D. Wills

Broad emission features in QSOs and active galactic nuclei. II - New observations and theory of Fe II and H I emission

Seven QSOs of low to intermediate redshift are characterized on the basis of: 320-850-nm spectra obtained with the UVITS spectrograph and image-dissector scanner at the f/9 Cassegrain focus of the 2.7-m reflecting telescope at McDonald Observatory; improved model calculations for the Fe II, Mg II, and Balmer lines and the Balmer continuum; and the theoretical results of Netzer and Wills (1983). The data are presented in tables, spectra, and difference spectra and described in detail. Fe II is found to be the largest contributor to the emission line spectrum, with strong UV Fe II lines in all QSOs (regardless of the strength of the optical Fe II lines) and an abundance ratio suggesting a factor-of-three overabundance of Fe relative to Mg and probably H. A discrepancy between the observed Fe II strength and the predictions of dustless standard photoionization models is noted, and the addition of a high-density component to the models is suggested.

A survey for high optical polarization in quasars with core-dominant radio structure - Is there a beamed optical continuum?

129 new optical linear polarization measurements of 84 quasars (defined as starlike on Sky Survey prints) are presented. 23 new highly polarized objects (p > 3%) were discovered, of which 14 are known to have broad emission lines. This represents a significant increase in the numbers of these objects that were known. With the addition of data from the literature, our measurements constitute well-defined samples of flat-spectrum core-dominant radio quasars brighter than about 18 mag, one selected from the list published by Perley (1982, AJ, 87), and another from that by Kuhr et al. (1981)

The Next Generation Atlas of Quasar Spectral Energy Distributions from Radio To X-Rays

We have produced the next generation of quasar spectral energy distributions (SEDs), essentially updating the work of Elvis et al. by using high-quality data obtained with several space- and ground-based telescopes, including NASAs Great Observatories. We present an atlas of SEDs of 85 optically bright, non-blazar quasars over the electromagnetic spectrum from radio to X-rays. The heterogeneous sample includes 27 radio-quiet and 58 radio-loud quasars. Most objects have quasi-simultaneous ultraviolet-optical spectroscopic data, supplemented with some far-ultraviolet spectra, and more than half also have Spitzer mid-infrared Infrared Spectrograph spectra. The X-ray spectral parameters are collected from the literature where available. The radio, far-infrared, and near-infrared photometric data are also obtained from either the literature or new observations. We construct composite SEDs for radio-loud and radio-quiet objects and compare these to those of Elvis et al., finding that ours have similar overall shapes, but our improved spectral resolution reveals more detailed features, especially in the mid- and near-infrared.

Polarimetry and spectrophotometry of the QSO IRAS 13349 + 2438 and the unification of active galaxies

We have made new observations of the bright (V=14.7) infrared-selected QSO IRAS 13349+2438 (Beichman et al.), which provide important clues about the structure of the inner few parsecs of active galactic nuclei (AGNs). The principal observational facts are as follows: 1. There is high linear optical polarization, increasing with decreasing wavelength from 1.4% at 2.2 μm (K-band) to 8% at 0.36 μm (U-band). 2. The position angle of polarization is independent of wavelength in the optical region and is aligned with the direction of elongation of the r-band optical image, presumably the major axis of the host galaxy

Spectral Properties from Lyα to Hα for an Essentially Complete Sample of Quasars. I. Data

We have obtained quasi-simultaneous ultraviolet-optical spectra for 22 out of 23 quasars in the complete Palomar-Green X-ray sample with redshift z < 0.4 and MB < -23. The spectra cover rest-frame wavelengths from at least Lyα to Hα. Here we provide a detailed description of the data, including careful spectrophotometry and redshift determination. We also present direct measurements of the continua, strong emission lines, and features, including Lyα, Si IV+O IV] λ1400, C IV, C III], Si III], Mg II, Hβ, [O III], He I λ5876+Na I λλ5890,5896, Hα, and blended iron emission in the UV and optical. The widths, asymmetries, and velocity shifts of profiles of strong emission lines show that C IV and Lyα are very different from Hβ and Hα. This suggests that the motion of the broad-line region is related to the ionization structure, but the data appear to not agree with the radially stratified ionization structure supported by reverberation mapping studies, and therefore suggest that outflows contribute additional velocity components to the broad emission line profiles.

The narrow-line region of high-luminosity active galactic nuclei

We have made high signal-to-noise spectroscopic observations of seven radio-loud quasars with the Faint Object Spectrograph on the Hubble Space Telescope and from the ground at McDonald Observatory and at Kitt Peak National Observatory. The resolution is 300-400 km s -1 over the wavelength range 1000-8500 A, enabling us to separate the broad and narrow components of the emission lines. This is the first study of the optical and UV narrow lines in such high-luminosity active galactic nuclei (AGNs). The most important and striking observational result is the relative weakness of the narrow ultraviolet lines, assuming that they have the same widths as the narrow [O III] λ5007 emission lines. We do not have a single definite detection of a narrow UV line in any of the seven quasars

Supernovae 1983i and 1983v - Evidence for abundance variations in type Ib supernovae

Spectra are presented of SN 1983i 5 days after discovery and of SN 1983v 13 days after discovery. The similarity of these two spectra argues that they are of similar origin and phase. Theoretical atmosphere calculations provide evidence for a connection to the type Ib supernovae 1983n and 1984l, with SN 1983i and 1983v having a similar structure but less helium and more carbon and oxygen. Available photometry suggests that the spectra correspond to a phase about 20 days after maximum light. These spectra are consistent with an interpretation of type Ib supernovae arising in the bare cores of moderately massive stars, with individual events showing a range in He/O mass ratio from approximately 10 to less than 1.

The Optical Polarization and Warm Absorber in IRAS 17020+4544

We report the detection of ionized absorption in the ASCA spectrum of the narrow-line Seyfert 1 galaxy IRAS 17020+4544. Subsequent optical spectropolarimetry revealed high polarization increasing from 3% in the red to 5% in the blue, which indicates electron or dust scattering as a likely origin. The broad emission line Hα is somewhat less polarized than the continuum, which supports a location of the polarizing material within the active galactic nucleus. The Balmer line decrement and reddened optical spectrum support the presence of a dusty warm absorber in this object. We compared the broadband optical polarization and ionized X-ray absorption of a collection of Seyfert 1 and 1.5 galaxies, excluding classes of objects that are likely to have significant neutral X-ray absorption. Warm absorber objects are generally more likely to have high optical polarization than objects with no detected ionized absorption. This result lends additional support to the idea that the warm absorber is associated with dust and implies either that dust transmission is responsible for at least part of the polarization or that the polarization is revealed because of the dimming of the optical spectrum. Spectropolarimetry of Seyfert 1 galaxies generally locates the scattering material inside the narrow-line region and often close to or within the broad-line region, consistent with estimates of the location of the dusty warm absorber.

THE OPTICAL-ULTRAVIOLET-GAMMA-RAY SPECTRUM OF 3C 279

We have obtained spectrosocpy of the violently variable quasar 3C 279, simultaneous with gamma-ray observations, in 1992 April. Our combined optical (McDonald Observatory and Cerro Tololo InterAmerican Observatory (CTIO) and ultraviolet (HST) observations, made when the source was faint, show a very steep power-law continuum (F(sub nu) is proportional to nu(exp -1.95), and strong broad emission lines. This is the first time that the broad ultraviolet lines of this object have been measured, and we note several unusual properties of the spectrum. In particular, the profiles of C IV lambda 1549 and Mg II lambda 2798 are asymmetric, with very strong red wings, in contrast to the symmetic profiles of Ly alpha C III lambda 1909, and possible H-beta. The observed asymmetry cannot be explained by a simple outflow associted with the eruption of the source. In addition, the C IV lambda 1549/Ly-alpha and C III lambda 1909/Ly-alpha line intensity ratios are the largest we have observed in out Hubble Space Telescope (HST) sample of more than 30 radio-loud quasars, even though the C III llambda 1909/C IV lambda 1549 ratio is quite typical. 3C 279 was observed in the gamma-ray region by EGRET (Energetic Gamma-Ray Experiment Telescope) at the same time as our optical-ultraviolet observations. The extrapolated ultraviolet continuum falls nine orders of magnitude below the gamma-ray point and we show that this, combined with the optical UV continuum slope, is enough to rule out several synchtoyotron-self-Compton models suggested to explain the multiwavelength spectra of blazars.

Optical and ultraviolet observations of 3C 279 during outburst

An ongoing program of photometric monitoring of selected active galactic nuclei has revealed a significant outburst in the optically violently variable (OVV) quasi-steller object (QSO) 3C 279. The event occurred during May and June of 1992, and was characterized by a peak amplitude of 2.3 mag in the R band. We obtained nearly simultaneous optical and ultraviolet spectroscopy from 1150 to 8600 A of the source at the approximate midpoint of the outburst. The outburst spectrum is well represented by a power law with index alpha = -1.77 (where F(sub nu) varies as nu (exp alpha) which is relatively flat in comparison with typical quiescent spectra for this source. No emission features are discernable in our data, nor is there any significant Lyman-edge absorption. The observations and data analysis procedures are described, and the resulting photometric light curves and spectra are presented. We also present a long baseline photometric light curve for context. Comparisons with previously published optical-UV outburst and quiescent spectra are made, and luminosity-dependent spectral variations are discussed.