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.