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Unveiling Galactic Evolution with Confusion: Insights from 1–10 GHz Surveys

Explore the power of continuum surveys in understanding galaxy evolution using insights from EVLA and SKA pathfinders. Discover how deep confusion surveys pave the way for unraveling cosmic mysteries and measuring spectral indices.

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Unveiling Galactic Evolution with Confusion: Insights from 1–10 GHz Surveys

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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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