Post on 12-Jan-2016
description
KVNKVN
VVLBI LBI EExtragalactic xtragalactic CoCompact mpact RRadio adio SSource ource
SSurvey urvey Lee, Sang-SungLee, Sang-Sung 2009EastAsiaVLBIWorkshop2009EastAsiaVLBIWorkshop
KVN
CollaborationCollaboration
Initiated by collaboration btw VERA and KVN VERA
• Mareki Honma
KVN• Bong Won Sohn
• S. Lee
Accelerated by motivation from Yuri Y. Kovalev (MPIfR) Leonid Petrov (GSFC/NASA)
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ContentsContents
IntroductionProject: VECoRSS
Goals Motivations Substance Plan
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Active Galactic Nuclei (AGN)Active Galactic Nuclei (AGN)
Marscher 2005Marscher 2005
Observables:Observables:
Flux density (Flux density (SS))Angular Size (Angular Size (θθFWHMFWHM))
Apparent jet speed (Apparent jet speed (ββappapp)) Brightness Temperature Brightness Temperature TTbb
Observables:Observables:
Flux density (Flux density (SS))Angular Size (Angular Size (θθFWHMFWHM))
Apparent jet speed (Apparent jet speed (ββappapp)) Brightness Temperature Brightness Temperature TTbb
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Brightness TemperatureBrightness Temperature
Brightness temperature:
A temperature that a source should have as if it was a black body to radiate a specific intensity
* Gaussian pattern of brightness distribution* Source rest frame
Inverse Compton limit:
Whenever Tb > 1012 K, inverse Compton scattering of radio photons dominates, and most of the energy will be radiated in X-ray. (Kellermann & Pauliny-Toth 1969)(Kellermann & Pauliny-Toth 1969)
Equipartition limit:
Sources radiate at Tb ~ 5 x 1010 K when energy densities in relativistic particles and magnetic fields are in equipartition. (Readhead 1994)(Readhead 1994)
High-resolution VLBI surveys enable to statistically study the brightness High-resolution VLBI surveys enable to statistically study the brightness temperatures of compact radio sources and temperatures of compact radio sources and to test the theoretical models of to test the theoretical models of relativistic outflowsrelativistic outflows (e.g., Marscher 1995). (e.g., Marscher 1995).
High-resolution VLBI surveys enable to statistically study the brightness High-resolution VLBI surveys enable to statistically study the brightness temperatures of compact radio sources and temperatures of compact radio sources and to test the theoretical models of to test the theoretical models of relativistic outflowsrelativistic outflows (e.g., Marscher 1995). (e.g., Marscher 1995).
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Relativistic effects and lower limitRelativistic effects and lower limit
Relativistic effects:
Radiation emitted from a jet component moving at a velocity of with an angle to the line of sight can be Doppler boosted.
Doppler factor
Apparent jet speed
Lower limit of Tb:
Minimum resolvable size dmin
a,b: axes of restoring beamSNR: signal-to-noise ratio : weighting function
When d < dmin, the lower limit of Tb should be estimated with d = dmin.
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VLBI Core and its opacity effectVLBI Core and its opacity effect
Lobanov (1996)Lobanov (1996) • VLBI core is located at a region where in the jet.
• Under the equipartition condition, the absolute position of the VLBI core rr is related to the total radiated synchrotron luminosity LLsynsyn
• VLBI core is located at a region where in the jet.
• Under the equipartition condition, the absolute position of the VLBI core rr is related to the total radiated synchrotron luminosity LLsynsyn
1
In order to investigate the physics of compact radio jets in sub-parsec scale In order to investigate the physics of compact radio jets in sub-parsec scale regions, we need to observe them at higher frequencies with high resolution regions, we need to observe them at higher frequencies with high resolution (high resolution VLBI survey). (high resolution VLBI survey).
In order to investigate the physics of compact radio jets in sub-parsec scale In order to investigate the physics of compact radio jets in sub-parsec scale regions, we need to observe them at higher frequencies with high resolution regions, we need to observe them at higher frequencies with high resolution (high resolution VLBI survey). (high resolution VLBI survey).
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FS43:FringeSurvey
at 43GHz
VIS43:VLBI Imaging Survey at 43GHz
pFS43:pilotFringeSurveyat 43GHz
Project: VECoRSSProject: VECoRSS
VECoRSS: VLBI Extragalactic Compact Radio Source Survey
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ICRFICRFICRFICRF
CalibratorCalibrator
43GHz43GHz
CalibratorCalibrator
43GHz43GHz
VECoRSS: GoalsVECoRSS: Goals
TrainingTraining
VLBI expertsVLBI experts
TrainingTraining
VLBI expertsVLBI experts
PC-scale structurePC-scale structureof compact radio of compact radio
sourcessources
PC-scale structurePC-scale structureof compact radio of compact radio
sourcessources
InternationalInternational
collaborationcollaboration
InternationalInternational
collaborationcollaboration
KVNKVNKVNKVN
NASANASA
GSFCGSFC
NASANASA
GSFCGSFCMPIfRMPIfRMPIfRMPIfR
VERAVERAVERAVERA
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Large VLBI surveysLarge VLBI surveys
*sub-sample.**VERA 22 GHz survey is done in collaboration withH. Kobayashi, T. Jike, M. Honma, K.M. Shibata, T. Hirota.
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VECoRSS: MotivationVECoRSS: Motivation
Only a few 100 sources have been observed/imaged at 43 GHz for geodetic/astrometric purpose (VLBA, Lanyi et al).
A KVN/VERA fringe survey at 43 GHz should be considered for VERA, KVN, VSOP-2, etc. VERA: needs a full list of extragalactic calibrators at 22/43 GHz for
dual-beam Galactic astrometry. (e.g., VERA fringe survey at 22 GHz; Petrov et al 2007, Full sky VERA fringe survey at 22GHz ongoing; Petrov et al.)
KVN: needs the list of calibrators at 22/43 GHz for multi-freq. phase-referencing observation at 22/43/86/129 GHz.
VSOP-2: needs preparatory surveys for identifying suitable radio sources for phase referencing observation at 8/22/43 GHz (VSOP-2 pre-launch survey at 43 GHz).
A follow-up VLBI imaging survey at 43 GHz with a complete sample of compact radio sources is required to study compact AGN jets.
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ppFS43: FS43: pilotpilot Fringe Survey at 43 GHz Fringe Survey at 43 GHz
pFS43 (2009) : A 24-hr pilot observation of ~ 270 compact radio sources out of 550 candidates selected (with VERA+KVNYS). Goals: to answer the following questions;
• What is the baseline sensitivity of VERA (+KVN) at 43 GHz : ∆SVERA. Expected value ∆SVERA ~ 150 mJy (VERA team, priv. comm.)
• How to schedule the fringe survey?• How to fringe-fit?• What are the criteria for selecting the candidate sources?• What are the amplitude calibrators?• How often the amplitude calibrators should be observed?• What will be the accuracy of amplitude calibration?• What is maximal integration time?
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ppFS43 - proposalFS43 - proposal
Source selection criteria: 270 out of 550 candidates• Correlated flux density of Sc ≥ 300 mJy on baselines of 170 ~ 250
Mλ at 8 GHz based on the catalogs of VCS1-6 and ICRF• Compactness of Sc/SVLBA ≥ 0.4 at 8 GHz• Detected sources in 3mm VLBI survey (Lee et al. 2008)• Correlated flux density of S22 ≥ 500 mJy on baselines of 100 ~ 200
Mλ at 22 GHz base on the VERA Fringe survey at 22 GHz (Petrov et al. 2007)
Amplitude calibration:• Amplitude calibrator : 20 sources from the Blazar (2-3 months)
monitoring program at 43GHz (Marscher et al. Boston Univ.) Observation:
• Six 4-hour observations with dynamic scheduling• Each source will be observed for one/two scan(s) of 2-min
duration.• Amplitude calibrator should be observed every 20 min.
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Selected sourcesSelected sources
270 objects selected for the pilot observations Group1 (90)Group1 (90) : Sc > 500 mJy, Sc/SVLBA ≥ 0.4
Group2 (133)Group2 (133) : 500 mJy ≥ Sc ≥ 300 mJy, Sc/SVLBA ≥ 0.4
Group3 (47)Group3 (47) : Sc < 300 mJy, Sc/SVLBA ≥ 0.4
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Sky distributionSky distribution
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Observed sources at 1Observed sources at 1stst epoch epoch
Preliminary detection rate
40% with FRING(AIPS)
70% with VEDA
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Observed sources at 1Observed sources at 1stst and 2 and 2ndnd epochs epochs
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FS43: Fringe Survey at 43 GHzFS43: Fringe Survey at 43 GHz
FS43 (2010-2011) : Survey observations with EAVN-Array43 (VERA, KVN, Nobeyama, Kashima) Sources with expected Sc > ∆SVERA
Each source observed for one or two scans. The first whole-sky fringe survey at 43 GHz in Northern
hemisphere. Spectral index (at 22-43GHz) obtained from KVN data.
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East Asian VLBI Network (EAVN)East Asian VLBI Network (EAVN)
EAVN-Array-QEAVN-Array-Q (so called) : KVN(3x21m) + VERA(4x20m) + Kashima(34m) +
Nobeyama (45m)
EAVN-Array43
0.7 mas@43GHz
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VIS43: VLBI Imaging Survey at 43 GHzVIS43: VLBI Imaging Survey at 43 GHz
VIS43 (2012-2013) : A follow-up VLBI imaging survey with a complete sample (EAVN-Array-Q + VLBA) A complete sample based on the results of FS43 Improve the data base of AGN VLBI images at 43 GHz A good database for International Celestial Ref. Frame (ICRF-ext2) Statistical study of intrinsic properties of relativistic jets. Resolution of the global VLBI survey at 43 GHz will be matched with
that of VSOP-2 at 22 GHz• Comparison of structural information and morphology at matched
resolution
• Comparison of Tb distribution at 22/43 GHz
– To see if there is any difference.
– To see if the difference is coming from jet stratification or opacity effect.
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Statistical study of compact jetsStatistical study of compact jets
Change of Tb in a jet => acceleration/deceleration of relativistic jets
Change of Tb
Tb increases up to
20 GHz and then starts to decrease
At 86 GHz, Tb are
systematically low.
Change of Tb
Tb increases up to
20 GHz and then starts to decrease
At 86 GHz, Tb are
systematically low.
A VLBI imaging survey at 43 GHz is required to fill this gap to confirm
the possible trend of Tb
A VLBI imaging survey at 43 GHz is required to fill this gap to confirm
the possible trend of Tb
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Change of Change of TTbb in a jet in a jet
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Change of Change of TTbb in a jet in a jet
(Vlahakis & Koenigl (2004)
r [pc]
Compact jets may be accelerated by magnetohydrodynamic (MHD) forces.
Compact jets may be accelerated by magnetohydrodynamic (MHD) forces.
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ICRF-ext2
VECoRSS: PlanVECoRSS: Plan
2009
2010
A completesample of calibrators
2011
2012
2013
pFS43
VIS43
FS43
VIS43
VSOP-2
VSOP-2
VERAVERAFS43
KVN
Thank you!