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Everything you wanted to know about (e-)VLBI… …and more Zsolt Paragi, JIVE.

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Presentation on theme: "Everything you wanted to know about (e-)VLBI… …and more Zsolt Paragi, JIVE."— Presentation transcript:

1 Everything you wanted to know about (e-)VLBI… …and more Zsolt Paragi, JIVE

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

3 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #3 Resolution: = 1.22 /D This translates to about an arcminute or more even with the great, 100m Effelsberg radio telescope at cm wavelengths.

4 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #4 Very Long Baseline Interferometry (VLBI) (Long long time ago, in a far away galaxy…) Data recorded on mag- netic tapes Later processed in a correlator This need thorough knowledge of geometry and very precise timing information Earth diameter limits resolution (tipically mas) Number of telescopes, their diameter and performance, as well as the recording rate limits the sensitivity Magnetic tapes could do 256 Mbps (512 with two heads)

5 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide # Fringes

6 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #6 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 phase and amplitude at each of these sampled spatial frequencies The data are pre-processed, and a dirty image is formed by Fourier transform Further calibration of fringe amplitudes and phases is done parallel to the deconvolution of this dirty image

7 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #7 And what can I do with this? Objects with fairly compact structures and astrometry studies: e.g. parallax measurements up to several kpc ( < 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, and MASERs of stellar and extragalactic origin. NGC4258 Miyoshi et al. (1995), Nature 373, 127

8 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #8 VLBI networks VLBA VERA

9 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #9 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

10 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #10 The end of the tape era Tape recording had limited performance (parity errors), 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

11 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #11 MERLIN archive 1.6 GHz data, 1997 Just a flavour of what is possible: SNR in M82 1 sigma noise 15 Jy/beam (limited by the noisy host galaxy) Paragi et al. (in prep.)

12 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #12 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… Predicted radio flux densities of ULXs in nearby galaxies, if these are powered by IMBHs Paragi et al. (2006)

13 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #13 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 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…

14 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #14 Select your source Write an observing proposal EVN PC makes a decision Publishing results EVN scheduler provides 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!

15 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #15 Target of Opportunity projects An example: the huge flare of SGR SGR is a soft gamma-ray repeater a neutron star with very strong magnetic fields, a magnetar Produced the greatest explosion witnessed by humans in our Galaxy, on 27 December 2004 Observations with various instruments, also VLBI (with the VLBA array) Could not image reliably because of lack of known 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 them quickly??? Fender et al. (2005), MNRAS 367, L6

16 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #16 e-VLBI Proof-of-Concept Project (long, long time ago…) DANTE/GÉANT Pan-European Network SURFnetDutch NREN GARR Italian NREN UKERNAUK NREN PSNC Polish NREN DFN German NREN KTHNOC/NORDUnet Nordic NREN Manchester UniversityNetwork application software JIVEEVN Correlator Westerbork telescopeNetherlands Onsala Space Observatory Sweden MROFinland MPIfRGermany Jodrell Bank UK TCfAPoland CNR IRA Italy

17 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #17 0 SISI GRGR CZCZ IEIE LULU EEEE SKSK ILIL LTLTCYCY ESES HUHU ITIT FRFR UKUK BEBE NLNL DEDE SESE CHCH PTPT ATAT GEANT GEANT 2.5 G 1.2 G 622M 155 M BGBG LVLV RORO HRHR PLPL 45 M 34 M 310 M GÉANT: Access of NRENs to GÉANT EVN telescope

18 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #18 Westerbork Netherlands Dedicated Gbit link Network Topology for eVLBI Onsala Sweden Gbit link Network North-West 150Mbit link Jodrell Bank UK Dwingeloo DWDM link Cambridge UK MERLIN Microwave link Medicina Italy Chalmers University of Technology, Gothenburg Torun Poland Gbit link

19 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #19 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 First real-time eVLBI Image

20 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #20 MERLIN, March 2002 e-VLBI, September 2004 IRC Richards et al. (2004) The first e-VLBI science result (line, 32 Mbps)

21 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #21 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 emission due 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

22 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #22 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 # 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

23 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #23 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

24 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #24 Telescope sites participating Image courtesy of Dr. Francisco Colomer

25 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #25 Activities #Description Leader PC Project Coordinator Michael Garrett, JIVE NA1 Management of I3 T. Charles Yun, JIVE NA2 EVN-NREN Forum John Chevers, DANTE NA3 eVLBI Science Forum John Conway, Chalmers NA4 Public Outreach Kristine Yun, JIVE SA1 Production Services Arpad Szomoru, JIVE SA2 Network Provisioning Francisco Colomer, CNIG-IGN JRA1 FABRIC Huib Jan van Langevelde, JIVE

26 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #26 Jodrell Bank UK Onsala Sweden Medicina Italy Torun Poland Westerbork Netherlands Telescopes connections (early 2007) JIVE 1Gb/s 155Mb/s Cambridge UK 2.5Gb/s 1Gb/s e-MERLIN ? ? ? ? ? Soon available: Effelsberg, Yebes 40m, Shanghai …

27 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #27 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 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 , 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.

28 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #28 First refereed journal papers: Rushton et al. (2007), MNRAS 374, L47 Tudose et al. (2007), MNRAS… very soon Cyg X-3

29 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #29 Want to propose e-VLBI observations? e-VLBI proposals must be submitted by to the EVN PC; a web proposal tool 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 to find out if preferred correlation mode is 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!

30 2007 January 15Everything you wanted to know about (e-)VLBI...and moreSlide #30 Future plans 16 Gbps connection to correlator at JIVE Dynamic scheduling – is this possible? Next generation (software?) correlator …GRID processing


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