L O F A R The Low-Frequency Array
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Transcript of L O F A R The Low-Frequency Array
L O F A RThe Low-Frequency Array
ASTRON / MIT / NRL / UvA / UL / RUG / KUNIBM / BSIK partners /Many others...
LOFAR_E211003.exe
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…
ground basedradio techniques
10 MHz
350VLAALMAATCAGMRT
LOFARLOFAR
Radio sky in 408 MHz continuum (Haslam et al)
LOFAR in The Netherlands
Hang on, what are these things?
They are theLow-band antennae(LBAs)
Optimised for 30-80 MHz range(10-90 MHz full)
Sky response
The high-band antennae (HBAs) will be optimised for the 110-240 MHz band, and are in the design phase
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)
Freq (MHz)
11s array (mJy)
11s VC (mJy)
Beam array
Beam VC
f.o.v. array
f.o.v. VC
30 118 290 25” 21’ 650’ 90O
120 4.2 10 6.0” 5.2’ 160’ 230
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.
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
Z = 20 ……………. 15 ………. 10 8 7 6
coldHI
HII
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
70 MHz 90 MHz 130 160 190 MHz
10 arcmin
QuasarQuasardistributeddistributedstar formationstar formation
(Groningen)
Mapping all radio loud AGN
Physics of radio sourcesRadio galaxies as probes of blackhole, galaxy and cluster formation
• 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
Radio galaxy surveys(Leiden)
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
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
Galaxy surveys with LOFAR will be an overwhelmingly statistical exercise
(Leiden, 5 years from now…)
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
• 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
Cluster ‘relics’ and ‘haloes’
Detections with `ASM’can be rapidly (<sec)followed up with full array
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…)
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)
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)
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)
LOFAR and radio pulsarsBecause 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)
LOFAR Prototype StationsTHETA ~ 10 elements
Location: Dwingeloo
LOPES 10 elements
Location: Karlsruhe/Kaskade
Test Station
(ITS & FTS)
60-100 elements
Location: LOFAR Core (Borger Odoorn)
Remote Station 01
100 elements
Location: between Core and WSRT
LOPES10 at KASCADE
Andreas Horneffer, Heino Falcke
Radio emission from air showers:Coherent ‘Geo-synchrotron emission’
Falcke & Gorham (2003)Huege & Falcke (2003)
Hardware of LOPES10
LOPES-Antenna
Promising EventLayout (8 antennas)
E/-Detector RFI
Promising EventE-Field
Promising EventE-Field after Beamforming
Promising EventBeamformed Power
LOFAR Test Station
ITS 24h-movie of the sky at ~ 30
MHz 200 frames, one per ~ 7
minT=0.2s ,
B=10 kHz, N=25
antennas
Full cross correlation
matrix obtained
Beam forming for the whole
sky
Noise ~ 2000 Jy
Resolution ~70
N
W
S
E
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
ITS image at ~30 MHz N= 60 dipoles T=6 sec , B=40 kHz (CLEANED)
Cas A
(SNR)
Cyg A (radio galaxy)
Virgo A
(radio galaxy)
North Polar Spur
(diffuse structure)
NORTH
LOFAR is (a) reality:
The Netherlands / Europe will be at the forefront of radio astronomy for the next ~decade
What does the future hold ?
1. Astroparticle physics…
• Cosmic-ray astrophysics (already happening…)
• Coordination with neutrino detectors
2. An expanded pan-European LOFAR
• Long baselines
• Physical (and psychological) preparation for SKA
The End.