Karen M. Leighly

REVERBERATION MAPPING MEASUREMENTS OF BLACK HOLE MASSES IN SIX LOCAL SEYFERT GALAXIES

We present the final results from a high sampling rate, multi-month, spectrophotometric reverberation mapping campaign undertaken to obtain either new or improved Hβ reverberation lag measurements for several relatively low-luminosity active galactic nuclei (AGNs). We have reliably measured the time delay between variations in the continuum and Hβ emission line in six local Seyfert 1 galaxies. These measurements are used to calculate the mass of the supermassive black hole at the center of each of these AGNs. We place our results in context to the most current calibration of the broad-line region (BLR) RBLR–L relationship, where our results remove outliers and reduce the scatter at the low-luminosity end of this relationship. We also present velocity-resolved Hβ time-delay measurements for our complete sample, though the clearest velocity-resolved kinematic signatures have already been published.

A Comprehensive Spectral and Variability Study of Narrow-Line Seyfert 1 Galaxies Observed by ASCA. II. Spectral Analysis and Correlations

I present a comprehensive and uniform analysis of 25 ASCA observations from 23 narrow-line Seyfert 1 galaxies (NLS1s). The spectral analysis and correlations are presented in this paper; the reduction and time series analysis are presented in the companion paper. A maximum likelihood analysis confirms that the hard X-ray photon index is significantly steeper at more than 90% confidence in this sample of NLS1s compared with a random sample of Seyfert galaxies with broad optical lines. Soft excess emission was detected in 17 of the 19 objects that had no significant absorption, a result that demonstrates that soft excesses appear considerably more frequently in NLS1s than in Seyfert 1 galaxies with broad optical lines. The strength of the soft excess, parameterized using a flux ratio obtained from the blackbody plus power-law model, has a wide range of values in these objects (a factor of 50). The photon index was found to be correlated with the Hβ FWHM, despite the small range of the latter parameter; however, neither parameter is correlated with the strength of the soft excess or ROSAT slope. Therefore, assuming that an excess of soft photons causes the steep photon index and narrow Hβ FWHM, that excess may lie primarily in the unobservable EUV. The strength of the soft excess is correlated with the variability parameters, so that objects with strong soft excesses show higher amplitude variability; this potentially important result is not easily explained. While a range of 2 orders of magnitude in luminosity is represented, the temperature of the soft excess is approximately consistent throughout the sample, in contrast with expectations of simple accretion disk models. The presence of ionized absorption was sought using a two-edge model. It was found that this component appears to be typically less common in NLS1s and some evidence was found that the typical ionization state is lower compared with broad-line Seyfert galaxies. This fact, plus evidence for a correlation between the presence of the warm absorber and significant optical polarization, may imply that the inner warm absorber is missing or is too highly ionized to be detected, and only the outer, dusty, less ionized warm absorber is present in many cases. The iron line equivalent width appears to be similar among narrow and broad-line Seyfert galaxies. This could mean that reprocessing occurs with similar geometry in both classes of objects; however, the detection of ionized iron lines in a few objects, implying possibly altered fluorescence yields, and poor statistics, makes this conclusion tentative. Constraints on physical processes and models based on extreme values of orientation and accretion rate for NLS1s are examined in light of the observational results.

UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C IV EMISSION

Using a sample of ~30,000 quasars from the 7th Data Release of the Sloan Digital Sky Survey, we explore the range of properties exhibited by high-ionization, broad emission lines, such as C IV λ1549. Specifically, we investigate the anti-correlation between continuum luminosity and emission-line equivalent width (the Baldwin Effect (BEff)) and the blueshifting of the high-ionization emission lines with respect to low-ionization emission lines. Employing improved redshift determinations from Hewett & Wild, the blueshift of the C IV emission line is found to be nearly ubiquitous, with a mean shift of ~810 km s–1 for radio-quiet (RQ) quasars and ~360 km s–1 for radio-loud (RL) quasars. The BEff is present in both RQ and RL samples. We consider these phenomena within the context of an accretion disk-wind model that is modulated by the nonlinear correlation between ultraviolet and X-ray continuum luminosity. Composite spectra are constructed as a function of C IV emission-line properties in an attempt to reveal empirical relationships between different line species and the continuum. Within a two-component disk+wind model of the broad emission-line region (BELR), where the wind filters the continuum seen by the disk component, we find that RL quasars are consistent with being dominated by the disk component, while broad absorption line quasars are consistent with being dominated by the wind component. Some RQ objects have emission-line features similar to RL quasars; they may simply have insufficient black hole (BH) spin to form radio jets. Our results suggest that there could be significant systematic errors in the determination of L bol and BH mass that make it difficult to place these findings in a more physical context. However, it is possible to classify quasars in a paradigm where the diversity of BELR parameters is due to differences in an accretion disk wind between quasars (and over time); these differences are underlain primarily by the spectral energy distribution, which ultimately must be tied to BH mass and accretion rate.

A Comprehensive Spectral and Variability Study of Narrow-Line Seyfert 1 Galaxies Observed by ASCA. I. Observations and Time Series Analysis

I present a comprehensive and uniform analysis of 25 ASCA observations from 23 narrow-line Seyfert 1 galaxies. The time series analysis is presented in this paper, Part 1, and the spectral analysis and correlations are presented in the companion paper, Part 2. Time series analysis shows that the excess variance from the NLS1 light curves is inversely correlated with their X-ray luminosity. However, with a logarithmic slope of ~-0.3, the dependence of the excess variance on luminosity is flat compared with broad-line objects and the expected value of -1 from simple models. At a particular X-ray luminosity, the excess variance is typically an order of magnitude larger for NLS1s than for Seyfert 1 with broad optical lines. There is, however, a large scatter, and a few objects show an even larger excess variance. The excess variance can be interpreted as a timescale if the shape of the variability power spectrum, the length of the observation, and the window function are the same for all observations, and the properties of the sample objects are shown to be roughly consistent with this requirement. In particular, no strong evidence for changes during an observation in the shape or normalization of the power spectrum was found once the systematic errors due to the 1/f nature of the power spectrum was accounted for properly. Some of the more variable light curves are shown to be inconsistent with a linear, Gaussian process, implying that the process is non-Gaussian. It is possible that the process is nonlinear, but while the distinction between these possibilities is very important for differentiating between models, such a distinction cannot be made using these data. The enhanced excess variance exhibited by NLS1s can be interpreted as evidence that they are scaled-down versions of broad-line objects, having black hole masses roughly an order of magnitude smaller and requiring an accretion rate an order of magnitude higher. Alternatively, NLS1s may exhibit an inherently different type of variability, characterized by high-amplitude flares, in which case a smaller black hole mass would not be required.

HUBBLE SPACE TELESCOPE STIS ULTRAVIOLET SPECTRAL EVIDENCE OF OUTFLOW IN EXTREME NARROW-LINE SEYFERT 1 GALAXIES. I. DATA AND ANALYSIS

We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of two extreme narrow-line Seyfert 1 galaxies (NLS1s), IRAS 13224-3809 and 1H 0707-495. The spectra are characterized by very blue continua; broad, strongly blueshifted high-ionization lines (including C IV and N V); and narrow, symmetric intermediate- (including C III], Si III], and Al III) and low-ionization (e.g., Mg II) lines centered at the rest wavelength. The emission-line profiles suggest that the high-ionization lines are produced in a wind and that the intermediate- and low-ionization lines are produced in low-velocity gas associated with the accretion disk or base of the wind. In this paper, we present the analysis of the spectra from these two objects; in a companion paper, we present photoionization analysis and a toy dynamical model for the wind. The highly asymmetric profile of C IV suggests that it is dominated by emission from the wind, so we develop a template for the wind from the C IV line. We model the bright emission lines in the spectra using a combination of this template and a narrow symmetric line centered at the rest wavelength. We also analyzed a comparison sample of Hubble Space Telescope spectra from 14 additional NLS1s and constructed a correlation matrix of emission-line and continuum properties. A number of strong correlations were observed, including several involving the asymmetry of the C IV line.

Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. XII. Ground-based monitoring of 3C 390.3

Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V, R, and I), the spectrophotometric optical continuum flux Fλ(5177 A), and the integrated emission-line fluxes of Hα, Hβ, Hγ, He I λ5876, and He II λ4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000 A). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the cross-correlation functions, typically around 5 days, but with uncertainties also typically around 5 days; zero time delay between the high-energy and low-energy continuum variations cannot be ruled out. The strong optical emission lines Hα, Hβ, Hγ, and He I λ5876 respond to the high-energy continuum variations with time delays typically about 20 days, with uncertainties of about 8 days. There is some evidence that He II λ4686 responds somewhat more rapidly, with a time delay of around 10 days, but again, the uncertainties are quite large (~8 days). The mean and rms spectra of the Hα and Hβ line profiles provide indications for the existence of at least three distinct components located at ±4000 and 0 km s-1 relative to the line peak. The emission-line profile variations are largest near line center.

Hubble Space Telescope STIS ultraviolet spectral evidence of outflow in extreme narrow-line Seyfert 1 galaxies. II: Modeling and interpretation

We present modeling to explore the conditions of the broad-line-emitting gas in two extreme narrow-line Seyfert 1 galaxies, using the observational results described in the first paper of this series. Photoionization modeling using CLOUDY was conducted for the broad blueshifted wind lines and the narrow, symmetric, rest-wavelength-centered disk lines separately. A broad range of physical conditions was explored for the wind component, and a figure of merit was used to quantitatively evaluate the simulation results. Of the three minima in the figure-of-merit parameter space, we favor the solution characterized by an X-ray-weak continuum, elevated abundances, a small column density (log NH ? 21.4), a relatively high ionization parameter (log U ? -1.2 to -0.2), a wide range of densities (log n ? 7-11), and a covering fraction of ~0.15. The presence of low-ionization emission lines implies that the disk component is optically thick to the continuum, and the Si III]/C III] ratio implies a density of 1010-1010.25 cm-3. A low ionization parameter (log U = -3) is inferred for the intermediate-ionization lines, unless the continuum is filtered through the wind before illuminating the intermediate-line-emitting gas, in which case log U = -2.1. The location of the emission regions was inferred from the photoionization modeling and a simple toy dynamical model. A large black hole mass (1.3 ? 108 M?) radiating at 11% of the Eddington luminosity is consistent with the kinematics of both the disk and wind lines, and an emission radius of ~104 RS is inferred for both. We compare these results with previous work and discuss implications.

A REVISED BROAD-LINE REGION RADIUS AND BLACK HOLE MASS FOR THE NARROW-LINE SEYFERT 1 NGC 4051

We present the first results from a high sampling rate, multimonth reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations from telescopes around the world. The primary goal of this campaign was to obtain either new or improved Hβ reverberation lag measurements for several relatively low luminosity active galactic nuclei (AGNs). We feature results for NGC 4051 here because, until now, this object has been a significant outlier from AGN scaling relationships, e.g., it was previously a ∼2–3σ outlier on the relationship between the broad-line region (BLR) radius and the optical continuum luminosity—the RBLR–L relationship. Our new measurements of the lag time between variations in the continuum and Hβ emission line made from spectroscopic monitoring of NGC 4051 lead to a measured BLR radius of RBLR = 1.87 +0.54 −0.50 light days and black hole mass of MBH = (1.73 +0.55 −0.52 ) × 10 6 M� . This radius is consistent with that expected from the RBLR–L relationship, based on the present luminosity of NGC 4051 and the most current calibration of the relation by Bentz et al.. We also present a preliminary look at velocity-resolved Hβ light curves and time delay measurements, although we are unable to reconstruct an unambiguous velocity-resolved reverberation signal.

DIVERSE KINEMATIC SIGNATURES FROM REVERBERATION MAPPING OF THE BROAD-LINE REGION IN AGNs

A detailed analysis of the data from a high sampling rate, multi-month reverberation mapping campaign, undertaken primarily at MDM Observatory with supporting observations from telescopes around the world, reveals that the Hbeta emission region within the broad line regions (BLRs) of several nearby AGNs exhibit a variety of kinematic behaviors. While the primary goal of this campaign was to obtain either new or improved Hbeta reverberation lag measurements for several relatively low luminosity AGNs (presented in a separate work), we were also able to unambiguously reconstruct velocity-resolved reverberation signals from a subset of our targets. Through high cadence spectroscopic monitoring of the optical continuum and broad Hbeta emission line variations observed in the nuclear regions of NGC 3227, NGC 3516, and NGC 5548, we clearly see evidence for outflowing, infalling, and virialized BLR gas motions, respectively.

Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XIII. Ultraviolet Observations of the Broad-Line Radio Galaxy 3C 390.3

As part of an extensive multiwavelength monitoring campaign, the International Ultraviolet Explorer satellite was used to observe the broad-line radio galaxy 3C 390.3 during the period 1994 December 31E1996 March 5. Spectra were obtained every 6E10 days. The UV continuum varied by a factor of 7 through the campaign, while the broad emission lines varied by factors of 2E5. Unlike previously moni- tored Seyfert 1 galaxies, in which the X-ray continuum generally varies with a larger amplitude than the UV, in 3C 390.3 the UV continuum light curve is similar in both amplitude and shape to the X-ray light curve observed by ROSAT . The UV broad emission-line variability lags that of the UV continuum by 35E70 days for Lya and C IV, values larger than those found for Seyfert 1 galaxies of comparable UV luminosity. These lags are also larger than those found for the Balmer lines in 3C 390.3 over the same period. The red and blue wings of C IV and Lya vary in phase, suggesting that radial motion does not dominate the kinematics of the UV line-emitting gas. Comparison with archival data provides evidence for velocity-dependent changes in the Lya and C IV line pro-les, indicating evolution in the detailed properties and/or distribution of the broad-line emitting gas. Subject headings: galaxies: active E galaxies: individual (3C 390.3) E ultraviolet: galaxies