Deep Radio Surveys

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Deep Radio Surveys

• Jim Condon

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Isotropy of strong sources
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Isotropy of faint sources
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Nearby (recent) sources evolutionary goal for
distant (past) sources

• lt 1 of sources stronger than 2.5 mJy at 1.4
  GHz can be identified with the nearby (z lt 0.04)
  galaxies in the UGC catalog.
• All sky low-resolution surveys are needed
  to characterize the nearby source populations.

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• The typical radio / far-infrared (FIR)
  spectrum of a star-forming galaxy (M82)
• Radio from
• M gt 8 M?
• T lt 3?107 yr
• stars.

synchrotron
dust
free-free
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The FIR/radio Correlation

• The remarkably tight FIR/radio correlation
  implies that radio luminosity is nearly
  proportional to the star-formation rate and
  nearly independent of magnetic field strength and
  other parameters.
• Fails at B lt 3(1z)2 µG?
• Otherwise good to z1
• (2004, ApJS, 154, 147).

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• FIR and radio flux-limited samples overlap, so
  
• the rescaled FIR (dashed curve) and radio (solid
  curve) LLFs of star-forming galaxies coincide.
• FIR and radio imply the same recent SFRD.

solid curve 1.4 GHz dashed curve FIR
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• The 1.4 GHz local luminosity functions for two
  source populations star-forming galaxies and AGNs

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Local 1.4 GHz Power-density Functions
Vir A

• The recent SFRD is proportional to
• ?um d log(L)
• 1.5 ?1019 W Hz-1
• Mpc-3 at 1.4 GHz

M82
Arp 220
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Detecting distant sources and characterizing
source populations

• Wedding-cake surveys
• AGN and star-forming galaxies

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• Protocluster containing the steep-spectrum
  source PKS 1138-262 (RG) z 2.156

Croft et al. 2005, AJ, 130, 867
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Radio Surveys

• Resolution
• Sensitivity
• Position accuracy
• Frequency
• Field of view

FLS/VLA 1.4 GHz survey fields
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• 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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Faint-source counts (1.4 GHz)
P(D)
Huynh et al. (2005)
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Luminosity Evolution (Cosmic Downsizing)
stars

• Local visibility function
• yields
• counts normalized by
• static Euclidean counts
• ? log(L) 1.2 evolution
• for all radio sources
• ltzgt 0.8, ? log(z) 0.5
• over wide flux range

AGN
stars
AGN
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Evolution of Star Formation Radio View
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• Visibility function
• versus
• power density function
• sky background

AGN
AGN
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A New Look at Source Counts
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Radio Survey Limits

• confusion
• ?c .03 K
• (1.4 GHz)
• instrumental
• natural
• field of view ?
• dynamic range
• noise ?

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• Early star formation
• EVLA for ULIRGs
• ALMA or SKA(?) to characterize populations