Ph.D. Defense: Neetika Sharma
Location
Physics : 401
Date & Time
April 20, 2016, 8:00 am – 10:00 am
Description
ADVISOR: Dr. T. Jane Turner
TITLE: Physical Conditions in the X-ray Emission-Line gas in the Seyfert 2 galaxy NGC 1068
ABSTRACT: Active Galactic Nuclei (AGN) reside in the centers of many (10%) galaxies. The nuclear spectra exhibit a broad (from radio to gamma-rays) non-stellar continuum which exceeds the luminosity of the host. AGN are thought to be powered by accretion of matter onto a supermassive black hole (BH~106-109 times the mass of the Sun). Since this activity takes place in a relatively small region (<< 3 light years), the central engine of even the closest AGN cannot be imaged directly with current technology. Nevertheless, spectroscopic observations can help us constrain the conditions of the gas very close to the BH.
I examined the physical conditions in the circumnuclear X-ray emitting gas of the Seyfert 2 galaxy NGC 1068. The soft X-ray spectrum comprises a multitude of emission lines including those of C, N, O, Ne, Mg, that arise in gas that is spatially extended over ~ 1000 light years. Radiative recombination continuum widths indicate the gas is photoionized and I model it finding a two-zone solution with unusual abundances attributed to the star formation history of the galaxy. Also of interest are the Fe K complex of emission lines, spanning neutral to highly ionized gas. These lines are produced in a separate, clumpy gas component, much closer to the BH.
TITLE: Physical Conditions in the X-ray Emission-Line gas in the Seyfert 2 galaxy NGC 1068
ABSTRACT: Active Galactic Nuclei (AGN) reside in the centers of many (10%) galaxies. The nuclear spectra exhibit a broad (from radio to gamma-rays) non-stellar continuum which exceeds the luminosity of the host. AGN are thought to be powered by accretion of matter onto a supermassive black hole (BH~106-109 times the mass of the Sun). Since this activity takes place in a relatively small region (<< 3 light years), the central engine of even the closest AGN cannot be imaged directly with current technology. Nevertheless, spectroscopic observations can help us constrain the conditions of the gas very close to the BH.
I examined the physical conditions in the circumnuclear X-ray emitting gas of the Seyfert 2 galaxy NGC 1068. The soft X-ray spectrum comprises a multitude of emission lines including those of C, N, O, Ne, Mg, that arise in gas that is spatially extended over ~ 1000 light years. Radiative recombination continuum widths indicate the gas is photoionized and I model it finding a two-zone solution with unusual abundances attributed to the star formation history of the galaxy. Also of interest are the Fe K complex of emission lines, spanning neutral to highly ionized gas. These lines are produced in a separate, clumpy gas component, much closer to the BH.
