A Global 86 GHz VLBI Survey of Compact Radio Sources Sang-Sung Lee MPIfR In collaboration with A.P....
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Transcript of A Global 86 GHz VLBI Survey of Compact Radio Sources Sang-Sung Lee MPIfR In collaboration with A.P....
A Global 86 GHz VLBI Survey of Compact Radio Sources
Sang-Sung LeeMPIfR
In collaboration withA.P. Lobanov, T.P. Krichbaum, A. Witzel, J.A. Zensus (MPIfR, Bonn)
M. Bremer, A. Greve, M. Grewing (IRAM, Grenoble)
26.09.20068th EVN Symposium, Torun, Poland
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
Millimeter VLBIIntroduction Results Tb and Jet physics Summary
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. 1983
1995
CMVA (86GHz)
(The Coordinated MM VLBI Array)
2004
GMVA (86 GHz)
(The Global MM-VLBI Array)
present
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/
Previous surveysIntroduction Results Tb and Jet physics Summary
VLBI Surveys at 86 GHz
0
20
40
60
80
100
120
140
Numberof
sources
1 2 3 4 5
Surveys
Comparison of VLBI surveys at 86 GHz
ObservedDetectedImaged
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.
- 121(95%) were detected and 109 imaged
This Survey
ImagesIntroduction Results Tb and Jet physics Summary
Lee et al. 2006 in prep
Brightness Temperature (TB)Introduction Results Tb and Jet physics Summary
And if , then the lower limit of TB is obtained with d = dmin.
(e.g. SNR = 6.5; Beam ( a x b ) = ( 0.1 x 0.07 mas) => dmin = 0.035mas)
2
2tot
ΒΒ
z)(1λS
k
π2log(2)Τ
d
(A.P. Lobanov 2005)
TB distributionIntroduction Results Tb and Jet physics Summary
(Lobanov et al. 2000)
limit)ion Equipartit(~
105
limit)compton Inverse(~
104~1
10int,
11int,
KT
KT
jet
core
VLBI cores Jet components
(Lee et al. 2006, in prep.)
VLBI cores Jet components
TB vs. Apparent jet speedIntroduction Results Tb and Jet physics Summary
TB,core vs. Jet speed (N=86)
Apparent Jet speeds from 2cm survey (Kellermann et al. 1998)
TB,jet vs. Jet speed (N=39)
Red triangles are lower limits of TB
Evolution of TB along the jetsIntroduction Results Tb and Jet physics Summary
NRAO 140
3C 454.3OJ 287
NRAO 190
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.)
Assumptions are made like the following:
(Lobanov et al. 2000)
SummaryIntroduction Results Tb and Jet physics Summary
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 (rmsImage< 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 (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.
5. 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.