Counts and spectral indices at 8.44GHz Virtual Observatory Resource

Authors
  1. WINDHORST R.A.
  2. FOMALONT E.B.
  3. PARTRIDGE R.B.
  4. LOWENTHAL J.D.
  5. Published by
    CDS
Abstract

We used the VLA to make deep images of two 7x7' fields at 8.44 GHz with 10" resolution. With an rms noise of 3.2 and 5.1 {micro}Jy, respectively, in the two fields, we compiled a catalog of 82 sources. The normalized differential 8.44 GHz counts are similar to those at 1.41 and 4.86 GHz. All show a similarly steep submillijansky slope, which is only somewhat flatter than that expected for a nonevolving Euclidean population ({gamma}=2.5). Microjansky radio sources at 4.86 GHz have been identified with faint blue galaxies (18<~V<~28 mag). We argue that their expected median redshift is about 0.5-0.75. Hence, cosmological evolution may be needed to explain the steep slope of the microjansky counts. The 8.44 GHz counts must converge with slope {gamma}<2.0 below S(8.44)~300 nJy, or they would exceed the available field galaxy counts down to V~28 mag, and they must permanently converge below S(8.44)~20 nJy, or their integrated sky brightness would distort the observed thermal cosmic background radiation spectrum at centimeter wavelengths. The estimated 31.5 GHz sky brightness from nanojansky to jansky levels is <36 {micro}K (3{sigma}). Even if weak radio sources cluster on scales of degrees as faint galaxies do, their anisotropic contribution to the COBE DMR experiment (with 7deg FWHM-beam) would not exceed ~1.2{micro}K.

Keywords
  1. radio-sources
Bibliographic source Bibcode
1993ApJ...405..498W
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/405/498
IVOA Identifier IVOID
ivo://CDS.VizieR/J/ApJ/405/498
Document Object Identifer DOI
doi:10.26093/cds/vizier.14050498

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History

1997-12-09T20:48:06Z
Resource record created
1997-12-09T20:48:06Z
Created
2013-03-05T06:34:13Z
Updated

Contact

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CDS support team
Postal Address
CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France
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