May24 th 2011 FGC2011 - Zadar,, Croatia Simona Righini,, INAF-IRA IRA KNoWS an all-northern sky survey at 20 GHz for extragalactic sources as CMB foregrounds
Outline Overview on KNoWS project Impact on CMB experiments Status What s next
Who KNoWS? K-band Northern Wide Survey: PI Ettore Carretti (CASS-CSIRO) CSIRO) Group (INAF-IRA): IRA): Simona Righini, Karl-Heinz Mack, Alessandra Zanichelli, Isabella Prandoni, Roberto Ricci, Loretta Gregorini, Franco Mantovani, Marcella Massardi, Rashmi Verma (Estrela( PhD) - INAF-IRA IRA Medicina 32-m dish - New 7-feed 7 18-26.5 GHz receiver (SRT)
Why do we want to KNoW(S)? No wide-area surveys exist at these high frequencies for the northern hemisphere Goal: to survey the northern sky at 20 GHz to detect sources down to 50 mjy study of extragalactic compact sources as foregrounds for CMB observations study of the Astrophysics of extragalactic sources Complementary to the AT20G survey (Murphy et al. 2010, Massardi et al. 2011) carried out in the southern sky with ATNF-ATCA ATCA
Radio Sources as extragalactic CMB foregrounds Statistical approach? It s better to know all of them to mask them out of your map; Reliability of extrapolations? Radio sources counts and their high-frequency fluxes extrapolated from lower frequency catalogues have proven to be inaccurate. Need to survey the whole sky at high-freq and pinpoint position and flux of each contaminating source
Impact on CMB experiments The KNoWS survey closely matches the AT20G one, both in terms of spatial resolution (~ 1.8 arcmin) and sensitivity (detections down to 50 mjy at 5 sigma). Such a catalogue will allow to better estimate the residual contamination after the map masking, which takes place at a brighter flux limit (e.g. 1.1 Jy if using WMAP sources).
18-26.5 GHz 7-feed 7 receiver Tsys = 70 K (22 GHz, El=45, τ = 0.1) Gain = 0.11 K/Jy (22 GHz, El=45 ) HPBW = 92 (22 GHz) Sky distance between beam couples = 212 14 output channels (7 LCP + 7 RCP) with 2 GHz-wide IF bands
Receiver Antenna Control System Total Power Backend OTF observations All new items under development and/or commissioning Data reduction pipeline for SRT s sake, but also for Medicina and Noto
KNoWS strategy: azimuth scans Fast scans at constant elevation, moving back and forth within the desired azimuth range, exploiting the sky apparent rotation to map the wanted area. Pros - All acquisition at same elevation, i.e. same airmass Cons - If there s s RFI, it affects all scans - Strictly LST-based strategy Strategy by E.Carretti developed at Parkes (for S-PASS survey) see presentation by M. Haverkorn
Details: pilot survey setup Azimuth range: : 1-25 (Dec > 73.2 ) Fixed elevation: 44.52 Scanning speed: : 15 /m (10.7 /min on sky) Sampling interval: : 40 ms Beamsize (FWHM): : 108'' Samples/beam, single subscan: : 4.2 Integration/beam beam,, full map: : 0.672 s Final average rms: ~20 mjy Main source extraction software by Marcos Lopez Caniego: : found about 100 candidates > 100 mjy
Status: pilot survey Pilot survey for Dec > 73.2 (~ ~ 1000 sq deg) was performed in total intensity in winter 2009-2010 2010 (heavily affected by bad weather) Map: all diffuse contributions are subtracted, looking for point like sources. Data reduction confirmed the expected system performances. Use of different source extraction tools identification of ~ 100 candidate sources down to 100 mjy, in agreement with model predictions (De Zotti et al, 2005). in agreement with DeZotti s
Status: follow-up Confirmation and multi-frequency continuum follow-up (5, 8.3, 20 GHz) of pilot survey candidates,, in Feb-Apr 2011 (+ 30 GHz OCRA observations for a sample of sources) 77 sources were confirmed Righini et al., in prep. (+Ricci et al., in prep.)
Integral counts Sources with S >= Flux_lim 80 70 60 50 40 30 20 10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 20 GHz Flux_lim (Jy)
Status: equatorial stripe map Area for -1 < Dec < 15 ( ~5700 sq deg) mapped during winter 2010-2011 2011 data reduction is ongoing, though data is RFI-affected
What s next Source extraction and follow-up of the equatorial stripe map New observations including polarimetry (digital backends on the way) Further areas to be mapped with Medicina (22 dual beam almost ready), SRT and/or other telescopes (22 GHz Notice: : new software and hardware updates are making the Medicina dish, historically focused on VLBI, an up-to to-date single-dish facility