Erin Wells Bonning

A SEARCH FOR BINARY ACTIVE GALACTIC NUCLEI: DOUBLE-PEAKED [O III] AGNs IN THE SLOAN DIGITAL SKY SURVEY

We present active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS) having double-peaked profiles of [O III]λλ5007, 4959 and other narrow emission lines, motivated by the prospect of finding candidate binary AGNs. These objects were identified by means of a visual examination of 21,592 quasars at z < 0.7 in SDSS Data Release 7 (DR7). Of the spectra with adequate signal-to-noise, 148 spectra exhibit a double-peaked [O III] profile. Of these, 86 are Type 1 AGNs and 62 are Type 2 AGNs. Only two give the appearance of possibly being optically resolved double AGNs in the SDSS images, but many show close companions or signs of recent interaction. Radio-detected quasars are three times more likely to exhibit a double-peaked [O III] profile than quasars with no detected radio flux, suggesting a role for jet interactions in producing the double-peaked profiles. Of the 66 broad-line (Type 1) AGNs that are undetected in the FIRST survey, 0.9% show double-peaked [O III] profiles. We discuss statistical tests of the nature of the double-peaked objects. Further study is needed to determine which of them are binary AGNs rather than disturbed narrow line regions, and how many additional binaries may remain undetected because of insufficient line-of-sight velocity splitting. Previous studies indicate that 0.1% of SDSS quasars are spatially resolved binaries, with typical spacings of ~10-100 kpc. If a substantial fraction of the double-peaked objects are indeed binaries, then our results imply that binaries occur more frequently at smaller separations (<10 kpc). This suggests that simultaneous fueling of both black holes is more common as the binary orbit decays through these spacings.

CORRELATED VARIABILITY IN THE BLAZAR 3C 454.3

The blazar 3C 454.3 was revealed by the Fermi Gamma-ray Space Telescope to be in an exceptionally high flux state in 2008 July. Accordingly, we performed a multiwavelength monitoring campaign from 2008 August through December on this blazar using infrared (IR) and optical observations from the Small and Moderate Aperture Research Telescope System telescopes, optical, ultraviolet (UV), and X-ray data from the Swift satellite, and public-release gamma-ray data from Fermi. We find an excellent correlation between the IR, optical, UV, and gamma-ray light curves, with a time lag of less than one day. The amplitude of the IR variability is comparable to that in gamma-rays, and larger than at optical or UV wavelengths. The X-ray flux is not correlated with either the gamma-rays or longer wavelength data. These variability characteristics find a natural explanation in the external Compton model, in which electrons with Lorentz factor ? ~ 103-4 radiate synchrotron emission in the IR-optical and also scatter accretion disk or emission line photons to gamma-ray energies, while much cooler electrons (? ~ 101-2) produce X-rays by scattering synchrotron or other ambient photons.

An Optical-Near-infrared Outburst with no Accompanying γ-Rays in the Blazar PKS 0208–512

We report the discovery of an anomalous flare in a bright blazar, namely, PKS 0208–512, one of the targets of the Yale/SMARTS optical-near-IR (OIR) monitoring program of Fermi blazars. We identify three intervals during which PKS 0208–512 undergoes outbursts at OIR wavelengths lasting for 3 months. Its brightness increases and then decreases again by at least 1 mag in these intervals. In contrast, the source undergoes bright phases in GeV energies lasting 1 month during intervals 1 and 3 only. The OIR outburst during interval 2 is comparable in brightness and temporal extent to the OIR flares during intervals 1 and 3, which do have γ-ray counterparts. By analyzing the γ-ray, OIR, and supporting multi-wavelength variability data in details, we speculate that the OIR outburst during interval 2 was caused by a change in the magnetic field without any change in the total number of emitting electrons or Doppler factor of the emitting region. Alternatively, it is possible that the location of the outburst in the jet during interval 2 was closer to the black hole where the jet is more compact and the bulk Lorentz factor of the material in the jet is smaller. We also discuss the complex OIR spectral behavior during these three intervals.

CHANDRA OBSERVATIONS OF GALAXY ZOO MERGERS: FREQUENCY OF BINARY ACTIVE NUCLEI IN MASSIVE MERGERS

We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 1011 M ☉ that already have optical active galactic nucleus (AGN) signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (N H 1.1 × 1022 cm–2) X-ray nuclei are relatively common (8/12), but the detections are too faint (<40 counts per nucleus; f 2-10 keV 1.2 × 10–13 erg s–1 cm–2) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGNs in these mergers are rare (0%-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.

Magnetic field amplification and flat spectrum radio quasars

Helmholtz Alliance for Astroparticle Physics. Initiative and Networking Fund of the Helmholtz Association. NASA through Fermi Guest Investigator Grant no. NNX12AP20G, and by the LANL/LDRD programme and by DoE/Office of Fusion Energy Science through CMSO. NASA grant NNX12AE43G. South African Research Chair Initiative of the National Research Foundation and the Department of Science and Technology of South Africa

Accretion Disk Temperatures Of QSOs: Constraints From The Emission Lines

We compare QSO emission-line spectra to predictions based on theoretical ionizing continua of accretion disks. The observed line intensities do not show the expected trend of higher ionization with theoretical accretion disk temperature as predicted from the black hole mass and accretion rate. Consistent with earlier studies, this suggests that the inner disk does not reach temperatures as high as expected from standard disk theory. Modified radial temperature profiles, taking account of winds or advection in the inner disk, achieve better agreement with observation. The emission lines of radio-detected and radio-undetected sources show different trends as a function of the theoretically predicted disk temperature.

THE BLACK HOLE MASS-GALAXY LUMINOSITY RELATIONSHIP FOR SLOAN DIGITAL SKY SURVEY QUASARS

We investigate the relationship between the mass of the central supermassive black hole, M BH, and the host galaxy luminosity, L gal, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M BH-L gal relationship by examining the redshift dependence of Δ log M BH, the offset in M BH from the local M BH-L gal relationship. There is little systematic trend in Δ log M BH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, σ*, we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for σ* in statistical studies.

LBQS 0103-2753: a binary quasar in a major merger

We present Hubble Space Telescope (HST) and United Kingdom Infrared Telescope spectra and images of the 2 kpc (03) binary quasar LBQS 0103-2753 (z = 0.858). The HST images (V and I bands) show tidal features demonstrating that this system is a major galaxy merger in progress. A two-color composite image brings out knots of star formation along the tidal arc and elsewhere. The infrared spectrum shows that both objects are at the same redshift and that the discrepant redshift of C IV in component A is not representative of the true systemic redshift of this component. LBQS 0103-2753 is one of the most closely spaced binary QSOs known and is one of the relatively few dual active galactic nuclei showing confirmed broad emission lines from both components. While statistical studies of binary QSOs suggest that simultaneous fueling of both black holes during a merger may be relatively rare, LBQS 0103-2753 demonstrates that such fueling can occur at high luminosity at a late stage in the merger at nuclear spacing of only a few kpc, without severe obscuration of the nuclei.

Variability in Active Galactic Nuclei

This talk explored variability in active galactic nuclei (AGN) for a variety of scales across the time domain. From billion-year-scale intermittency to a quasi-periodic oscillation signal with a period of one hour, time-varying signals offer insights into a myriad of complex processes driven by the AGN central engine. Athough the era of time-domain observations of AGN across the spectrum has but just begun, already observations reveal the rich detail of phenomena associated with actively accreting black holes which challenge theoretical models.