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Interstellar Scattering of Sgr A*

Get insights on the scattering phenomena of Sgr A* from a variety of sources including early research, demagnification effects, OH maser scattering, and more. Learn about the properties of scattering plasma and X-ray emitting hot plasma in the vicinity. Dive into the implications of bipolar winds and observational surveys of background quasars and active galactic nuclei.

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Interstellar Scattering of Sgr A*

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  1. Interstellar Scattering of Sgr A* D. C. Backer Astronomy Department & Radio Astronomy Laboratory UC Berkeley Credit: B4, F. Lo, G. Bower, Y. Lithwick, et multi-alia Sgr A* 30th Fest -- 2004 March

  2. An Early View on Scatter Broadening Backer 1978 ApJ, 222, L9 b zb/Z Sgr A* 30th Fest -- 2004 March

  3. Origins of DCB 1978… Sgr A* 30th Fest -- 2004 March

  4. Demagnification of Angular Broadening • Scattering angle is property of screen • Observed source apparent size is result of magnification Sgr A* 30th Fest -- 2004 March

  5. 1985 Nature, 315, 124 Sgr A* 30th Fest -- 2004 March

  6. OH Maser Scattering Frail et al. (1994) ApJ427, L43 Sgr A* 30th Fest -- 2004 March

  7. Wide Field Source Scattering Bower et al. (2001) ApJ, 558, L27 Lazio & Cordes (1998) ApJ, 505, 715 Sgr A* 30th Fest -- 2004 March

  8. Summary • Sgr A* has 2:1 image size dependent on lambda2.0 & image shape on baseline2.0 • OH masers within ~0.5o (lat; 65 pc) have similar sizes & ellipticities. • Required scattering measure: few pc cm-6 on scales of 10’s km (from max b & z/Z estimate). Sgr A* 30th Fest -- 2004 March

  9. Location of Scattering Plasma-I • Mezger & Pauls, 1979 IAU Symposium84, p.357 • EI: 300 pc (l); 120 pc (b); 1.4x104 pc cm-6; 7 cm-3 • EII: 130 pc (l); 80 pc (b); 3.1x104 pc cm-6; 16 cm-3 Sgr A* 30th Fest -- 2004 March

  10. X-Ray Emitting Hot Plasma • Koyama et al. (1996) PASJ, 48, 249; Munro et al. (2003) ApJ, 589, 225 -- 8.5’ x 8.5’ (20 pc x 20 pc) • Koyama et al. (1996): 3x10-13 ergs cm-2 s-1 arcmin-2; Mereghetti et al. (1999) 5/3 larger; something like 2-8 keV; point sources 10% Sgr A* 30th Fest -- 2004 March

  11. Bipolar Wind Bland-Hawthorne & Cohen (2003) ApJ, 582, 246 At apex cylindrical shell: Sgr A* 30th Fest -- 2004 March

  12. Location of Scattering Plasma-II Sgr A* 30th Fest -- 2004 March

  13. IPS Survey of Backgrnd QSO/AGN Cohen & Gunderman (1968) ApJ, 145, 165 Sgr A* 30th Fest -- 2004 March

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