LOFAR and the low frequency universe Probing the formation ... · LOFAR and the low frequency...
Transcript of LOFAR and the low frequency universe Probing the formation ... · LOFAR and the low frequency...
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.