Karen Leighly

Associate Professor

leighly

Education

B.S. 1983 New Mexico Institute of Mining and Technology

Ph.D. 1991 Montana State University

 

Contact

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Ph: (405) 325-7045

Office: 243 Nielsen Hall

 

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Research Description

Active Galactic Nuclei (AGN) are the most luminous, persistently emitting individual objects in the Universe. My overall research goal is to understand how the primary physical parameters for black hole accretion, the black hole mass and accretion rate, manifest themselves in the broad band continuum and line emission from AGN.

My research uses the observations of the optical through X-ray emission, coupled with modeling, to understand how the black hole mass and accretion rate influence the observable properties of AGN. The X-ray emission emerges from the AGN central engine, just before the accreting gas falls into the black hole. The X-ray spectrum and variability properties reflect the geometry and physical conditions in this region. The shape of the broad-band continuum emerging from the central engine is expected to be a function of the black hole mass and accretion rate. The optical and UV line emission, a hallmark feature of AGN, is powered by photoionization by this continuum, and thus the signature of the continuum shape should be detectable in the line emission properties. Recently, we have discovered links between the continuum shape and line properties. We found that the continnum shape can influence the kinetics of the gas emitting high-ionization lines, and it can influence the line emission through variations in relative photon density as a function of energy, and through variations in gas cooling.

Recently I have begun to focus on understanding the low-ionization line emitting gas in quasars. Understanding the low-ionization line-emitting gas is important because it emits the higydrogen, iron and magnesium lines whose ratios are used for metallicity estimates, and whose velocity widths are used for black-hole mass estimates. My research leverages large uniformly-selected samples from the Sloan Digital Sky Survey, carefully-targeted new observations, new perspectives combined with large-scale photoionization modeling, and a state-of-the-art spectral synthesis model. Altogether, valuable constraints on the physical conditions including density, ionization, illuminating spectral energy distribution, column density, and metallicity will be obtained by this research, leading to a better understanding of quasar broad-line region emission, and of quasars in general.

Selected Publications

"Emergence of a Broad Absorption Line Outflow in the Narrow-line Seyfert 1 Galaxy WPVS 007," Karen M. Leighly, Fred Hamann, Darrin A. Casebeer, Dirk Grupe, ApJ, 701, 176, (2009) ADS: 2009ApJ...701..176L

"The Intrinsically X-ray Weak Quasar PHL 1811. II. Optical and UV Spectra and Analysis," Karen M. Leighly, Jules P. Halpern, Edward B. Jenkins, Darrin Casebeer, ApJS, 173, 1, (2007) ADS: 2007ApJS..173....1L

"The Intrinsically X-ray Weak Quasar PHL 1811. I. X-ray Observations and Spectral Energy Distribution," Karen M. Leighly, Jules P. Halpern, Edward B. Jenkins, Dirk Grupe, Jiehae Choi, Kimberly B. Prescott, ApJ, 663, 103, (2007) ADS: 2007ApJ...663..103L

"Fe II and Mg II in Luminous, Intermediate-Redshift Narrow-line Seyfert 1 Galaxies from the Sloan Digital Sky Survey," Karen M. Leighly, John R. Moore, ApJ, 644, 748, (2006) ADS: 2006ApJ...644..748L

Research Group

Joseph Hyunseop Choi, Graduate Student
Francis MacInnis, Graduate Student