beyond vlbi micro-arcsecond resolution with inter-stellar scintillation d.l. jauncey 1,2, j.e.j....
TRANSCRIPT
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Beyond VLBIMicro-arcsecond Resolution with
Inter-Stellar Scintillation
D.L. Jauncey1,2, J.E.J. Lovell3, J.Y. Koay4,
J-P. Macquart4 , B.J. Rickett5, H.E. Bignall4, L. Kedziora-Chudczer6, T. Pursimo7,
C. Reynolds4, and R. Ojah8
1: CASS, 2: MSO, 3: Utas, 4: ICRA, 5: UCSD, 6: UNSW, 7: NOT, 8: GSFC
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Intra-Day Variables from the beautiful MPI 100 m Bonn Machine.
But is it intrinsic or extrinsic?
Where it got going………
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In 1996 at the ATCA, as part of her IDV Survey,
Lucyna Kedziora-Chudczer found
PKS0405-385 the first of the 3 rapid
variables
8.4 GHz
4.8 GHz
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Here’s the full 3 days of ATCA data at 8.4, 4.8, 2.4 and 1.4 GHz. The pattern of strong variability at 5 and 8 GHz,
and decreasing variability at the lower frequencies
suggests ISS as the cause. Otherwise Tb ~ 1021 K !!!
8.4 GHz
4.8 GHz
2.4 GHz
1.4 GHz
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How to tell the difference between
intrinsic variability and
inter-stellar scintillation?
through one of the more elegant “VLBI” experiments undertaken
between the ATCA and the VLA……
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PKS1257-326 pattern
time-delay
ISS implies -arcsecond
sizes
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During the discovery observations of PKS1257-326, Hayley found this beautiful
annual-cycle, again, clearly it’s ISS!
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What next?Our objective was to obtain a sample
of ~ 100 scintillators for reliable statistics. At the time (2000), this implied a sample size of ~ 500 flat-spectrum sources. The only instrument capable of achieving this
is the VLA. 5 GHz is in the weak scattering regime and is where the VLA
works well.
Micro-Arcsecond Scintillation Induced Variability Survey
MASIV
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MASIV: VLA ObservationsMASIV: VLA Observations Four 72 hr epochs: Four 72 hr epochs:
Jan, May and Sep 2002 (96h), Jan 2003 during reconfiguration.Jan, May and Sep 2002 (96h), Jan 2003 during reconfiguration. 5 sub-arrays of 5 or 6 antennas each.5 sub-arrays of 5 or 6 antennas each.
Core sample of 500 compact, flat-spectrum sources at 5 GHz Core sample of 500 compact, flat-spectrum sources at 5 GHz 60 sec on-source per scan 60 sec on-source per scan ~6 scans per source per day (10,000 scans per epoch)~6 scans per source per day (10,000 scans per epoch)
Micro-Arcsecond Interstellar Scintillation-Induced Variability: MASIV
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B0059+581 B1156+295
annual cycle high RMS
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Integrated VLBI flux density curve of B1156+295, obtained by averaging the correlated flux density at projected baselines shorter than 100 M.
from Savolainen & Kovalev 2008
ISS effects on VLBI
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Important implications for Space VLBI……
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Galactic Distribution
The high WHAM correlation strongly supports ISS
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Redshift dependence
For more on this you’ll have to wait for Hayley Bignall’s talk tomorrow…..
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“Twinkle, twinkle, quasi-star Biggest puzzle from afarHow unlike the other ones Brighter than a billion sunsTwinkle, twinkle, quasi-star How I wonder what you are.”
George GamowNewsweek
Reprinted from the Proceedings of the
First Texas Symposium on Relativistic Astrophysics
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