressively smaller scales, and drives disk evolution. Deep inside the bar, two massive molecular spirals cover nearly 180° in azimuth, show streamin…
Toward the Secondary Bar: Gas Morphology and Dynamics in NGC 4303
Schinnerer, Eva; Scoville, Nick; Moustakas, Leonidas A. +1 more
We report on the molecular gas properties in the central kiloparsec of the almost face-on double-barred galaxy NGC 4303 (M61), using the 12CO 1-0 line emission observed with the Owens Valley Radio Observatory (OVRO) millimeter interferometer. The bulk of the molecular line emission comes from two straight gas lanes that run north-south …
Modeling the Hubble Space Telescope Ultraviolet and Optical Spectrum of Spot 1 on the Circumstellar Ring of SN 1987A
Filippenko, Alexei V.; Zhekov, Svetozar A.; Pun, Chun S. J. +18 more
We report and interpret Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) long-slit observations of the optical and ultraviolet (1150-10270 Å) emission line spectra of the rapidly brightening spot 1 on the equatorial ring of SN 1987A between 1997 September and 1999 October (days 3869-4606 after outburst). The emission is cau…
Boron Abundances in B-Type Stars: A Test of Rotational Depletion during Main-Sequence Evolution
Lennon, D. J.; Keenan, F. P.; Lambert, David L. +4 more
Boron abundances have been derived for seven main-sequence B-type stars from Hubble Space Telescope STIS spectra around the B III λ2066 line. In two stars, boron appears to be undepleted with respect to the presumed initial abundance. In one star, boron is detectable but is clearly depleted. In the other four stars, boron is undetectable, implying…
Determination of the Distance to M33 Based on Single-Epoch I-Band Hubble Space Telescope Observations of Cepheids
Sarajedini, Ata; Lee, Myung Gyoon; Gieren, Wolfgang +2 more
We have determined the distance to M33 using single-epoch I-band observations of Cepheids based on Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 (WFPC2) images of five fields in M33. Combining the HST I-band photometry and the periods determined from the ground-based observations (DIRECT) for 21 Cepheids with logP>0.8 in the sample…
Detection of a Super-Star Cluster as the Ionizing Source in the Low-Luminosity Active Galactic Nucleus NGC 4303
Leitherer, Claus; Colina, Luis; Mas-Hesse, J. Miguel +1 more
Hubble Space Telescope (HST) ultraviolet Space Telescope Imaging Spectrograph (STIS) imaging and spectroscopy of the low-luminosity active galactic nucleus (LLAGN) NGC 4303 have identified the previously detected UV-bright nucleus of this galaxy as a compact, massive, and luminous stellar cluster. The cluster with a size (FWHM) of 3.1 pc and an ul…