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Leonid Gurvits in collaboration with S.Frey, L.Mosoni, S.Garrington, M.Garrett, Z.Tsvetanov

Milli-jansky milli-arcsecond extragalactic radio sky. Leonid Gurvits in collaboration with S.Frey, L.Mosoni, S.Garrington, M.Garrett, Z.Tsvetanov. Joint VLBI in Europe Dwingeloo, The Netherlands. The challenge: to mine the terra incognita.

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Leonid Gurvits in collaboration with S.Frey, L.Mosoni, S.Garrington, M.Garrett, Z.Tsvetanov

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  1. Milli-jansky milli-arcsecond extragalactic radio sky Leonid Gurvits in collaboration with S.Frey, L.Mosoni, S.Garrington, M.Garrett, Z.Tsvetanov Joint VLBI in Europe Dwingeloo, The Netherlands

  2. The challenge: to mine the terra incognita Need to observe mJy-level sources to study 1023 – 1025 W/Hz objects at z>0.5 VLBA-10 Workshop, Socorro

  3. Imaging VLBI surveys of extragalactic sources Pearson-Readhead and Caltech-Jodrell surveys: ~250 sources at 5 GHz: www.astro.caltech.edu/~tjp/cj/ USNO VLBI survey at 2.3 and 8.4 GHz (Fey & Charlot, 1998): rorf.usno.navy.mil/rrfid.html VLBA Calibrator survey at 2.3 and 8.4 GHz (Peck & Beasley, 1998): magnolia.nrao.edu/vlba_calib/index.html VLBA-VSOP pre-launch survey at 5 GHz (Fomalont et al. 2000): www.jive.nl/jive/jive/svlbi/vlbapls/ VSOP survey at 5 GHz (Fomalont et al. 2000): oj287.vsop.isas.ac.jp/survey/ VLBA surveys at 15 GHz (Kellermann et al. 1998, Zensus et al. 2001, Gurvits et al. 2003): www.cv.nrao.edu/2cmsurvey/ VLBA-10 Workshop, Socorro

  4. Deep Extragalactic VLBI-Optical Survey (DEVOS): the approach • To observe weak compact sources around bright ones using phase-referencing technique (Garrington, Garrett, Polatidis 1999 – he field around 1156+295); • To select targets using multi-step filtering: • Overlay of optical and radio surveys; e.g. FIRST VLA and the Sloan Digital Sky Survey (SDSS) can provide 105 targets • MERLIN observations filter out sources too resolved for further VLBI observations • DEVOS (Deep Extragalactic VLBI-Optical Survey) criteria: • SLOAN-identified quasars (other types of AGN) identified as FIRST sources with S1.4 > 30 mJy (Note: NO spectral index criteria) • MERLIN detection of compact components brighter than ~2 mJy/beam VLBA-10 Workshop, Socorro

  5. The reference source: J1257+3229 VLBA Calibrator source 2.3 GHz 2° 8.4 GHz 47 FIRST/SDSS sources within 2° From J1257+3229 The sky area of DEVOS NGP (North Galactic Pole) VLBA-10 Workshop, Socorro

  6. DEVOS NGP – the sample of 47 sources FIRST data: 30 <S1.4 < 490 mJy VLBA-10 Workshop, Socorro

  7. Observed at 5 GHz, 24 March 2001 J1257+3229, 2 min NGP target, 4.5 min J1257+3229, 2 min NGP target, 4.5 min … Filter passed Total: 15h 18m MERLIN filter for DEVOS NGP + improved astrometry for VLBI φ-ref ! VLBA-10 Workshop, Socorro

  8. Filter passed Global VLBI filter for DEVOS NGP Observed at 5 GHz, 30 May 2001 J1257+3229, 2 min NGP target, 2 min NGP target, 2 min J1257+3229, 2 min … Total: 21 hr (7 hr global), 12-14 min/target, 1σthermal = 200 μJy/beam VLBA-10 Workshop, Socorro

  9. NGP01: VLBI detection at 4.4 mJy/beam VLBA-10 Workshop, Socorro

  10. NGP14: 12.2 (MERLIN) and 2.2 (VLBI) mJy/beam VLBA-10 Workshop, Socorro

  11. NGP15: 47 (MERLIN) and 20 (VLBI) mJy/beam VLBA-10 Workshop, Socorro

  12. NGP32: 10 (MERLIN) and 7.9 (VLBI) mJy/beam VLBA-10 Workshop, Socorro

  13. NGP36: 13.3 (MERLIN) and 1.4 (VLBI) mJy/beam VLBA-10 Workshop, Socorro

  14. NGP47: 13.3 (MERLIN) and 13.5 (VLBI) mJy/beam VLBA-10 Workshop, Socorro

  15. DEVOS NGP: the final yield 16/47 NGP sources detected with VLBI 30% VLBA-10 Workshop, Socorro

  16. Conclusions: what to expect at the VLBA-20 Workshop • DEVOS NGP produced 16 mJy-level VLBI detections in ~12 deg2; • Quarter of the sky (~10,000 deg2) would result in ~15,000 mJy-level detections! • Things to be sorted out: • Optimum “yield – filter threshold” relation • At least one more pilot required (lower declination field, in preparation) • Observing and man-power resources • Higher recording data rate (e.g. 1 Gbit/s) reduces integration required • Pipelining helps to keep post-docs alive and smiling • New instruments (“e”-Radio Astronomy) will make mJy-level VLBI surveys inevitable VLBA-10 Workshop, Socorro

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