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) th EVN Symposium, Torun, Poland

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

Outline  Introduction - mm VLBI, Previous Surveys  Observation - Source selection, Calibration  Results - Images  Brightness temperature (T B ) and jet physics - T B – Apparent jet speed, T B along the jets  Summary

Millimeter VLBI IntroductionResultsTb and Jet physicsSummary 1.VLBI experiments at mm wavelengths (e.g. 43GHz, 86GHz, 150GHz, 230GHz) 2.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 3.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 First VLBI fringe detection at 89GHz Readhead et al CMVA (86GHz) (The C oordinated M M V LBI A rray) 2004 GMVA (86 GHz) (The G lobal M M- V LBI A rray) present Haystack + (Ef, On, Pv, Pb, Mh) + VLBA ( 8x25m) VLBA (8x25m) + (Ef, On,Pv,Pb,Mh) GMVA web -

Previous surveys IntroductionResultsTb and Jet physicsSummary VLBI Surveys at 86 GHz 1.Beasley et al. (1996) 2.Lonsdale et al. (1998) 3.Rantakyro et al. (1998) 4.Lobanov et al. (2000) 5.This survey - 3~4 times better sensitivity - larger sample (127sources) taken from surveys at lower freq (95%) were detected and 109 imaged This Survey

Source selection IntroductionObservationResultsTb and Jet physicsSummary References of source selection 1. The VLBI samples: - 22 GHz (Moellenbrock et al. 1996) - 15 GHz (Kellermann et al. 1998) 2. The multi-frequency monitoring data: - Metsahovi at 22, 37, and 86 GHz (Terasranta et al. 1998) - Pico Veleta at 90, 150, and 230 GHz (Ungerechts, priv. comm). Flux density > 0.3 Jy at 86 GHz Declination > - 40 degree Excluded some bright sources imaged at 3mm before Survey Observations with Global 3mm VLBI Three sessions: Oct. 01, Apr. 02 and Oct.02 3~4 scans of 7-min dur. per a source Antennas : 8 VLBA + 5 European Ant. Max. baseline sensitivity ~ 0.1 Jy Image sensitivity < 10 mJy/beam Bandwidth: 64 or 128 MHz Sampling : 1-bit or 2-bit Correlation : Mark IV at MPIfR Bonn Sky distribution of the sources RA [hrs] Dec [Degrees]

Calibration IntroductionObservationResultsTb and Jet physicsSummary Correlation CalibrationImaging FOURFIT MK4IN Amp. calibration FRING MAPPLOT CLEAN Fringe detection : FOURFIT with subsequently narrowing the search window Amplitude Calibration : Tsys measurements, Gain curves,opacity correction and amplitude self-calibration Phase Calibration : manual phase-calibration and self-calibration Imaging : t avg = 30 sec, natural weighting, no uv-tapering, beam size = 0.05 x 0.36 mas Correlator at MPIfR Software (Alef et al. 1998) AIPS DIFMAP (Shepherd et al. 1994)

Images IntroductionResultsTb and Jet physicsSummary Lee et al in prep

Brightness Temperature (T B ) IntroductionResultsTb and Jet physicsSummary And if, then the lower limit of T B is obtained with d = d min. (e.g. SNR = 6.5; Beam ( a x b ) = ( 0.1 x 0.07 mas) => d min = 0.035mas) (A.P. Lobanov 2005)

T B distribution IntroductionResultsTb and Jet physicsSummary (Lobanov et al. 2000) VLBI coresJet components (Lee et al. 2006, in prep.) VLBI cores Jet components

T B vs. Apparent jet speed IntroductionResultsTb and Jet physicsSummary T B,core vs. Jet speed (N=86) Apparent Jet speeds from 2cm survey (Kellermann et al. 1998) T B,jet vs. Jet speed (N=39) Red triangles are lower limits of T B

Evolution of T B along the jets IntroductionResultsTb and Jet physicsSummary NRAO 140 3C OJ 287 NRAO 190 Red circles are the predicted T B in shocks with adiabatic losses dominating the radio emission. Blue circles are the observed T B. (Lee et al in prep.) Assumptions are made like the following: (Lobanov et al. 2000)

Summary IntroductionResultsTb and Jet physicsSummary 1.We conducted a large global 86 GHz VLBI survey of compact radio sources, using a global 3mm VLBI array. 2.The survey is the largest and most sensitive one (rms Image < 10 mJy/beam) 3.It provides a detection rate of 95% out of 127 sources and a total set of images of 109 sources. 4.We estimated brightness temperatures (T B ) 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. 5.The T B 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.