Vesa T. Junkkarinen

Continuum and Emission-Line Strength Relations for a Large Active Galactic Nuclei Sample

We report on the analysis of a large sample of 744 type 1 active galactic nuclei, including quasars and Seyfert 1 galaxies across the redshift from 0 z 5 and spanning nearly 6 orders of magnitude in continuum luminosity. We discuss correlations of continuum and emission-line properties in the rest-frame ultraviolet and optical spectral ranges. The well-established Baldwin effect is detected for almost all emission lines from O VI ?1034 to [O III] ?5007. Their equivalent widths are significantly anticorrelated with the continuum strength, while they are nearly independent of redshift. This is the well-known Baldwin effect. Its slope ?, measured as log W? ? log ?L?(1450 ?), shows a tendency to become steeper toward higher luminosity. The slope of the Baldwin effect also increases with the ionization energy needed to create the individual lines. In contrast to this general trend, the N V ?1240 equivalent width is nearly independent of continuum luminosity and remains nearly constant. The overall line behaviors are consistent with softer UV continuum shapes and perhaps increasing gas metallicity in more luminous active galactic nuclei.

HST STIS Observations of PG 0946+301: The Highest Quality UV Spectrum of a BALQSO

We describe deep (40 orbits) Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of the broad absorption line (BAL) quasi-stellar object (QSO) PG 0946+301 and make them available to the community. These observations are the major part of a multiwavelength campaign on this object aimed at determining the ionization equilibrium and abundances (IEAs) in BALQSOs. We present simple template fits to the entire data set, which yield firm identifications for more than two dozen BALs from 18 ions and give lower limits for the ionic column densities. We find that the outflows metallicity is consistent with being solar, while the abundance ratio of phosphorus to other metals is at least 10 times solar. These findings are based on diagnostics that are not sensitive to saturation and partial covering effects in the BALs, which considerably weakened previous claims for enhanced metallicity. Ample evidence for these effects is seen in the spectrum. We also discuss several options for extracting tighter IEA constraints in future analyses and present the significant temporal changes that are detected between these spectra and those taken by the HST Faint Object Spectrograph in 1992.

Hubble Space Telescope Observations of the Broad Absorption Line QuasarPG 0946+301

We analyze HST and ground based spectra of the brightest BALQSO in the UV: PG~0946+301. A detailed study of the absorption troughs as a function of velocity is presented, facilitated by the use of a new algorithm to solve for the optical depth as a function of velocity for multiplet lines. We find convincing evidence for saturation in parts of the troughs. This supports our previous assertion that saturation is common in BALs and therefore cast doubts on claims for very high metallicity in BAL flows. Due to the importance of BAL saturation we also discuss its evidence in other objects. In PG~0946+301 large differences in ionization as a function of velocity are detected and our findings supports the hypothesis that the line of sight intersects a number of flow components that combine to give the appearance of the whole trough. Based on the optical depth profiles, we develop a geometrical-kinematical model for the flow. We have positively identified 16 ions of 8 elements (H~I, C~III, C~IV, N~III, N~IV, N~V, O~III, O~IV, O~V, O~VI, Ne~V, Ne~VIII, P~V, Si~IV, S~V, S~VI) and have a probable identifications of Mg~X and S~IV. Unlike earlier analysis of IUE data, we find no evidence for BALs arising from excited ionic states in the HST spectrum of PG~0946+301.

The Type IC supernova 1994I in M51: detection of helium and spectral evolution

We present a series of spectra of SN 1994I in M51, starting 1 week prior to maximum brightness. The nebular phase began about 2 months after the explosion; together with the rapid decline of the optical light, this suggests that the ejected mass was small. Although lines of He I in the optical region are weak or absent, consistent with the Type Ic classification, we detect strong He I λ10830 absorption during the first month past maximum. Thus, if SN 1994I is a typical Type Ic supernova, the atmospheres of these objects cannot be completely devoid of helium. The emission-line widths are smaller than predicted by the model of Nomoto and coworkers, in which the iron core of a low-mass carbon-oxygen star collapses. They are, however, larger than in Type Ib supernovae.

Time-variable Intrinsic Absorption Lines in the Quasi-stellar Object Q2343+125

We discuss high-resolution Keck Observatory spectra of an intrinsic absorption-line system at redshift za ≈ 2.24 in the radio-quiet QSO Q2343+125 (ze = 2.515). The absorbers physical relationship to the QSO is confirmed by time-variable line strengths and partial line-of-sight coverage of the QSO continuum source. The N V, C IV, and Si IV doublets varied in unison by factors of 4 in less than 0.3 yr in the QSO rest frame. The resolved C IV doublet ratios show that the absorber occults 20% of the QSO continuum source; therefore, the absorbing clouds are likely to have characteristic sizes less than 0.01 pc. There is evidence for smaller coverage fractions when the lines were weaker, which could explain the line-strength changes. Lower ionization species such as C II and Si II are not detected. The Lyα line at za ≈ 2.24 is contaminated by the dense forest of cosmologically intervening absorption lines, but also appears to be weak or absent. The large uncertainties in the H I column prevent reliable constraints on the metal abundances. The za ≈ 2.24 lines clearly form in high-velocity ejecta from the QSO. The line profiles are smooth and rounded, with FWHM ~ 400 km s-1 and centroids shifted -24,000 km s-1 from the QSO emission redshift. Several narrow-line systems are present inside the broader absorption profiles, but they did not vary in strength and may be due to intervening gas. The large-amplitude variability, low coverage fractions, and large ratio of centroid to FWHM velocities imply different outflow properties than those inferred from the broad absorption lines (BALs) in other sources. Nonetheless, the ejecta identified by the za ≈ 2.24 absorber could be related to the BAL phenomenon and could be ubiquitous in QSOs if the gas subtends a small fraction of the sky as seen from the emission source(s).

The nature of the BL Lacertae object AO 0235 + 164

Emission features in the optical spectrum of the highly variable BL Lac object AO 0235 + 164 have been detected which are identified as Mg II, forbidden Ne V, and forbidden O II at a redshift of 0.9399, consistent with a cosmological interpretation of the two absorption systems at z = 0.524 and z = 0.851. The spectrum also shows emission features associated with the z = 0.524 system at a projected separation of 20 kpc from the apparent central concentration of the material producing that absorption. This implies a highly extended and very luminous line-emitting region for the material at z = 0.524. A comparison of the new data with previous spectroscopic observations of the BL Lac object when it was faint suggests that the Mg II emission may be variable on a time scale of approximately 2 yr. 45 references.

Broad absorption-line time variability in the QSO CSO 203

We present spectroscopy of the BALQSO CSO 203 during four epochs over a 17-month time span. These data show three distinct levels in the broad absorption lines (BALs) of Si IV 1397A and C IV 1549A. We also note possible variations in the N V 1240A and Al III 1857A absorption troughs. A broad-band monitoring effort during this period shows that the continuum level remained constant to within 10 percent. We argue that the triggering mechanism for the absorption-line changes is most likely synchronous with the continuum source photons; however, no correlation with the central source has yet been found. The observed variations are consistent with changes in the ionization level in the broad absorption-line region (BALR). We discuss possible mechanisms for these changes and the implications for the structure of the BALR.

Hubble Space Telescope Faint Object Spectrograph and ground-based observations of the broad absorption line quasar 0226-1024

Faint Object Spectrograph data from the Hubble Space Telescope of the broad absorption line quasar 0226-1024 have revealed the presence of 8-10 absorbing ions between 680 and 1000 A (restframe): C III, N III, N IV, O III, O IV, O VI, S V, S VI, possibly Ne VIII, and possibly O V* arising from a metastable excited state. We also present ground-based optical observations of the broad line troughs for the following ions: H I, C IV, N V, Si IV, and possibly Fe III, S IV, P V, and C III* (also arising from a metastable excited state). The results of this fit are used to estimate the absorbing ionic column densities. There is evidence that the broad absorption line clouds are optically thick and either do not completely cover the continuum source or narrow unresolved lines are present.

LBQS 0103–2753: A 0.″3 Binary Quasar*

Imaging and spectroscopy with HST show that LBQS 0103-2753 (V = 17.8, z = 0.848) is a binary quasar with a separation of 0.3 arcsec or 2.3 kpc. This is by far the smallest separation binary quasar reported to date. The two components have very different spectra, including the presence of strong broad absorption lines (BALs) in component A only. The emission-line redshifts, based on the broad high ionization C IV lines, are z_A = 0.834 and z_B = 0.858; their difference is 3900 km/s in velocity units. The broad C IV lines, however, are probably not a good indicator of systemic redshift; and LBQS 0103-2753 A and B could have a much smaller systemic redshift difference, like the other known binary quasars. If the systemic redshift difference is small, then LBQS 0103-2753 would most likely be a galaxy merger that has led to a binary supermassive black hole. There is now one known 0.3 arcsec binary among roughly 500 QSOs that have been observed in a way that would reveal such a close binary. This suggests that QSO activity is substantially more likely for black hole binaries at spacings ~2 kpc than at ~15 to 60 kpc. Between 1987 and 1998, the observed Mg II BAL disappeared.

The Dust-to-Gas Ratio in the Damped Lyα Clouds toward the Gravitationally Lensed QSO 0957+561

We present HST/FOS spectra of the two bright images (A and B) of the gravitationally lensed QSO 0957+561 in the wavelength range 2200-3300 A. We find that the absorption system (zabs = 1.3911) near zem is a weak, damped Lyα system with strong Lyα absorption lines seen in both images. However, the H I column densities are different, with the line of sight to image A intersecting a larger column density. The continuum shapes of the two spectra differ in the sense that the flux level of image A increases more slowly toward shorter wavelengths than that of image B. We explain this as the result of differential reddening by dust grains in the damped Lyα absorber. A direct outcome of this explanation is a determination of the dust-to-gas ratio, k, in the damped Lyα system. We derive k = 0.55 ± 0.18 for a simple 1/λ extinction law and k = 0.31 ± 0.10 for the Galactic extinction curve. For gravitationally lensed systems with damped Lyα absorbers, our method is a powerful tool for determining the values and dispersion of k, and the shapes of extinction curves, especially in the FUV and EUV regions. We compare our results with previous work.