1. LOFAR Low Frequency Radio Array Veres Péter

4. Structure of the presentation Introduction Introduction Technical data Technical data Low Frequency Sky Surveys Low Frequency Sky Surveys Z>>6 Radio Galaxies Z>>6 Radio Galaxies Mpc Radio Galaxies Mpc Radio Galaxies Radio Haloes Radio Haloes Low Frequency Variables Low Frequency Variables Large –Scale Structure Large –Scale Structure Global Reionization of the Universe Global Reionization of the Universe Thermal & Nonthermal Emission Thermal & Nonthermal Emission Compact Sources in Nearby Galaxies Compact Sources in Nearby Galaxies Polarization @ Low Frequencies Polarization @ Low Frequencies HII Regions with Low Frequecy HII Regions with Low Frequecy Supernova Remnants Supernova Remnants (Extrasolar) Planets (Extrasolar) Planets

5. Introduction Netherlands Foundation for Research in Astronomy Inventory of scientific programmes using a LOFAR Hierarchical array of fixed elements operating at:10 - 300MHz Existing LFRTs: GMRT in India and VLA in th US LOFAR will provide: Greater sensitivity Greater spatial resolution Greater frequency range Greater freq. coverage & agility

6. In general Multi beaming capability at full strength Multi beaming capability at full strength High speed data processing High speed data processing Extreme agility in frequency & pointing Extreme agility in frequency & pointing Ionospheric compensation Ionospheric compensation Advanced computational techniques Advanced computational techniques In general

9. Low Frequency Sky Surveys At 20-100 MHz the sky is virtually unexplored Expected from LOFAR: distant (z>6) radio galaxies distant (z>6) radio galaxies extended (Mpc sized) and powerful galaxies @ z>1 extended (Mpc sized) and powerful galaxies @ z>1 radio halos associated with X-ray clusters radio halos associated with X-ray clusters Low Frequency Variables & constraints on LSS of the Universe with TPCF Low Frequency Variables & constraints on LSS of the Universe with TPCF new galaxies in the neighborhood new galaxies in the neighborhood

10. Mpc-Sized Radio Galaxies @ z>1 Giant Radio Galaxies (GRG) projected linear dimensions >1 Mpc projected linear dimensions >1 Mpc 3C 236>5.7 Mpc 3C 236>5.7 Mpc expand well out of their clusters into the IGM probe of IGM expand well out of their clusters into the IGM probe of IGM verify AGN endstage theories verify AGN endstage theories many of these large sources are quasars () many of these large sources are quasars ()

11. WNB 2147+816 z=0.15 linear size : 3.7 Mpc

12. Radio Haloes Things to know about RH extended radio emitting plasma ~1 Mpc extended radio emitting plasma ~1 Mpc Mostly present in clusters that: are extremely rich are extremely rich few spiral galaxies (~10%) few spiral galaxies (~10%) large velocity dispersion (~1000 km/s) large velocity dispersion (~1000 km/s) large X-ray luminosity large X-ray luminosity Large core radii (>0.3 Mpc) Large core radii (>0.3 Mpc) Explanation: a massive merger going on in the cluster, distorting its morphology Things sought: Few radio haloes are catalogued (~10) because of low surface density. LOFAR will provide large samples: study of merging activity associated with still forming clustres LOFAR is expected to find a few hundreds galaxies with radio haloes

13. Low-Frequency Variables Things to know about LFR: deeply burried inside the host galaxy deeply burried inside the host galaxy size less than a few tenths of arcsecs size less than a few tenths of arcsecs the cause: Refractive Interstellar Scintilation the cause: Refractive Interstellar Scintilation only present at low frequencies only present at low frequencies Things to expect if the LFVs turn out to be high redshift objects they define a clean sample of galaxies if the LFVs turn out to be high redshift objects they define a clean sample of galaxies if they are as small as we think they’re very young, we can obtain data abut how strong radio sources form if they are as small as we think they’re very young, we can obtain data abut how strong radio sources form perhaps they’re confined in dense ISM might explain why is ISM so dense perhaps they’re confined in dense ISM might explain why is ISM so dense

14. Large-Scale Structure Things known: at z~1 there were a hundred times more galaxies than is today at z~1 there were a hundred times more galaxies than is today evidence of anisotropies of radio sources evidence of anisotropies of radio sources e.g. bright sources seem to be more concentrated than fainter ones (but we don’t know why) Expected from LOFAR: cleaner sample of intrinsically bright, not because of Doppler boosting cleaner sample of intrinsically bright, not because of Doppler boosting

15. Global Reionization of the Universe What we know: the epopch of galaxy formation lies somewhere between z=5-10 the epopch of galaxy formation lies somewhere between z=5-10 protogalaxy contenders are very abundent (one per square minute) (search for high –z quasars takes very long optical time) protogalaxy contenders are very abundent (one per square minute) (search for high –z quasars takes very long optical time) at z>5 (today’s record) the 21cm line is shifted below 230MHz at z>5 (today’s record) the 21cm line is shifted below 230MHz What is thought, expected: Individual structures around the reionization era aren’t massive enough to detect with e.g. SKA Individual structures around the reionization era aren’t massive enough to detect with e.g. SKA Reionization edge may be detectable (Shaver) Consequence: direct measurement of th e baryon content of the Univese. For this a full range (110- 250MHz) is needed Reionization edge may be detectable (Shaver) Consequence: direct measurement of th e baryon content of the Univese. For this a full range (110- 250MHz) is needed LOFAR is perfectly suitable for this job. Expected integration time is one day LOFAR is perfectly suitable for this job. Expected integration time is one day

16. Thermal & Nonthermal Emission in Nearby Galaxies Basics: Continuum emission from galaxies give off information about their ISM Continuum emission from galaxies give off information about their ISM @ low frequencies synchrotron is th dominating mechanism @ low frequencies synchrotron is th dominating mechanism In the 20-300 MHz range we expect to see th e old population of relativistic electrons coming from SNRs In the 20-300 MHz range we expect to see th e old population of relativistic electrons coming from SNRs With LOFAR separation of thermal and non-thermal emission will be possible With LOFAR separation of thermal and non-thermal emission will be possible Spectral index variation across galaxies clues to relativistic electron production & evolution Spectral index variation across galaxies clues to relativistic electron production & evolution Thermal component dominates above 300 MHz Thermal component dominates above 300 MHz Importance: least biased view of star formation

17. Compact Sources in Nearby Galaxies LOFAR may be used to search for compact non-thermal sources in the neighbouring galaxies LOFAR may be used to search for compact non-thermal sources in the neighbouring galaxies Possibly SNRs but there’s a chance for detexting pulsars as well Possibly SNRs but there’s a chance for detexting pulsars as well Search for low frequency nuclear emission is also an issue (e.g. in the center of the MW & M31). Their nature is uncertain Search for low frequency nuclear emission is also an issue (e.g. in the center of the MW & M31). Their nature is uncertain

18. Radio Polarization @ Low Frequencies The polarization offers insight into: Galactic magnetic field Galactic magnetic field plasma turbulence plasma turbulence ionized components at any temperature ionized components at any temperature Mechanism: Faraday rotation

19. Low Frequency Recombination Line Observations of Galactic HII Regions What we know about the ionized ISM: from optical and radio samples: T=5000 to 15000K from optical and radio samples: T=5000 to 15000K What we would like to see: cool ionized gas sampled by low frequecy radio recombination lines (20-100MHz) cool ionized gas sampled by low frequecy radio recombination lines (20-100MHz) n=400-700(alpha) n=400-700(alpha) n=500-750(beta) n=500-750(beta) atoms are ~20 microns and very sensitive to their surroundings – probes of ambient physical conditions atoms are ~20 microns and very sensitive to their surroundings – probes of ambient physical conditions probably carbon, not hydrogen probably carbon, not hydrogen

20. Supernova Remnants and Pulsars Continuum imaging and spectral indices What we know: SNR are responsable for the Galactic cosmic rays and most of the synchrotron radiation SNR are responsable for the Galactic cosmic rays and most of the synchrotron radiation models constructed agree with observations alpha=-0.5 (-0.3 thru -0.8) models constructed agree with observations alpha=-0.5 (-0.3 thru -0.8) same spectral index everywhere (ENIGMA) same spectral index everywhere (ENIGMA) What is needed: high resolution SNR images over a wide Freq. range (wide range = more precise alpha) high resolution SNR images over a wide Freq. range (wide range = more precise alpha) filaments vs. smooth component problem filaments vs. smooth component problem IC 443 IC 443

21. Jupiter Things known: Jupiter produces decametric bursts at frequencies up to 40 MHz (cause: rotation, placement & Io ) Jupiter produces decametric bursts at frequencies up to 40 MHz (cause: rotation, placement & Io ) size of source : less than 500 km size of source : less than 500 km process: unknown process: unknown highly circularly polarized suggesting cyclotron emission highly circularly polarized suggesting cyclotron emission What is expected? the resolution of 1/10 D (Jup) enables to track the source the resolution of 1/10 D (Jup) enables to track the source

22. Extrasolar Planets What is known about exoplanets? Jupier sized (if we’re lucky) Jupier sized (if we’re lucky) d<1 A.U. d<1 A.U. their observation is possibly selection bias? their observation is possibly selection bias? How does Radio Astronomy fit in? as seen at Jupiter (Jupiter has Io within its magnetosphere) as seen at Jupiter (Jupiter has Io within its magnetosphere) detection of decameter bursts offers lower mass planets at any distances form their parent star detection of decameter bursts offers lower mass planets at any distances form their parent star Sun’s interference: sporadic bursts can be detached from the signal Sun’s interference: sporadic bursts can be detached from the signal chances: 0.4 mJ @ 1pc or 4 microJ @ 10 pc (marginal) chances: 0.4 mJ @ 1pc or 4 microJ @ 10 pc (marginal)

23. Summary Science Taxonomy LOFAR Science is being categorized according to the Science Taxonomy. The main categories, together with the initial point of contact (SCB Member) are: 100 : Cosmological Studies (Reionization) - Ger de Bruyn (ASTRON) 100 : Cosmological Studies (Reionization) - Ger de Bruyn (ASTRON) 200 : Extragalactic Surveys - Huub Röttgering (Leiden) 200 : Extragalactic Surveys - Huub Röttgering (Leiden) 300 : Acceleration, Turbulence & Propagation in the ISM - Jim Cordes (Cornell) 300 : Acceleration, Turbulence & Propagation in the ISM - Jim Cordes (Cornell) 400 : Targeted Extragalactic Observations - Frazer Owen (NRAO) 400 : Targeted Extragalactic Observations - Frazer Owen (NRAO) 500 : Galactic Surveys - Bryan Gaensler (Harvard) 500 : Galactic Surveys - Bryan Gaensler (Harvard) 600 : Transients - Rob Fender (Amsterdam) and Colin Lonsdale (Haystack) 600 : Transients - Rob Fender (Amsterdam) and Colin Lonsdale (Haystack) 700 : Solar System - Namir Kassim (NRL) 700 : Solar System - Namir Kassim (NRL) 800 : Ionosphere - Namir Kassim (NRL) 800 : Ionosphere - Namir Kassim (NRL) 900 : Active Observations - Namir Kassim (NRL) 900 : Active Observations - Namir Kassim (NRL)

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