A Simultaneous Multi-Frequency Receiving
System as a Powerful Tool for mm-VLBI Study

Taehyun Jung
鄭太現
Korean VLBI Network (KVN)
Korea Astronomy & Space Science Institute (KASI)VERA User’s Meeting @ Mizusawa, Janpn Sep 24-25, 2015

Errors coming from the ATMOSPHERE are still remain themost serious difficulty which significantly degrade thesensitivity and imaging capability of mm and sub-mm VLBI
observation

Coherence

Coherence Function

VLBI Sensitivity

Pico Veleta – Onsala baseline
Source : BL Lac
Frequency : 86 GHz

Coherence Time*Typical value of atmospheric phase stability ~ 10 -13(A. Roy)

Phase Referencing Techniques

VERA & KVN System for VLBI Phase Referencing••

Increase coherence time by removing atmospheric fluctuations
 weak source detection with high SNR
Precise Astrometry
Atmospheric phase errors are calibrated bynear by calibrators
lower frequency phase solutions

KVN multi-freq. receiving system

VERA dual-beamFirst Light from 22/43/86/129 GHz
Simultaneous Single Dish Observation
22 / 43 / 86 / 129 GHz

Dec 60°129 GHz86 GHz43 GHz22 GHz

4CH UV Coverage

H20/SiO Masers in Orion KL

VERA Dual-Beam Experiment
Correlation Coefficient > 0.9

Jung et al. 2011

An Ideal System for mm-VLBI
KVN
Multi-Frequency Feeds• Target itself is the reference resolving the reference
source problem• No coherence loss due to the same sky position• Integrate mm VLBI fringes aslong as a single dish telescopedoes weak source detection at mm

KVN Multi-Freq. Simultaneous Observation

129 GHz86 GHz43 GHzCeff

22GHz

43GHz

86GHz

129GHz22 GHz

-0.97

0.91

0.88

43 GHz

0.97

-0.97

0.96

86 GHz

0.91

0.97

-0.99

129GHz0.88

0.960.99-𝜈ℎ
𝜙 ℎ𝑖𝑔ℎ ∝ 𝜙𝑙𝑜𝑤
𝜈𝑙non-dispersive characteristicof troposphere

22 GHz30min

High frequency VLBI Phase Calibration by Lower Frequency Phase Solutions

NRAO1500133+476
3C84
1308+326
3C279
3C345
NRAO530
SGR-A
3C454.3
2255-282
0202+149
1023+131
3C273
1633+382
NRAO512
FAS
1921-293
BLLAC
NRAO150

MFPR applied with K-band solint 0.3

24 hours

43GHz

MFPR applied with Q-band solint 0.1

86GHz

MFPR applied with K-band solint 0.3

129GHz

NRAO1500133+476
3C84
1308+326
3C279
3C345
NRAO530
SGR-A
3C454.3
2255-282
0202+149
1023+131
3C273
1633+382
NRAO512
FAS
1921-293
BLLAC
NRAO150

24 hours

129GHz Visibility Phase Calibrated by 22GHz

NRAO1500133+476
3C84
1308+326
3C279
3C345
NRAO530
SGR-A
3C454.3
2255-282
0202+149
1023+131
3C273
1633+382
NRAO512
FAS
1921-293
BLLAC
NRAO150

MFPR applied with K-band solint 0.3

24 hours

43GHz

MFPR applied with Q-band solint 0.1

86GHz

MFPR applied with K-band solint 0.3

129GHz

NRAO1500133+476
3C84
1308+326
3C279
3C345
NRAO530
SGR-A
3C454.32255-282
0202+149
1023+131
3C273
1633+382
NRAO512
FAS
1921-293
BLLAC
NRAO150

24 hours

Increase coherence time  weak source detection with high SNR
Before Rx Room Temp. Stabilization

SNR~213(~90% of theoretical SNR)

example of 3C279

After Rx Room Temp. Stabilization First
Simultaneous
4-channel
Observation
VLBI Images

21.7GHz
Peak ~ 26.4 Jy/beam
Beam 8.5 x 3.5 mas -78.8°

43.4GHz
Peak ~ 20.6 Jy/beam
Beam 3.12 x 1.78 mas -82.6°

86.8GHz
Peak ~ 12.7 Jy/beam
Beam 1.59 x 0.87 mas -81.8°

130 GHz
Peak ~ 5.0 Jy/beam
Beam 1.09 x 0.58 mas -81.4°

Source: 3C279

43/86/130GHz
visibility phases arecalibrated by 22Ghz

Multifrequency AGN Survey with the KVN
Discovering high-frequency sources & Maximizing the KVN uniquenessTotal: 1304 sources

858 known + 446 newKVN Calibrator Survey (22/43GHz) by J.A. Lee

iMOGABA by S.S. Lee

Multi-frequency source catalogue of selected samples• Physical properties at 2-13mm wavelengths-•

flux density, spectral index, compactness, populations etc.

Provides high frequency VLBI catalogue

Two Main Reasons in VLBI Phase Referencing
2. Astrometry  high-precision astrometry at mm wavelengths
SiO v=1 & 2 ~ 1 mas ± 35 μas
Separation H20/SiO ~ 70 ± 2 mas
Ring size ~ 20 mas•••

Dodson et al. 2014
Simultaneous observation of H2O &SiO (v=1 & 2) maser lines for R LeoMinoris
SiO maser phase referenced to H2Omaser••

Rioja et al. 2014
Simultaneous 22/43GHz––••••0854+213 w/ reference OJ287
1.2deg awayCore shift accuracy ~ 40 μas
Consistent with VLBA within 1σ-error
Structure blending effect should be considered
Flux recovery ~ 94% using KVN SFPR

New Method in mm-VLBI Astrometry

43GHz86GHz

129GHzKVN MFPR

Simultaneous multi-frequency observation
Perfect calibration to the troposphere
Ideal methods, especially mm/sub-mm VLBI
Unique access to the inner most region of the Jets
 High precision VLBI astrometry can be achieved
at mm/sub-mm wavelengths with unprecedented
sensitivity

Quasi-Optics as a Powerful Tool of mm-VLBIin Collaboration with VERA 20m
History & Plans▫ 2013 Nov : Manufacture▫ 2013 Dec. : Shipping & Installation▫ 2014 Jun : K/Q VLBI fringe test
▫ 2014 Sep : Fringe Detection▫ 2014 Dec : Science verification test
▫ 2015 VERA QO for Miz & Iri stations

K/Q simultaneous fringes of OJ287

H20/SiO Simultaneous fringes of ORION-KL

H2O
22GHz

43GHz

SiO

Phase Correction with QO systems (KQ, OJ287)
Q-band Visibility Phase

Q-band Visibility Phase

No calibration applied

Calibrated by K-band Phase Solutions

KVN LHCP solutions

KVN RHCP solutions• K-band fringe phase solutions of OJ287 were applied to calibrate Q-band data
• Visibility phase of Q-band calibrated by K-band shows more stable phase thanraw data although there are high phase rates at MIZ related baselines
 The feasibility of K/Q simultaneous observing system has been demonstrated !!
• Science demonstrations has been conducted on be half of KaVA science subworking group in Feb 2014.

Upgraded Quasi-Optics
for VERA Mizusawa & Iriki Radio Telescopes
Delivery : Next week

Multi-Frequency System@ YEBES!!

22GHz

First Light !!!
Jan. 12th 2015
Source : Orion-KLLPF
2LPF
143GHz86GHz

2000x1450mm

Quasi-Optics as a Powerful Tool of mm-VLBI
in Collaboration with Yebes 40m
History & Plans▫ 2013 Nov. : K/Q/W QO discussion▫ 2014 Jan-Aug : QO design▫ 2014 Jun : KASI-IGN MOU▫ 2014 Sep : Manufacture▫ 2014 Oct : Shipping to Yebes▫ 2014 Nov : Installation & Initial test
▫ 2015 Apr : First K/Q band fringe test
▫ 2015 Jun : Scientific demonstration test
First K/Q simultaneous fringes between KVN Ulsan and Yebes44/86GHz VLBI Observation with ATCA
80 micro-arcsecond
fringes between northernand southern hemispherebaselines !!

3C273 44/88 GHz(North-South Baseline)•Better Resolution & More Sensitivity
with Global Multi-Frequency Systembecause it’s Simple & Powerful
more observing time, multi-frequency data, tropospheric calibration~70 micro arcseconds @ 3mmInternationalCollaborations!!

VERA 20m. 22/43 Fringe Test 2014 June

VLBA (MK) 25m
discussion on QO
22/43/86 (2014 May)

Yebes 40m
22/43/(86/129)
22/43 Installationin 2014 Nov

ATCA 22m x 6
43/86 Test in 2014 Sep

Noto or Sardinia in near future??

International
Collaborations!!

VERA 20m. 22/43 Fringe Test 2014 June

VLBA (MK) 25m
discussion on QO
22/43/86 (2014 May)

Yebes 40m
22/43/(86/129)
22/43 Installationin 2014 Nov

ATCA 22m x 6
43/86 Test in 2014 Sep

Noto or Sardinia in near future??

http://www.ira.inaf.it/eratec/florence

Topics to address are the following:
FOR THE IMPLEMENTATION OF (NEAR) SIMULTANEOUS OBSERVATIONS AT MM-WAVE BANDS:• mm-VLBI Studies and Key Science Case(s):o Astronomical Studies using continuum and spectral line observationso Analysis Methods and Results from current instruments using multi- frequency observations• Defining science driven requirementso Achievable sensitivity and mapping fidelity
o Simulation studies of the performance of a multi-frequency mm-VLBI network of European telescopes• Exploring the engineering possibilities:o Existing technical solutions for simultaneous multi-frequency observations;o Possibilities of technical solutions for other sites.
• Plan for a realization of a European network.

Thank you for your attention!
For the best mm-VLBI networkwith Multi-frequency System