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Deeper Knowledge Through Confusion

Deeper Knowledge Through Confusion. Jim Condon. Outline:. What can sensitive 1–10 GHz continuum surveys tell us about galaxy evolution? Current problems with continuum surveys

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Deeper Knowledge Through Confusion

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  1. Deeper Knowledge Through Confusion Jim Condon

  2. Outline: • What can sensitive 1–10 GHz continuum surveys tell us about galaxy evolution? • Current problems with continuum surveys • EVLA: 5X deeper knowledge through confusion ( ~ 1000 nJy at 1.4 GHz, 600 nJy at 3 GHz, 400 nJy at 6 GHz, and 250 nJy at 10 GHz) • Unique EVLA contributions as a continuum pathfinder for the SKA

  3. solid curve: 1.4 GHz dashed curve: FIR FIR and radio flux densities of star-forming galaxies are correlated so the rescaled FIR (dashed curve) and radio (solid curve) LLFs of star-forming galaxies coincide; FIR and radio trace the same SFRD.

  4. Luminosity Evolution stars AGN Local visibility function yields counts normalized by static Euclidean counts ∆ log(L) ~ 1.2 evolution for all radio sources <z> ~ 0.8, ∆ log(z) ~ 0.5 over wide flux range stars AGN

  5. Condon (1989) and Wilner et al. (2008) models

  6. Evolution of Star Formation: Radio View

  7. Problems with current faint-source counts 1.4 GHz P(D) Huynh et al. (2005)

  8. Deepest counts seem to disagree

  9. Isotropy of faint NVSS sources

  10. 1.4 GHz source counts in 17 FLS fields • 2 is consistent with no clustering (P > 30%) • “Cosmic rms” < 16% (P > 99%)

  11. Faint sources and sky brightness

  12. EVLA sensitivity and confusion surveys

  13. EVLA confusion surveys as pathfinders for SKA

  14. Ultimate radio survey limits • confusion: c~ .03 K (1.4 GHz) instrumental natural • field of view Ω • dynamic range • noise 

  15. Summary: • S ~ 1 Jy surveys at 1.4 GHz can constrain the evolution of the SFRD to z ~ 1.5 • Current surveys disagree below S ~ 100 Jy • EVLA confusion surveys could yield source counts to S ~ 1 Jy at 1.4 GHz and measure the effective spectral index at this level. • EVLA confusion surveys will be the deepest pathfinders for SKA continuum surveys, and they will approach the natural confusion limit.

  16. X-band surveys • Small numbers of sources • Spectral-index distributions differ?

  17. Isotropy of strong sources

  18. Detecting distant sources and characterizing source populations

  19. Power-density functions Vir A M82 The recent SFRD is proportional to ∫um d log(L) = 1.5 1019 W Hz-1 Mpc-3 at 1.4 GHz Arp 220

  20. The 1.4 GHz sky at 5 arcsec resolution, 23 µJy/beam = 0.6 K rms noise ~1/2 AGN ~1/2 star-forming galaxies part of the Spitzer FLS / VLA survey

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