EDP Sciences
Free access
Volume 371, Number 2, May IV 2001
Page(s) 708 - 717
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20010384

A&A 371, 708-717 (2001)
DOI: 10.1051/0004-6361:20010384

The angular power spectrum of radio emission at 2.3 GHz

G. Giardino1, A. J. Banday2, P. Fosalba1, K. M. Górski3, 4, J. L. Jonas5, W. O'Mullane1 and J. Tauber1

1  Astrophysics Division -Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2  Max-Planck-Institut für Astrophysik, Garching bei München, 85741, Germany
3  ESO, Garching bei München, 85748, Germany
4  Warsaw university observatory, Warsaw, Poland
5  Department of Physics & Electronics, Rhodes University, PO Box 94, Grahamstown 6140, South Africa

(Received 24 November 2000 / Accepted 9 March 2001 )

We have analysed the Rhodes/HartRAO survey at 2326 MHz and derived the global angular power spectrum of Galactic continuum emission. In order to measure the angular power spectrum of the diffuse component, point sources were removed from the map by median filtering. A least-square fit to the angular power spectrum of the entire survey with a power law spectrum $C_l \propto l^{-\alpha}$, gives $\alpha = 2.43 \pm 0.01$ in the l range 2-100. The angular power spectrum of radio emission appears to steepen at high Galactic latitudes and for observed regions with ${\vert b\vert} > 20^{\circ}$, the fitted spectral index is $\alpha = 2.92 \pm 0.07$. We have extrapolated this result to 30 GHz (the lowest frequency channel of Planck) and estimate that no significant contribution to the sky temperature fluctuation is likely to come from synchrotron at degree-angular scales.

Key words: radio continuum: ISM -- surveys -- cosmic microwave background -- techniques: image processing

Offprint request: G. Giardino, ggiardin@astro.estec.esa.nl

© ESO 2001