everything you wanted to know about (e-)vlbi… …and more zsolt paragi, jive

Everything you wanted to know about (e-)VLBI…

…and more

Zsolt Paragi, JIVE

2007 January 15 Everything you wanted to know about (e-)VLBI ...and more Slide #2

Abstract

I will talk briefly about the Very Long Baseline Interferometry (VLBI) technique and what we can do with it. The European VLBI Network (EVN) will be shortly introduced. Then I will describe the recent e-VLBI developments at JIVE. Science examples will be mixed in all over the talk. The following 30 minutes will be about

RESOLUTION

SENSITIVITY

RAPID RESPONSE SCIENCE


Resolution:

= 1.22/D

This translates toabout an arcminuteor more even with the great, 100m Effelsberg radio telescope at cm wavelengths.


Very Long Baseline Interferometry (VLBI)(Long long time ago, in a far away galaxy…)

• Data recorded on mag-netic tapes• Later processed in acorrelator• This need thoroughknowledge of geometryand very precise timinginformation• Earth diameter limitsresolution (tipically mas)• Number of telescopes,their diameter and performance, as well asthe recording rate limitsthe sensitivity• Magnetic tapes could do256 Mbps (512 with twoheads)


001011101010011001010001100101111001011101010011

Fringes


• An interferometer measures the Fourier-components of the sky brightness distribution

• As the Earth rotates, the projected baselines sample various spatial frequencies, that provide information on the target source structure at various angular scales

• We measure the fringe phaseand amplitude at each of thesesampled spatial frequencies

• The data are pre-processed, and a “dirty image” is formedby Fourier transform

• Further calibration of fringeamplitudes and phases is doneparallel to the deconvolution of this dirty image


And what can I do with this?

Objects with fairly compact structures andastrometry studies:• e.g. parallax measurements up to several kpc( < 0.001 arcsecond)• may resolve nearby stars and their environment,(0.1 AU resolution at 100 pc)• Active Galactic Nuclei, (compact jets of several pc have mas structures at even high redshifts)• black hole astrophysics, gravitational lenses and much more…• Geodetic VLBI: tectonics on Earth, time service end EOPs, International Celestial Reference Frame (ICRF)

And of course spectral line observations of HI, andMASERs of stellar and extragalactic origin.

NGC4258 Miyoshi et al. (1995), Nature 373, 127


VLBI networksVLBA

VERA


The European VLBI Network• Some of the worlds greatest radio telescopes, e.g. Effelsberg 100m, Lovell 76m telescopes, Westerbork Synthesis Radio Telescope• Outside Europe includes Hartebeesthoek (South Africa), Urumqi and Shanghai (China)• Several telescopes are being built that will join the EVN: Yebes 40m (this year), telescopes in Sardinia, Latvia, Ireland and China • Operating in three observing sessions per year, sometimes jointly with MERLIN (UK) and the VLBA (USA) – global VLBI• Observing wavelength ranges from 92cm to 1.3cm• The most sensitive standalone VLBI array (the so-called High Sensitivity Array formed occasionally by the VLBA, VLA, GBT and maybe Arecibo competes with it)• The data are correlated in the EVN MkIV correlator at JIVE

http://www.evlbi.org/

http://www.jive.nl/

http://www.evlbi.org/

http://www.jive.nl/


The end of the tape era• Tape recording had limited performance (parityerrors), and • limited data rate (256 Mbps; 512 Mbps with two write heads).• Tapes were expensive• Tape playback units were not easy to maintain

• Disk based recording systems were developed at Haystack (Mark5A) and Metsahovi Radio Observatory (PC EVN)• And it worked!• The EVN is fully disk operational (Mark5A) since early 2004• Cheaper, off the shelf technology, perfect recording; data rate up to 1 Gbps

http://www.haystack.edu/tech/vlbi/mark5/

http://www.haystack.edu/tech/vlbi/mark5/


MERLIN archive 1.6 GHz data, 1997

Just a flavour of what is possible:SNR in M821 sigma noise 15 Jy/beam (limitedby the noisy host galaxy)

Paragi et al. (in prep.)


The sensitivity

For six hours on-source integration in the C-band (6cm) the theoretical 1 sigma rms noises are

VLBA, 128 Mbps: 80 Jy/beam

HSA (VLBA+VLA27+GBT), 128 Mbps: 18 Jy/beam

Full EVN, 1 Gbps: 8 Jy/beam

Another example why the sensitivity limits are pushed so hard…

Predictedradio flux densities of ULXs innearby galaxies, ifthese are powered byIMBHs

Paragi et al.(2006)


The reliability

• Disk recording is better quality, but it also provides a way to quickly check telescope performance: ftp tests

• 2-4s data at 256 Mbps 64-128 MB files, may be transferred through the Internet!

• Data processed by a software correlator developed in NICT, Japan

• Since late 2004 there are regular ftp tests during EVN sessions.

• The software correlator runs on a PC cluster

• Feedback to telescopes used to take at least a week, now it is a matter of minutes

• OK, let us see what else can we improve…


Select your source

Write an observingproposal

EVN PC makesa decision

Publishingresults

EVN schedulerprovides a date

1-2 weeks 2-3 months 2-3 months

Observe with VLBI

Data correlation

Data processing

… another 2-3 months well, why would you hurry?

VLBI observations timeline

THIS MUST CHANGE!


Target of Opportunity projects

An example: the huge flare of SGR1806-20

• SGR1806-20 is a soft gamma-ray repeater aneutron star with very strong magnetic fields, a magnetar

• Produced the greatest explosion witnessed byhumans in our Galaxy, on 27 December 2004

• Observations with various instruments, also VLBI (with the VLBA array)

• Could not image reliably because of lack ofknown calibrator in the vicinity of the target!

Is there a way to do these projects more efficiently?Is there a way to get the data and analyze themquickly???

Fender et al. (2005), MNRAS 367, L6


e-VLBI Proof-of-Concept Project(long, long time ago…)

• DANTE/GÉANT Pan-European Network• SURFnet Dutch NREN• GARR Italian NREN • UKERNA UK NREN• PSNC Polish NREN • DFN German NREN• KTHNOC/NORDUnet Nordic NREN • Manchester University Network application software • JIVE EVN Correlator• Westerbork telescope Netherlands• Onsala Space Observatory Sweden• MRO Finland• MPIfR Germany• Jodrell Bank UK• TCfA Poland • CNR IRA Italy


0SISISISI

GRGRGRGRCZCZCZCZ

IEIEIEIE

LULULULU

EEEEEEEESKSKSKSK

ILILILILLTLTLTLTCYCYCYCY

ESESESES

HUHUHUHUITITITIT

FRFRFRFR

UKUKUKUK

BEBEBEBE

NLNLNLNLDEDEDEDE SESESESE CHCHCHCH

PTPTPTPT

ATATATAT

GEANTGEANTGEANTGEANT

2.5 G 1.2 G622M

155 M

BGBGBGBGLVLVLVLVRORORORO

HRHRHRHR

PLPLPLPL

45 M34 M

310 M

GÉANT:Access of NRENs to GÉANT

EVN telescope


WesterborkNetherlands

Dedicated

Gbit link

Network Topology for eVLBI

OnsalaSweden

Gbit link

NetworkNorth-West

150Mbit link

Jodrell BankUK

DwingelooDWDM linkCambridge

UK

MERLINMicrowave

link

MedicinaItaly

Chalmers University

of Technolog

y, Gothenbur

g

TorunPoland

Gbit link


The beginning of e-VLBI in Europe

• With e-VLBI one could continuously monitor telescope performance• Results would be available almost immediately• Could be more flexible to ToO projects• May make quick decisions about the use of a calibrator, or follow-up observations • The EVN would be more competent in ‘hot topic’ science

• Had to prove that the EVN MkIV correlator can be upgraded to realtime operations• Had to prove that the research networks can cope with the network load• Had to test and tune transfer protocols

First tests were promising, and then came the first real e-VLBI image in 2004


MERLIN, March 2002 e-VLBI, September 2004

IRC+10420 Richards et al. (2004)

The first e-VLBI science result (line, 32 Mbps)


The first e-VLBI science result (continuum)• SN2001em was discovered on 15 September 2001 in UGC11794 galaxy (Pepenkova 2001).

• Redshift z~0.02 corresponding to a distance of 80~Mpc.

• Filippenko and Chornok (2001) classified it as type Ib/c, most likely Ic.

• Exceptional radio and X-ray luminosities(off axis GRB, developing late radio emissiondue to jet break?),

• Not quite a 1 mJy radio source

• EVN observations: Cm, Jb2, On, Tr, Wb (128Mbps), +Arecibo 300m (64 Mbps)at 18cm, on 2005 Mar 11

• Tentative detection (4.5 ) of the first real faint target with e-VLBI

Paragi et al. (2005), MSAIt 76, 570


What is EXPReS?• EXPReS = Express Production Real-time e-VLBI Service• Three year project, started March 2006, funded by the European

Commission (DG-INFSO), Sixth Framework Programme, Contract #026642

• Objective: to create a distributed, large-scale astronomical instrument of continental and inter-continental dimensions

• Means: high-speed communication networks operating in real-time and connecting some of the largest and most sensitive radio telescopes on the planet

http://www.expres-eu.org/

http://www.expres-eu.org/


EXPReS Partners• Joint Institute for VLBI in Europe (coordinator)• AARNET Pty Ltd., Australia• ASTRON, The Netherlands• Centro Nacional de Informacion Geografica, Spain• Chalmers Tekniska Hoegskola Aktiebolag, Sweden• Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia• Cornell University, USA• Delivery of Advanced Network Technology to Europe Ltd. (DANTE), UK• Instituto Nazionale di Astrofisica, Italy• Instytut Chemii Bioorganicznej PAN, Poland• Max Planck Gesellschaft zur Foerderung der Wissenschaften e.V., Germany• National Research Foundation, South Africa• Shanghai Astronomical Observatory, Chinese Academy of Sciences, China• SURFNet b.v., The Netherlands• Teknillinen Korkeakoulu, Finland• The University of Manchester, UK• Universidad de Concepcion, Chile• Uniwersytet Mikolaja Kopernika, Poland• Ventspils Augstskola, Latvia


Telescope sites participating

Image courtesy of Dr. Francisco Colomer


Activities# Description LeaderPC Project Coordinator Michael Garrett, JIVENA1 Management of I3 T. Charles Yun, JIVENA2 EVN-NREN Forum John Chevers, DANTENA3 eVLBI Science Forum John Conway, ChalmersNA4 Public Outreach Kristine Yun, JIVESA1 Production Services Arpad Szomoru, JIVESA2 Network Provisioning Francisco Colomer, CNIG-IGN JRA1 FABRIC Huib Jan van Langevelde, JIVE


Jodrell BankUK

OnsalaSweden

MedicinaItaly

TorunPoland

WesterborkNetherlands

Telescopes connections (early 2007)

JIVE

1Gb/s

1Gb/s

1Gb/s

155Mb/s

CambridgeUK

2.5Gb/s

1Gb/s

e-MERLIN

?????

Soon available: Effelsberg,Yebes 40m, Shanghai …

http://www.jive.nl/jivecam


e-VLBI activities in 2006• There are regular e-VLBI test observations in every six week (on average)

• Normal operations at 256 Mbps (Cm, Jb2, Mc, On, Tr, Wb)

• Fringes to several telescopes at 512 Mbps, most recently to Mc

• 24h time is pre-allocated for science observation during each e-VLBI test

• Observing proposals may be submitted two weeks before the advertised date

• More info at http://www.evlbi.org/evlbi/evlbi.html

Science projects observed in 2006:

Cyg X-3, 20 Apr/18 May, 128 Mbps, Tudose et al.

GRS1915, 20 Apr, 128 Mbps, Rushton et al.

LSI +61.303, 256 Mbps, 26 Oct, Perez-Torres et al.

Algol, 26 Oct/14 Dec, 256 Mbps, Paragi et al.

Calibrators near M81, 14 Dec, 256 Mbps, Brunthaler et al.

INTEGRAL microquasar candidates, 14 Dec, Pandey et al.

http://www.evlbi.org/evlbi/evlbi.html


First refereed journal papers:Rushton et al. (2007), MNRAS 374, L47

Tudose et al. (2007), MNRAS… very soon

Cyg X-3


Want to propose e-VLBI observations?e-VLBI proposals must be submitted by e-mail to the EVN PC; a web proposaltool will be available in a couple of days…

e-VLBI proposals are just like other EVN proposals, but you must take additional care to

• justify properly why urgency is needed (target of opportunity, e.g. known transient flares, or need to check calibrators quickly for another project, taking part in an observational campagin)

• give accurate coordinates (sub-arcsecond accuracy)

• specify all the details of the proposed observations – schedule will be made by JIVE staff

• contact Bob Campbell ([email protected]), to find out if preferred correlation mode is OK

• keep in mind the limited resolution (~6*8 mas at 6cm), uv-coverage and sensitivity at the moment

• When 512 Mbps is possible and Effelsberg joins the array, the sensitivity will improve greatly; with Shanghai joining during 2007, the resolution will be better as well

• Be ready to travel to JIVE for quick data processing

• Think creatively, find projects that make appropriate use of this unique service!

mailto:[email protected]


Future plans

16 Gbps connection to correlator at JIVE

Dynamic scheduling – is this possible?

Next generation (software?) correlator

…GRID processing

everything you wanted to know about (e-)vlbi… …and more zsolt paragi, jive

Documents

geodetic vlbi

recent evlbi developments

vlbi networks vlba vera

sensitive standalone

european vlbi network

jive slide

vlba usa global vlbi

dirty image slide