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A Global 86 GHz VLBI Survey of Compact Radio Sources

A Global 86 GHz VLBI Survey of Compact Radio Sources. Sang-Sung Lee MPIfR In collaboration with A.P. Lobanov, T.P. Krichbaum, A. Witzel, J.A. Zensus (MPIfR, Bonn) M. Bremer, A. Greve, M. Grewing (IRAM, Grenoble) 26.09.2006 8 th EVN Symposium, Torun, Poland. Outline. Introduction

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A Global 86 GHz VLBI Survey of Compact Radio Sources

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  1. A Global 86 GHz VLBI Survey of Compact Radio Sources Sang-Sung Lee MPIfR In collaboration with A.P. Lobanov, T.P. Krichbaum, A. Witzel, J.A. Zensus (MPIfR, Bonn) M. Bremer, A. Greve, M. Grewing (IRAM, Grenoble) 26.09.2006 8th EVN Symposium, Torun, Poland

  2. Outline • Introduction - mm VLBI,Previous Surveys • Results - Images • Brightness temperature (TB) and jet physics - TB distribution, TB vs. Apparent jet speed, TB along the jets • Summary

  3. Millimeter VLBI • VLBI experiments at mm wavelengths (e.g. 43GHz, 86GHz, 150GHz, 230GHz) • A unique tool for exploring the physics of compact radio sources with about 6 times better resolution (40 micro-arcsec at 86 GHz) than space-VLBI at 6 cm wavelength • At mm wavelengths, synchrotron radiation becomes optically thin, so mm-VLBI makes it possible to look deeper in the “VLBI core”, invisible at cm wavelengths 1983 1995 2004 present First VLBI fringe detection at 89GHz Readhead et al. 1983 CMVA (86GHz) (The Coordinated MM VLBI Array) GMVA (86 GHz) (The Global MM-VLBI Array) Haystack + (Ef, On, Pv, Pb, Mh) + VLBA ( 8x25m) VLBA (8x25m) + (Ef, On,Pv,Pb,Mh) GMVA web - http://www.mpifr-bonn.mpg.de/div/vlbi/globalmm/

  4. Previous surveys VLBI Surveys at 86 GHz • Beasley et al. (1996) • Lonsdale et al. (1998) • Rantakyro et al. (1998) • Lobanov et al. (2000) • This survey • - 3~4 times better sensitivity • - larger sample (127sources) • taken from surveys at lower freq. • - 121(95%) were detected and 109 imaged This Survey

  5. Images Lee et al. 2006 in prep

  6. Brightness Temperature (TB) (A.P. Lobanov 2005) (e.g. SNR = 6.5; Beam ( a x b ) = ( 0.1 x 0.07 mas) => dmin = 0.035mas) And if , then the lower limit of TB is obtained with d = dmin.

  7. TB distribution VLBI cores Jet components (Lobanov et al. 2000) (Lee et al. 2006, in prep.) VLBI cores Jet components

  8. TB vs. Apparent jet speed TB,jetvs. Jet speed (N=39) TB,corevs. Jet speed (N=86) Apparent Jet speeds from 2cm survey (Kellermann et al. 1998) Red triangles are lower limits of TB

  9. NRAO 140 NRAO 190 3C 454.3 OJ 287 Evolution of TB alongthe jets Assumptions are made like the following: (Lobanov et al. 2000) Red circles are the predicted TB in shocks with adiabatic losses dominating the radio emission. Blue circles are the observed TB. (Lee et al. 2006 in prep.)

  10. Summary • We conducted a large global 86 GHz VLBI survey of compact radio sources, using a global 3mm VLBI array. • The survey is the largest and most sensitive one (rmsImage< 10 mJy/beam) • It provides a detection rate of 95% out of 127 sources and a total set of images of 109 sources. • We estimated brightness temperatures (TB) of the cores and secondary jet components from the measurements of flux densities and sizes of the components, taking into account resolution limits of the data. • The TB of the cores are higher than those of the secondary jet components and seem to be correlated with apparent jet speeds rather than those of the secondary jet components.

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