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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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slide1

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
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

imaging vlbi surveys of extragalactic sources
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

deep extragalactic vlbi optical survey devos the approach
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

the sky area of devos ngp north galactic pole

The reference source: J1257+3229

VLBA Calibrator source

2.3 GHz

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

devos ngp the sample of 47 sources
DEVOS NGP – the sample of 47 sources

FIRST data:

30 <S1.4 < 490 mJy

VLBA-10 Workshop, Socorro

merlin filter for devos ngp

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

global vlbi filter for devos ngp

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

ngp01 vlbi detection at 4 4 mjy beam
NGP01: VLBI detection at 4.4 mJy/beam

VLBA-10 Workshop, Socorro

devos ngp the final yield
DEVOS NGP: the final yield

16/47 NGP sources

detected with VLBI

30%

VLBA-10 Workshop, Socorro

conclusions what to expect at the vlba 20 workshop
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