LOFAR and the low frequency universe Probing the formation and evolution of massive galaxies, AGN and clusters Huub Röttgering Leiden Observatory
LOFAR and the low frequency universe
Probing the formation and evolution of massive galaxies, AGN and clusters
Huub RöttgeringLeiden Observatory
LOFAR is a naturalsurvey instrument
Green: HBA mosaic at 130 MHz
Magenta: LBA mosaic at 50 Mhz/per pointing
~3 Abell clusters~3 NGC galaxies
(courtesy: Rafferty and Mohan)
50 million sources at key frequencies 15,30, 60, 120, 150, 200 MHz
APERTIF will play a crucial role
Reduction - talk de Bruyn• Current Steps
• RFI rejection
• initial calibration
• many rounds of self calibration
• accurate model target + 10-100 bright sources
• widefield imaging
• Software
• speed: BBS
• fine-tuning: AIPS, CASA,MIRIAD,DIFMAP
• Next:
• calibrate station beamformer
• use full data set (images shown use only ~10 % of subbands)
• widefield imaging taking the varying beam into account
• apply ionospheric corrections
Ionospheric correction on Cygnus A - Bas vd Tol, Huib Intema
Significant datasets• 3C196 - Olaf Wucknitz
• M51 - George Heald
• Cygnus A (210-240 MHz, 8 core, 4 remote)- McKean, Ker
• 3C61.1: de Bruyn, Yattawatta, Shulevski, van Loo, Tjibaria
• NGC 6251 - Rafferty, Birzan, Tasse,Morganti
• Clusters: Abell 2256, 0406 - van Weeren, Ferrari, Macario, Pizzo, Orru, Bonafede, Shulevski
• Virgo A - Busy week 7 (Sept 13-17)
• 3 target beam observation - Bw-7
• 10 minute observations of a section of 3C sources -Bw-7
Cygnus A, 210-240 MHz9*5 arcsec, 0.3 mJy DR 1000
Data:12 core -, 4 remote stations, 120-155 MHz, 4 hours
Image: rms 6 mJy, DR 500 59 *53 arcsec
3C61.1
60 hours, 8core, 4 remote, 14MHz BW, noise ~0.6 mJy, DR~15000, 2160 sources
tekst
3C61.1
alpha^130_1400
-0.5
-0.7
-1.0
van Loo Shulevski
NG NGC 6251
Rafferty, Birzan, Tasse
LOFAR and (proto-)clusters• Low-z
• AGN feedback and studies of cavities on long time scales (>10^8) yrs
• Magnetic field strength and configuration
• Cluster weather through morphologies of extremely old tailed radio sources
• Inventory of shocks traced by radio emission in (merging) clusters and even the cosmic web
• z~1
• Sample of clusters with diffuse emission
• Location of radio sources wrt to LSS
• z>2
• through the study of high RM sources
• in combination with Herschel
• z>6
• associated with high radio galaxies
Shocks and clusters
Do cluster wide shocks
• enable diffuse shock acceleration?
• form a central steep spectrum turbulent region?
• with a very steep radio spectrum?
Sausage clusterat z=0.2
van Weeren, HR, Bruggen, Hoeft
GMRT at 610 MHz
2 Mpc * 50 kpc!
The spectral index alpha =-0.6 - 2.0 from fit to matched GMRT and WSRT observations at 2.3, 1.7, 1.4, 1.2, and 0.61 GHzResolution: 16.7 * 12.7 arcsec.
• Mach number 4.6 +/- 1
• Downstream velocity ~1000 km/s
• B = 5 microGauss
Van Weeren, HR, Bruggen, Hoeft, in press
Shock properties
Shocks and clusters
Can cluster wide shocks
• enable diffuse shock acceleration? : YES
• form a central spectrum turbulent region?
• with a very steep radio spectrum?
0406: Tooth brush cluster
GMRT 610 MHzROSAT X-ray contours
van Weeren etal. in prep
LOFAR120-140MHzvan Weeren
Shocks and clusters
Can cluster wide shocks
• enable diffuse shock acceleration? : YES
• form a central spectrum turbulent region? YES
• with a very steep radio spectrum?
Intema et al. submitted, see also Kale and Dwarakanath 2010
A2256: Where is the steep spectrum halo?
Data:10 core -, 5 remote stations, 115-165 MHz, 8 hoursImage: 4 MHz @135 MHz, rms 5 mJy, 31*19 arcsec
Shocks and clusters
Can cluster wide shocks
• enable diffuse shock acceleration? : YES
• form a central spectrum turbulent region? YES
• with a very steep radio spectrum? YES
LOFAR will be instrumental in mapping out the entire shock system in clusters
Conclusion• LOFAR works!
• The planned surveys will be important for our understanding on the formation and evolution of galaxies, clusters and AGN
• More information:
• Heald et al. Progress with the LOFAR Imaging Pipeline in proceedings of ISKAF2010 Science Meeting
• A.R. Offringa et al., A LOFAR RFI detection pipeline and its first results, in proceedings of RFI mitigation workshop, PoS(RFI2010)036.
• O. Wucknitz, Long baseline experiments with LOFAR, in proceedings of ISKAF2010 Science Meeting
• H.J.A. Rottgering et al, LOFAR and the low frequency Universe, in proceedings of ISKAF2010 Science Meeting, PoS(ISKAF2010)050.