Evolution of Black Hole Masses from Spectra of Quasar Gas Dynamics

1. Evolution of Black Hole Masses from Spectra of Quasar Gas Dynamics Amanda Schilling, University of Arkansas Mentor: Dr. Julia Kennefick, University of Arkansas Strategy • Spectra • Every chemical element has a unique spectrum • Because of the wave nature of light an object in motion will have a shifted spectrum - called Doppler shift Example of Doppler shift2 • SDSS has cataloged hundreds of quasar spectra Sample quasar spectrum from SDSS3 • Velocity of gas from the Broad Line Region can be determined from spectra • broad line: the slope on the left of a peak corresponds to blueshift and on the right to redshift • gas in BLR has blue and red shifts indicating its orbit around the black hole • Dynamics Keplerian motion gives a correlation between the orbital velocity of the gas in the BLR and the black hole it is orbiting Introduction - Quasars • Active galactic nuclei that are an intense source of radiation • First discovered as radio-wave emitting objects in the 1960s though most found since are not radio emitters • Unique because: • billions of light years away and yet luminous enough to be detected • More numerous in the distant past • powered by massive black holes • Believed to be early galaxies Objective - Calculate masses of the black holes that power quasars • Why? To determine if the mass evolves with redshift • The sample: 47 quasars with redshifts between 1.8 and 4.3 correlating to look-back-times of 10-12 billion years (most quasars have a redshift around 2) • Data: spectra of quasars from SDSS, Sloan Digital Sky Survey, database Anatomy of a Quasar • Massive Black Hole in center powers the quasar • Accretion Disk - disk of gas and dust orbiting the black hole • Jets • perpendicular to accretion disk • can extend very far from the black hole • emit some visible but mostly radio light waves • BLR - broad line region • gas orbiting at high velocities • noticeable Doppler shifts in spectra- broad lines refers to the width of a peak on a spectrum • NLR - narrow line region, larger in volume than BLR but gas is slower and less dense • Torus of cool gas and dust Quasar diagram1 References 1. Strobel, Nick. “Doppler Effect.” <http://www.astronomynotes.com/light/s10.htm> 2. From “Introduction to Active Galactic Nuclei” NASA’s HEASARC: Education & Public Information. <http://heasarc.gsfc.nasa.gov/docs/objects/agn/agntext.html> 3. <http://cas.sdss.org/dr6/en/tools/explore/obj.asp?ra=157.13368&dec=-0.76863>