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L O F A R The Low-Frequency Array

L O F A R The Low-Frequency Array. ASTRON / MIT / NRL / UvA / UL / RUG / KUN IBM / BSIK partners / Many others. A brief history of LOFAR… Late 1990s : George Miley comes up with the concept 1999-2003 : Internal consortium of ASTRON – MIT – NRL signs a Memorandum of Understanding (M.O.U.)

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L O F A R The Low-Frequency Array

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  1. L O F A R The Low-Frequency Array ASTRON / MIT / NRL / UvA / UL / RUG / KUN IBM / BSIK partners / Many others...

  2. A brief history of LOFAR… Late 1990s: George Miley comes up with the concept 1999-2003: Internal consortium of ASTRON – MIT – NRL signs a Memorandum of Understanding (M.O.U.) Nov 2003: BSIK proposal (including UvA/UL/RUG/KUN and industrial partners) approved: 52MEuro for LOFAR in NL Dec 31, 2003: International M.O.U. terminates Feb 2004: US and Australia indicate that they do not wish to participate in a Dutch LOFAR. IBM agrees to provide BlueGene/L supercomputer for the project. 2004+ : Increasing interest from European partners (notably Germany and Sweden, also France, UK, and entire EVN consortium). LOFAR test stations in operation…

  3. LOFAR VLA ALMA GMRT ground based radio techniques 350m 10 MHz ATCA

  4. Radio sky in 408 MHz continuum (Haslam et al)

  5. LOFAR in The Netherlands Hang on, what are these things?

  6. They are the Low-band antennae (LBAs) Optimised for 30-80 MHz range (10-90 MHz full) The high-band antennae (HBAs) will be optimised for the 110-240 MHz band, and are in the design phase Sky response

  7. LOFAR will consist of a central virtual core of diameter ~2km containing 3200 LBA, 3200 HBA (~10-20% of total) There will be ~100 stations further afield, each with ~100 LBA / HBA ‘compound elements’ Maximum baselines of 100-150km with design allowing extensions towards Bremen (E-W) and Limburg (N-S) Has LOFAR been de-scoped ? Only significantly in terms of longest baselines (virtual core exactly as spec’d)

  8. Real specifications for the LOFAR we expect to build… An example mode for transients: the VC scans a huge area, delivers the position of a transient with arcmin-accuracy, the full array ‘zooms in’ and delivers arcsec position… within seconds.

  9. Key Science Areas • The epoch of reionization (RUG, de Bruyn) • The high redshift Universe (UL, Rottgering) • The bursting and transient Universe (UvA, Fender  Wijers) • Cosmic ray showers (KUN, Kuijpers) • (Space Weather) • (Ionosphere) NOVA-II proposal

  10. 21cm (1.4 GHz) emission/absorption from • Epoch of Reionisation • mapping of neutral residue of IGM as first sources of ionising radiation appear at redshifts between 7 and 20(?) • WMAP results suggest EoR at 15<z<20… there could be multiple phases Z = 20 ……………. 15 ………. 10 8 7 6 cold HI HII 70 MHz 90 MHz 130 160 190 MHz

  11. Quasar distributed star formation 10 arcmin (Groningen)

  12. Mapping all radio loud AGN Physics of radio sources Radio galaxies as probes of blackhole, galaxy and cluster formation

  13. Radio galaxy surveys (Leiden) • Basis • Redshift ~ spectral index • Most distant radio sources luminous at low frequencies • Science • Formation and evolution of massive blackholes, galaxies and clusters • As probes of epoch before reionisation to study HI absorption

  14. Starbursts: SFR > 10 M/yr Many starclusters with OB stars • That are initally dust-enshrouded • SN explosion  radio emission The Hunt: • (sub-)millimeters survey • UV dropout techniques, • Lya/Ha emission lines • mJy radio sources Importance • Study star fomation in galaxies • Significant fraction of the starformation rate • Mark transition of spirals to ellipticals

  15. Distant starburst galaxies • dominant population at low flux densities • in few years observing: 108 galaxies • Star formation rate of 10 M/yr up to z=3 • important complement • SIRTF, Omegacam, NGST, VISTA, ALMA • star formation history, nature of starbursts, clustering

  16. Galaxy surveys with LOFAR will be an overwhelmingly statistical exercise (Leiden, 5 years from now…)

  17. Observing Frequency (MHz) Angular Resolution (arcsec) limit 1 (10 σ) (mJy) Surface density of sources (No. per arcmin) Area covered after 1 year (sq. deg) Total number of sources after 1 year 10 15 30 0.5 3000 5.4 million 30 5.2 2 4 3000 4.3 million 75 2.1 0.3 25 60 5.3 million 120 1.3 0.1 66 62 15 million 200 0.8 10 125 7.5 3.3 million

  18. Cluster ‘relics’ and ‘haloes’ • Diffuse, extended and bright at low frequencies > LOFAR • 1. Relics • 2. Smooth centrally located radio halos • 1 yr LOFAR survey at 120 MHz should detect 800 halos, 140 with z>0.3

  19. Detections with `ASM’ can be rapidly (<sec) followed up with full array

  20. Object Variability Timescale No. of Events per year How far? Radio Supernovae days-months 3 2 - 3 further than Virgo Cluster GRB Afterglows days-months 100 Observable Universe GalacticBlackHoles and Neutron Stars days - months 10 Local Group Pulsars milli-second few thousand Whole Galaxy and M31 Intermediate mass BH days? 1 - 5 Virgo Cluster Exoplanets minutes-hours 10 ? 20 pc Flare Stars millisec - hours 100 <1kpc LIGO events millisec few ? Observable Universe Transients we expect to see… (don’t forget serendipity…)

  21. Black holes, neutron stars and gamma-ray bursts: mapping out in-situ particle acceleration Comparing directly to current X-ray all-sky monitors, LOFAR will be x10 more sensitive and provide (very rapidly) ~arcsec positions. This will be the instrument providing the alerts for Target-of-Opportunity observations with ‘pointed’ instruments e.g. Chandra, XMM-Newton, H(JW)ST, VLT, VLBI etc. Decelerating relativistic jets from a black hole binary system  in-situ acceleration of particles to TeV energies via deceleration of the jets… (Amsterdam)

  22. Radio emission from extrasolar ‘hot Jupiters’ Jupiter is very bright at low radio frequencies ‘Hot Jupiters’ closer to their parent stars (not uncommon judging by other planet-finding surveys…) will be detected to distances of tens of pc. (Nancay group) Gamma-ray bursts: we expect to detect O~1 afterglow/day, and be able to deliver arcsec-accuracy positions immediately. Maybe even ‘prompt emission’… ? (Amsterdam)

  23. Will we see many of these variable sources ? Yes ! Sky distribution of known flare stars and X-ray binaries north of -30 (Geers & Fender 2003)

  24. LOFAR and radio pulsars Because of their steep radio spectrum, LOFAR will discover many faint nearby pulsars In this large sample, LOFAR is likely to find: Geminga-like pulsars SGRs / AXPs Exotic systems (e.g. PSR-PSR, PSR-BH), probing GR… LOFAR should also discover ~10 radio pulsars in a ~10hr observation of M31!! Van Leeuwen & Stappers (2004) (ASTRON/Amsterdam)

  25. LOFAR Prototype Stations

  26. LOPES10 at KASCADE Andreas Horneffer, Heino Falcke

  27. Radio emission from air showers: Coherent ‘Geo-synchrotron emission’ Falcke & Gorham (2003) Huege & Falcke (2003)

  28. Hardware of LOPES10 LOPES-Antenna

  29. Promising EventLayout (8 antennas) E/-Detector RFI

  30. Promising EventE-Field

  31. Promising EventE-Field after Beamforming

  32. Promising EventBeamformed Power

  33. LOFAR Test Station

  34. ITS 24h-movie of the sky at ~ 30 MHz 200 frames, one per ~ 7 minT=0.2s , B=10 kHz, N=25 antennas LOFAR as an all-sky monitor (ASM) – it works!! ITS 24h-movie of the sky at ~ 30 MHz 200 frames, one per ~ 7 minT=0.2s , B=10 kHz, N=25 antennas E Full cross correlation matrix obtained Beam forming for the whole sky Noise ~ 2000 Jy Resolution ~70 N S W

  35. ITS image at ~30 MHz N= 60 dipoles T=6 sec , B=40 kHz (CLEANED) Cyg A (radio galaxy) Cas A (SNR) North Polar Spur (diffuse structure) NORTH Virgo A (radio galaxy)

  36. LOFAR is (a) reality: • The Netherlands / Europe will be at the forefront of radio astronomy for the next ~decade • What does the future hold ? • Astroparticle physics… • Cosmic-ray astrophysics (already happening…) • Coordination with neutrino detectors • An expanded pan-European LOFAR • Long baselines • Physical (and psychological) preparation for SKA

  37. The End.

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