to the Background at 3 GHz B Jim Condon NRAO, Charlottesville The - - PowerPoint PPT Presentation

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to the background at 3 ghz

to the Background at 3 GHz B Jim Condon NRAO, Charlottesville The - - PowerPoint PPT Presentation

Jan 25, 2024 305 likes •640 views

The Contribution of Galaxies to the Background at 3 GHz B Jim Condon NRAO, Charlottesville The blind men and the elephant Due to extreme delusion produced on account of a partial viewpoint, the immature deny one aspect and try to establish

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The Contribution of Galaxies to the Background at 3 GHz

B

Jim Condon

NRAO, Charlottesville

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The blind men and the elephant

“Due to extreme delusion produced on account of a partial viewpoint, the immature deny one aspect and try to establish another. This is the maxim of the blind (men) and the elephant.”

Radio Synchrotron Background Workshop 2017 July 19

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Radio Synchrotron Background Workshop 2017 July 19

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At 45 arcsec resolution, 1.4 GHz sources are mostly extragalactic,

Galactic center

Radio Synchrotron Background Workshop 2017 July 19

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very isotropic, and hence very distant

Radio Synchrotron Background Workshop 2017 July 19

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very isotropic, and hence very distant

12○ ARCADE beam

Radio Synchrotron Background Workshop 2017 July 19

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T wo source populations dominate locally

Two populations (AGNs and star forming galaxies) With no major “new population” (energy source or spectral index) since 3CR

Radio Synchrotron Background Workshop 2017 July 19

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Source counts and “simple” evolution

10×luminosity evolution + S∝(1+z)-3.7  <z> ~ 0.8 shell, S∝L

Radio Synchrotron Background Workshop 2017 July 19

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Confusion-limited 3 GHz sky image, 8 arcsec resolution

Radio Synchrotron Background Workshop 2017 July 19

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Image noise

A perfect Gaussian with nearly zero mean and rms σn = 1.012 ± 0.007 μJy/beam after Δν Δτ ≈ 1014 (1 μJy/beam = 2.1 mK)

Radio Synchrotron Background Workshop 2017 July 19

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Observed P(D) distribution and evolutionary models

Radio Synchrotron Background Workshop 2017 July 19

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Galaxy M82 Arp220

Radio Synchrotron Background Workshop 2017 July 19

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Source counts and sky brightness

model AGN starburst

Radio Synchrotron Background Workshop 2017 July 19

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Source counts and sky brightnesses: linear ordinates

Current data limit

Radio Synchrotron Background Workshop 2017 July 19

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The radio and FIR backgrounds from star- forming galaxies

Local FIR/radio correlation <q> = log(S80 μm)/log(S1.4 GHz) = 2.3 At z ~ 0.8, expect background q = log(S160 μm)/log(S1.4 GHz) = 2.5 COBE νIν ~ 1.3×10-8W m2 sr-1 at λ = 160 μm so Iν ~ 6.9×10-21W m2 Hz-1 sr-1 (ν = 1.88×1012 Hz) Radio T = 37 mK at 1.4 GHz so Iν ~ 2.2×10-23W m2 Hz-1 sr-1 Background q ~ log(6.9×10-21 / 2.2×10-23) ~ 2.5

Radio Synchrotron Background Workshop 2017 July 19

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Data points and box: 160 μm Herschel counts converted to 1.4 GHz by the FIR/radio ratio q = log(S160 μm)/log(S1.4 GHz) = 2.5 96% of the radio source background is resolved by S1.4 GHz ~ 1.7 μJy

Radio Synchrotron Background Workshop 2017 July 19

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Gray scale: JVLA μJy/beam (3.02 GHz) Crosses: Owen & Morrison (2008) sources

Radio Synchrotron Background Workshop 2017 July 19

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8 arcsec

Grey scale flux range= -7.00 40.00 MicroJY/BEAM Declination (J2000) Right Ascension (J2000) 10 46 10 05 00 45 55 50 59 02 30 00 01 30 00 00 30 00 58 59 30

Radio Synchrotron Background Workshop 2017 July 19

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2.8 arcsec

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ARCADE F IPOL ARCADEB.CROP.1 Grey scale flux range= -7.00 40.00 MicroJY/BEAM Declination (J2000) Right Ascension (J2000) 10 46 10 05 00 45 55 50 59 02 30 00 01 30 00 00 30 00 58 59 30

Radio Synchrotron Background Workshop 2017 July 19

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0.65 arcsec

Radio Synchrotron Background Workshop 2017 July 19

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The source sky is bumpy: rms confusion ~ 0.3 of background from stronger sources

Example: θ = 8 arcsec FWHM at ν = 3 GHz so σS ≈ 27 × 82 x (3/1.4)-0.7 nJy/beam ≈ 1.0 μJy/beam σS ~ ν-0.7 σT ~ ν-2.7

σT = 1 mK @ 3 GHz σT = 2 mK @ 3 GHz

Radio Synchrotron Background Workshop 2017 July 19

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Gaussian confusion and ARCADE 2: many more sources than galaxies?

Radio Synchrotron Background Workshop 2017 July 19

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What new discrete sources could produce the ARCADE 2 background?

Radio Synchrotron Background Workshop 2017 July 19

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Previous plot with linear ordinate

Radio Synchrotron Background Workshop 2017 July 19

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What new discrete sources could produce the ARCADE 2 background?

Radio Synchrotron Background Workshop 2017 July 19

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What can one blind man say about the elephant?

Radio Synchrotron Background Workshop 2017 July 19

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Radio Synchrotron Background Workshop 2017 July 19

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Summary:

1) The JVLA has resolved about 96% of the radio background produced by AGNs (63 mK at 1.4 GHz) and by star-forming galaxies (37 mK at 1.4 GHz). 2) The radio background produced by star-forming galaxies agrees well with the COBE 160 μm background and the FIR/radio correlation. 3) If the high ARCADE 2 background is real, it is too smooth to be produced by galaxies. If it consists of discrete sources, most are too faint to be detected individually even by the SKA.

(Condon, Cotton, Fomalont, Kellermann, Miller, Perley, Scott, Vernstrom, & Wall 2012, ApJ, 758:23)

Radio Synchrotron Background Workshop 2017 July 19

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Largest beamwidth θmax for a given source detection limit

Radio Synchrotron Background Workshop 2017 July 19

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Radio Synchrotron Background Workshop 2017 July 19

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No-noise P(D) distributions

Radio Synchrotron Background Workshop 2017 July 19