Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/whats_on/workshops/mm_science2002/talks/rricci.pdf Дата изменения: Tue Nov 26 05:49:39 2002 Дата индексирования: Wed Dec 26 09:07:41 2007 Кодировка: Поисковые слова: m 63

First Results from the 20 GHz Pilot Survey
PI: R. Ekers, L. Staveley-Smith, W. Wilson, M. Kesteven, R. Subrahmanyan (ATNF) , E. Sadler, M. Walker (Sydney University), C. Jackson (MSO), R. Ricci (SISSA/Italy), G. De Zotti (Padua Observatory/Italy)

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Introduction
Why to survey the radio sky @ 20 GHz?
- New source populations -CMB foregrounds -New ATCA high frequency calibrators -A. Taylor et al. (2001) ! state of the art

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Survey Strategy
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1 ATCA baseline: CA02 ­CA03 WB analogue correlator - frequency range: 16-20 GHz - BW: 4 GHz (8 frequency channels) high scan rate: 10 degrees/min No delay correction: scan along meridian
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Survey Characteristics
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Surveyed area: ~1200 sq. deg. Slim = 60 mJy (4 ) Sky strip covered: = -70 to ­60

PMNS sources present in 20 GHz Survey area
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Survey Observations
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Date: Sep 13-17, 2002 Observing time scheduled: 96 hrs Surveyed time: 65 hrs Survey samplings no.= 2700000

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Example of survey raster scan time sequence
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Raster scan data reduction
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Antenna encoders ! sampling position WB correlator ! fringe visibilities Frequency channel averaging Denoising ! Boxcar smoothing Search for amplitude peaks Candidate source ! peak position & amp 574 candidates found at S/N = 4
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Follow-up observations
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Date: Oct 8-12, 2002 (96 hrs) Obs type: - double band (17-19 GHz) - BW = 128 MHz - snapshots (1 min each) - 4 Stokes ATCA config: H168B (3 antennas) 574 candidates & 22 calibrators observed Primary calibrator: Mars (0.4 Jy) 5 - 7 cuts per source
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uv plane of J0025-6028 (candidate source)

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Beam pattern of J0025-6028

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Follow-up preliminary results
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All 574 candidates calibrated and imaged in all the Stokes parameters 286/574 sources confirmed (S/N > 5) Some of them are multiple detections ! final source number = 226 On primary beam corrected restored maps: - accurate position & flux density - IMFITted source size ! deconvolution for resolved sources
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Contour plot of J0023-6820

Contour levs at ­1%, 1%, 2%, 4%, 8%, 16%, 32% of the peak flux = 312 mJy/beam
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Follow-up sources sky maps

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Aitoff equal area projection of the Follow-up sources sky map in galactic coordinates

· two populations (galactic & extragalactic)
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· Extragalactic population (b(II) < -10o) · 20 GHz Survey extragalactic source no. = 127 · PMN source no. = 118/127
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Differential Source Counts of survey extragalactic sources
Incompletess: S18 GHz < 100 mJy Linear Fit: N(S) S-1.97+/-0.24 Taylor et al. 2001 N(S) S-2.0+/-0.5 Slim, 15 GHz ~ 30 mJy over 63 sq. deg.

Surveyed area = 925 sq. deg.

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Survey Source Density

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Steep source density increase toward the galactic centre
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Future Work
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Radio spectra of confirmed source sample Redshift determination Better constraints to models of radio source confusion noise contaminating CMB anisotropies Plans for a 20 GHz all southern sky survey in 2003 - 3 ATCA baselines -WB correlator (8 GHz BW) - simultaneous follow-up capabilities
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