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Theoretical Astrophysics at GSU

Theoretical Astrophysics at GSU. Paul J. Wiita Department of Physics & Astronomy www.chara.gsu.edu/~wiita. Brief CV. Born 1953, The Bronx, New York Attended NYC public schools, graduated from The Bronx HS of Science in 1969

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Theoretical Astrophysics at GSU

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  1. Theoretical Astrophysics at GSU Paul J. Wiita Department of Physics & Astronomy www.chara.gsu.edu/~wiita

  2. Brief CV • Born 1953, The Bronx, New York • Attended NYC public schools, graduated from The Bronx HS of Science in 1969 • BS in Physics in 1972 from The Cooper Union for the Advancement of Science and Art • PhD in Physics in 1976 from Princeton University • Post-doctoral fellowships at U. of Chicago and Cambridge U.; 3 month visit to Warsaw • Assistant Prof at U. Pennsylvania, 1979-1986 • Assistant (‘86), Associate (‘89) and Full Professor (‘93) at GSU. Astronomy Graduate Director, ‘95-’00 • Visiting Prof. at TIFR, IIA, & RRI (India) & Princeton • Affiliated Faculty @ Princeton; Adjunct Prof @ GaTech

  3. Research Interests • Theoretical astrophysics • Mainly extragalactic • Specifically Active Galactic Nuclei • More specifically, Quasars & Radio Galaxies • Other interests: accretion disks, black holes, variability in AGN classes, microquasars • Tools: combination of analytical modeling and numerical simulations (jet propagation) • Requirement: close interaction with observational astronomers, so models can be checked against data

  4. Big Radio Telescopes • NRAO Very Large Array • NRAO Very Long Baseline Array • NRAO Green Bank Telescope • TIFR Giant Metrewave Radio Telescope • MPIfRA Effelsberg Radio Telescope • NAIC Arecibo Radio Dish

  5. VLA in Closest Array

  6. More VLA photos • 27 antennas, each 25 m diameter • Maximum baseline 36 km

  7. VLBA:10 25m dishes, 8000km baseline

  8. GBT:largest single dish steerable RT: • Asymmetric design (110x100 m) keeps feeds off to side: no struts and diffraction from them • Works from 3m down to 3mm • Best for pulsar studies and molecular lines

  9. GMRT: largest collecting area • Mesh design, good enough for long wavelengths • 30 telescopes, 45 m aperture, maximum baseline, 25 km: near Narayangoan, India

  10. Arecibo: 305m fixed dish

  11. Radiographs • Colors usually indicate fluxes: red is (ususally) brightest, blue faintest • Images of supernova remnants • Pulsars and nearby shocks and jets • Black holes: jets in microquasars • Galactic structure • Radio galaxies • Quasars

  12. Tycho’s SN remnant

  13. W50, SNR home of microquasar SS433

  14. SN 1993J in M81 from some VLBA+ VLA+ EVN+ NASA

  15. “The Duck”, pulsar moving at ~500 km/s

  16. SS 433: bullets at 0.26c

  17. Microquasar GRS 1915+105Apparent v = 1.25 c from v = 0.92 cBH mass about 16 Suns

  18. Superluminal Motion? • Vapp=Vsin/[1-(V/c)cos] • =1/(1-2)1/2 , with =V/c • =1/ (1- cos) • Sobs=Sem n+ , with n=2 for smooth jet and n=3 for knot or shock • For large  and small  (~1/ ) this boosting factor can be > 10000!

  19. Atomic H in Our Galaxy: GBT et al.

  20. M33: Doppler shifts show rotation • Used VLA measuring H 21cm spin-flip line to map atomic hydrogen, with spatial resolution of 10” • Color coded to blue approaching and red receding: velocity resolution - 1.3 km/s, • Includes Westerbork data for total intensity

  21. 3C31: FR I Radio Galaxy

  22. 3C 130 & 3C 449: FR I’s

  23. M87 Jet to Bubble Montage

  24. Canonical FR II: Cygnus A

  25. Quasar: 3C 175

  26. 3C353: Peculiar FR II

  27. VLBA of 3C279:Apparent Superluminal Motionwith Vapp=3.5c: really V=0.997c at viewing angle of 2 degrees

  28. The Theory Side • My collaborators, graduate students and I have produced models that explain (some aspects) of all of these objects. • We use many branches of physics to do this: hydrodynamics (mechanics for gases) plasma physics (magnetohydrodynamics) electricity & magnetism (for radiation processes) general relativity (if close to central black hole) • Equations are set up and (with any luck) solved • Usually at least some numerical work is needed to solve the equations that describe the situation • Approximations sometimes allow analytical solutions using algebra, calculus & differential equations • Sometimes, full bore simulations on supercomputers are necessary

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