Download - Deeper Knowledge Through Confusion
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National Radio Astronomy Observatory EVLA Workshop
Deeper Knowledge Through Confusion
Jim Condon
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EVLA Workshop 2008 Dec 17
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
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EVLA Workshop 2008 Dec 17
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.
solid curve: 1.4
GHz
dashed curve: FIR
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EVLA Workshop 2008 Dec 17
Luminosity Evolution
Local visibility functionyieldscounts normalized by static Euclidean counts
∆ log(L) ~ 1.2 evolutionfor all radio sources <z> ~ 0.8, ∆ log(z) ~ 0.5over wide flux range
stars
AGN
AGN
stars
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EVLA Workshop 2008 Dec 17
Condon (1989) and Wilner et al. (2008) models
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EVLA Workshop 2008 Dec 17
Evolution of Star Formation: Radio View
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EVLA Workshop 2008 Dec 17
Problems with current faint-source counts
Huynh et al. (2005)
P(D)1.4 GHz
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EVLA Workshop 2008 Dec 17
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EVLA Workshop 2008 Dec 17
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EVLA Workshop 2008 Dec 17
Deepest counts seem to disagree
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EVLA Workshop 2008 Dec 17Isotropy of faint NVSS sources
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EVLA Workshop 2008 Dec 17
1.4 GHz source counts in 17 FLS fields
2 is consistent with no clustering (P > 30%)• “Cosmic rms” < 16% (P > 99%)
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EVLA Workshop 2008 Dec 17
Faint sources and sky brightness
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EVLA Workshop 2008 Dec 17
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EVLA Workshop 2008 Dec 17
EVLA sensitivity and confusion surveys
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EVLA Workshop 2008 Dec 17
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EVLA Workshop 2008 Dec 17
EVLA confusion surveys as pathfinders for SKA
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EVLA Workshop 2008 Dec 17
Ultimate radio survey limits
• confusion:
c~ .03 K (1.4 GHz) instrumental natural• field of view Ω• dynamic range• noise
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EVLA Workshop 2008 Dec 17
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.
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EVLA Workshop 2008 Dec 17
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EVLA Workshop 2008 Dec 17
X-band surveys
• Small numbers of sources• Spectral-index distributions differ?
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EVLA Workshop 2008 Dec 17Isotropy of strong sources
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EVLA Workshop 2008 Dec 17
Detecting distant sources and characterizing source populations
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EVLA Workshop 2008 Dec 17
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
Power-density functions
Vir A
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EVLA Workshop 2008 Dec 17
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EVLA Workshop 2008 Dec 17
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